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Laboratory Testing of Three Intracranial Pressure Microtransducers: Technical Report
Abstract
Three comparatively priced intracranial pressure (ICP) microtransducers are now available, each characterized by the manufacturer as having very low zero drift over long periods, an excellent frequency response, and a low measurement error. The three microtransducers, coded Transducer A (Camino OLM ICP monitor; Camino Laboratories, San Diego, CA), Transducer B (Codman Microsensor ICP Transducer; Codman & Shurtlef Inc., Randolph, MA), and Transducer C (ICP Monitoring Catheter Kit OPX-SD [4F]; InnerSpace Medical, Irvine, CA), were examined in a pressure-flow test rig designed for assessment of hydrocephalus shunts. All three microtransducers compiled with the manufacturers' specifications and gave high-quality readings under test conditions. However, some differences were noted; Transducer C had the lowest 24-hour zero drift (drifts in all transducers were < 0.8 mm Hg). The temperature drift was very low in Transducer B and C, but Transducer A had a significantly higher drift (0.27 mm Hg/degrees C). Transducer A had a static error < 0.3 mm Hg, Transducer B < 2 mm Hg, and Transducer C < 8 mm Hg. Frequency detection in Transducers A and B were very good (bandwidth, > 30 Hz), whereas Transducer C had a limited bandwidth of 20 Hz. Transducer B scored the best overall, but all three scored satisfactorily during bench testing.
... The bottle is then submerged horizontally in a water bath at a constant temperature of 35 • C. Static pressure on the bottle (representing pressure detected by ICP catheters) and reference static pressure (representing true ventricular pressure) are compared by changing the height of a water column in a 1.5 m graded vertical tube. Static pressure is released at intervals by allowing the water to flow out of an opened stopcock; conversely, pressure is increased by infusing fluid into the tubing [34,41]. ...
... Every sensor is susceptible to zero drift. Large studies by [40][41][42][43] found varying drifts between a variety of sensor types. Refs. ...
... Refs. [40,41] reported <0.8 (mm Hg/day) zero drifts for several sensor types such as fiberoptic, piezoelectric, and pneumatic during a 24 h period. Refs. ...
Intracranial hypertension and adequacy of brain blood flow are primary concerns following traumatic brain injury. Intracranial pressure (ICP) monitoring is a critical diagnostic tool in neurocritical care. However, all ICP sensors, irrespective of design, are subject to systematic and random measurement inaccuracies that can affect patient care if overlooked or disregarded. The wide choice of sensors available to surgeons raises questions about performance and suitability for treatment. This observational study offers a critical review of the clinical and experimental assessment of ICP sensor accuracy and comments on the relationship between actual clinical performance, bench testing, and manufacturer specifications. Critically, on this basis, the study offers guidelines for the selection of ICP monitoring technologies, an important clinical decision. To complement this, a literature review on important ICP monitoring considerations was included. This study utilises illustrative clinical and laboratory material from 1200 TBI patients (collected from 1992 to 2019) to present several important points regarding the accuracy of in vivo implementation of contemporary ICP transducers. In addition, a thorough literature search was performed, with sources dating from 1960 to 2021. Sources considered to be relevant matched the keywords: “intraparenchymal ICP sensors”, “fiberoptic ICP sensors”, “piezoelectric strain gauge sensors”, “external ventricular drains”, “CSF reference pressure”, “ICP zero drift”, and “ICP measurement accuracy”. Based on single centre observations and the 76 sources reviewed in this paper, this material reports an overall anticipated measurement accuracy for intraparenchymal transducers of around ± 6.0 mm Hg with an average zero drift of
... The manufacturer's specification of the zero drift of the catheter is Ϯ2 mm Hg for the first day and then Ϯ1 mm Hg/d thereafter. Bench test studies have confirmed these findings (6). In clinical practice, however, the zero drift observed upon removal of the device from the patient has recently been reported to be greater than the manufacturer's specifications. ...
... The InnerSpace OPX 100 system (InnerSpace Medical) is, like the Camino system, a fiberoptic system. Bench test reports regarding this system show it to have good zero-drift and sensitivity stability (6). A recent clinical evaluation of this system in 51 patients, however, reported a high (17%) incidence of hematoma formation around the ICP sensor (11). ...
... The Camino device manufacturer's specification for zero drift of the catheter is Ϯ2 mm Hg for the first day and Ϯ1 mm Hg/d thereafter. Czosnyka et al. (6) confirmed these zero-drift findings in bench test studies, although they also reported, in agreement with our findings, that the temperature drift of the device was significant (0.3 mm Hg/1°C). They reported that if the transducer is zeroed before implantation at room temperature, the temperature-induced overreading can be as much as 5 mm Hg, depending on the patient's brain temperature. ...
... conversely, pressure is increased by infusing fluid into the tubing (143,144) (Figure 4. A sophisticated, computer-controlled rig was used to assess the compliance of ICP sensors and responsiveness to increased pressure loads. A detailed description can be found in Czosnyka et al. (142) . ...
... Intraparenchymal ICP probes, particularly the fiberoptic Camino 110-4B sensor, and strain gauge probes, particularly the Codman MicroSensor, are very popular among neurocritical care centers for TBI management. In a laboratory bench test (144) , both the Camino and Codman sensors exhibited zero drift <0.8 mm Hg over 24 hours at a static pressure of 20 mm Hg. In comparison, the Camino sensors were found to have significantly higher temperature drift than the Codman sensors (142) . ...
... conversely, pressure is increased by infusing fluid into the tubing (143,144) (Figure 4. A sophisticated, computer-controlled rig was used to assess the compliance of ICP sensors and responsiveness to increased pressure loads. A detailed description can be found in Czosnyka et al. (142) . ...
... Intraparenchymal ICP probes, particularly the fiberoptic Camino 110-4B sensor, and strain gauge probes, particularly the Codman MicroSensor, are very popular among neurocritical care centers for TBI management. In a laboratory bench test (144) , both the Camino and Codman sensors exhibited zero drift <0.8 mm Hg over 24 hours at a static pressure of 20 mm Hg. In comparison, the Camino sensors were found to have significantly higher temperature drift than the Codman sensors (142) . ...
Various invasive and non-invasive cranial monitoring techniques can be applied clinically to describe the extent to which cerebral hemodynamics and subsequently, patient outcome, have been impacted following acute brain injury (ABI). This Ph.D. thesis examines both prospective and retrospective patient data in both neurocritical and general intensive care patients. Thirty neurotrauma patients and forty general intensive care patients with neurological complications were prospectively monitored after ABI. Retrospective patient data was harvested from a database of 1,023 traumatic brain injury (TBI) patients with invasive intracranial pressure (ICP), arterial blood pressure (ABP), and transcranial Doppler ultrasonography (TCD) recordings. Data analysis focused on ICP microsensor accuracy, compensatory reserve, the pulsatility of brain signals (ICP and TCD), and cerebral arterial blood volume (CaBV) based on TCD. The main results are summarized below: I. Intracranial hypertension has a profound negative influence on cerebrovascular parameters and patient outcome. II. ICP microsensor accuracy is limited, with an average error of approximately ± 6.0 mm Hg. III. ICP weighted with the compensatory reserve better predicts outcome than mean ICP alone. IV. ICP and TCD pulsatility are functions of mean ICP and cerebral perfusion pressure (CPP). V. Continuous blood flow forward (CFF) and pulsatile blood flow forward (PFF) models can approximate CaBV with derived TCD signals; CFF best models TCD pulsatility. VI. The pressure reactivity index (PRx) and the pulse amplitude index (PAx) can be estimated non-invasively using slow waves of TCD estimated by CaBV with similar outcome-predictive power. VII. Multi-parametric TCD-based monitoring of general intensive care patients is clinically feasible; the joint estimation of autoregulation, dysautonomia, non-invasive ICP, and critical closing pressure is possible. The culmination of these projects should have an impact on current monitoring practices in ABI patients, emphasizing the continued validation and refinement of TCD methodology in clinical neurosciences.
... 32,42,43,58,59 Previous studies validated FO for intraparenchymal ICP monitoring in vivo, 27,60,61 and several articles analyzed safety, baseline drift, and complications in neurocritical patients with reliable results in comparison with the available piezoelectric and pneumatic sensors. 17,[46][47][48][49][50][62][63][64][65][66] The FO described in this article followed the principles of an optomechanical and diaphragm-based sensor for intraparenchymal monitoring. As a preliminary study, the FO catheter was constructed with a 3.5 mm tip for more robustness and diaphragm integrity, in comparison with the 1-mm reference sensor. ...
Background:
Continuous invasive monitoring of intracranial pressure (ICP) is essential in neurocritical care for surveillance and management of raised ICP. Fluid-based systems and strain gauge microsensors remain the current standard. In the past few decades, several studies with wireless monitoring were developed aiming to reduce invasiveness and complications.
Objective:
To describe a novel Wi-Fi fiber-optic device for continuous ICP monitoring using smartphone in a swine model.
Methods:
Two ICP sensors (wireless prototype and wire-based reference) were implanted in the cerebral parenchyma of a swine model for a total of 120 minutes of continuous monitoring. Every 5 minutes, jugular veins compression was performed to evaluate ICP changes. The experimentation was divided in 3 phases for comparison and analysis.
Results:
Phase 1 showed agreement in ICP changes for both sensors during jugular compression and releasing, with a positive and strong Spearman correlation (r = 0.829, P < .001). Phase 2 started after inversion of the sensors in the burr holes; there was a positive and moderately weak Spearman correlation (r = 0.262, P < .001). For phase 3, the sensors were returned to the first burr holes; the prototype behaved similarly to the reference sensor, presenting a positive and moderately strong Spearman correlation (r = 0.669, P < .001).
Conclusion:
A Wi-Fi ICP monitoring system was demonstrated in a comprehensive and feasible way. It was possible to observe, using smartphone, an adequate correlation regarding ICP variations. Further adaptations are already being developed.
... However, four main shortcomings discourage intraventricular monitoring: (1) It may lead to CSF leakage, causing untrusty low readings (Zhang et al. 2017); (2) It is associated with infections and mechanical complications (Czosnyka et al. 1996a ...
Monitoring intracranial pressure (ICP) is vital to decide the appropriate clinical treatment of patients with conditions potentially causing high ICP (e.g. brain injury, cerebral tumor, and hydrocephalus). On the path for finding an alternative means to invasive ICP measurement, the only means to date for accurate ICP monitoring, this study investigates the relationship of ICP with systemic cardiovascular signals ─heart rate (HR), aortic blood pressure (aBP), and carotid blood flow (cBF)─ via rat experiments and signal analysis techniques. Whilst induced changes in aBP and cBF resulted in evident alterations of ICP magnitude, increases of mean ICP up to 49 mmHg showed minimal effect on HR, aBP, or cBF signals. Thus, a stepwise mixed-model regression proved that the cardiovascular parameters here studied have minimal but significant predictive value of ICP magnitude. Changes in HR were found to modify the waveforms observed in ICP, aBP, and cBF signals, without altering the magnitude or phase of transfer function models. The transfer function models were constructed as a function of mean ICP, mean aBP, and aBP or cBF waveforms, and they showed potential to reproduce the ICP waveform (Root Mean Square Error (RMSE)≤4 mmHg), being more accurate for mean aBP above 100 mmHg and mean ICP below 20 mmHg (RMSE≤0.5 mmHg). Likewise, estimation of pulse ICP showed a small error (<1±1.0 mmHg) for mean ICP below 20 mmHg across a range of mean aBP (70-130 mmHg), proving considerable accuracy improvement in relation to previous studies.
... Intraparenchymal probes for ICP monitoring were introduced into clinical practice in the 1980s. They provided reliable and accurate ICP measurements in experimental and clinical validation studies (38,(46)(47)(48)(49), which made them a veritable alternative to EVD-based measurements (13). Placement of intraparenchymal probes still requires neurosurgical expertise for penetration of the skull and meninges and for positioning of the probe in the brain tissue, usually only a few centimeters into the frontal cerebral cortex. ...
Patients with acute brain injuries tend to be physiologically unstable and at risk of rapid and potentially life-threatening decompensation due to shifts in intracranial compartment volumes and consequent intracranial hypertension. Invasive intracranial pressure (ICP) monitoring therefore remains a cornerstone of modern neurocritical care, despite the attendant risks of infection and damage to brain tissue arising from the surgical placement of a catheter or pressure transducer into the cerebrospinal fluid or brain tissue compartments. In addition to ICP monitoring, tracking of the intracranial capacity to buffer shifts in compartment volumes would help in the assessment of patient state, inform clinical decision making, and guide therapeutic interventions. We review the anatomy, physiology, and current technology relevant to clinical management of patients with acute brain injury and outline unmet clinical needs to advance patient monitoring in neurocritical care.
... This technique is common for many pressure transducers used in medicine. A principle difference from the intraventricular technique is the inability to recalibrate the intra parenchymal transducers (5)(6)(7)(8). In addition, these devises may measure a compartmentalized local pressure (9). ...
Neurocritical care (NCC) is a branch of intensive care medicine characterized by specific physiological and biochemical monitoring techniques necessary for identifying cerebral adverse events and for evaluating specific therapies. Information is primarily obtained from physiological variables related to intracranial pressure (ICP) and cerebral blood flow (CBF) and from physiological and biochemical variables related to cerebral energy metabolism. Non-surgical therapies developed for treating increased ICP are based on knowledge regarding transport of water across the intact and injured blood–brain barrier (BBB) and the regulation of CBF. Brain volume is strictly controlled as the BBB permeability to crystalloids is very low restricting net transport of water across the capillary wall. Cerebral pressure autoregulation prevents changes in intracranial blood volume and intracapillary hydrostatic pressure at variations in arterial blood pressure. Information regarding cerebral oxidative metabolism is obtained from measurements of brain tissue oxygen tension (PbtO2) and biochemical data obtained from intracerebral microdialysis. As interstitial lactate/pyruvate (LP) ratio instantaneously reflects shifts in intracellular cytoplasmatic redox state, it is an important indicator of compromised cerebral oxidative metabolism. The combined information obtained from PbtO2, LP ratio, and the pattern of biochemical variables reveals whether impaired oxidative metabolism is due to insufficient perfusion (ischemia) or mitochondrial dysfunction. Intracerebral microdialysis and PbtO2 give information from a very small volume of tissue. Accordingly, clinical interpretation of the data must be based on information of the probe location in relation to focal brain damage. Attempts to evaluate global cerebral energy state from microdialysis of intraventricular fluid and from the LP ratio of the draining venous blood have recently been presented. To be of clinical relevance, the information from all monitoring techniques should be presented bedside online. Accordingly, in the future, the chemical variables obtained from microdialysis will probably be analyzed by biochemical sensors.
... (1) CSF leakage may lead to falsely low readings. (2) There is a higher risk of CSF infection (up to 10% in some series) and mechanical complications than when using ICP probes (Czosnyka et al 1996). EVD catheter infections can be mild and easily treatable or can be severe such as meningitis and ventriculitis, causing neurological symptoms and possible death. ...
Objective:
We performed a comprehensive literature review on how to measure ICP invasively and noninvasively.
Approach:
This review discusses the advantages and disadvantages of current invasive and noninvasive approaches.
Main results:
Invasive methods remain the most accurate at measuring ICP, but they are prone to a variety of complications including infection, hemorrhage and neurological deficits. Ventricular catheters remain the gold standard but also carry the highest risk of complications, including difficult or incorrect placement. Direct telemetric intraparenchymal ICP monitoring devices are a good alternative. Noninvasive methods for measuring and evaluating ICP have been developed and classified in five broad categories, but have not been reliable enough to use on a routine basis. These methods include the fluid dynamic, ophthalmic, otic, and electrophysiologic methods, as well as magnetic resonance imaging, transcranial Doppler ultrasonography (TCD), cerebral blood flow velocity, near-infrared spectroscopy, transcranial time-of-flight, spontaneous venous pulsations, venous ophthalmodynamometry, optical coherence tomography of retina, optic nerve sheath diameter (ONSD) assessment, pupillometry constriction, sensing tympanic membrane displacement, analyzing otoacoustic emissions/acoustic measure, transcranial acoustic signals, visual-evoked potentials, electroencephalography, skull vibrations, brain tissue resonance and the jugular vein.
Significance:
This review provides a current perspective of invasive and noninvasive ICP measurements, along with a sense of their relative strengths, drawbacks and areas for further improvement. At present, none of the noninvasive methods demonstrates sufficient accuracy and ease of use while allowing continuous monitoring in routine clinical use. However, they provide a realizable ICP measurement in specific patients especially when invasive monitoring is contraindicated or unavailable. Among all noninvasive ICP measurement methods, ONSD and TCD are attractive and may be useful in selected settings though they cannot be used as invasive ICP measurement substitutes. For a sufficiently accurate and universal continuous ICP monitoring method/device, future research and developments are needed to integrate further refinements of the existing methods, combine telemetric sensors and/or technologies, and validate large numbers of clinical studies on relevant patient populations.
... These authors found that all three devices scored satisfactorily, with the Codman device scoring best overall. [70] The Association for Advancement of Medical Instrumentation, in association with the Neurosurgery committee has developed the American Standard for ICP monitoring devices. According to their standards, an ICP device should have the following specifications: • Pressure range from 0 to 100 mm Hg; ...
Brain specific monitoring enables detection and prevention of secondary cerebral insults, especially in the injured brain, thereby preventing permanent neurological damage. Intracranial pressure (ICP) monitoring is widely used in various neurological, neurosurgical and even medical conditions, both intraoperatively and in critical care, to improve patient outcome. It is especially useful in patients with traumatic brain injury, as a robust predictor of cerebral perfusion, and can help to guide therapy and assess long-term prognosis. Intraventricular catheters remain the gold standard for ICP monitoring, as they are the most reliable, accurate and cost-effective, and allow therapeutic cerebrospinal fluid drainage. Newer fibreoptic catheter tip and microchip transducer techniques have revolutionised ICP monitoring, with their ease of insertion in patients with narrow ventricles, and reduced risk of infection and haemorrhage. Furthermore, non-invasive methods of ICP monitoring, such as transcranial Doppler, optic nerve sheath diameter, etc., have emerged as promising techniques for screening patients with raised ICP in settings where invasive techniques are either not feasible (patients with severe coagulopathy) or not available (setups without access to a neurosurgeon). Therefore, ICP monitoring, as a part of multi-modality neuromonitoring, is a useful tool in the armamentarium of the neuro-intensivist in decreasing morbidity and mortality of critically ill neurological patients.
... Most importantly, long-term monitoring of ICP provides a quantitative method for diagnosis in contrast to vague symptoms (e.g., headaches, nausea). Two commonly used EVDs are the Codman Microsensor ICP (Codman & Shurtleff, Inc., Raynham, MA, USA) and Camino (Integra LifeSciences Corporation, Plainsboro, NJ, USA), which feature a sensor-tipped catheter that enables location-specific pressure measurement in the intracranial space [100]. Unfortunately, long-term monitoring with the EVD confines patients to the clinic and the extended period of opening of the blood-brain barrier increases risk of meningitis and other infections (exacerbating intracranial hypertension) [4]. ...
Several conditions and diseases are linked to the elevation or depression of internal pressures from a healthy, normal range, motivating the need for chronic implantable pressure sensors. A simple implantable pressure transduction system consists of a pressure-sensing element with a method to transmit the data to an external unit. The biological environment presents a host of engineering issues that must be considered for long term monitoring. Therefore, the design of such systems must carefully consider interactions between the implanted system and the body, including biocompatibility, surgical placement, and patient comfort. Here we review research developments on implantable sensors for chronic pressure monitoring within the body, focusing on general design requirements for implantable pressure sensors as well as specifications for different medical applications. We also discuss recent efforts to address biocompatibility, efficient telemetry, and drift management, and explore emerging trends.
While there is no level I recommendation for intracranial pressure (ICP) monitoring, it is typically indicated for patients with severe traumatic brain injury (TBI) with a Glasgow Coma Scale (GCS) score of 3-8 (class II). Even for moderate TBI patients with GCS 9-12, ICP monitoring should be considered for risk of increased ICP. The impact of ICP monitoring on patient outcomes is still not well-established, but recent studies reported a reduction of early mortality (class III) in TBI patients. There is no standard protocol for the application of ICP monitoring. In cases where cerebrospinal fluid drainage is required, an external ventricular drain is commonly used. In other cases, parenchymal ICP monitoring devices are generally employed. Subdural or non-invasive forms are not suitable for ICP monitoring. The mean value of ICP is the parameter recommended for observation in many guidelines. In TBI, values above 22 mmHg are associated with increased mortality. However, recent studies proposed various parameters including cumulative time with ICP above 20 mmHg (pressure-time dose), pressure reactivity index, ICP waveform characteristics (pulse amplitude of ICP, mean ICP wave amplitude), and the compensatory reserve of the brain (reserve-amplitude-pressure), which are useful in predicting patient outcomes and guiding treatment. Further research is required for validation of these parameters compared to simple ICP monitoring.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Traumatic Brain and Spinal Cord Injury comprehensively covers the medical and pathological issues related to neurotrauma and its often devastating consequences. Written by globally renowned experts in the field, both clinicians and researchers will find this book invaluable to update their knowledge. This volume is divided into two sections, one covering the brain, the other the spinal cord. Each section discusses the following topics: • The demographic in the developed and developing world where neurotrauma is witnessing a massive expansion • Major clinical issues including advanced semi-experimental monitoring techniques utilized by neurosurgeons and intensivists and the potential use of identifying markers of tissue injury • Overview of major pathophysiological changes • The development of animal models; successes and limitations • Past, current and future therapeutic strategies including rehabilitative opportunities. Presenting the most up-to-date clinical and experimental research in neurotrauma, this volume is essential reading for neurologists, neurosurgeons, intensive care physicians and rehabilitative physicians.
Monitoring physiological parameters in the brain is important to identify early signs of secondary brain injuries. A variety of different intracranial sensors enable continuous monitoring of important brain parameters in clinical applications. However, many of the clinically approved and established technologies show drawbacks in zero‐drift properties, accuracy and magnet resonance imaging (MRI) compatibility. This review gives a comparative overview of the established technologies and provides an outlook on fiber‐optic sensors (FOS) with potential use in future intracranial monitoring applications. Neurophysiological parameters recorded by bioelectrical signals include intracranial pressure (ICP), brain temperature, brain tissue oxygenation, cerebral blood flow, and cerebral metabolism. The comparison of ICP sensors revealed that piezoresistive strain gauge sensors provide the highest accuracy and the smallest zero‐drift in clinical catheters. Fiber‐optic pressure sensors show a potential to be used in future intracranial applications. Thermistors and thermocouples prove to be reliable for temperature measurement in intracranial catheters, but have limited MRI compatibility. FOS show potential to be used in future intracranial catheters for temperature and oxygen measurement, as they provide higher accuracy and a better response time. Microdialysis catheters, in combination with new automated electrochemical and optical analyzers, provide the possibility of routine metabolism monitoring in clinics.
Intracranial and intraocular pressures are interrelated and relatively independent pressure systems, which keeps themselves in a relatively stable state through aqueous and cerebrospinal fluid circulations. Recently, researchers have focused on intracranial pressure role in eye diseases. This chapter summarizes various instruments to measure and visualize geometrical and functional parameters related to the fluid dynamics of cerebrospinal fluid in the eye.
Objective:
A drawback in the use of an external ventricular drain (EVD) originates in the fact that draining cerebrospinal fluid (CSF) (open system) and intracranial pressure (ICP) monitoring can be done at the same time but is considered to be unreliable regarding the ICP trace. Furthermore, with the more widespread use of autoregulation monitoring using blood pressure and ICP signals, the question arises of whether an ICP signal from an open EVD can be used for this purpose. Using an EVD system with an integrated parenchymal ICP probe we compared the different traces of an ICP signal and their derived parameters under opened and closed CSF drainage.
Methods:
Twenty patients with either subarachnoid or intraventricular hemorrhage and indication for ventriculostomy plus ICP monitoring received an EVD in combination with an air-pouch-based ICP probe. ICP was monitored via an open ventricular catheter (ICP_evd) and ICP probe (ICP_probe) simultaneously. Neuromonitoring data (ICP, arterial blood pressure, cerebral perfusion pressure, pressure reactivity index (PRx)) were recorded by ICM+ software for the time of ICU intensive care treatment. Routinely (at least every 4 h) ICP was recorded with a closed CSF drainage system for at least 15 min. ICP, ICP amplitude, and the autoregulation parameters (PRx_probe, PRx_evd) were evaluated for every episode with closed CSF drainage and during the 3 h prior with an open drainage system.
Results:
One hundred and forty-four episodes with open/closed drainage were evaluated. During open drainage, overall mean ICP_evd levels were nonsignificantly different from those of ICP_probe, with 9.8 + 3.3 versus 8.2 + 3.2 mmHg, respectively. Limits of agreement ranged between 5.2 and -8.3 mmHg. However, 51 increases of ICP >20 mmHg with a duration of 3-30 min were missed by ICP_evd, and in 101 episodes the difference between ICPs was greater than 10 mmHg. After closure of the EVD, ICP increased moderately using both methods. Mean PRx_evd was significantly higher (falsely indicating impaired autoregulation) and more subjected to fluctuations than PRx_probe.
Conclusion:
The general practice of draining CSF and monitoring ICP via a (usually open) EVD plus frequently performed catheter closure for ICP reading is feasible for assessment of overall ICP trends. However, it does have clinically relevant drawbacks, namely, a significant amount of undetected increases in ICP above thresholds, and continuous assessment of cerebrovascular autoregulation is less reliable. In conclusion, all patients who need CSF drainage plus ICP monitoring due to the severity of their brain insult need either an EVD with integrated ICP probe or an EVD line plus a separate ICP probe.
OBJECTIVE
The Sophysa Pressio (Sophysa Ltd., Orsay, France) is a new intracranial pressure monitoring system. This study aimed to evaluate its accuracy and compare it with the popular Codman intracranial pressure transducer (Codman/Johnson & Johnson, Raynham, MA) in vitro.
METHODS
A computerized rig was used to test the Pressio and Codman transducers simultaneously. Properties that were tested included drift over 7 days, the effect of temperature on drift, frequency response, the accuracy of measurement of static and pulsatile pressures, and connectivity of the system.
RESULTS
Long-term (7 d) relative zero drift was less than 0.05 mmHg. The temperature drift was low (0.3 mmHg/207C). Absolute static accuracy was better than 0.5 mmHg over the range of 0 to 100 mmHg. Pulse waveform accuracy, relative to the Codman transducer, was better than 0.2 mmHg over the range of 1 to 20 mmHg. The frequency bandwidth of the Pressio transducer was 22 Hz. The Pressio monitor can transmit data directly to an external computer without the use of a pressure bridge amplifier.
CONCLUSION
The new Pressio transducer proved to be accurate for measuring static and dynamic pressure during in vitro evaluation.
Intracranial pressure (ICP) monitoring is widely used in critically ill patients after traumatic brain injury (TBI) and with other mass-occupying lesions that disturb the balance of pressure and volume in the intracranial vault. The primary goal of continuous ICP monitoring is guiding clinical management toward normal ICP, one of the determinants of cerebral perfusion pressure (CPP). Intracranial hypertension will alter cerebral perfusion and can result in secondary brain injury, poor neurologic outcome, and death. Several types of ICP monitors exist with different risks and benefits. Interpretation of the ICP waveform can provide information about the mean ICP, intracranial compliance, and autoregulatory capacity. ICP monitoring may be best used as one component of multimodal monitoring of cerebral perfusion in patients with brain injury.
This chapter introduces the use of fiber optic sensors in biomechanics applications. It starts by presenting the field of biomechanics and the technical reasons that make fiber optic sensors an interesting tool for measuring in biomechanics applications. It then explains the application of fiber optic sensors in biomechanics of rigid bodies, then to deformable bodies and finished with fluids, in particular intramuscular and intra-articular pressures. The chapter ends with final remarks about the application of fiber optic sensor technology in biomechanics.
Die Messung des intrakraniellen Liquordrucks („intracranial pressure“, ICP) mittels eines Steigrohrs wurde erstmals 1841 von Magendi in Paris bei einem subokzipital punktierten Hund vorgenommen. Die epidurale Druckmessung mittels einer Hohlschraube und wassergefülltem Steigrohr hatte Leyden 1866 in Königsberg eingeführt. Pagenstecher hatte 1871 in Heidelberg bereits ein Manometer benutzt, um den Druck epidural eingepreßten flüssigen Wachses als experimentelle Raumforderung bei Hunden zu kontrollieren. Simultane mechanische oder plethysmographische Registrierungen von Hirndruck, Puls und Atmung, also ein „multimodales Monitoring“, aufgezeichnet mit kymo-graphischen Trommelschreibern, gab es tierexperimentell schon im 19. Jahrhundert, ebenso wie direkte Beobachtungen der Hirngefäße und -durchblu-tung durch implantierte Glasfenster.
In 1998, the Guidelines Committee on the Management of Severe Head Injury was established by the Japan Society of Neurotraumatology, and performed a critical review of national and international studies published over the past 10 years. The guidelines were first published in 2000 based on the results of this literature review and the Committee consensus, and the 2nd revised edition was published in 2006. This English version of the 2nd edition of the guidelines is intended to promote its concepts and use worldwide.
Introduction. Intracranial pressure (ICP) monitoring has become the standard in management and care of acute neurosurgical and neurological patients with raised ICP. Objectives. Describing the intracranial pathology leading to ICP monitoring, the therapies applied, and the infection and hemorrhage rates among patients monitored with Camino(R) ICP fiberoptic devices. Material and methods. A retrospective study was performed, including all the patients monitored with Camino devices in their three modalities. The study lasted from 1992 to 1995. We placed 239 ICP devices (120 intraparenchymal, 93 subdural, and 26 intraventricular). Results. Mean monitoring time was 5,17 days. Most common cause of monitoring was head injury in 152 cases. Most common therapy because of raised ICP was medical treatment (hyperventilation, sedation and barbituric coma). Most common related complications were hemorrhage and infection. Hemorrhage rate was 1,6% in the whole group, but among the patient with disorders it increased to 11%. Infection rate was 1,6%. Conclusions. ICP monitoring with fiberoptic devices is an accurate and safe method, but it has its own limits. In those patients with coagulation disorders we recomend ICP monitoring with other, less invasive devices, such epidural sensors. We have noticed an increased infection rate in patients monitored for more than 5 days, especially with the intraventricular sensor. We recommend changing the device if the expected period of monitoring is long more than 5 days.
The cranium is uniquely intolerant to changes in volume. The classical thinking of the relationship between components of the cranium and the pressure created by their presence is defined by the Monroe Kellie Doctrine [1]. Under normal physiologic conditions tissue cells, blood, and cerebrospinal fluid (CSF) maintain a consistent presence within the cranium and spinal cord areas. When any single component increases, the other two have a limited capacity to accommodate by shifting into accessory spaces so as to avoid a rise in intracranial pressure (ICP) and thus maintain stable cerebral perfusion pressure (CPP). © 2012 Springer science+Business Media New York. All rights reserved.
Introduction:
Intracranial pressure (ICP) measurement is used to tailor interventions and to assist in formulating the prognosis for traumatic brain injury patients. Accurate data are therefore essential. The aim of this study was to verify the accuracy of ICP monitoring systems on the basis of a literature review.
Methods:
A PubMed search was conducted from 1982 to 2014, plus additional references from the selected papers. Accuracy was defined as the degree of correspondence between the pressure read by the catheter and a reference "real" ICP measurement. Studies comparing simultaneous readings from at least two catheters were included. Drift was defined as the loss of accuracy over the monitoring period. Meta-analyses of data from the studies were used to estimate the overall mean difference between simultaneous ICP measurements and their variability. Individual studies were weighted using both a fixed and a random effects model.
Results:
Of 163 articles screened, 83 compared two intracranial catheters: 64 reported accuracy and 37 drift (some reported both). Of these, 10 and 17, respectively, fulfilled the inclusion criteria for accuracy and zero drift analysis. The combined mean differences between probes were 1.5 mmHg (95 % confidence interval (CI) 0.7-2.3) with the random effects model and 1.6 mmHg (95 % CI 1.3-1.9) with the fixed effects model. The reported mean drift over a long observation period was 0.75 mmHg. No relation was found with the duration of monitoring or differences between various probes.
Conclusions:
This study confirms that the average error between ICP measures is clinically negligible. The random effects model, however, indicates that a high percentage of readings may vary over a wide range, with clinical implications both for future comparison studies and for daily care.
La monitorización invasiva de la presión intracraneal (PIC) se ha convertido en el estandar en el manejo y cuidado de pacientes neurológicos agudos y neuroquirúrgicos susceptibles de padecer hipertensión intracraneal.
Intracranial pressure (ICP) monitoring has become an important parameter in the assessment of comatose patients, with raised intracranial pressure. The transducers in use have to fulfill the criteria of measurement accuracy, practicability and cost-effectiveness. However, these requirements are not always met in clinical practice. The need for ongoing quality control through independent laboratories remains. We have developed a laboratory set-up for the evaluation of intracranial pressure probes. Seven different types of currently used transducers have been tested for measurement accuracy. Under in vitro conditions 3 parameters were assessed: measurement accuracy, a 24 h drift and 10 day drifts. Tests for measurement accuracy were performed at increasing pressure levels of up to 80 mmHg. They were repeated 10 times per probe. This test allowed the simultaneous assessment of 5 different ICP probes. Drift was evaluated for 24 h and 10 days, at 6 pressure levels between 0 and 50 mmHg. Seven different types o...
Cerebrospinal dynamics has been investigated by statistical analysis of results of computerised monitoring of 80 head injured patients admitted to the Intensive Care Unit at Pinderfields General Hospital. One minute average values of intracranial pressure (ICP), systemic arterial pressure (ABP), cerebral perfusion pressure (CPP), amplitude of the fundamental component of the intracranial pressure pulse wave and the short-term moving correlation coefficient between that amplitude and mean ICP (RAP) were recorded. It was found that reduction of CPP down to 40 mmHg was more often caused by decrease in ABP than increase in ICP. Further falls in CPP below 40 mmHg were caused by substantial increases in ICP above 25 mmHg. The relationship between the ICP pulse wave amplitude and CPP showed a significant gradual increase in amplitude with CPP decreasing from 75 to 30 mmHg. For CPP below 30 mmHg there is a sharp decrease in amplitude followed by a change in the coefficient RAP from positive to negative values. This was interpreted as a sign of critical disturbance in cerebral circulation.
Many devices have been developed for the clinical monitoring of intracranial pressure (ICP). Each system has its advantages, and each device has its limitations and complications. In 1985, we participated in the development of a system which can accurately measure ICP from several intracranial sites, including the brain parenchyma. Initial laboratory evaluations of the accuracy of this system, along with the results of an initial clinical trial, have now been reported (Ostrup et al. 1987). After this trial, we began using this device routinely and have accumulated over three years of further experience using this system in a variety of clinical situations.
Many data have been published on different methods for measuring “ICP” via ventricular, epidural, subdural or parenchymal record. Also during this meeting, several new devices are presented. However, most investigations only consider the static criteria of the methods, like linearity, zero point stability and hysteresis (Gaab and Heissler 1984, 1988). Little attention has been paid to the dynamic properties of the devices. Such data on frequency resolution (band width) and phase, however, are especially important for computerized evaluation of ICP dynamics including waveform analysis (Chopp and Portnoy 1980; Gaab et al. 1983; Gaab and Heissler 1984, 1988; Portnoy et al. 1983; Varju 1977). ICP pulse waves and the transfer characteristics from arterial blood pressure (SAP) to ICP contain continuous information on intracranial elastance, vasoregulation and CSF dynamics (Branch et al. 1988; Chopp and Portnoy 1980; Portnoy et al. 1983). Dynamic analysis could therefore replace invasive methods like bolus and infusion tests (Anile et al. 1988; Branch et al. 1988; Chopp and Portnoy 1980; Portnoy et al. 1983). However, the waveform investigation e.g., with Fourier transformation up to the 5th harmonic of the ICP pulsation (Piper et al. 1988) requires a bandwidth for recording of > 40 Hz (Gaab and Heissler 1984, 1988). We therefore investigated the frequency resolution and the phase lag of current methods used for measuring ICP and blood pressures.
The Camino pressure transducer is accurate experimentally over a range of clinically relevant intracranial pressures (ICPs). Three clinical studies have shown that intraparenchymal pressure mirrors intraventricular pressure. In two a different type of transducer was used, and one was a mixed animal and human study [3, 4, 2]. This study compares intraparenchymal pressure, measured with a Camino fibre-optic transducer, with intraventricular pressure, using a fluid filled catheter, in unconscious head injured patients and evaluates the clinical efficacy of the Camino system.
Evaluation of a recently available intracranial pressure monitor (MMI Gaeltec Model ICT/b) has been undertaken in a series of dogs. Additional research and clinical experience has been gained with subdural and epidural ICP measurements.
Intracranial compliance, as estimated from a computerized frequency analysis of the intracranial pressure (ICP) waveform, was continuously monitored during the acute postinjury phase in 55 head-injured patients. In previous studies, the high-frequency centroid (HFC), which was defined as the power-weighted average frequency within the 4- to 15-Hz band of the ICP power density spectrum, was found to inversely correlate with the pressure-volume index (PVI). An HFC of 6.5 to 7.0 Hz was normal, while an increase in the HFC to 9.0 Hz coincided with a reduction in the PVI to 13 ml and indicated exhaustion of intracranial volume-buffering capacity. The mean HFC for individual patients in the present study ranged from 6.8 to 9.0 Hz, and the length of time that the HFC was greater than 9.0 Hz ranged from 0 to 104.8 hours. The mortality rate increased concomitantly with the mean HFC, from 7% when the mean HFC was less than 7.5 Hz to 46% when the mean HFC was 8.5 Hz or greater. The length of time that the HFC was 9.0 Hz or greater was also associated with an increased mortality rate, which ranged from 16% if the HFC was never above 9.0 Hz to 60% if the HFC was 9.0 Hz or greater for more than 12 hours. In 12 patients who developed uncontrollable intracranial hypertension or clinical signs of tentorial herniation during the monitoring period, 75% were observed to have had an increase in the HFC to 9.0 Hz or more 1 to 36 hours prior to the clinical decompensation. The more rapid the increase in the HFC, the more likely the deterioration was to be caused by an intracranial hematoma. Continuous monitoring of intracranial compliance by computerized analysis of the ICP waveform may provide an earlier warning of neurological decompensation than ICP per se and, unlike PVI, does not require volumetric manipulation of intracranial volume.
A No. 4 French fiberoptic catheter initially developed as an intravascular pressure sensor was incorporated into a system to be used as an intracranial pressure (ICP) monitor. Initially, a series of acute and chronic animal experiments carried out in the rabbit and pig, respectively, demonstrated the reliability and safety of the device. Subsequently, this new monitor was compared to a concurrently functioning ICP monitor in 15 adult and five pediatric patients. This clinical experience also confirmed the safety, accuracy, and reliability of the device. Since these initial studies, this monitor has been used to routinely measure ICP in a large number of adult and pediatric patients. The monitor has functioned well, and there have been no complications related to its use except for an occasional problem with breakage of the optic fiber as a result of patient movement or nursing maneuvers, which has been easily corrected by replacement of the probe. As nursing personnel and ancillary services have become familiar with this new monitor, breakage has not been a problem. This new device can be placed into the ventricular system, the brain parenchyma, or the subdural space, and appears to offer substantial advantages over other monitors presently in use.
Systems analysis of the systemic arterial (SAPW), cerebrospinal fluid (CSFPW), and sagittal sinus (SSPW) pulse waves was carried out in 13 dogs during hypercapnia (5% CO2), intracranial normotension (inhalation of 100% O2), and intracranial hypertension (inhalation of 100% O2 plus an intraventricular infusion). Power amplitude and phase spectra were determined for each wave, and the power amplitude and phase transfer functions calculated between the cerebrospinal fluid (CSF) pressure and systemic arterial pressures, and between the sagittal sinus pressure and CSF pressure. The study indicates that the CSFPW and SSPW were virtually identical when impedance between the cerebral veins and sagittal sinus was minimal, which argues that the CSF pulse was derived from the cerebral venous bed. During inhalation of 100% O2, transmission of the SAPW across the precapillary resistance vessels into the cerebral venous pulse (as represented by the CSFPW) was nonlinear, while transmission across the lateral lacunae into the sagittal sinus was linear. During intracranial hypertension, wave transmission across the precapillary resistance vessels was linear, and across the lateral lacunae was nonlinear. During hypercapnia, wave transmission across the precapillary resistance vessels and the lateral lacunae was linear. When the wave transmission was nonlinear, there was also suppression in transmission of the lower harmonics, particularly the fundamental frequency, and a more positive phase transfer function, suggesting an inertial effect or decrease in acceleration of the pulse. Conversion from a nonlinear to linear transmission across the precapillary resistance vessels is evidence of loss of vasomotor tone, and is accompanied by rounding of the CSFPW. A vascular model which encompasses the above data and is based on flow in collapsible tubes and changes in vasomotor tone is posited to explain control of pulsatile flow and pulse waveform changes in the cerebrovascular bed. The model helps to clarify the strong interrelationship between intracranial pressure, cerebral blood flow, and cerebral autoregulation.
The authors have analyzed their experience with intracranial pressure (ICP) monitoring in 207 patients over a 4-year period. Patients with either high-density or low-density lesions on computerized tomography (CT) at admission had a high incidence (53% to 63%) of intracranial hypertension (ICP persistently over 20 mm Hg). In contrast, patients with normal CT scans at admission had a relatively low incidence of ICP elevation (13%). Among these patients, three features were found to be strongly associated with the development of intracranial hypertension: 1) age over 40 years; 2) systolic blood pressure under 90 mm Hg; and 3) motor posturing — unilateral or bilateral. When two or more of these features were noted at admission, the incidence of intracranial hypertension was 60%, as compared to 4% when only one, or none, of these features were present. Thus, the patients at high risk for developing intracranial hypertension after severe head injury are those with abnormal CT scans at admission, and those with normal CT scans who demonstrate two or more of the above-mentioned adverse features. Based on these criteria, only 16% of this series of patients with normal CT scans would have qualified for monitoring.
In addition to the three clinical features noted above, multimodality evoked potential (MEP) studies were also found to be strong predictors of ICP elevation in the normal CT scan group, with a 75% incidence of intracranial hypertension in patients with disseminated deficits. There was no statistically significant correlation between the Glasgow Coma Scale score, eye movements, pupillary reaction, hypoxia, or anemia at admission and subsequent ICP elevation in the group with normal CT scans.
In this series, an intraventricular catheter was used as the sole monitoring device in 91% of the cases. In the remaining 9%, subarachnoid screws were employed, either alone, or upon failure of the ventriculostomy. While no mortality was directly ascribed to the monitoring process, there was a 7.7% complication rate (infection 6.3% + hemorrhage 1.4%). Eighty-five percent of the infections occurred in patients who had been monitored for 5 days or more, while no infections were noted in those monitored for less than 3 days. Used judiciously, this technique can be valuable in the monitoring and treatment of the brain-injured patient.
Studies of long-term shunt performance in vivo demonstrate that some 81% fail within 12 years. Such failure is multifactorial in origin: the patient, the surgical technique and the shunt may all prove fallible. Recent studies have shown that there is considerable variability of the performance characteristics of individual shunts when tested for short time periods in relatively simple rigs, and that they do not always behave according to the manufacturers' specifications. We have developed a computerized shunt rig for the long-term evaluation of a valve's performance in vitro using both pressure-flow studies (where flow through the shunt is evaluated for controlled differential pressure across the shunt) and flow-pressure studies (where the differential pressure across the shunt is evaluated for controlled flow rates through the shunt). This rig consists of a pressure transducer, electronic balance, computer-controlled infusion pump and blood pressure systems calibrator that stimulates different wave form patterns. An IBM PC controls all the devices and evaluates the performances characteristics according to various test protocols. Our initial observations with this rig confirm that progressive changes in shunt function occur over long periods of time (weeks).
Intracranial pressure: To monitor or not to monitor?
Cerebrospinal fluid pulse waveform as an indicator of cerebral autoregulation