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To examine a decrease in heart rate (HR) following the initial rise associated with increased central blood volume (CBV) due to the muscle pump after onset of light exercise, eight untrained male subjects were studied at rest and during cycle exercise at 20% peak oxygen uptake in upright (sitting) and supine positions. During upright exercise, HR i...
Treatment with beta-blockers is characterized by inferior reduction of central versus peripheral blood pressure. We examined changes in blood pressure, cardiac function, and vascular resistance after 3 weeks of bisoprolol treatment (5 mg/day) during passive head-up tilt in 16 never-treated Caucasian males with grade I–II primary hypertension. A dou...
This prospective single-center observational study compared impedance cardiography [electrical velocimetry (EV)] with transthoracic echocardiography (TTE, based on trans-aortic flow) and analyzed the influence of physiological shunts, such as patent ductus arteriosus (PDA) or patent foramen ovale (PFO), on measurement accuracy. Two hundred and nine...
Background
The correlation between impedance cardiography (ICG) and 6 min walk distance (6MWD) in atrial fibrillation (AF) patients remains unknown.
Methods
We recruited 49 subjects in the study (21 AF patients and 28 patients without AF) and estimated hemodynamic parameters: cardiac output (CO), stroke volume (SV), stroke volume index (SVI), left...
Citations
... After ECG, blood pressure, respiration, temperature, and noninvasively measured saturated oxygen, ICG is considered the sixth vital sign which can have an effective role in the prevention, prognosis, and diagnosis of cardiovascular diseases. [52] The major goal of this study was to develop a precise and convenient system for monitoring the ICG signal. Different blocks of the system were designed based on the required SNR. ...
Measurement of the stroke volume (SV) and its changes over time can be very helpful for diagnosis of dysfunctions in the blood circulatory system and monitoring their treatments. Impedance cardiography (ICG) is a simple method of measuring the SV based on changes in the instantaneous mean impedance of the thorax. This method has received much attention in the last two decades because it is noninvasive, easy to be used, and applicable for continuous monitoring of SV as well as other hemodynamic parameters. The aim of this study was to develop a low-cost portable ICG system with high accuracy for monitoring SV. The proposed wireless system uses a tetrapolar configuration to measure the impedance of the thorax at 50 kHz. The system consists of carefully designed precise voltage-controlled current source, biopotential recorder, and demodulator. The measured impedance was analyzed on a computer to determine SV. After evaluating the system's electronic performance, its accuracy was assessed by comparing its measurements with the values obtained from Doppler echocardiography (DE) on 5 participants. The implemented ICG system can noninvasively provide a continuous measure of SV. The signal to noise ratio of the system was measured above 50 dB. The experiments revealed that a strong correlation (r = 0.89) exists between the measurements by the developed system and DE (P < 0.05). ICG as the sixth vital sign can be measured simply and reliably by the developed system, but more detailed validation studies should be conducted to evaluate the system performance. There is a good promise to upgrade the system to a commercial version domestically for clinical use in the future.
... Moreover, [73], in their review stated that ''impedance cardiography is becoming an accepted method for safe, reliable, and reproducible assessment of hemodynamics in heart failure''. ICG has been successfully used in many studies performed in the author's home laboratory on cardiovascular response to the handgrip [25], orthostatic manoeuvre [15] and other physiological tests including dynamic exercise [16,98]. ...
In this chapter the necessary physical background of impedance cardiography will be presented, especially regarding the electrical
properties of the biological tissues, the methods applied for measurement of the bioimpedance and the inaccuracy the models
and limitations of the technique.
Over the years, the spectrum of medical devices has been diversified from very simple to the highly complex platform, simultaneously the risk factor associated with the devices also diverges. So, now to be in no doubt and maintain the performance feasibility and clinical safety issues of any devices throughout the product life cycle, various regulatory organizations of different countries put some clause in the name of “clinical validation,” “clinical investigation,” or “clinical assessment report.” This clinical validation process makes convinced and justifies all the clinical assessment data regarding the devices’ safety, effectiveness, and performance feasibility to the regulatory agency to market the product in the specific market across the globe. The clinical validation procedure and requirement are very much specialized and succinct to answer all the queries of the regulatory body depending upon the device class, working principle, and risk associated with it. In recent times, various established regulatory frameworks like USFDA, TGA, and CDSCO make the clinical investigation and validation of the devices mandatory to launch the product into the respective market. The process of clinical confirmatory and validation is a never-ending procedure for high risk associated devices, as per the recent implementation of post marketing clinical follow-up (PMCF), post-market surveillance (PMS), and periodic safety update report (PSUR) by the regulatory authorities of various countries. In the following chapter, we are tried to give a broad impression and a detailed account of prerequisites, procedures, and strategies of various clinical validation plans concerning various regulatory authorities. The goal or intention of the clinical validation process of medical devices is to make assured that the device does not exhibit any surplus effect or events throughout its life cycle, which are questionable or reasons for product fiasco.
World Health Organization (WHO) predicts cardiovascular ailments as one of the major causes of death worldwide. American Heart Association (AHA), in one of its reports in 2017, predicted the number of deaths due to cardiovascular diseases (CVD) to be 23.6 million by 2030. This alarming trend, in the advent of CVDs, calls for an accurate and cost-effective method for detection of precursors to CVDs.
Anatomy of the ventilatory apparatus refers to its architecture, bulk structure, vascularization, and innervation. Dimensions of tree-like structures, such as the pulmonary arterial, venous, and bronchial circuits, determine the efficiency of fluid distribution and drainage via an optimal structure–function relation.
Breathing is a vital function under both autonomous and voluntary control. Breathing is a continuous process during wakefulness and sleep that can transiently stop during speech, defecation, and emesis.
The cardiovascular apparatus is a transport circuit that carries blood cells, oxygen and nutrients to cells of the body’s organs, and wastes produced by working cells to their final destinations (mainly lungs, liver, and kidneys). It is involved in both mass and heat transfer.
The cardiovascular apparatus supplies blood to the body’s organs and responds to sudden changes in demand for nutrients according to the organism’s activity. Blood velocity and pressure can be associated with kinetic and potential energy, respectively.
Many visualization techniques are available to explore the cardiovascular system from usual ultrasound echography and velocimetry, multislice spiral computed tomography particularly for cardiac imaging, and magnetic resonance imaging for blood flow assessment, to magnetocardiography, diode laser, and optical coherence tomography. Functional magnetic resonance imaging is based on increased blood flow gushing in target regions that are responding to imposed stimuli. Ultrasound scattering from Rayleigh fractal aggregates is proposed for imaging flow dynamics of deformable or hardened red cell clusters in dense suspension.
In this chapter is described the importance of the transient changes noninvasive monitoring of physiological variables in living objects. It also contains the rationale for the development of an ambulatory monitoring equipment including long-term recording of a heart mechanical activity.
