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Purpose:
We describe the temporal concordance of 3 hemodynamic monitors.
Materials and methods:
Healthy volunteers performed preload changes while simultaneously wearing a non-invasive, pulse-contour stroke volume (SV) monitor, a bioreactance SV monitor and a wireless, wearable Doppler ultrasound patch over the common carotid artery. The sensiti...
Context in source publication
Context 1
... U.S. Food and Drug Administration-cleared carotid ultrasound patch (Flosonics Medical, Sudbury, ON.) (Fig 1) was placed by palpation over the carotid artery below the angle of the jaw to ensure Doppler sampling below the carotid artery bifurcation. The maximum velocity of the continuous wave (CW) Doppler pulse was automatically traced using an algorithm based on the approach described by Li et al [12]. ...
Similar publications
Background
Doppler ultrasound of the common carotid artery is used to infer central hemodynamics. For example, change in the common carotid artery corrected flow time (ccFT) and velocity time integral (VTI) are proposed surrogates of changing stroke volume. However, conflicting data exist which may be due to inadequate beat sample size and measurem...
Background
Using peripheral arteries to infer central hemodynamics is common among hemodynamic monitors. Doppler ultrasound of the common carotid artery has been used in this manner with conflicting results. We investigated the relationship between changing common carotid artery Doppler measures and stroke volume (SV), hypothesizing that more conse...
Providing intravenous (IV) fluids to a patient with signs or symptoms of hypoperfusion is common. However, evaluating the IV fluid 'dose-response' curve of the heart is elusive. Two patients were studied in the emergency department with a wireless, wearable Doppler ultrasound system. Change in the common carotid arterial and internal jugular Dopple...
Citations
... With the rise of point-of-care ultrasound use in acute care, a similar approach has been adopted with ultrasonographic measures. As an example, the common carotid artery Doppler pulse is used to assess both absolute [2,3] and changing [4][5][6][7][8][9][10][11] stroke volume (SV). With respect to the critically ill population, this approach is important during resuscitation as flow-guided preload administration reduces morbidity and mortality [12,13]; furthermore, detecting diminished SV could help diagnose early hemorrhage [14]. ...
Background
Using peripheral arteries to infer central hemodynamics is common among hemodynamic monitors. Doppler ultrasound of the common carotid artery has been used in this manner with conflicting results. We investigated the relationship between changing common carotid artery Doppler measures and stroke volume (SV), hypothesizing that more consecutively-averaged cardiac cycles would improve SV-carotid Doppler correlation.
Methods
Twenty-seven healthy volunteers were recruited and studied in a physiology laboratory. Carotid artery Doppler pulse was measured with a wearable, wireless ultrasound during central hypovolemia and resuscitation induced by a stepped lower body negative pressure protocol. The change in maximum velocity time integral (VTI) and corrected flow time of the carotid artery (ccFT) were compared with changing SV using repeated measures correlation.
Results
In total, 73,431 cardiac cycles were compared across 27 subjects. There was a strong linear correlation between changing SV and carotid Doppler measures during simulated hemorrhage (repeated-measures linear correlation [Rrm]=0.91 for VTI; 0.88 for ccFT). This relationship improved with larger numbers of consecutively-averaged cardiac cycles. For ccFT, beyond four consecutively-averaged cardiac cycles the correlation coefficient remained strong (i.e., Rrm of at least 0.80). For VTI, the correlation coefficient with SV was strong for any number of averaged cardiac cycles. For both ccFT and VTI, Rrm remained stable around 25 consecutively-averaged cardiac cycles.
Conclusions
There was a strong linear correlation between changing SV and carotid Doppler measures during central blood volume loss. The strength of this relationship was dependent upon the number of consecutively-averaged cardiac cycles.
... Applying a mathematical correction for heart rate (e.g., Wodey equation [23]) yields the corrected flow time which better approximates SV and especially its change. To investigate whether ccFT measured using the wearable ultrasound is a surrogate for SV ∆ -and, therefore, for preload responsiveness-we have shown in healthy volunteers that there is a strong, linear relationship between changing ccFT (ccFT ∆ ) and SV ∆ using non-invasive pulse contour analysis, bioreactance and aortic Doppler velocity as gold standards [23][24][25][26]. Furthermore, in these studies comprising roughly 90 preload augmentations in approximately 50 healthy subjects, SV ∆ of at least +10% (i.e., preload responsiveness) was ubiquitous and the optimal ccFT ∆ threshold for detecting +10% SV ∆ was above +2 ccFT ∆ . ...
... First, we expected that, in this cohort of healthy volunteers, preload augmentation via the Trendelenburg position would increase ccFT by a clinically significant degree (i.e., ≥7 ms or +2% ccFT ∆ ) in the vast majority of subjects. In other words, the fraction of 'preload-responsive' subjects would be congruent with earlier findings in healthy volunteers [23,24,26,32]. Second, we predicted that preload responsiveness would be accompanied by a collapsing IVC (i.e., >25%), based on the previous literature [33]. ...
... The device is a 4 MHz, continuous-wave Doppler ultrasound that generates a 2 cm wide and 4 cm deep sonic curtain and is placed without image guidance. As previously described [23,24,26], the common carotid artery Doppler spectrogram is obtained via simultaneously acquired visual and audio cues from the wearable system. Given that a normal common carotid artery is 6-7 mm in diameter, the 2 cm ultrasound beam generated by the wearable device generally insonates all red blood cells moving through the artery. ...
(1) Background: The inspiratory collapse of the inferior vena cava (IVC), a non-invasive surrogate for right atrial pressure, is often used to predict whether a patient will augment stroke volume (SV) in response to a preload challenge. There is a correlation between changing stroke volume (SV∆) and corrected flow time of the common carotid artery (ccFT∆). (2) Objective: We studied the relationship between IVC collapsibility and ccFT∆ in healthy volunteers during preload challenges. (3) Methods: A prospective, observational, pilot study in euvolemic, healthy volunteers with no cardiovascular history was undertaken in a local physiology lab. Using a tilt-table, we studied two degrees of preload augmentation from (a) supine to 30-degrees head-down and (b) fully-upright to 30-degrees head down. In the supine position, % of IVC collapse with respiration, sphericity index and portal vein pulsatility was calculated. The common carotid artery Doppler pulse was continuously captured using a wireless, wearable ultrasound system. (4) Results: Fourteen subjects were included. IVC % collapse with respiration ranged between 10% and 84% across all subjects. Preload responsiveness was defined as an increase in ccFT∆ of at least 7 milliseconds. A total of 79% (supine baseline) and 100% (head-up baseline) of subjects were preload-responsive. No supine venous measures (including IVC % collapse) were significantly related to ccFT∆. (5) Conclusions: From head-up baseline, 100% of healthy subjects were ‘preload-responsive’ as per the ccFT∆. Based on the 42% and 25% IVC collapse thresholds in the supine position, only 50% and 71% would have been labeled ‘preload-responsive’.
... Nevertheless, we have not fully-described the fraction of preload unresponsive, ambulatory volunteers during PLR. Finally, our group [23,25,26,28] and others [29] have successfully used the common carotid artery corrected flow time (ccFT) to assess preload reserve. The ccFT is easily obtained from the Doppler spectrogram; it is the duration of mechanical systole (in milliseconds) corrected for heart rate and the direct relationship between the duration of systole and venous return (i.e., cardiac output) has been known for nearly a century [23,30]. ...
Background:
The change in the corrected flow time of the common carotid artery (ccFTΔ) has been used as a surrogate of changing stroke volume (SVΔ) in the critically-ill. Thus, this relatively easy-to-obtain Doppler measure may help clinicians better define the intended effect of intravenous fluids. Yet the temporal evolution of SVΔ and ccFTΔ has not been reported in volunteers undergoing a passive leg raise (PLR).
Methods:
We recruited clinically-euvolemic, non-fasted, adult, volunteers in a local physiology lab to perform 2 PLR maneuvers, each separated by a 5 minute 'wash-out'. During each PLR, SV was measured by a non-invasive pulse contour analysis device. SV was temporally-synchronized with a wireless, wearable Doppler ultrasound worn over the common carotid artery that continuously measured ccFT.
Results:
36 PLR maneuvers were obtained across 19 ambulatory volunteers. 8856 carotid Doppler cardiac cycles were analyzed. The ccFT increased nearly ubiquitously during the PLR and within 40-60 seconds of PLR onset; the rise in SV from the pulse contour device was more gradual. SVΔ by +5% and +10% were both detected by a +7% ccFTΔ with sensitivities, specificities and areas under the receiver operator curve of 59%, 95% and 0.77 (p < 0.001) and 66%, 76% and 0.73 (p < 0.001), respectively.
Conclusions:
The ccFTΔ during the PLR in ambulatory volunteers was rapid and sustained. Within the limits of precision for detecting a clinically-significant rise in SV by a non-invasive pulse contour analysis device, simultaneously-acquired ccFT from a wireless, wearable ultrasound system was accurate at detecting 'preload responsiveness'.
... Thus, we instantaneously synchronized change in the reference standard with the carotid signal. This is in distinction to other reference standards where there can be clinically significant algorithm lag (12). Indeed, classical transpulmonary thermodilution does not have the temporal resolution needed to assess preload responsiveness (13). ...
Unlabelled:
Measuring fluid responsiveness is important in the management of critically ill patients, with a 10-15% change in cardiac output typically being used to indicate "fluid responsiveness." Ideally, these changes would be measured noninvasively and peripherally. The aim of this study was to determine how the common carotid artery (CCA) maximum velocity changes with total circulatory flow when confounding factors are mitigated and determine a value for CCA maximum velocity corresponding to a 10% change in total circulatory flow.
Design:
Prospective observational pilot study.
Setting:
Patients undergoing elective, on-pump coronary artery bypass grafting (CABG) surgery.
Patients:
Fourteen patients were referred for elective coronary artery bypass grafting surgery.
Interventions:
Cardiopulmonary bypass (CPB) pump flow changes during surgery, as chosen by the perfusionist.
Measurements:
A hands-free, wearable Doppler patch was used for CCA velocity measurements with the aim of preventing user errors in ultrasound measurements. Maximum CCA velocity was determined from the spectrogram acquired by the Doppler patch. CPB flow rates were recorded as displayed on the CPB console, and further measured from the peristaltic pulsation frequency visible on the recorded Doppler spectrograms.
Main results:
Changes in CCA maximum velocity tracked well with changes in CPB flow. On average, a 13.6% change in CCA maximum velocity was found to correspond to a 10% change in CPB flow rate.
Conclusions:
Changes in CCA velocity may be a useful surrogate for determining fluid responsiveness when user error can be mitigated.
... Internal jugular vein Doppler was obtained using a novel, wireless, wearable Doppler ultrasound system. As previously described [18,21,22], the common carotid artery and internal jugular vein Doppler signals are obtained by simultaneously-acquired visual and audio cues from the wearable system. Once common carotid and internal jugular venous Doppler signals were seen and heard, the wearable Doppler was adhered in place on the subject's neck; jugular vein Doppler was monitored throughout the protocol. ...
Background
The venous excess ultrasound (VExUS) score is a multi-organ Doppler approach to assess venous congestion. Despite growing use of VExUS in research and clinical practice, other veins can be visualized to assess for venous hypertension, which may overcome acquisition barriers of the VExUS exam. In this pilot, observational study, we used a wearable Doppler ultrasound to assess the relationship between jugular venous Doppler and the VExUS score under different preload conditions. We hypothesized that jugular Doppler morphology would accurately distinguish preload conditions, that it would most closely relate to the hepatic venous Doppler morphology in the fully supine position and that the VExUS score would be influenced by preload condition.
Results
We recruited 15 healthy volunteers with no cardiovascular history. Preload change was achieved using a tilt-table with three positions: supine, fully upright, and 30-degree head-down tilt. In each position, a VExUS score was performed; furthermore, inferior vena collapsibility and sphericity index were calculated. At the same time, jugular venous Doppler was captured by a novel, wireless, wearable ultrasound system. A continuous jugular venous Doppler morphology was 96% accurate for detecting the low preload condition. The jugular venous Doppler morphology was highly correlated with the hepatic vein, but only in the supine position. Gravitational position did not significantly affect the sphericity index or the VExUS score.
Conclusions
The jugular vein Doppler morphology was able to accurately distinguish low from high preload conditions in healthy volunteers. Comparisons between VExUS Doppler morphologies and other veins should occur in the supine position when gravitational pressure gradients are minimized; finally, different preload conditions in healthy subjects did not affect the VExUS score.
... IQR: -0.01-0.54). In fact, even algorithm-lag was found to have an impact on the ability of a system to track rapid haemodynamic changes [66]. ...
Accurate haemodynamic monitoring is the cornerstone in the management of critically ill patients. It guides the optimization of tissue and organ perfusion in order to prevent multiple organ failure. In the past decades, carotid Doppler ultrasound (CDU) has been explored as a non-invasive alternative for long-established invasive haemodynamic monitoring techniques. Considering the large heterogeneity in reported studies, we conducted a review of the literature to clarify the current status of CDU as a haemodynamic monitoring tool. In this article, firstly an overview is given of the equipment and workflow required to perform a CDU exam in clinical practice, the limitations and technical challenges potentially faced by the CDU sonographer, and the cerebrovascular mechanisms that may influence CDU measurement outcomes. The following chapter describes alternative techniques for non-invasive haemodynamic monitoring, detailing advantages and limitations compared to CDU. Next, a comprehensive review of the literature regarding the use of CDU for haemodynamic monitoring is presented. Based on the outcomes of these studies, we assess the applicability of CDU-derived parameters within three clinical domains (cardiac output, volume status, and fluid responsiveness), and amongst different patient groups. Furthermore, feasibility aspects, training requirements and technical developments of CDU are addressed. Finally, recommendations are provided to improve the quality and standardization of future research and clinical practice in this field. Although CDU is not yet interchangeable with invasive “gold standard” cardiac output monitoring, the present work shows that certain CDU-derived parameters prove promising in the context of functional haemodynamic monitoring.
Background:
Little data exist on the time spent by emergency department (ED) personnel providing intravenous (IV) fluid to 'responsive' versus 'unresponsive' patients.
Methods:
A prospective, convenience sample of adult ED patients was studied; patients were enrolled if preload expansion was indicated for any reason. Using a novel, wireless, wearable ultrasound, carotid artery Doppler was obtained before and throughout a preload challenge (PC) prior to each bag of ordered IV fluid. The treating clinician was blinded to the results of the ultrasound. IV fluid was deemed 'effective' or 'ineffective' based on the greatest change in carotid artery corrected flow time (ccFT∆) during the PC. The duration, in minutes, of each bag of IV fluid administered was recorded.
Results:
53 patients were recruited and 2 excluded for Doppler artifact. There were 86 total PCs included in the investigation comprising 81.7 L of administered IV fluid. 19,667 carotid Doppler cardiac cycles were analyzed. Using ccFT∆ ≥ + 7 ms to discriminate 'physiologically effective' from 'ineffective' IV fluid, we observed that 54 PCs (63%) were 'effective', comprising 51.7 L of IV fluid, whereas, 32 (37%) were 'ineffective' comprising 30 L of IV fluid. 29.75 total hours across all 51 patients were spent in the ED providing IV fluids categorized as 'ineffective.'
Conclusions:
We report the largest-known carotid artery Doppler analysis (i.e., roughly 20,000 cardiac cycles) in ED patients requiring IV fluid expansion. A clinically significant amount of time was spent providing physiologically ineffective IV fluid. This may represent an avenue to improve ED care efficiency.
