Finger Cuff Research Articles

Comparison of the ClearSight™ finger cuff monitor versus invasive arterial blood pressure measurement in elective cardiac surgery patients: a prospective observational study.

To determine the acceptability of the ClearSight™ system (Edwards Lifesciences Corp., Irvine, CA, USA) for continuous blood pressure monitoring during elective cardiac surgery compared with arterial catheterization. We enrolled 30 patients undergoing elective cardiac surgery in a prospective observational study. Blood pressure measurements were recorded every 10 sec intraoperatively. We determined agreement based on the Association for the Advancement of Medical Instrumentation (AAMI) recommendations. Statistical analysis included fixed bias (difference of measurements between methods), percentage error (accuracy between ClearSight measurement and expected measurement from arterial line), and interchangeability (ability to substitute ClearSight monitor without effecting overall outcome of analysis). We used a paired samples t test to compare the time required for placing each monitor. We found fixed bias in the differences between the ClearSight monitor and invasive arterial blood pressure measurement in systolic blood pressure (SBP; mean difference, 8.7; P < 0.001) and diastolic blood pressure (DBP; mean difference, -2.2; P < 0.001), but not in mean arterial pressure (MAP; mean difference, -0.5; P < 0.001). Bland-Altman plots showed that the means of the limits of agreement were greater than 5mm Hg for SBP, DBP, and MAP. The percentage errors for SBP, DBP, and MAP were lower than the cutoff we calculated from the invasive arterial blood pressure measurements. Average interchangeability rates were 38% for SBP, 50% for DBP, and 50% for MAP. Placement of the ClearSight finger cuff was significantly faster compared with arterial catheterization (mean [standard deviation], 1.7 [0.6] min vs 5.6 [4.1] min; P < 0.001). In this prospective observational study, we did not find the ClearSight system to be an acceptable substitute for invasive arterial blood pressure measurement in elective cardiac surgery patients according to AAMI guidelines. Nevertheless, based on statistical standards, there is evidence to suggest otherwise. ClinicalTrials.gov ( NCT05825937 ); first submitted 11 April 2023.

Continuous non-invasive vs. invasive arterial blood pressure monitoring during neuroradiological procedure: a comparative, prospective, monocentric, observational study

BackgroundIn the perioperative setting, the most accurate way to continuously measure arterial blood pressure (ABP) is using an arterial catheter. Surrogate methods such as finger cuff have been developed to allow non-invasive measurements and are increasingly used, but need further evaluation. The aim of this study is to evaluate the accuracy and clinical concordance between two devices for the measurement of ABP during neuroradiological procedure.MethodsThis is a prospective, monocentric, observational study. All consecutive patients undergoing a neuroradiological procedure were eligible. Patients who needed arterial catheter for blood pressure measurement were included. During neuroradiological procedure, ABP (systolic, mean and diatolic blood pressure) was measured with two different technologies: radial artery catheter and Nexfin. Bland-Altman and error grid analyses were performed to evaluate the accuracy and clinical concordance between devices.ResultsFrom March 2022 to November 2022, we included 50 patients, mostly ASA 3 (60%) and required a cerebral embolization (94%) under general anaesthesia (96%). Error grid analysis showed that 99% of non-invasive ABP measures obtained with the Nexfin were located in the risk zone A or B. However, 65.7% of hypertension events and 41% of hypotensive events were respectively not detected by Nexfin. Compared to the artery catheter, a significant relationship was found for SAP (r2 = 0.78) and MAP (r2 = 0.80) with the Nexfin (p < 0.001). Bias and limits of agreement (LOA) were respectively 9.6 mmHg (− 15.6 to 34.8 mmHg) and − 0.8 mmHg (− 17.2 to 15.6 mmHg), for SAP and MAP.ConclusionsNexfin is not strictly interchangeable with artery catheter for ABP measuring. Further studies are needed to define its clinical use during neuroradiological procedure.Trial registrationClinicaltrials.gov, registration number: NCT05283824.

Continuous Blood Pressure Monitoring with a Finger Cuff is Unsuitable for Intradialytic Blood Pressure Monitoring

Continuous Blood Pressure Monitoring with a Finger Cuff is Unsuitable for Intradialytic Blood Pressure Monitoring

Differences in Systemic Pulse Waveform Between Individuals With Glaucoma, Glaucoma Suspects, and Healthy Controls.

It has been hypothesized that compromised ocular circulation in glaucoma may be concomitant of systemic changes. The purpose of this study is to test whether systemic blood flow pulse waveform patterns differ between individuals with glaucoma (GL), glaucoma suspects (GLS), and normal healthy controls (HC). The study included 35 bilateral GL, 67 bilateral GLS, 29 individuals with unilateral GL who were considered GLS in the other eye, and 44 healthy controls. Systemic pulsatile blood pressure waveforms were recorded using a finger cuff. A continuous 200Hz plethysmography recording is made to obtain a pulse waveform. Waveform parameters were extracted using custom software from an average of eight pulse cycles. These were compared between GL, GLS, and HC groups on a per-eye basis, using generalized estimating equation models to account for intereye correlations; and plotted against disease severity by visual field linearized mean deviation (MDlin) and retinal nerve fiber layer thickness (RNFLT). Averaged blood pressure was significantly lower in the HC group (mean ± standard deviation 91.7 ±11.7 mm Hg) than the GLS (102.4 ± 13.9) or GL (102.8 ± 13.7) groups, with P < 0.0001 (generalized estimating equation regression). Waveform parameters representing vascular resistance were higher in both GLS and GL groups than the HC group; and were correlated with RNFLT and MDlin (P ≤ 0.05). The shape of the systemic pulsatile waveform differs in individuals with GL/GLS suspects, compared to HC eyes. Blood pressure changes more rapidly in individuals with GL, which suggests higher arterial stiffness.

#2812 Continuous blood pressure monitoring with a finger cuff is unreliable in chronic hemodialysis patients

Abstract Background and Aims Intradialytic hypotension (IDH) is the most common complication of hemodialysis (HD), which is often related to ultrafiltration. Due to the high prevalence of cardiovascular disease (CVD), compensatory mechanisms often fail. In clinical practice, BP is measured 2x/hour, while additional readings are only performed when symptoms arise. However, since IDH defined by a nadir systolic BP (SBP)&amp;lt;90 mmHg or &amp;lt;100 mmHg (depending on pre-dialysis SBP), regardless of symptoms, is most strongly associated with mortality, current BP measurement frequency may severely underestimate the true incidence of IDH. Continuous BP-monitoring may offer a solution to this issue. The Clearsight device (CSD) is a non-invasive continuous BP-monitoring system that measures arterial pressure and waveforms through a finger cuff by photoplethysmography. Yet, a compromised peripheral circulation may hamper its reliability in HD patients. This study aims to assess the agreement between intradialytic CSD-monitoring and standard oscillometric brachial arterial pressure (oBAP) assessment. Methods 40 Chronic HD patients were cross-over randomized to 4 modalities, each for 2 weeks: [standard HD (S-HD), cool HD (C-HD), low volume hemodiafiltration (LV-HDF) and high-volume HDF (HV-HDF)]. During one session of each second week, BP and heart rate (HR) were continuously recorded with the CSD (BMEYE/Edwards Lifesciences) and every 15 minutes with a brachial arterial cuff (contralateral of the fistula or graft, if applicable). Simultaneous measurements of SBP, diastolic BP (DBP) and HR were compared with descriptive statistics (mean difference [bias, BAP minus CSD], standard deviation (SD) and range) and Bland-Altman analysis. Bias was defined as the mean difference between oBAP and CSD, and 95% limits of agreement (LA) as the mean difference ±1.96 SD. Post-hoc, patients were stratified into tertiles of unexplained missing CSD-readings, to explore whether specific patient characteristics explain failed readings. Results 75% of patients was male, with a mean age 69.7 (±13.5 years) and median dialysis vintage 3.0 years (IQR 1.0-5.8). Diabetes mellitus and CVD were present in 48% and 73%, resp. Of the 2720 paired BP-measurements, 42% CSD and 6% of oBAP-readings were missing, leaving 36% of absent CSD-readings unexplained. Bland-Altman analysis, comparing oBAP and CSD-measurements, revealed a mean bias ± LA of 13.3 ± 44.5 mmHg for SBP, a mean bias ± LA of 13.3 ± 25.5 for DBP, and a mean bias ± LA of −0.03 ± 22.9 for HR. Surprisingly, the group with a high (&amp;gt;38%) proportion of unexplained missing CSD-values was significantly younger compared to the low (&amp;lt;21%) and intermediate group (21-38%) (p = 0.015), whereas no significant differences were observed with respect to dialysis vintage, diabetes mellitus or CVD. Conclusions 1) Compared to the oBAP method, finger cuff-monitoring shows poor precision and accuracy in BP-measurements, but good accuracy and poor precision in HR-readings; 2) 1/3 of readings failed for unknown reasons. Thus, CSD-monitoring is unsuitable for intradialytic hemodynamic monitoring in chronic HD patients.

Antioxidant-induced modulation of sympathetic transduction to arterial blood pressure in humans

Purpose: Excess plasma free fatty acids (FAA) promote oxidative stress and an increase in peripheral resistance. Therefore, we tested the hypothesis that excess FAA limits sympathetic control of arterial blood pressure (BP) and that sympathetic control would be restored during co-administration of ascorbic acid, which is an antioxidant with vasodilatory properties. Methods: A 20% IV fat emulsion (Intralipid) was administered for 2 hours to 5 lean, healthy adults with and without co-infusion of ascorbic acid (separate visits) in a double-blinded, crossover study design. Sympathetic control of BP was examined by determining the BP response to individual bursts of muscle sympathetic nerve activity (MSNA) (microneurography). Briefly, beat-to-beat mean arterial pressure (MAP) was measured continuously (finger cuff) and signal-averaged over 15 cardiac cycles following each detected burst of MSNA over a 10-min resting period. Results: In contrast to our hypothesis, no change was observed in sympathetic transduction during lipid infusion (1.5 ± 0.4 vs. 1.4 ± 3 mmHg, P=0.75). However, co-infusion of ascorbic acid significantly increased sympathetic transduction compared with baseline (1.5 ± 0.4 vs. 2.0 ± 3 mmHg, P=0.04), in addition to reducing peripheral resistance (0.73 ± 0.11 vs. 0.53 ± 12 mmHg·min·mL−1, P=0.07). MSNA and MAP were not significantly changed during the 2-hr infusions. Conclusions: These preliminary findings suggest that excess FAA do not modulate sympathetic transduction in lean, healthy adults. However, ascorbic acid infusion reduces peripheral resistance and increases sympathetic transduction, demonstrating an inverse relation between peripheral resistance and sympathetic transduction in healthy adults. Funding and support: R01HL159370-01 (S.W.H.). This work was also supported by a CTSA grant from NCATS awarded to the University of Kansas for Frontiers: University of Kansas Clinical and Translational Science Institute (# UL1TR002366) The contents are solely the responsibility of the authors and do not necessarily represent the offcial views of the NIH or NCATS. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Finger cuff versus invasive and noninvasive arterial pressure measurement in pregnant patients with obesity.

Pregnant patients with obesity may have compromised noninvasive blood pressure (NIBP) measurement. We assessed the accuracy and trending ability of the ClearSight™ finger cuff (FC) with invasive arterial monitoring (INV) and arm NIBP, in obese patients having cesarean delivery. Participants were aged ≥18 years, ≥34 weeks gestation, and body mass index (BMI) ≥ 40 kg m-2. FC, INV, and NIBP measurements were obtained across 5-min intervals. The primary outcome was agreement of FC measurements with those of the reference standard INV, using modified Bland-Altman plots. Secondary outcomes included comparisons between FC and NIBP and NIBP versus INV, with four-quadrant plots performed to report discordance rates and evaluate trending ability. Twenty-three participants had a median (IQR) BMI of 45 kg m-2 (44-48). When comparing FC and INV the mean bias (SD, 95% limits of agreement) for systolic blood pressure (SBP) was 16 mmHg (17, -17.3 to 49.3 mmHg), for diastolic blood pressure (DBP) -0.2 mmHg (10.5, -20.7 to 20.3), and for mean arterial pressure (MAP) 5.2 mmHg (11.1, -16.6 to 27.0 mmHg). Discordance occurred in 54 (26%) pairs for SBP, 41 (23%) for DBP, and 41 (21.7%) for MAP. Error grid analysis showed 92.1% of SBP readings in Zone A (no-risk zone). When comparing NIBP and INV, the mean bias (95% limits of agreement) for SBP was 13.0 mmHg (16.7, -19.7 to 29.3), for DBP 5.9 mmHg (11.9, -17.4 to 42.0), and for MAP 8.2 mmHg (11.9, -15.2 to 31.6). Discordance occurred in SBP (84 of 209, 40.2%), DBP (74 of 187, 39.6%), and MAP (63 of 191, 33.0%). The FC and NIBP techniques were not adequately in agreement with INV. Trending capability was better for FC than NIBP. Clinically important differences may occur in the setting of the perfusion-dependent fetus.

Can Currently Available Non-invasive Continuous Blood Pressure Monitors Replace Invasive Measurement With an Arterial Catheter?

Deviations from normal blood pressure (BP) during general anesthesia have been clearly linked to several adverse outcomes. Measuring BP accurately is therefore critically important for producing excellent outcomes in health care. Normal BP does not necessarily guarantee adequate organ perfusion however and adverse events have occurred even when BP seemed adequate. Invasive blood pressure monitoring has recently evolved beyond merely measuring BP. Arterial line-derived pulse contour analysis is used now to assess both cardiac output and stroke volume variation as indices of adequate intravascular volume. Confirmation of acceptable cardiac output with data derived from invasive intra-arterial catheters has become very important when managing high-risk patients. Newer devices that measure BP continuously and non-invasively in the digital arteries via a finger cuff have also become available. Many clinicians contemplate now if these new devices are ready to replace invasive monitoring with an arterial catheter. Unlike non-invasive devices, intra-arterial catheters allow frequent blood sampling. This makes it possible to assess vital parameters like pH, hemoglobin concentration, ionized calcium, potassium, glucose, and arterial partial pressure of oxygen and carbon dioxide frequently. Non-invasive continuous BP measurement has been found to be unreliable in critically ill patients, the elderly, and patients with calcified arteries. Pulse contour-derived estimates of cardiac output and stroke volume variation have been validated better with data derived from arterial lines than that from the newer finger cuff monitors. Significant advances have been recently made with non-invasive continuous BP monitors. Invasive monitoring with an arterial line however remains the gold standard for measuring BP and assessing pulse contour analysis-derived hemodynamic variables in critically ill patients. In the future, non-invasive continuous BP monitors will likely replace intermittent oscillometers in the operating room and the postoperative period. They will however not eliminate the need for arterial catheterization in critically ill patients.

Risk factors for poor performance in finger cuff non-invasive monitoring of arterial pressure: A prospective multicenter study

BackgroundCompared to the invasive technique, non-invasive monitoring of arterial pressure favors easier and faster implementation while potentially sacrificing some reliability. This may be particularly true for the Clearsight™ system (Edwards Lifesciences), which enables continuous monitoring. We evaluated the risk factors for its poor performance. MethodsPatients with an arterial catheter and stable mean arterial pressure (MAP) over a 5-min period were included. Six pairs of invasive and Clearsight measurements of MAP were collected and the bias between the two techniques was calculated. Poor performance of the Clearsight™ system was defined as either a failure to measure and display MAP or displaying an erroneous MAP (individual bias > 5 mmHg). Fingertip perfusion was assessed using the plethysmographic perfusion index (PI) and the capillary refill time (CRT). ResultsAmong 152 ICU patients (MAP of 81 ± 14 mmHg, norepinephrine in 78 [51%]), 78 (51%) experienced a poor performance of the Clearsight™ system: failure to display MAP in 19 (13%) patients, and erroneous value displayed in 59 (44%). In multivariate analysis, PI ≤ 0.85% (adjusted odds ratio [aOR] = 2.94 [95% confidence interval (95%CI):1.34;6.45]), CRT > 4 s (aOR = 5.28 [95%CI 1.39;20.05]), and the presence of hand edema (aOR = 2.06 [95%CI 1.01;4.21]) were associated with a higher likelihood of poor performance. Cardiac arrhythmia (aOR = 1.39 [95%CI 0.64;3.02]) and other tested variables were not associated with poor performance. ConclusionsHalf of the included patients exhibited poor Clearsight™ system performance. Our results caution against using finger cuff arterial pressure monitoring in patients with low PI (≤0.85%), protracted CRT (>4 s), or hand edema. RegistrationClinicalTrials.gov, NCT04269382, Dr. G. Muller, February 13, 2020. https://classic.clinicaltrials.gov/ct2/show/NCT04269382.

Abstract 14381: A Novel Non-Invasive Screening Device for Aortic Stenosis

Introduction: Severe AS is a significant health concern in the elderly population, and a large proportion of asymptomatic cases are not receiving appropriate care. Early intervention is associated with a significant reduction in long-term mortality making early diagnosis and intervention crucial. Hypothesis: Recent progress in non-invasive (NI) hemodynamic measurements and AI has prompted the exploration of NI screening tools for AS. The ClearSight® system (Edwards) is a NI monitoring device using a finger cuff for continuous hemodynamic assessment. This study aims to evaluate its accuracy as a severe AS screening tool. Methods: 7,000 consecutive patients referred for TTE were enrolled prospectively, between 12/2020 and 04/2022 and underwent concomitant non-invasive hemodynamic monitoring using the ClearSight ® system. Complete data were obtained on 6,858 patients. The development cohort consisted of 5,334 patients, whereby an AI system was trained to interpret the data obtained from the device with the TTE data serving as the gold standard for diagnosis of severe AS. After the development phase, 1,036 patients were included in the validation cohort, whereby the trained AI system used the data obtained from the device to predict the presence of severe AS. Results: Severe AS was confirmed by TTE in 54 patients. Based on the optimal threshold (ROC curve), the sensitivity for detecting severe AS in patients without other VHD was 87%, with a NPV of 98.1%, and a specificity of 80%. When including all patients, with and without concomitant non-aortic VHD, the sensitivity remained at 87% for the same threshold, with a similarly very high NPV at 98.9%, while the specificity decreased to 70.7%. Conclusions: The ClearSight ® system, a finger-cuff NI hemodynamic monitoring tool, serves as an excellent screening test for the early detection of severe AS, with high sensitivity and specificity, and a very high NPV in a large cohort of patients consecutively referred to a TTE laboratory.

Abstract 17573: Reliability of Non-Invasive Arterial Pressure Monitoring via ClearSight System™ During Cardiac Ablation and Transvenous Pacemaker Lead Removal

Background: Invasive arterial catheter (IAC) placement can lead to hematoma, vessel occlusion, pain and &amp; procedure delay. The ClearSight System™ (CSS) is a non-invasive blood pressure (NIBP) device that measures beat-to-beat arterial pressures (AP) via a finger cuff. The validity of CSS during cardiac ablation &amp; transvenous pacemaker lead removal has not been described. Therefore, we performed a single center observational study to validate AP monitoring by CSS compared to IAC in such patients (pts). Methods: Pts undergoing cardiac ablation or lead removal from June-November 2022 were included. AP was simultaneously measured via CSS &amp; IAC. Measurements were compared using Bland-Altman analysis. Acceptable bias &amp; precision (standard deviation) were defined as &lt;5 mm Hg &amp; &lt;8 mm Hg respectively based on Association for the Advancement of Medical Instrumentation standards. An exploratory analysis on impacts of BMI, sex, &amp; type of procedure on validity of CSS was also assessed. Results: Paired AP measurements were available for 61 pts (6967 paired measurements). Median age was 67 (IQR 60.5-73.5), BMI 29.2 (IQR 26.1-37.1) &amp; 31% of pts were female. Procedures included atrial fibrillation ablation (n=32), SVT ablation (n=13), lead extraction (n=9), &amp; VT ablation (n=7). Bland-Altman analysis comparing AP via CSS vs IAC showed that the CSS overestimated systolic arterial pressure (SAP) &amp; underestimated both diastolic arterial pressure (DAP) &amp; mean arterial pressure (MAP). Mean bias was 4.2 ± 12.9 (SAP), -4.99 ± 9.2 (DAP) &amp; -2.4 ± 11.78 (MAP) (Figure 1). Exploratory analysis showed that CSS was not interchangeable with IAC monitoring regardless of subgroup (MAP male sex -1.9 ± 11.1; BMI ≥30 -2.7 ± 9.7; ablation -1.8 ± 12.2). Conclusion: Continuous NIBP monitoring via CSS was not interchangeable with IAC monitoring in pts undergoing cardiac ablation &amp; lead extraction.

Comparison of direct intra-arterial pressure and ClearSight finger cuff arterial pressure measurements in elderly patients undergoing transcatheter aortic valve replacement.

This study aimed to assess the agreement between direct intra-arterial pressure and ClearSight finger cuff arterial pressure measurements in elderly patients undergoing transcatheter aortic valve replacement (TAVR). A prospective observational study was conducted at Hitachi General Hospital, Japan, involving 30 patients aged 65 years and older who underwent TAVR under general anesthesia. Intra-arterial pressure and finger cuff arterial pressure measurements were recorded for 30 min after valve deployment. Bland-Altman analysis, four-quadrant plot analysis, and error grid analysis were used to assess the concordance between the two methods. Multiple regression analysis was performed to explore potential confounding factors affecting the agreement. The bias and precision of ClearSight measurements were -4.88 ± 15.46 (mmHg) for SBP, 4.73 ± 8.95 (mmHg) for mean, and 9.53 ± 9.01 (mmHg) for DBP. The Bland-Altman analysis demonstrated acceptable agreement between intra-arterial pressure and finger cuff arterial pressure measurements. The four-quadrant plot analysis showed good trend-tracking ability, and the error grid analysis revealed that most of the observed values fell into the no-risk category. The mean BP match ratio and SBP match ratio were influenced by several factors such as age, BSA, ejection fraction, valve size, and gender. The ClearSight finger cuff arterial pressure measurement showed good agreement with direct intra-arterial pressure in elderly patients undergoing TAVR. However, factors such as age, BSA, ejection fraction, valve size, and gender may influence the agreement between the two methods.

Abstract P323: Going Beyond Spot 30-minute Nocturnal Blood Pressure (bp) Check With The Continuous Nocturnal Bp Monitoring

Background: Ambulatory Blood Pressure Monitoring (ABPM) is useful to determine nocturnal BP. However, the major limitation is the spot-check nature. The main objective of the study is to compare the nocturnal blood pressure (BP) results derived from continuous nocturnal (beat-to-beat) finger cuff BP monitoring device (CNBPM) based on pulse decomposition analysis and from conventional arm cuff-based ABPM. Methods: We prospectively enrolled 17 subjects from the community. Each subject underwent 1 day of standard 24-hour ABPM. On a second day, the subjects underwent continuous BP monitoring at nighttime only. Systolic BPs (BP hereafter) 12 AM - 6 AM constituted nocturnal BP. We compared the maximum nocturnal BP from ABPM with that from CNBPM. For paired comparison, we matched every 30-minute nocturnal BPs by ABPM, with the corresponding 30 min-averaged nocturnal BPs from CNBPM. Using these data points, we also examined nocturnal dipping by both methods. For continuous BP dipping calculation, we used late night and early AM BP recording (outside 12 AM-6 AM window) derived from continuous BP monitoring. Non-dipping was defined by &lt; 10% BP reduction at nighttime. Results: All enrolled subjects recorded both ABPM and CNBPM. Maximum nocturnal BP was lower by ABPM than by CNBPM ( M 71.28, SD 8.65 vs. M 96.11, SD 13.74), p&lt;0.0001). Paired comparison of every 30 min nocturnal BP yielded a lower nocturnal BP by ABPM than CNBPM (113.65 mmHg (18.31) vs. 113.43 (SD 27.32), p = 0.978). The mean absolute dipping was similar between ABPM and CNBPM (13.2% (7) and 9.5 (10.6), p=NS) respectively. Among 8 subjects with normal dipping, 9 subjects were categorized as non-dipping by CNBPM. Among 11 subjects who had normal dipping by ABPM, 6 subjects met non-dipping by ABPM. CNBPM was better tolerated than ABPM according to subjects. Conclusion: This study demonstrates that the clusters of BP variability overnight may be missed by a spot-check nocturnal BP measurement by ABPM. There was bias toward the underestimation of BP by ABPM when compared to CNBPM. Further studies should determine a subset of high-risk patients who may benefit from using CNBPM for accurate nocturnal BP monitoring.

Noninvasive Monitoring of Arterial Pressure: Finger or Lower Leg As Alternatives to the Upper Arm: A Prospective Study in Three ICUs.

When the upper arm is inaccessible for measurements of arterial pressure (AP), the best alternative site is unknown. We performed a between-site comparison of the agreement between invasive and noninvasive readings of AP taken at the lower leg, the finger, and the upper arm. The risk associated with measurement errors and the trending ability were also assessed. Prospective observational study. Three ICUs. Patients having an arterial catheter and an arm circumference less than 42 cm. None. Three triplicates of AP measurements were collected via an arterial catheter (reference AP), a finger cuff system (ClearSight; Edward Lifesciences, Irvine, CA), and an oscillometric cuff (at the lower leg then the upper arm). Trending ability was assessed through an additional set of measurements after a cardiovascular intervention. The default bed backrest angle was respected. Failure to measure and display AP occurred in 19 patients (13%) at the finger, never at other sites. In 130 patients analyzed, the agreement between noninvasive and invasive readings was worse at the lower leg than that observed at the upper arm or the finger (for mean AP, bias ± sd of 6.0 ± 15.8 vs 3.6 ± 7.1 and 0.1 ± 7.4 mm Hg, respectively; p < 0.05), yielding a higher frequency of error-associated clinical risk (no risk for 64% vs 84% and 86% of measurements, respectively, p < 0.0001). According to the International Organization for Standardization (ISO) 81060-2:2018 standard, mean AP measurements were reliable at the upper arm and the finger, not the lower leg. In 33 patients reassessed after a cardiovascular intervention, both the concordance rate for change in mean AP and the ability to detect a therapy-induced significant change were good and similar at the three sites. As compared with lower leg measurements of AP, finger measurements were, when possible, a preferable alternative to upper arm ones.

A new continuous noninvasive finger cuff device (Vitalstream) for cardiac output that communicates wirelessly via bluetooth or Wi-Fi

BackgroundThe new noninvasive Vitalstream (VS) continuous physiological monitor (Caretaker Medical LLC, Charlottesville, Virginia), allows continuous cardiac output by a low pump-inflated, finger cuff that pneumatically couples arterial pulsations via a pressure line to a pressure sensor for detection and analysis. Physiological data are communicated wirelessly to a tablet-based user interface via Bluetooth or Wi-Fi. We evaluated its performance against thermodilution cardiac output in patients undergoing cardiac surgery.MethodsWe compared the agreement between thermodilution cardiac output to that obtained by the continuous noninvasive system during cardiac surgery pre and post-cardiac bypass. Thermodilution cardiac output was performed routinely when clinically indicated by an iced saline cold injectate system. All comparisons between VS and TD/CCO data were post-processed. In order to match the VS CO readings to the averaged discrete TD bolus data, the averaged CO readings of the ten seconds of VS CO data points prior to a sequence of TD bolus injections was matched. Time alignment was based on the medical record time and the VS time-stamped data points. The accuracy against reference TD measurements was assessed via Bland–Altman analysis of the CO values and standard concordance analysis of the ΔCO values (with a 15% exclusion zone).ResultsAnalysis of the data compared the accuracy of the matched measurement pairs of VS and TD/CCO VS absolute CO values with and without initial calibration to the discrete TD CO values, as well as the trending ability, i.e., ΔCO values of the VS physiological monitor compared to those of the reference. The results were comparable with other non-invasive as well as invasive technologies and Bland-Altman analyses showed high agreement between devices in a diverse patient population. The results are significant regarding the goal of expanding access to effective, wireless and readily implemented fluid management monitoring tools to hospital sections previously not covered because of the limitations of traditional technologies.ConclusionThis study demonstrated that the agreement between the VS CO and TD CO was clinically acceptable with a percent error (PE) of 34.5 to 38% with and without external calibration. The threshold for an acceptable agreement between the VS and TD was considered to be below 40% which is below the threshold recommended by others.

Noninvasive finger plethysmography for continuous blood pressure monitoring in patients with left ventricular assist device.

Accurate blood pressure (BP) measurement remains challenging in patients with HeartMate 3™ left ventricular assist devices (HM3 LVADs). The Finapres® NOVA is a promising non-invasive continuous BP monitor that uses the volume clamp method via a finger cuff, so here we aimed to validate the instrument in HM3 patients. In a single-center cohort, BP was monitored in 15 patients within 72 h following HM3 implantation. A radial artery catheter quantified arterial blood pressure (ABP), while the NOVA measured finger arterial pressure (fiAP) and reconstructed brachial artery pressure (reBAP). Waveforms were recorded for 10 min, and mean values were calculated in 15-s intervals. fiAP and ABP were moderately correlated during both the first (ICC 0.61, p = 0.04) and final measurements (ICC 0.66, p = 0.03). reBAP and ABP were strongly correlated during both the first (ICC 0.81, p = 0.002) and final measurements (ICC 0.83, p = 0.001). Both NOVA-derived values may underestimate low BP values while overestimating relatively high BP values. The reBAP was within 5 mm Hg of the ABP in 40% of patients (and within 10 mm Hg in 67%). This pilot represents the first evidence in support of the Finapres® NOVA for non-invasive BP measurement in select patients with HM3 LVADs. The instrument may provide useful data during BP medication adjustments or pump titration, but despite the correlation between the non-invasive reBAP and invasive ABP, individual-level inaccuracy may be clinically meaningful. Further investigation is needed to clarify these limitations and optimize accuracy before widespread adoption in this unique patient population.

Concomitantly higher resting arterial blood pressure and transduction of sympathetic neural activity in human obesity without hypertension.

Central (abdominal) obesity is associated with elevated adrenergic activity and arterial blood pressure (BP). Therefore, we tested the hypothesis that transduction of spontaneous muscle sympathetic nerve activity (MSNA) to BP, that is, sympathetic transduction, is augmented in abdominal obesity (increased waist circumference) and positively related to prevailing BP. Young/middle-aged obese (32 ± 7 years; BMI: 36 ± 5 kg/m2, n = 14) and nonobese (29 ± 10 years; BMI: 23 ± 4 kg/m2, n = 14) without hypertension (24-h ambulatory average BP < 130/80 mmHg) were included. MSNA (microneurography) and beat-to-beat BP (finger cuff) were measured continuously and the increase in mean arterial pressure (MAP) during 15 cardiac cycles following MSNA bursts of different patterns (single, multiples) and amplitude (quartiles) was signal-averaged over a 10 min baseline period. MSNA burst frequency was not significantly higher in obese vs. nonobese (21 ± 3 vs. 17 ± 3 bursts/min, P = 0.34). However, resting supine BP was significantly higher in obese compared with nonobese (systolic: 127 ± 3 vs. 114 ± 3; diastolic: 76 ± 2 vs. 64 ± 1 mmHg, both P < 0.01). Importantly, obese showed greater increases in MAP following multiple MSNA bursts (P = 0.02) and MSNA bursts of higher amplitude (P = 0.02), but not single MSNA bursts (P = 0.24), compared with nonobese when adjusting for MSNA burst frequency. The increase in MAP following higher amplitude bursts among all participants was associated with higher resting supine systolic (R = 0.48; P = 0.01) and diastolic (R = 0.48; P = 0.01) BP when controlling for MSNA burst frequency, but not when also controlling for waist circumference (P > 0.05). In contrast, sympathetic transduction was not correlated with 24-h ambulatory average BP. Sympathetic transduction to BP is augmented in abdominal obesity and positively related to higher resting supine BP but not 24-h ambulatory average BP.

Associations Between Cardiovascular Reactivity and Automatic Evaluation of Physical Activity and Sedentary Behaviors

Effort mobilization, or the amount of resources individuals mobilize to execute behavior, is central to the dual-process theory. One’s evaluation or perception of task difficulty (target behavior) is directly related to effort. Automatic or habitual behaviors require little effort, while reflective or controlled processes require greater effort mobilization, and even greater effort when behavioral automaticity and the goal task conflict. Cardiovascular (CV) reactivity to cognitive challenge is an objective and reliable measure of effort mobilization, but has yet to be evaluated in the automatic evaluation (AE) of PA behavior. PURPOSE: To explore relationships among CV reactivity, AE and reflective measures of PA behavior. METHODS: This pilot study includes a subset of 30 subjects (57% women, 24±10 y, 27±5 kg/m2) from a larger project examining interactions between AE and reflective processes in relation to PA behavior. A computerized test (Single Category Implicit Association Test [SCIAT]) was used to measure AE of PA behaviors (positive scores reflected positive AE of the target behavior). Heart rate (HR) and systolic blood pressure (SBP) were measured continuously and noninvasively using a finger cuff. CV reactivity was quantified using average values obtained during the SCIAT and percentage change (∆) from rest. Accelerometers measured habitual PA (min/d) and questionnaires captured reflective PA outcomes (e.g., intention, enjoyment). Bivariate correlations were used to explore the relationships among variables (α=0.05). RESULTS: SBP during the SCIAT correlated with habitual PA (r=0.41). HR during the SCIAT correlated with intention to perform exercise (r=-0.51) and PA enjoyment scale (r=-0.56), while ∆HR correlated with light intensity PA SCIAT scores (r=-0.40; all p≤0.03). CONCLUSIONS: Lower CV reactivity during the SCIAT was related to positive AE toward PA behavior and greater PA intention, suggesting that these subjects found PA stimuli to be less stressful (required less effort). Conversely, CV reactivity was higher among those with positive AE toward sedentary behavior, suggesting that PA stimuli was more stressful (required greater effort). By focusing efforts on changing how individuals perceive PA, future PA guidelines may be more successful in increasing long-term PA adherence.

Validity and success rate of noninvasive mean arterial blood pressure measurements in cf-LVAD patients: A technical review.

The life expectancy of patients with a continuous flow left ventricular assist device (cf-LVAD) is increasing. Adequate determination and regulation of mean arterial pressure (MAP) is important to prevent adverse events. Given the low pulsatility characteristics in these patients, standard blood pressure equipment is inadequate to monitor MAP and not recommended. We provide an overview of currently available noninvasive techniques, using an extensive search strategy in three online databases (Pubmed, Scopus and Google Scholar) to find validation studies using invasive intra-arterial blood pressure measurement as a reference. Mean differences with the reference values smaller than 5 ± 8 mm Hg were considered acceptable. After deduplication, screening, and exclusion of incorrect sources, eleven studies remained with 3139 successful MAP measurements in 386 patients. Four noninvasive techniques, using Doppler, pulse oximetry, finger cuff volume clamp, or slow upper arm cuff deflation, were identified and evaluated for validity and success rate in cf-LVAD patients. Here, a comprehensive technical background of the blood pressure measurement methods is provided in combination with a clinical use comparison. Of the reported noninvasive techniques, slow cuff devices performed most optimally (mean difference 1.3 ± 5.2 mm Hg). Our results are encouraging and indicate that noninvasive blood pressure monitoring options with acceptable validity and success rate are available. Further technical development and validation is warranted for the growing population of patients on long-term cf-LVAD support.

The Effect of Intermittent versus Continuous Non-Invasive Blood Pressure Monitoring on the Detection of Intraoperative Hypotension, a Sub-Study.

Intraoperative hypotension is associated with postoperative complications. However, in the majority of surgical patients, blood pressure (BP) is measured intermittently with a non-invasive cuff around the upper arm (NIBP-arm). We hypothesized that NIBP-arm, compared with a non-invasive continuous alternative, would result in missed events and in delayed recognition of hypotensive events. This was a sub-study of a previously published cohort study in adult patients undergoing surgery. The detection of hypotension (mean arterial pressure below 65 mmHg) was compared using two non-invasive methods; intermittent oscillometric NIBP-arm versus continuous NIBP measured with a finger cuff (cNIBP-finger) (Nexfin, Edwards Lifesciences). cNIBP-finger was used as the reference standard. Out of 350 patients, 268 patients (77%) had one or more hypotensive events during surgery. Out of the 286 patients, 72 (27%) had one or more missed hypotensive events. The majority of hypotensive events (92%) were detected with NIBP-arm, but were recognized at a median of 1.2 (0.6–2.2) minutes later. Intermittent BP monitoring resulted in missed hypotensive events and the hypotensive events that were detected were recognized with a delay. This study highlights the advantage of continuous monitoring. Future studies are needed to understand the effect on patient outcomes.