The CNAP™ Finger Cuff for Noninvasive Beat-To-Beat Monitoring of Arterial Blood Pressure

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

BACKGROUND

Compared 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.

METHODS

Patients 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).

RESULTS

Among 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.

CONCLUSIONS

Half 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.

REGISTRATION

ClinicalTrials.gov, NCT04269382, Dr. G. Muller, February 13, 2020. https://classic.

CLINICALTRIALS

gov/ct2/show/NCT04269382.

Toward Real-Time Blood Pressure Monitoring via High-Fidelity Iontronic Tonometric Sensors with High Sensitivity and Large Dynamic Ranges

Continuous, noninvasive blood pressure (CNIBP) monitoring provides valuable hemodynamic information that renders detection of the early onset of cardiovascular diseases. Wearable mechano-electric pressure sensors that mount on the skin are promising candidates for monitoring continuous blood pressure (BP) pulse waveforms due to their excellent conformability, simple sensing mechanisms, and convenient signal acquisition. However, it is challenging to acquire high-fidelity BP pulse waveforms since it requires highly sensitive sensors (sensitivity larger than 4 × 10-5 kPa-1 ) that respond linearly with pressure change over a large dynamic range, covering the typical BP range (5-25 kPa). Herein, this work introduces a high-fidelity, iontronic-based tonometric sensor (ITS) with high sensitivity (4.82 kPa-1 ), good linearity (R2 > 0.995), and a large dynamic range (up to 180% output change) over a broad working range (0 to 38 kPa). Additionally, the ITS demonstrates a low limit of detection at 40 Pa, a fast load response time (35 ms) and release time (35 ms), as well as a stable response over 5000 load per release cycles, paving ways for potential applications in human-interface interaction, electronic skins, and robotic haptics. This work further explores the application of the ITS in monitoring real-time, beat-to-beat BP by measuring the brachial and radial pulse waveforms. This work provides a rational design of a wearable pressure sensor with high sensitivity, good linearity, and a large dynamic range for real-time CNIBP monitoring.

Clinical Validation of a Soft Wireless Continuous Blood Pressure Sensor During Surgery

We test a new wireless soft capacitance sensor (CAP) based on applanation tonometry at the radial and dorsalis pedis arteries against the gold standard, invasive arterial line (A-Line), for continuous beat to beat blood pressure (BP) measurements in the Operating Room during surgical procedures under anesthesia in 17 subjects with the mean age and body mass index (BMI) of 57. 35 ± 18.72 years and 27.36 ± 4.20 kg/m², respectively. We have identified several parameters to monitor in order to compare how well the CAP sensor tracks the entire hemodynamic waveform as compared to the A-Line. This includes waveform similarity, heart rate (HR), absolute systolic BP (SBP), diastolic BP (DBP), and temporal response to a vasopressor. Overall, the CAP sensor shows good correlations with A-Line with respect to hemodynamic shape (r > 0.89), HR (mean bias = 0.0006; SD = 0.17), absolute SBP, and DBP in a line of best fit (slope = 0.98 in SBP; 1.08 in DBP) and the mean bias derived from Bland-Altman method to be 1.92 (SD = 12.55) in SBP and 2.38 (SD = 12.19) in DBP across body habitus and age in OR patients under general anesthesia. While we do observe drifts in the system, we still obtain decent correlations with respect to the A-Line as evidenced by excellent linear fit and low mean bias across patients. When we post-process using a different calibration method to account for the drift, the mean bias and SD improve dramatically to −1.85 and 7.19 DBP as well as 1.43 and 7.43 SBP, respectively, indicating a promising potential for improvement when we integrate strategies to account for movement identified by our integrated accelerometer data.

Early vesus differed arterial catheterisation in critically ill patients with acute circulatory failure: a multicentre, open-label, pragmatic, randomised, non-inferiority controlled trial: the EVERDAC protocol

INTRODUCTION

The use of peripheral indwelling arterial catheter for haemodynamic monitoring is widespread in the intensive care unit and is recommended in patients with shock. However, there is no evidence that the arterial catheter could improve patient's outcome, whereas the burden of morbidity generated is significant (pain, thrombosis, infections). We hypothesise that patients with shock may be managed without an arterial catheter.

METHODS AND ANALYSIS

The EVERDAC study is an investigator-initiated, pragmatic, multicentre, randomised, controlled, open-label, non-inferiority clinical trial, comparing a less invasive intervention (ie, no arterial catheter insertion until felt absolutely needed, according to predefined safety criteria) or usual care (ie, systematic arterial catheter insertion in the early hours of shock). 1010 patients will be randomised with a 1:1 ratio in two groups according to the strategy. The primary outcome is all-cause mortality by 28 days after inclusion. A health economic analysis will be carried out.

ETHICS AND DISSEMINATION

The study has been approved by the Ethics Committee (Comité de Protection des Personnes Île de France V, registration number 61606 CAT 2, 19 july 2018) and patients will be included after informed consent. The results will be submitted for publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT03680963.

Accuracy and precision of continuous non-invasive arterial pressure monitoring in critical care: A systematic review and meta-analysis

OBJECTIVE

To summarize the evidence regarding the accuracy of continuous non-invasive arterial pressure measurements in adult critical care patients.

RESEARCH METHODOLOGY

Medline, EMBASE, and CINAHL were searched for studies that included adult critical care patients reporting the agreement between continuous non-invasive and invasive arterial pressure measurements. The studies were selected and assessed for risk of bias using the Revised Quality Assessment of Diagnostic Accuracy Studies tool by two independent reviewers. The Grading of Recommendations, Assessment, Development and Evaluations approach was used. Pooled estimates of the mean bias and limits of agreement with outer 95% confidence intervals (termed population limits of agreement) were calculated.

RESULTS

Population limits of agreement for systolic blood pressure were wide, spanning from -36.13 mmHg to 28.28 mmHg (18 studies; 785 participants). Accuracy of diastolic blood pressure measurements was highly inconsistent across studies, resulting in imprecise estimates for the population limits of agreement. Population limits of agreement for mean arterial pressure spanned from -39.96 mmHg to 44.36 mmHg (17 studies; 765 participants). The evidence was rated as very low-quality due to very serious concerns about heterogeneity and imprecision.

CONCLUSION

Substantial differences in blood pressure were identified between measurements taken from continuous non-invasive and invasive monitoring devices. Clinicians should consider this broad range of uncertainty if using these devices to inform clinical decision-making in critical care.

Agreement between continuous noninvasive finger cuff-derived and invasive arterial blood pressure measurements: Effect of data sampling and data processing

BACKGROUND

The effect of different methods for data sampling and data processing on the results of comparative statistical analyses in method comparison studies of continuous arterial blood pressure (AP) monitoring systems remains unknown.

OBJECTIVE

We sought to investigate the effect of different methods for data sampling and data processing on the results of statistical analyses in method comparison studies of continuous AP monitoring systems.

DESIGN

Prospective observational study.

SETTING

University Medical Center Hamburg-Eppendorf, Hamburg, Germany, from April to October 2019.

PATIENTS

49 patients scheduled for neurosurgery with AP measurement using a radial artery catheter.

MAIN OUTCOME MEASURES

We assessed the agreement between continuous noninvasive finger cuff-derived (CNAP Monitor 500; CNSystems Medizintechnik, Graz, Austria) and invasive AP measurements in a prospective method comparison study in patients having neurosurgery using all beat-to-beat AP measurements (Methodall), 10-s averages (Methodavg), one 30-min period of 10-s averages (Method30), Method30 with additional offset subtraction (Method30off), and 10 30-s periods without (Methodiso) or with (Methodiso-zero) application of the zero zone. The agreement was analysed using Bland-Altman and error grid analysis.

RESULTS

For mean AP, the mean of the differences (95% limits of agreement) was 9.0 (-12.9 to 30.9) mmHg for Methodall, 9.2 (-12.5 to 30.9) mmHg for Methodavg, 6.5 (-9.3 to 22.2) mmHg for Method30, 0.5 (-9.5 to 10.5) mmHg for Method30off, 4.9 (-6.0 to 15.7) mmHg for Methodiso, and 3.4 (-5.9 to 12.7) mmHg for Methodiso-zero. Similar trends were found for systolic and diastolic AP. Results of error grid analysis were also influenced by using different methods for data sampling and data processing.

CONCLUSION

Data sampling and data processing substantially impact the results of comparative statistics in method comparison studies of continuous AP monitoring systems. Depending on the method used for data sampling and data processing, the performance of an AP test method may be considered clinically acceptable or unacceptable.

Accuracy of noninvasive blood pressure measured at the ankle during cesarean delivery under spinal anesthesia

In this study, we evaluated the accuracy of oscillometric noninvasive blood pressure (NIBP) measured at the ankle in detecting low arm NIBP during cesarean delivery under spinal anesthesia. In this prospective observational study, a cohort of full-term mothers undergoing elective cesarean delivery under spinal anesthesia was examined. Simultaneous NIBP measurements were obtained from the arm and the ankle. The primary outcome was the accuracy of the ankle NIBP in detecting arm systolic blood pressure (SBP) < 90 mmHg. Other outcomes included the accuracy of ankle NIBP in detecting SBP < 80% of the baseline value. The area under the receiver operating characteristic curve (AUC) was calculated to evaluate the accuracy of ankle NIBP in detecting low arm NIBP. The Bland-Altman analysis was conducted to evaluate the agreement between values. We analyzed 1729 pairs of readings obtained from 97 mothers. Ankle SBP showed good accuracy in detecting SBP < 90 mmHg, with an AUC (95% confidence interval [CI]) of 0.90 (0.89-0.91) and a negative predictive value (NPV) of 99 (98-99%) at a cutoff value of ≤ 103 mmHg. Furthermore, ankle SBP showed good accuracy in detecting SBP < 80% of the baseline value, with an AUC (95% CI) of 0.84 (0.82-0.89) and an NPV of 95 (93-96%) at a cutoff value of ≤ 76% of the ankle baseline SBP. The mean bias between the two sites of measurement was - 5.4 ± 15.5, - 2.0 ± 11, and 0.5 ± 12.1 mmHg for SBP, diastolic blood pressure, and mean arterial pressure, respectively. In conclusion, ankle NIBP measurement is not interchangeable with arm NIBP measurement. However, ankle NIBP measurement showed good accuracy for ruling out low arm NIBP during a cesarean delivery.Clinical trial rejistration: NCT04199156.

The perfusion index measured by the pulse oximeter affects the agreement between ClearSight and the arterial catheter-based blood pressures: A prospective observational study

Background

ClearSight is a noninvasive arterial blood pressure monitor, but it remains unknown whether it is affected by the state of perfusion to the fingers. We investigated whether the lower perfusion index (PI) measured with a pulse oximeter, which reflects finger perfusion, would affect the agreement between arterial pressures measured with ClearSight versus those obtained with an arterial catheter.

Methods

Paired arterial pressure data (ClearSight and arterial catheter-based pressures) and PI values were prospectively obtained from 30 patients undergoing major abdominal surgery. The primary outcome was standard deviation (SD) of the bias (precision) of blood pressure between ClearSight and arterial catheter. The ratio of the adjusted SD of the bias between PI≤1 and PI>1 was calculated using the linear mixed-effects model. The secondary outcomes were the bias and the limits of agreement (LOA) between the two devices (repeated measures Bland-Altman analysis).

Results

We analyzed 6312 paired data points. The adjusted SD of bias in PI ≤1 compared with those in PI >1 was 1.4-fold (95% confidence interval: 1.3- to 1.4-fold) for systolic arterial pressure, 1.5-fold (95% confidence interval: 1.3- to 1.6-fold) for diastolic arterial pressure, and 1.3-fold (95% confidence interval: 1.2- to 1.5-fold) for mean arterial pressure. The bias (LOA) were as follows: systolic arterial pressure in the PI ≤1 and PI >1 groups, -3.5 (-35.4 to 28.4) mmHg and 2.2 (-19.9 to 24.3) mmHg, respectively; diastolic arterial pressure in the PI ≤1 and PI >1 groups, 13.1 (-5.1 to 31.3) mmHg and 9.0, (-2.6 to 20.6) mmHg, respectively; and mean arterial pressure in the PI ≤1 and PI >1 groups, 8.7 (-11.3 to 28.7) mmHg and 7.6 (-6.2 to 21.3) mmHg, respectively.

Conclusions

PI ≤1 was associated with a large SD of the bias between the devices. The PI value could be a real-time indicator of ClearSight precision.

Prospective clinical study to evaluate an oscillometric blood pressure monitor in pet rabbits

Background

Rabbits are particularly sensitive to develop hypotension during sedation or anaesthesia. Values of systolic or mean non-invasive arterial blood pressure below 80 or 60 mmHg respectively are common under anaesthesia despite an ongoing surgery. A reliable method of monitoring arterial blood pressure is extremely important, although invasive technique is not always possible due to the anatomy and dimension of the artery. The aim of this study was to evaluate the agreement between a new oscillometric device for non-invasive arterial blood pressure measurement and the invasive method. Moreover the trending ability of the device, ability to identify changes in the same direction with the invasive methods, was evaluated as well as the sensibility of the device in identifying hypotension arbitrarily defined as invasive arterial blood pressure below 80 or 60 mmHg.

Results

Bland-Altman analysis for repeated measurements showed a poor agreement between the two methods; the oscillometric device overestimated the invasive arterial blood pressure, particularly at high arterial pressure values. The same analysis repeated considering oscillometric measurement that match invasive mean pressure lower or equal to 60 mmHg showed a decrease in biases and limits of agreement between methods. The trending ability of the device, evaluated with both the 4-quadrant plot and the polar plot was poor. Concordance rate of mean arterial blood pressure was higher than systolic and diastolic pressure although inferior to 90%. The sensibility of the device in detecting hypotension defined as systolic or mean invasive arterial blood pressure lower than 80 or 60 mmHg was superior for mean oscillometric pressure rather than systolic. A sensitivity of 92% was achieved with an oscillometric measurement for mean pressure below 65 mmHg instead of 60 mmHg. Non-invasive systolic blood pressure is less sensitive as indicator of hypotension regardless of the cutoff limit considered.

Conclusions

Although mean invasive arterial blood pressure is overestimated by the device, the sensitivity of this non-invasive oscillometric monitor in detecting invasive mean pressure below 60 mmHg is acceptable but a cutoff value of 65 mmHg needs to be used.

Continuous Non-Invasive Arterial Pressure Assessment during Surgery to Improve Outcome

Blood pressure (BP) is one of the most important variables evaluated during almost every medical examination. Most national anesthesiology societies recommend BP monitoring at least once every 5 min in anesthetized subjects undergoing surgical procedures. In most cases, BP is monitored non-invasively using oscillometric cuffs. Although the risk of arterial cannulation is not very high, the invasive BP monitoring is usually indicated only in the case of high-risk patients or in complex surgical procedures. However, recent evidence points out that when using intermittent BP monitoring short periods of hypotension may be overlooked. In addition, large datasets have demonstrated that even short periods of low BP (or their cumulative duration) may have a detrimental impact on the development of postoperative outcome including increased risk of acute kidney or myocardial injury development. Recently marketed continuous non-invasive blood pressure monitoring tools may help us to recognize the BP fluctuation without the associated burden of arterial cannulation filling the gap between intermittent non-invasive cuff and continuous invasive arterial pressure. Among others, several novel devices based either on volume clamp/vascular unloading method or on applanation tonometry are nowadays available. Moreover, several near-future smart technologies may lead to better hypotension recognition or even prediction potentially improving our ability to maintain BP stability throughout the anesthesia or surgical procedure. In this review, novel or emerging technologies of non-invasive continuous blood pressure assessment and their potential to improve postoperative outcome are discussed.

Noninvasive BP Monitoring in the Critically Ill: Time to Abandon the Arterial Catheter?

Although its reliability is often questioned, noninvasive BP (NIBP)-monitoring with an oscillometric arm cuff is widely used, even in critically ill patients in shock. When correctly implemented, modern arm NIBP devices can provide accurate and precise measurements of mean BP, as well as clinically meaningful information such as identification of hypotension and hypertension and monitoring of patient response to therapy. Even in specific circumstances such as arrhythmia, hypotension, vasopressor infusion, and possibly in obese patients, arm NIBP may be useful, contrary to widespread belief. Hence, postponing the arterial catheter insertion pending the initiation of more urgent diagnostic and therapeutic measures could be a suitable strategy. Given the arterial catheter-related burden, fully managing critically ill patients without any arterial catheter may also be an option. Indeed, the benefit that patients may experience from an arterial catheter has been questioned in studies failing to show that its use reduces mortality. However, randomized controlled trials to confirm that NIBP can safely fully replace the arterial catheter have yet to be performed. In addition to intermittent measurements, continuous NIBP monitoring is a booming field, as illustrated by the release onto the market of user-friendly devices, based on digital volume clamp and applanation tonometry. Although the imperfect accuracy and precision of these devices would probably benefit from technical refinements, their good ability to track, in real time, the direction of changes in BP is an undeniable asset. Their drawbacks and advantages and whether these devices are currently ready to use in the critically ill patient are discussed in this review.

Update on Finger-Application-Type Noninvasive Continuous Hemodynamic Monitors (CNAP and ccNexfin): Physical Principles, Validation, and Clinical Use

The CNAP HD Monitor (CNSystems, Graz, Austria) and the ccNexfin (The ClearSight System: Edwards Lifesciences Corporation, Irvine, CA) are continuous, noninvasive blood pressure monitors using a finger-application device. These devices show a promising ability to allow for rapid detection of hemodynamic derangement when compared with oscillometry. The accuracy and precision of these devices as blood pressure monitors has been evaluated when compared with intra-arterial catheters. Additionally, they can be used to measure beat-to-beat cardiac output (CO). As CO monitors, they are capable of trending changes in CO when compared with a transpulmonary thermodilution monitor. Difficulty with use in critically ill and awake patients has been encountered because of altered microvascular physiology and patient movement. The principles of operation and clinical validation of these devices are presented. The clinicians who are interested in using these devices in their clinical setting should be aware of the relatively large bias and CIs in the hemodynamic measurements.