Objective The objective of this study was to compare the systolic (S) and diastolic (D) blood pressure (BP) estimations from a new optical device at the wrist with invasive measurements performed on patients scheduled for radial arterial catheterization in the ICU. Optical signals were automatically processed by a library of algorithms from Aktiia SA (OBPM – optical blood pressure monitoring algorithms). Methods A total of 31 participants from both sexes, aged 32–87 years, were enrolled in the study (NCT03837769). The measurement protocol consisted of the simultaneous recording of reflective photoplethysmographic signals (PPG) from the cuffless optical device and the reference BP values recorded by a contralateral radial arterial catheter. From the 31 participants, 23 subjects whose reference data quality requirements were adequate were retained for further analysis. The PPG signals from these patients were then automatically processed by the Aktiia OBPM library of algorithms, which generated uncalibrated estimates of SBP and DBP. After the automatic assessment of optical signal quality, 326 pairs of uncalibrated SBP and DBP determinations from 16 patients were available for analysis. These values were finally transformed into calibrated estimations (in mmHg) using arterial catheter SBP and DBP values, respectively. Results For SBP, a mean difference (±SD) of 0.0 ± 7.1 mmHg between the arterial catheter and the optical device values was found, with 95% limits of agreement in the Bland-Altman method of –11.9 to + 12.2 mmHg (correlation of r = 0.87, P < 0.001). For DBP, a mean difference (±SD) of 0.0 ± 2.9 mmHg between arterial catheter and the optical device values was found, with 95% limits of agreement in the Bland-Altman method of –4.8 to + 5.5 mmHg (correlation of r = 0.98, P < 0.001). Conclusion SBP and DBP values obtained by radial artery catheterization and those obtained from optical measurements at the wrist were compared. The new optical technique appears to be capable of replacing more traditional methods of BP estimation.

Hypertension remains the leading risk factor for death worldwide. Despite its prevalence, success of blood pressure (BP) management efforts remains elusive, and part of the difficulty lies in the tool still used to diagnose, measure, and treat hypertension: the sphygmomanometer introduced by Samuel Siegfried Karl von Basch in 1867. In recent years, there has been an explosion of devices attempting to provide estimates of BP without a cuff, overcoming many limitations of cuff-based BP monitors. Unfortunately, the differences in underlying technologies between traditional BP cuffs and newer cuffless devices, as well as hesitancy of changing a well-implemented standard, still generate understandable skepticism about and reluctance to adopt cuffless BP monitors in clinical practice. This guidance document aims to navigate the scientific and medical communities through the types of cuffless devices and present examples of robust BP data collection which are better representations of a person's true BP. It highlights the differences between data collected by cuffless and traditional cuff-based devices and provides an initial framework of interpretation of the new cuffless datasets using, as an example, a CE-marked continual cuffless BP device (Aktiia BP Monitor, Aktiia, Switzerland). Demonstration of novel BP metrics, which have the potential to change the paradigm of hypertension diagnosis and treatment, are now possible for the first time with cuffless BP monitors that provide continual readings over long periods. Widespread adoption of continual cuffless BP monitors in healthcare will require a collaborative and thoughtful process, acknowledging that the transition from a legacy to a novel medical technology will be slow. Finally, this guidance concludes with a call to action to international scientific and expert associations to include cuffless BP monitors in original scientific research and in future versions of guidelines and standards.

The US and European guidelines for the diagnosis and management of hypertension recommend the introduction of systematic home and night Blood Pressure (BP) monitoring. Fully-automated wearable devices can address the needs of patients and clinicians by improving comfort while achieving measurement accuracy. Often located at the wrist and based on indirect BP measurements, these devices must address the challenges of ambulatory scenarios. New validation strategies are needed, but little guidance has been published so far. In this work, we propose an experimental protocol for the validation of cuffless wrist BP monitors that addresses ambulatory environment challenges in a controlled experimental setting. The protocol assesses the robustness of the measurement for different body postures, the ability of the device to track BP changes, and its ability to deal with hydrostatic pressure changes induced by different arm heights. Performance testing using Aktiia Bracelet is provided as an illustration. The results of this pilot study indicate that the Aktiia Bracelet can generate accurate BP estimates for sitting and lying positions and is not affected by hydrostatic pressure perturbations. Clinical Relevance-Automated cuffless BP monitoring is opening a new chapter in the way patients are being diagnosed and managed. This paper provides a guidance on how to assess the clinical utility of such devices when used in different body positions.

The recommended Kt/V is 1.2. Unfortunately there is no written policy for nurses on the procedure for taking blood urea nitrogen samples post haemodialysis. The aim of this study was to establish the Kt/V variability of haemodialysis patients depending on the method of collection of post-haemodialysis blood urea nitrogen. Twenty-two patients were analysed. A Kt/V was performed every 15 days during a period of 2 months. It was taken five times on each patient: 30 minutes before the end of a haemodialysis session (Kt/V30), at the end of haemodialysis (Kt/V1), after slowing flows (50 ml/min) for 2 minutes (Kt/V2) and after the blood circuit had been returned to the patient at 5 and 15 minutes respectively. (Kt/V5, Kt/V15). The Kt/V results were: Kt/V1 1.23 +/- 0.2 Vs Kt/V2 1.14 +/- 0.19 (p < 0.003); Kt/V5- 1.05 +/- 0.19 (p < 0.002 Vs Kt/V2); Kt/V15 1 +/- 0.16 (p < 0.05 Vs Kt/V5); Kt/V30 1.12 +/- 0.21 (pNS Vs Kt/V2). In conclusion, there was a large variability in the Kt/V depending on the method of collection of the blood urea nitrogen sample post-haemodialysis.

Objective: Cuffless wrist-based blood pressure (BP) monitors have a great potential to make ambulatory monitoring more appealing to patients and provide clinicians with better BP profiling. Investigators must be vigilant to validate these devices properly, as little guidance has been published. We propose a protocol that addresses ambulatory environment challenges, such as body posture changes and variable arm position. In addition to reporting the accuracy, we suggest reporting the number of successful automated measurements – the acceptance rate. Design and method: We tested the Aktiia Bracelet, a cuffless automated device that records optical signals at the wrist and requires an initial calibration, with the proposed protocol on 10 healthy volunteers. We simultaneously recorded the signals from the Aktiia Bracelet and a reference volume-clamp device positioned on the contralateral arm during the following interventions: sitting, lying supine, standing with both arms positioned at heart level; sitting with the Aktiia bracelet wrist positioned 30 cm lower than heart level; isometric leg extension inducing large BP changes. We calculated the mean and standard deviations of the error between Aktiia bracelet and the reference, as well as the acceptance rates in different measurement scenarios. Results: The figure illustrates the mean and standard deviation (STD) of the error between Aktiia bracelet and the reference, as well as the acceptance rate (Acc) for the diastolic BP (DBP). The dashed area illustrates the expected hydrostatic bias. The mean and the standard deviation of the error fell within ISO81060-2 limits. Aktiia bracelet readings were not affected by the hydrostatic bias intervention, even though one could expect an error of more than 20 mmHg. The maximum of the accepted measurements was achieved when patients were lying supine (67%) and sitting (52%). Thus, the user can expect a high density of measurements during night-time. However, when standing, the acceptance dropped (27%). Conclusions: This protocol provides more realistic testing of cuffless wrist-based BP monitors and suggests a way to improve the validation of this new family of devices.

The diagnosis and management of hypertension usually requires the estimation of blood pressure (BP) by means of an inflatable cuff. This procedure generates discomfort and limits patient compliance. Cuffless devices capture BP readings without performing any arterial occlusion. We believe that comfortable and cuffless BP monitoring devices can significantly aid in the fight against hypertension and support the expansion of ambulatory and remote patient monitoring programs, provided that these devices provide reliable BP readings. The purpose of this study was to compare the systolic (S) and diastolic (D) blood pressure (BP) estimations from a new optical device at the wrist (figure) against invasive measurements performed on patients scheduled for radial arterial catheterization. The first results from this study were recently published and demonstrated good agreement for the overall study population. Here we report expanded statistical analyses for different population subgroups such as gender, age, body mass index (BMI) and skin color. The study protocol consisted of the simultaneous recording of reflective photo-plethysmographic signals (PPG) from the optical device, and BP values recorded by a contralateral radial arterial catheter. The PPG signals were processed to generate estimates of SBP and DBP. Agreement of paired BP estimations was further calculated in terms of standard deviation (SD) of differences. The mean of differences were systematically zero because BP estimations from the optical device were calibrated for each patient. The table shows that, for the overall population, both SBP and DBP differences SDs were smaller than 8 mmHg (as already published). Furthermore, across different population groups, both genders, all BMIs and all skin colors also resulted in SDs smaller than 8 mmHg. Only patients whose age was above 65 years were associated with a higher SD. For the overall population and most subgroups the new optical technique appears to be capable of replacing more traditional methods of BP estimation. Only the SBP differences for the subgroup of older patients were larger. Additional studies are needed to confirm and expand these very encouraging results. Table 1. SD of measured BP differences Population N SD of SBP differences SD of DBP differences (mmHg) (mmHg) All 16 7.1 2.9 Gender Male 10 6.4 2.8 Female 6 8.0 3.1 Age (years) &lt;65 7 4.0 2.3 &gt;65 9 *9.3 3.4 BMI (kg/m2) &lt;26 10 7.9 2.9 &gt;26 6 5.7 2.8 Skin Color (Fitzpatrick) 2 13 7.7 3.0 3 3 4.5 2.6 *Only subgroup with a SD larger than 8mmHg. Figure 1. The investigational device Funding Acknowledgement Type of funding source: Private company. Main funding source(s): Aktiia SA