Objective The objective of this study (NCT04027777) was to assess the accuracy and precision of the Aktiia Bracelet, a CE-marked noninvasive optical blood pressure (BP) monitor worn at the wrist, over a period of 1 month. Methods In this study, participants aged between 21 and 65 years were recruited. The clinical investigation extended the ISO81060-2:2013 standard to the specificities of cuffless devices. Each BP assessment consisted of the simultaneous recording of optical signals with Aktiia Bracelet and double-blinded auscultation by two trained observers in the standard sitting position. The algorithms of Aktiia Bracelet further processed the recorded optical signals to perform a signal quality check and to calculate uncalibrated estimates of systolic BP (SBP) and diastolic BP (DBP). These estimates were transformed into mmHg using a subject-dependent calibration parameter, which was calculated using the first two available reference measurements per subject. Results Eighty-six participants were included in the analysis. The mean and SD of the differences between Aktiia Bracelet estimates and the reference (ISO81060-2 criterion 1) were 0.46 ± 7.75 mmHg for SBP and 0.39 ± 6.86 mmHg for DBP. The SD of the averaged paired difference per subject (ISO81060-2 criterion 2) were 3.9 mmHg for SBP and 3.6 mmHg for DBP. Conclusion After initialization and during 1 month, the overall accuracy of Aktiia Bracelet satisfied validation criteria 1 and 2 of ISO81060-2 in the sitting position. The Aktiia Bracelet can be recommended for BP measurement in the adult population.
Objective: Cuffless Blood Pressure (BP) monitoring is an emerging new technology with the potential to improve patients’ experience while providing physicians with a more comprehensive set out of office blood pressure measurements. The Aktiia Bracelet is a non-invasive BP monitor intended to measure optical photo-plethysmographic signals on the wrist and to calculate Systolic (SBP) and Diastolic (DBP) values using a pulse wave analysis technique. The Aktiia Bracelet requires an initialization procedure to be performed once per month. The objective of this study (NCT04027777) was to validate the accuracy and precision of the Aktiia Bracelet in the sitting position and over a period of one month. Design and method: A representative cohort of male and female, hypotensive, normotensive and hypertensive participants, aged 21 to 65 years, presenting different skin pigmentations (Fitzpatrick scale from 1 to 5) and different hair follicle densities were included. Four visits were scheduled for each participant. After initialization, the optical signals measured from the Aktiia Bracelet were used to calculate SBP and DBP values and were compared to auscultatory measurements obtained simultaneously by two double-blinded trained observers. The clinical investigation (including data analysis) was conducted by adapting the methods of ISO81060-2 to the requirements of a multi-visit validation of a cuffless device. Results: Data from a total of 91 participants in sitting position were included in the current analysis. For SBP, a mean difference (± SD) of 0.46 ± 7.74 mmHg between reference and Aktiia Bracelet values was found (criterion 1), with measured standard deviation of the averaged differences per subject of 3.9 mmHg (criterion 2). For DBP, a mean difference (± SD) of 0.39 ± 6.86 mmHg between reference and Aktiia Bracelet values was found, with measured standard deviation of the averaged differences per subject of 3.6 mmHg. Bland-Altman plots for SBP and DBP are shown in the following figure. Conclusions: The Aktiia Bracelet fulfilled the requirements of criterion 1 and 2 of the adapted ISO81060-2 protocol. The use of the Aktiia Bracelet could facilitate widespread use of accurate, longitudinal and easy out-of-office blood pressure measurements.
The diagnosis of hypertension and the adjustment of antihypertensive drugs are evolving from isolated measurements performed at the physician offices to the full phenotyping of patients in real-life conditions. Indeed, the strongest predictor of cardiovascular risk comes from night measurements. The aim of this study was to demonstrate that a wearable device (the Aktiia Bracelet) can accurately estimate BP in the most common body positions of daily life and thus become a candidate solution for the BP phenotyping of patients. We recruited 91 patients with BP ranging from low to hypertensive levels and compared BP values from the Aktiia Bracelet against auscultatory reference values for 4 weeks according to an extended ISO 81060-2 protocol. After initializing on day one, the observed means and standard deviations of differences for systolic BP were of 0.46 ± 7.75 mmHg in the sitting position, − 2.44 ± 10.15 mmHg in the lying, − 3.02 ± 6.10 mmHg in the sitting with the device on the lap, and − 0.62 ± 12.51 mmHg in the standing position. Differences for diastolic BP readings were respectively of 0.39 ± 6.86 mmHg, − 1.93 ± 7.65 mmHg, − 4.22 ± 6.56 mmHg and − 4.85 ± 9.11 mmHg. This study demonstrates that a wearable device can accurately estimate BP in the most common body positions compared to auscultation, although precision varies across positions. While wearable persistent BP monitors have the potential to facilitate the identification of individual BP phenotypes at scale, their prognostic value for cardiovascular events and its association with target organ damage will need cross-sectional and longitudinal studies. Deploying this technology at a community level may be also useful to drive public health interventions against the epidemy of hypertension.
A precise maintenance of sodium and fluid balance is an essential step in the regulation of blood pressure and alterations of this balance may lead to the development of hypertension. In recent years, several new advances were made in our understanding of the interaction between sodium and blood pressure regulation. The first is the discovery made possible with by new technology, such as 23Na-MRI, that sodium can be stored non-osmotically in tissues including the skin and muscles particularly when subjects are on a high sodium diet or have a reduced renal capacity to excrete sodium. These observations prompted the refinement of the original model of regulation of sodium balance from a two-compartment model comprising the extracellular fluid within the intravascular and interstitial spaces to a three-compartment model that includes the intracellular space of some tissues, most prominently the skin. In this new model, the immune system plays a role, thereby supporting many previous studies indicating that the immune system is a crucial co-contributor to the maintenance of hypertension through pro-hypertensive effects in the kidney, vasculature, and brain. Lastly, there is now evidence that sodium can affect the gut microbiome, and induce pro-inflammatory and immune responses, which might contribute to the development of salt-sensitive hypertension.
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