Development of beat-by-beat blood pressure monitoring device and nocturnal sec-surge detection algorithm.

The nocturnal blood pressure (BP) surge in seconds (sec-surge) is defined as a brief, acute transient BP elevation over several tens of seconds, triggered by obstructive sleep apnea (OSA) and sympathetic hyperactivity. Sec-surge imposes a significant strain on the cardiovascular system, potentially triggering cardiovascular events. Quantitative evaluation of sec-surge level could be valuable in assessing cardiovascular risks. To accurately measure the detailed sec-surge, including its shape as BP rises and falls, we developed a beat-by-beat (BbB) BP monitoring device using tonometry. In addition, we developed an automatic sec-surge detection algorithm to help identify sec-surge cases in the overnight BbB BP data. The device and algorithm successfully detected sec-surges in patients with OSA. Our results demonstrated that sec-surge was associated with left ventricular hypertrophy and arterial stiffness independently of nocturnal BP level or variability. Sec-surge would be worth monitoring for assessing cardiovascular risks, in addition to nocturnal BP level. Nocturnal blood pressure (BP) surge in seconds (sec-surge) places heavy load on the cardiovascular system and can trigger cardiovascular events. To identify sec-surges, we developed a beat-by-beat BP monitoring device and a sec-surge detection algorithm. Furthermore, sec-surge was more related to cardiovascular risks than conventional nocturnal BP parameters.

Nocturnal blood pressure surge in seconds is associated with arterial stiffness independently of conventional nocturnal blood pressure variability in suspected obstructive sleep apnea patients.

Nocturnal blood pressure (BP) surge in seconds (sec-surge), which is characterized as acute transient BP elevation over several tens of seconds is induced by obstructive sleep apnea (OSA) and OSA-related sympathetic hyperactivity. The authors assessed the relationship between sec-surge and arterial stiffness in 34 nocturnal hypertensive patients with suspected OSA (mean age 63.9 ± 12.6 years, 32.4% female). During the night, they had beat-by-beat (BbB) BP and cuff-oscillometric BP measurements, and brachial-ankle pulse wave velocity (baPWV) was assessed as an arterial stiffness index. Multiple linear regression analysis revealed that the upward duration (UD) of sec-surge was significantly associated with baPWV independently of nocturnal oscillometric systolic BP variability (ß = .365, p = .046). This study suggests that the UD of sec-surge, which can only be measured using a BbB BP monitoring device, may be worth monitoring in addition to nocturnal BP level.

Nocturnal blood pressure surge in seconds is a new determinant of left ventricular mass index.

Nocturnal blood pressure (BP) surge in seconds (sec-surge), which is characterized as acute transient BP elevation over several tens of seconds, could be a predictor of target organ damage. However, it is not clear that the severity of sec-surge is different between sec-surges induced by sleep apnea (SA) (apnea/hypopnea detected by polysomnography (PSG) or oxygen desaturation) and those induced by non-SA factors (rapid eye movement, micro arousal, etc.), and sec-surge variables associate with left ventricular hypertrophy (LVH) independently of conventional BP variables. The authors assessed these points with 41 patients (mean age 63.2±12.6 years, 29% female) who underwent full PSG, beat-by-beat (BbB) BP, and cuff-oscillometric BP measurement during the night. All patients were included for the analysis comparing sec-surge severity between inducing factors (SA and non-SA factors). There were no significant differences in the number of sec-surges/night between SA-related sec-surges and non-SA-related sec-surges (19.5±26.0 vs. 16.4±29.8 events/night). There were also no significant differences in the peak of sec-surges, defined as the maximum systolic BPs (SBPs) in each sec-surge, between SA-related sec-surges and non-SA-related sec-surges (148.2±18.5 vs. 149.3±19.2 mm Hg). Furthermore, as a result of multiple regression analysis (n = 18), the peak of sec-surge was significantly and strongly associated with the left ventricular mass index (standardized ß = 0.62, p = .02), compared with the mean nocturnal SBPs measured by oscillometric method (ß = -0.04, p = .87). This study suggests that peak of sec-surge could be a better predictor of LVH compared to parameters derived from regular nocturnal oscillometric SBP.

Stress-Induced Blood Pressure Elevation Self-Measured by a Wearable Watch-Type Device.

BACKGROUND: Psychological stress contributes to blood pressure (BP) variability, which is a significant and independent risk factor for cardiovascular events. We compared the effectiveness of a recently developed wearable watch-type BP monitoring (WBPM) device and an ambulatory BP monitoring (ABPM) device for detecting ambulatory stress-induced BP elevation in 50 outpatients with 1 or more cardiovascular risk factors. METHODS: The WBPM and ABPM were both worn on the subject's nondominant arm. ABPM was measured automatically at 30-minute intervals, and each ABPM measurement was followed by a self-measured WBPM measurement. We also collected self-reported information about situational conditions, including the emotional state of subjects at the time of each BP measurement. We analyzed 642 paired BP readings for which the self-reported emotional state in the corresponding diary entry was happy, calm, anxious, or tense. RESULTS: In a mixed-effect analysis, there were significant differences between the BP values measured during negative (anxious, tense) and positive (happy, calm) emotions in both the WBPM (systolic BP [SBP]: 9.3 ± 2.1 mm Hg, P < 0.001; diastolic BP [DBP]: 8.4 ± 1.4 mm Hg, P < 0.001) and ABPM (SBP: 10.7 ± 2.1 mm Hg, P < 0.001; DBP: 5.6 ± 1.4 mm Hg, P < 0.001). The absolute BP levels induced by emotional stress self-measured by the WBPM were similar to those automeasured by the ABPM (SBP, WBPM: 141.1 ± 2.7 mm Hg; ABPM: 140.3 ± 2.7 mm Hg; P = 0.724). The subject's location at the BP measurement was also significantly associated with BP elevation. CONCLUSIONS: The self-measurement by the WBPM could detect BP variability induced by multiple factors, including emotional stress, under ambulatory conditions as accurately as ABPM.

Validation of a wrist-type home nocturnal blood pressure monitor in the sitting and supine position according to the ANSI/AAMI/ISO81060-2:2013 guidelines: Omron HEM-9601T.

This study aimed to validate the accuracy of the Omron HEM-9601T, an automatic wrist-type device for self-blood pressure (BP) measurement with a timer function for automatic measurement of nocturnal BP, in the sitting position according to the American National Standards Institute/Association for the Advancement of Medical Instrumentation/International Organization for Standardization (ANSI/AAMI/ISO) 81060-2:2013 guidelines, and to assess its performance in the supine position by applying the same protocol as conducted in the sitting position. The mean differences between the reference BPs and HEM-9601T readings were 1.2 ± 6.9/1.1 ± 5.5 mmHg, 2.2 ± 6.5/1.8 ± 5.7 mmHg, 0.1 ± 6.6/1.5 ± 6.2 mmHg, and -0.8 ± 7.2/0.5 ± 6.4 mmHg for systolic BP/diastolic BP for criterion 1 in the sitting position, supine with sideways palm position, supine with upward palm position, and supine with downward palm position, respectively. In addition, the mean differences and their standard deviations for systolic BP and diastolic BP calculated according to criterion 2 in the ANSI/AAMI/ISO 81060-2:2013 guidelines were acceptable in all four positions. In conclusion, the Omron HEM-9601T fulfilled the validation criteria of the ANSI/AAMI/ISO81060-2:2013 guidelines when used in the sitting position with the wrist at heart level, and its accuracy in the supine position was acceptable and roughly equivalent to that in the sitting position. The wrist-type home BP monitor could be a more suitable tool for repeated nocturnal BP measurements at home than upper-arm devices, and could improve the reliability of diagnosis and management of nocturnal hypertension.

Automatic detection algorithm for establishing standard to identify "surge blood pressure".

Blood pressure (BP) variability is one of the important risk factors of cardiovascular disease (CVD). "Surge BP," which represents short-term BP variability, is defined as pathological exaggerated BP increase capable of triggering cardiovascular events. Surge BP is effectively evaluated by our new BP monitoring device. To the best of our knowledge, we are the first to develop an algorithm for the automatic detection of surge BP from continuous "beat-by-beat" (BbB) BP measurements. It enables clinicians to save significant time identifying surge BP in big data from their patients' continuous BbB BP measurements. A total of 94 subjects (74 males and 20 females) participated in our study to develop the surge BP detection algorithm, resulting in a total of 3272 surges collected from the study subjects. The surge BP detection algorithm is a simple classification model based on supervised learning which formulates shape of surge BP as detection rules. Surge BP identified with our algorithm was evaluated against surge BP manually labeled by experts with 5-fold cross validation. The recall and precision of the algorithm were 0.90 and 0.64, respectively. Processing time on each subject was 11.0 ± 4.7 s. Our algorithm is adequate for use in clinical practice and will be helpful in efforts to better understand this unique aspect of the onset of CVD. Graphical abstract Surge blood pressure (surge BP) which is defined as pathological short-term (several tens of seconds) exaggerated BP increase capable of triggering cardiovascular events. We have already developed a wearable continuous beat-by-beat (bBb) BP monitoring device and observed surge BPs successfully in obstructive sleep apnea patients. In this, we developed an algorithm for the automatic detection of surge BP from continuous BbB BP measurements to save significant time identifying surge BP among > 30,000 BbB BP measurements. Our result shows this algorithm can correctly detect surge BPs with a recall of over 0.9.

Validation of an automatic device for the self-measurement of blood pressure in sitting and supine positions according to the ANSI/AAMI/ISO81060-2: 2013 guidelines: the Omron HEM-9700T.

AIM: We evaluated the performance of the Omron HEM-9700T, an automatic upper-arm-type device for the self-measurement of blood pressure (BP), in the sitting and supine positions according to the ANSI/AAMI/ISO81060-2:2013 guidelines. PARTICIPANTS AND METHODS: We screened 106 participants for the validation study in both positions. After excluding 21 participants, a total of 85 participants [38 (44.7%) men; 47 (55.3%) women] with mean±SD age of 54.5±12.2 years (range: 21-78 years) were included. Their arm circumference was 27.5±1.4cm (range: 17.9-40.8cm). The arm circumference distribution met the ANSI/AAMI/ISO81060-2:2013 requirement. The participants' BP measurements alternated between the use of a conventional mercury sphygmomanometer and the automatic device according to the ANSI/AAMI/ISO81060-2:2013 guidelines to measure their BP. RESULTS: The mean differences between reference BPs and HEM-9700T readings in the sitting and supine positions were -0.6±6.4/1.3±5.5 and -1.0±6.2/1.9±5.4mmHg for systolic BP/diastolic BP, respectively. CONCLUSION: The Omron HEM-9700T fulfilled the validation criteria of the ANSI/AAMI/ISO81060-2:2013 guidelines for both the sitting and supine positions.

Validation of two watch-type wearable blood pressure monitors according to the ANSI/AAMI/ISO81060-2:2013 guidelines: Omron HEM-6410T-ZM and HEM-6410T-ZL.

There is growing evidence of the clinical significance of daytime masked hypertension (MHT) and blood pressure (BP) variability (BPV). Recently, watch-type wearable devices for self-BP measurement have become available. Such devices might be promising tools to identify patients with daytime MHT or large BPV in their real-life conditions. The present study aimed to validate the accuracy of the Omron HEM-6410T-ZM and the Omron HEM-6410T-ZL, which are automatic watch-type wearable devices for self-BP measurement, according to the American National Standards Institute, Inc/Association for the Advancement of Medical Instrumentation/International Organization for Standardization (ANSI/AAMI/ISO) 81060-2:2013 guideline. Watches were held with the wrist at heart level. The mean differences between reference BPs and HEM-6410T-ZM readings were -0.9 ± 7.6/-1.1 ± 6.1 mm Hg for systolic BP (SBP)/diastolic BP (DBP) for criterion 1, and -0.9 ± 6.8/-1.1 ± 5.5 mm Hg for SBP/DBP for criterion 2. The mean differences between reference BPs and HEM-6410T-ZL readings were 2.4 ± 7.3/0.7 ± 7.0 mm Hg for SBP/DBP for criterion 1, and 2.4 ± 6.5/0.7 ± 6.5 mm Hg for SBP/DBP for criterion 2. The Omron HEM-6410T-ZM and the Omron HEM-6410T-ZL both fulfilled both validation criteria 1 and 2 of the ANSI/AAMI/ISO 81060-2:2013 guidelines.

Validation of a wrist-type home nocturnal blood pressure monitor in the sitting and supine position according to the ANSI/AAMI/ISO81060-2:2013 guidelines: Omron HEM-9600T.

The purpose of the present study was to evaluate the performance of the Omron HEM-9600T, an automatic wrist-type device for self BP measurement, in the sitting position with the wrist at heart level and supine position according to the ANSI/AAMI/ISO81060-2:2013 guidelines. In the supine position, we evaluated the device under 3 different conditions: using the supine with sideways palm position, the supine with upwards palm position, and the supine with downwards palm position. After 106 subjects were screened and 21 subjects were excluded, the same 85 subjects (38 men [44.7%] and 47 women [55.3%]) were included in the analyses for each position. The average age of the subjects was 54.5 ± 12.2 years (mean ± SD). The mean wrist circumference was 17.0 ± 2.4 cm. The wrist size distribution fulfilled the requirements of the guidelines. The mean differences between reference BPs and HEM-9600T readings were 1.0 ± 6.7/1.4 ± 5.7 mm Hg, 6.6 ± 7.2/5.5 ± 6.0 mm Hg, 4.8 ± 7.2/4.9 ± 5.8 mm Hg, and 2.1 ± 7.2/2.8 ± 6.8 mm Hg for SBP/DBP in the sitting position, supine with sideways palm position, supine with upwards palm position, and supine with downwards palm position, respectively. In conclusion, the Omron HEM-9600T in the sitting position fulfilled the validation criteria of the ANSI/AAMI/ISO81060-2:2013 guidelines. On the other hand, the accuracies of HEM-9600T in the supine position differed depending on the positioning of the palm, with only the downwards palm-position measurement fulfilling both validation criteria of the ANSI/AAMI/ISO81060-2:2013 guidelines.

Associations Between Characteristics of Obstructive Sleep Apnea and Nocturnal Blood Pressure Surge.

Research suggests that oxygen desaturation and sleep stage during obstructive sleep apnea (OSA) are related to the magnitude of high blood pressure (BP) in a laboratory setting. However, in a clinical setting, these associations have not been well studied. We used a noninvasive oscillometric BP measurement device to investigate the association between oxygen-triggered BP levels at the end of each OSA episode and the characteristics of the preceding OSA episode. In 42 newly diagnosed OSA patients (average age, 63.5±12.5 years; average apnea-hypopnea index, 32.6±18.2 per hour), 258 BP measurements were obtained at the end of OSA episodes. Hypoxia-peak systolic BP (SBP), defined as the maximum oxygen-triggered SBP value, was significantly higher in rapid eye movement sleep (144.9±19.9 mm Hg) than in non-rapid eye movement stage 1 sleep (129.5±15.1 mm Hg; P<0.001) and non-rapid eye movement stage 2 sleep (129.4±14.7 mm Hg; P<0.001). In a multivariate-linear mixed model, the lowest oxygen saturation percentage during each OSA episode was associated with increased hypoxia-peak SBP (-0.501 mm Hg; P<0.001), nocturnal SBP surge (-0.395 mm Hg; P<0.001), defined as the difference between the hypoxia-peak SBP and the mean nocturnal SBP, and maximum value of SBP surge (-0.468 mm Hg; P<0.001), defined as the difference between the hypoxia-peak SBP and the minimum nocturnal SBP independent of sleep stage. These values were not associated with the duration of each OSA episode. The contribution of rapid eye movement sleep and severe oxygen desaturation to OSA-related BP elevation measured with a noninvasive oscillometric method was determined in a clinical setting.

Polysomnography-derived sleep parameters as a determinant of nocturnal blood pressure profile in patients with obstructive sleep apnea.

Obstructive sleep apnea causes blood pressure (BP) surges during sleep, which may lead to increased sleep-onset cardiovascular events. The authors recently developed an oxygen-triggered nocturnal BP monitoring system that initiates BP measurements when oxygen desaturation (SpO2 ) falls below a variable threshold. The association between nocturnal BP parameters obtained by nocturnal BP monitoring and simultaneously examined polysomnography-derived sleep parameters in 116 patients with obstructive sleep apnea (mean age 57.9 years, 85.3% men) was studied. In multivariable analysis with independent factors of age, body mass index, sex, and polysomnography-derived measures (apnea-hypopnea index, apnea index, arousal index, lowest SpO2 , and SpO2  < 90%), apnea-hypopnea index (ß = .26, P = .02) and lowest SpO2 (ß = -.34, P < .001) were independent determinants of hypoxia-peak systolic BP (SBP), defined as the maximum SBP value measured by nocturnal BP monitoring. Similarly, apnea-hypopnea index (ß = .21, P = .04) and lowest SpO2 (ß = -.49, P < .001) were independent determinants of nocturnal SBP surge, defined as the difference between the hypoxia-peak SBP and the average of the SBP values within 30 minutes before and after the hypoxia-peak SBP, measured by the fixed-interval function in the manner of conventional ambulatory BP monitoring. In conclusion, in polysomnography-derived parameters, lowest SpO2 , defined as the minimum SpO2 value during sleep, is the strongest independent determinant of hypoxia-peak SBP and nocturnal SBP surge measured by nocturnal BP monitoring. Our findings suggest that the severity of the decrease in SpO2 and the frequency of such decreases would be important indicators to identify high-risk patients who are likely to develop cardiovascular events specifically during sleep.

Novel Triggered Nocturnal Blood Pressure Monitoring for Sleep Apnea Syndrome: Distribution and Reproducibility of Hypoxia-Triggered Nocturnal Blood Pressure Measurements.

Obstructive sleep apnea (OSA) causes blood pressure (BP) surges during sleep, which may lead to increased sleep-onset cardiovascular events. The authors recently developed a triggered nocturnal BP monitoring system that initiates BP measurements when oxygen desaturation falls below a variable threshold. The distribution and reproducibility of hypoxia-triggered nocturnal BP parameters compared with those of fixed-interval nocturnal BP parameters for two consecutive nights in 147 OSA patients (mean age 59.4 years, 86.4% men) were evaluated. The mean and distribution (standard deviation [SD]) of the hypoxia-peak systolic BP (SBP) were significantly greater than that of the mean nocturnal SBP (mean±SD: 148.8±20.5 vs 123.4±14.2 mm Hg, P<.001). The repeatability coefficient (expressed as %MV) of hypoxia-peak SBP between night 1 and night 2 was comparable to that of mean nocturnal SBP (43% vs 32%). In conclusion, hypoxia-peak nocturnal BP was much higher than mean nocturnal BP, and it was as reproducible as mean nocturnal BP.

Recurrence of stroke caused by nocturnal hypoxia-induced blood pressure surge in a young adult male with severe obstructive sleep apnea syndrome.

Obstructive sleep apnea syndrome (OSAS) causes resistant hypertension and a hypopnea-related nocturnal blood pressure (BP) surge. This could lead to an increase of not only the nocturnal BP level but also nocturnal BP variability, both of which increase an individual's cardiovascular risk. We recently developed a trigger sleep BP monitoring method that initiates BP measurement when an individual's oxygen desaturation falls below a variable threshold, and we demonstrated that it can detect a BP surge during apnea episodes. We here report the case of a 36-year-old man with severe OSAS who experienced the recurrence of stroke due to nocturnal hypoxia and a nocturnal BP surge measured by this trigger sleep BP monitoring device. A nocturnal BP surge during sleep in OSAS patients could be a strong trigger of cardiovascular events.

Development of a Triggered Nocturnal Blood Pressure Monitoring which Detects Nighttime Blood Pressure Surges in Sleep Apnea Syndrome.

Obstructive sleep apnea (OSA) places an enormous pressure load on the cardiovascular system by inducing a temporary blood pressure (BP) surge during apnea episodes. This pressure load is regarded as a potential mechanism of development of cardiovascular diseases such as stroke. Therefore, accurate measurement of such BP surges would be valuable for the risk stratification of OSA patients. Recently we developed a new triggered nocturnal BP monitoring system (TNP) based on oxygen desaturation and have achieved success to detect BP surges with OSA. TNP would be a promising tool for assessment of cardiovascular risks in sleep apnea syndrome.

Effects of nighttime single-dose administration of vasodilating vs sympatholytic antihypertensive agents on sleep blood pressure in hypertensive patients with sleep apnea syndrome.

Obstructive sleep apneas syndrome (OSAS) is associated with nocturnal hypertension with higher sleep blood pressure (BP) and its variability, both of which increase cardiovascular risk. In this crossover design study, the effect of nighttime single-dose administration of vasodilating (nifedipine 40 mg) vs sympatholytic (carvedilol 20 mg) antihypertensive agents on sleep BP in 11 hypertensive OSAS patients was evaluated. The authors recently developed a trigger sleep BP monitor with an oxygen-triggered function that initiates BP measurement when oxygen desaturation falls. The BP-lowering effects of nifedipine on the mean (P<.05) and minimum sleep systolic BPs (SBPs) (P<.01) were stronger than those of carvedilol. Sleep SBP surge (difference between the hypoxia-peak SBP measured by oxygen-triggered function and SBPs within 30 minutes before and after the peak SBP) was only significantly reduced by carvedilol (P<.05). The nighttime dosing of both vasodilating and sympatholytic antihypertensive drugs is effective to reduce sleep BP but with different BP-lowering profiles.

Development and clinical application of a new technique for detecting 'sleep blood pressure surges' in sleep apnea patients based on a variable desaturation threshold.

Obstructive sleep apnea (OSA) places an enormous pressure load on the cardiovascular system by inducing a temporary blood pressure (BP) surge (sleep BP surge (SLBPS)), often resulting in target organ damage and cardiovascular events, such as left ventricular hypertrophy, sudden death, myocardial infarction and stroke. Accurate measurement of SLBPS would be valuable for the risk stratification of OSA patients. We developed a new oxygen-triggered BP monitoring system based on a variable SpO(2) threshold (VT algorithm) to selectively detect severe SLBPS, which are associated with morbidity, and evaluated its performance in comparison with a previous technique based on a fixed SpO(2) threshold (FT algorithm). In 23 OSA patients, the correlation between individual minimum SpO(2) values and SLBPS was not significant when the FT algorithm was used alone (r=0.400, P=0.058) but became significant (r=0.725, P<0.0001) when the VT algorithm was additionally used. In another 13 OSA patients, when the FT algorithm was eliminated from the FT+VT algorithm, the number of BP readings was drastically reduced (36±22.7 vs. 61±55.0 times, P=0.004) with a similar correlation between minimum SpO(2) and SLBPS. The correlation between the apnea hypopnea index and SLBPS was significant when measured with the present method, but not when assessed with ambulatory BP monitors (ABPM) simulation (r=0.519, P=0.001 vs. r=0.149, P=0.385). In conclusion, oxygen-triggered BP monitoring with a variable threshold is able to detect severe OSA-related BP surges more specifically and reduce the number of BP readings required during sleep compared with detection using a fixed threshold or the conventional ABPM method.