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.

New clinical validation method for automated sphygmomanometer: a proposal by Japan ISO-WG for sphygmomanometer standard.

INTRODUCTION: Owing to fast or stepwise cuff deflation, or measuring at places other than the upper arm, the clinical accuracy of most recent automated sphygmomanometers (auto-BPMs) cannot be validated by one-arm simultaneous comparison, which would be the only accurate validation method based on auscultation. Two main alternative methods are provided by current standards, that is, two-arm simultaneous comparison (method 1) and one-arm sequential comparison (method 2); however, the accuracy of these validation methods might not be sufficient to compensate for the suspicious accuracy in lateral blood pressure (BP) differences (LD) and/or BP variations (BPV) between the device and reference readings. Thus, the Japan ISO-WG for sphygmomanometer standards has been studying a new method that might improve validation accuracy (method 3). The purpose of this study is to determine the appropriateness of method 3 by comparing immunity to LD and BPV with those of the current validation methods (methods 1 and 2). METHOD: The validation accuracy of the above three methods was assessed in human participants [N=120, 45+/-15.3 years (mean+/-SD)]. An oscillometric automated monitor, Omron HEM-762, was used as the tested device. RESULTS: When compared with the others, methods 1 and 3 showed a smaller intra-individual standard deviation of device error (SD1), suggesting their higher reproducibility of validation. The SD1 by method 2 (P=0.004) significantly correlated with the participant's BP, supporting our hypothesis that the increased SD of device error by method 2 is at least partially caused by essential BPV. Method 3 showed a significantly (P=0.0044) smaller interparticipant SD of device error (SD2), suggesting its higher interparticipant consistency of validation. CONCLUSION: Among the methods of validation of the clinical accuracy of auto-BPMs, method 3, which showed the highest reproducibility and highest interparticipant consistency, can be proposed as being the most appropriate.

A new technique for detecting sleep apnea-related "midnight" surge of blood pressure.

Patients with obstructive sleep apnea syndrome (OSAS) have been reported to be at greater risk for cardiovascular events, and midnight surge of blood pressure (BP) may be a mechanism of sleep apnea-related cardiovascular risk. However, there has been no accurate noninvasive technique to detect intermittent BP surge at the time of each sleep apnea episode. We therefore developed an experimental system to detect apnea-related short-term BP surge based on BP measurement triggered by peripheral (finger-tip) oxygen desaturation (a desaturation-triggered BP monitoring system). In 16 patients with OSAS, this new system successfully detected BP surges at the time of the sleep apnea, and the BP values were found to be significantly higher than those detected using a conventional fixed interval BP monitoring system (systolic BP [SBP] difference: 13 +/- 5.8 mmHg, p = 0.039; diastolic BP [DBP] difference: 10 +/- 6.8 mmHg, p = 0.032). The maximum SBP time rate (velocity of BP surge) showed a strong positive correlation with the apnea-hypopnea index (r = 0.855, p < 0.0001). In conclusion, we developed a noninvasive oxygen desaturation-triggered BP monitoring system that can successfully detect sleep apnea-related BP surge. The midnight BP surge detected by this new method was significantly associated with the severity of OSAS.