Shingo Yamashita

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.

Comparison of the Omron RS6 wrist blood pressure monitor with the positioning sensor on or off with a standard mercury sphygmomanometer.

ObjectiveThe aim of the present study was to evaluate the measurement accuracy of Omron RS6 with positioning sensor on (PSON) in comparison with Omron RS6 with positioning sensor off (PSOFF). The Omron RS6 has passed the 2010 version of the European Society of Hypertension International Protocol previously. MethodsA total of 85 adult participants (39 male and 46 female) were recruited. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were sequentially measured using a standard mercury reference sphygmomanometer (ERKA 3000; two observers) and Omron RS6 with PSON or PSOFF. ResultsA total of 85 participants (39 men, 46 women) were included in this study, with a mean age of 53.5±16.4 years. SBP at entry was 133.0±19.9 mmHg and DBP was 81.3±11.8 mmHg. The two observers for SBP and DBP measurements were in good agreement, with agreements of −0.2±1.5 mmHg for SBP and −0.2±1.5 mmHg for DBP, respectively. The mean difference between PSON readings and readings from the standard device was –2.6±6.1 mmHg for SBP and −1.4±4.8 mmHg for DBP. The differences in PSOFF readings were −4.5±6.9 and −3.2±5.4 mm Hg, respectively (P<0.01; PSON vs. PSOFF). A higher proportion of patients had a small deviation (⩽5 mmHg) from the reference device when the positioning sensor was on (65 vs. 54% for SBP and 76 vs. 65% for DBP readings). Using the positioning sensor, the variation in wrist height compared with PSOFF decreased. ConclusionThe Omron RS6 position sensor is an important function for a wrist device that improves measurement accuracy by decreasing variations in wrist height.

Noninvasive simultaneous measurement of blood pressure and blood flow velocity for hemodynamic analysis

We describe a noninvasive and simultaneous measurement method of beat-by-beat blood pressure and blood flow velocity waveforms in the radial artery using tonometry and Doppler flowmetry. We conducted a subjective experiment in which hold-down pressure of tonometry was controlled for determining optimal hold-down pressure and the measurement accuracy under the optimal hold-down pressure was evaluated. As a result, blood pressure and blood flow velocity could be measured simultaneously without the influence of the hold-down pressure on the blood flow velocity. It was possible to analyze hemodynamic indicators, such as wave intensity and vascular impedance, with blood pressure and blood flow using the system. The proposed system for detecting unexpected fluctuations in blood pressure and the involved mechanisms may contribute to the treatment of cardiovascular diseases.We describe a noninvasive and simultaneous measurement method of beat-by-beat blood pressure and blood flow velocity waveforms in the radial artery using tonometry and Doppler flowmetry. We conducted a subjective experiment in which hold-down pressure of tonometry was controlled for determining optimal hold-down pressure and the measurement accuracy under the optimal hold-down pressure was evaluated. As a result, blood pressure and blood flow velocity could be measured simultaneously without the influence of the hold-down pressure on the blood flow velocity. It was possible to analyze hemodynamic indicators, such as wave intensity and vascular impedance, with blood pressure and blood flow using the system. The proposed system for detecting unexpected fluctuations in blood pressure and the involved mechanisms may contribute to the treatment of cardiovascular diseases.