Development and clinical application of a new technique for detecting 'sleep blood pressure surges' in sleep apnea...

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.