Reduced baroreceptor reflex sensitivity and increased blood pressure variability at 2400 m simulated cabin altitude.

In a hypobaric chamber nine healthy volunteers were exposed to an atmospheric pressure corresponding to 2400 m above sea level. This is similar to the lowest air pressure encountered inside pressurized commercial airplanes. Heart rate and blood pressure were monitored beat-to-beat in the supine position with a non-invasive device. Blood pressure variability and heart rate variability were measured in the mid-frequency band; subsequently, baroreceptor reflex sensitivity (BRS) was calculated with the transfer-function method. Compared with baseline, there were reduced BRS and increased blood pressure variability at 2400 m (16.5 +/- 3.1 vs. 13.2 +/- 2.0 ms x mm Hg(-1) and 5.4 +/- 1.3 vs. 8.2 +/- 1.1 mm Hg, respectively; p < 0.05). We conclude that autonomic cardiovascular control was disturbed during acute exposure to an air pressure corresponding to 2400 m.