Background: Previous research has reported that inhibition of breathing can be observed in hypertensive patients at rest during the daytime, as well as in sleep at night. The present study hypothesized that the variability of breathing and end-tidal CO(2) (PetCO(2)) in seated women at rest is positively associated with their 24-h blood pressure level.
Methods: Breath-to-breath measures of breathing rate and tidal volume were recorded via inductive plethysmography in each of 54 women during two 20-min sessions of seated rest, and in 32 women during night time sleep. PetCO(2) was also recorded during these sessions via a respiratory gas monitor. Ambulatory blood pressure was recorded for 24 h between the two clinic sessions via oscillometry.
Results: Breath pauses >10 s were observed significantly more often in women in the upper than the lower tertile of 24-h systolic blood pressure. Breath-to-breath variability in breathing rate, tidal volume, and minute ventilation were greater in the higher blood pressure tertile women. Variability in PetCO(2) was also greater in high blood pressure tertile. These associations were independent of age, weight, and body surface area (BSA). Breathing variability was inversely correlated with heart rate variability (HRV).
Conclusion: Greater variability in breathing at rest that is independent of metabolic activity characterizes women with elevated blood pressure. The linear association of breathing variability with 24-h blood pressure level is consistent with the hypothesis that intermittent breathing inhibition may predispose to the development of some forms of hypertension.