Gender and breathing route modulate cardio-respiratory variability in humans

During spontaneous breathing, there is an intrinsic scaling of respiratory variability and a correlation between respiratory and heart rate variabilities. To identify the effect of breathing route on respiratory and heart rate variabilities, breath-to-breath interval (BBI) and heartbeat-to-heartbeat interval (RRI) were recorded from 12 female and 12 male adult subjects breathing through the nose or mouth. Temporal scaling within the BBI and RRI was quantified with detrended fluctuation analysis (DFA). We identified a significant gender-based breathing route interaction in the short-term scaling of BBI (p = 0.007), a decrease in the short-term scaling of RRI during nose breathing (p = 0.026), and a significant interdependence of short-term scaling of BBI and RRI in female subjects. We conclude that there is a gender-based differential effect of breathing route on the control of respiration and an increase in the random behavior of RRI associated with nasal breathing. These data also suggest the presence cardio-respiratory coupling of scaling behavior in female subjects.