Ambulatory monitoring of respiration: inhibitory breathing in the natural environment.

Because previous work found that sustained inhibitory breathing (i.e., low frequency breathing without increased tidal volume) can occur in laboratory animals under conditions of behavioral stress, this study sought to determine whether a comparable respiratory pattern could be observed in ambulatory human subjects in their natural environments. Tidal volume, breathing frequency, and minute ventilation were monitored continuously during 24-hour sessions via inductive plethysmography and a portable microprocessor. Mean tidal volume and minute ventilation were significantly higher during the daytime than at night for all subjects. However, mean breathing frequency was not consistently higher during the daytime, because episodes of low frequency breathing offset episodes of high breathing frequency. Tidal volume during low frequency breathing was comparable to that observed during medium or high frequency breathing. Thus, low frequency breathing was indicative of low minute ventilation. The eliciting stimuli, physiological concomitants, and relevance to health of this energetically inefficient breathing pattern remain to be determined.