A reevaluation of the effect of transrespiratory pressure on the breathing pattern of intubated mice

• The effect of transrespiratory pressure on respiration is reevaluated.
• Pressure changes from thorax expansion are theoretically proportional to tidal volume.
• Effect of Ptr on respiration is not a simple function of the two-side pressure.
• Effect of Ptr on respiration is from the co-effects of the two-side pressure.

This study aimed to determine if the effect of transrespiratory pressure on respiration was due to alveolar pressure minus the body surface pressure or from the co-effects of two-sided pressure. After introducing air pressure into the trachea of intubated mice, the tidal volume (VT) showed no significant changes, but the respiratory frequency (f) and minute ventilation (VE) were significantly decreased. Positive body surface pressure significantly increased f and VE; however, VT was not significantly affected. Interestingly, f and VE at 2.5 cm H2O were higher than at 5 cm H2O. Simultaneous positive air pressure on both the alveoli and body surface demonstrated no significant effect on the VT but significantly decreased f and VE. This inhibitory effect consisted of the combined activities of the inhibitory effects of positive tracheal pressure and the activated effects of positive body surface pressure. Taken together, the effect of transrespiratory pressure on respiration was due to the co-effect of alveolar pressure and body surface pressure.