Novel method for transdiaphragmatic pressure measurements in mice

The diaphragm muscle (DIAm) is responsible for breathing and determines the ability to generate both ventilatory and non-ventilatory behaviors. Size limitations of the mouse make transdiaphragmatic pressure (Pdi) measurement using a dual balloon system untenable. Adult C57BL/6J mice (n=8) and C57BL/6×129 (n=9), underwent Pdi measurements using solid-state pressure catheters spanning the thoracic and abdominal surfaces of the DIAm. Measurements were conducted during eupnea, hypoxia (10% O₂)-hypercapnia (5% CO₂), chemical airway stimulation (i.e., sneezing), spontaneously occurring deep breaths, sustained tracheal occlusion, and bilateral phrenic nerve stimulation. There was a difference in the Pdi generated across the range of ventilatory and non-ventilatory behaviors (p=0.001). No difference in Pdi across behaviors was evident between mouse strains (p=0.161). This study establishes a novel method to determine Pdi across a range of DIAm behaviors in mice that may be useful in evaluating conditions associated with reduced ability to perform expulsive, non-ventilatory behaviors.