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Transdiaphragmatic pressure measurements reveal age‐related diaphragm muscle dysfunction during non‐ventilatory behaviors

The diaphragm muscle (DIAm) is responsible for breathing and must provide sufficient force to accomplish both ventilatory and non‐ventilatory behaviors. Age‐related changes to the DIAm, especially sarcopenia, may limit the ability to accomplish expulsive, non‐ventilatory behaviors essential for airway clearance, and thus contribute to respiratory complications. Age‐related changes in load (as a result of chest wall stiffening or lung compliance) may impact DIAm function. Adult male mice (6 and 24 months old) underwent measurements of respiratory system compliance and transdiaphragmatic pressure (Pdi) during: eupnea, hypoxia (10% O2) –hypercapnia (5% CO2), spontaneously occurring deep breaths, airway occlusion, and bilateral phrenic nerve stimulation. Overall respiratory system compliance decreased with age (increased load), while Pdi required for ventilatory behaviors did not change, consistent with the reserve capacity of the DIAm. The Pdi generated during deep breaths and airway occlusion were reduced 30–45% with age. These results indicate that DIAm dysfunction during aging is associated with reduced force to perform expulsive, non‐ventilatory behaviors. Reduced reserve capacity in old age may underlie increased susceptibility to lung infections and augment respiratory compromise associated with other age‐related diseases. Supported by T32‐HL‐105355 and the Mayo Clinic.