Regional diaphragm volume displacement is heterogeneous in dogs.

Muscle shortening and volume displacement (VD) are critical determinants of the pressure-generating capacity of the diaphragm. The present study was designed to test the hypothesis that diaphragm VD is heterogeneous and that distribution of VD is dependent on regional muscle shortening, posture, and the level of muscle activation. Radioopaque markers were sutured along muscle bundles of the peritoneal surface of the crural, dorsal costal, midcostal, and ventral costal regions of the left hemidiaphragm in four dogs.

Diaphragm muscle shortening modulates kinematics of lower rib cage in dogs.

We tested the hypothesis that diaphragm muscle shortening modulates volume displacement and kinematics of the lower rib cage in dogs and that posture and mode of ventilation affect such modulation. Radiopaque markers were surgically attached to the lower three ribs of the rib cage and to the midcostal region of the diaphragm in six dogs of ∼8 kg body masses, and the locations of these markers were determined by a biplane fluoroscopy system. Three-dimensional software modeling techniques were used to compute volume displacement and surface area of the midcostal diaphragm and the lower three ribs during quiet spontaneous breathing, mechanical ventilation, and bilateral phrenic nerve stimulation at different lung volumes spanning the vital capacity.