Transdiaphragmatic, esophageal and gastric pressures during maximal static inspiratory and expiratory efforts in young subjects: effects of maneuver and sex.

Esophageal (Pes), gastric (Pga) and transdiaphragmatic (Pdi) pressures were measured in 6 young healthy men and 6 women during maximal static inspiratory and expiratory efforts. Interindividual variations were large for all pressures, but the measurements were highly reproducible within each subject. During maximal inspiratory efforts without instruction as to the type of breathing, Pga was often around zero whereas during standardized maximal inspiratory efforts (i.e. with protruded abdomen), Pdi and Pga increased significantly and Pes tended to be less negative. Thus, maximal strength of the diaphragm is only measured during standardized efforts. During maximal expiratory efforts Pes and Pga tended to be larger during spontaneous than during standardized maneuvers (i.e. with retracted abdomen), and to increase with lung volume. The clinical information obtained from Pdi, Pes and Pga during maximal inspiratory and expiratory efforts is probably not more specific than that from transrespiratory pressures (i.e. measurements at the mouth), except for standardized inspiratory efforts which may allow differentiation of intercostal-accessory and diaphragm-abdominal dysfunction.