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.

Effects of thoracic or abdominal strapping on exercise performance.

In eleven young healthy subjects, vital capacity was reduced by 30% by thoracic or abdominal strapping and the effects of this on maximal work capacity, ventilation and circulation were examined. During exercise as well as at rest, tidal volume and stroke volume were reduced and respiratory frequency and heart rate were increased with both types of strapping. Cardiac output appeared to be decreased. Thoracic strapping was slightly but significantly more impeding than abdominal strapping: residual volume, tidal volume and maximal work capacity were smaller. In both instances, the decrease in maximal performance was apparently due to ventilatory as well as circulatory limitation.

Respiratory muscle dysfunction in systemic lupus erythematosus.

An assessment of pulmonary mechanics revealed weakness of inspiratory and expiratory muscles as cause of the restrictive ventilatory defect (vital capacity: 47 +/- 10 percent predicted) in seven (ages 33 to 62 years) out of 26 consecutive patients with systemic lupus erythematosus (SLE). Maximal inspiratory transdiaphragmatic pressures were reduced mainly due to the markedly increased (more positive) esophageal pressures. During maximal expiratory efforts, esophageal and gastric pressures were grossly decreased. These abnormalities probably may be considered part of a more generalized, yet subclinical muscle disorder due to the SLE with, however, predominant involvement of the respiratory muscles. The abnormalities were not related to the use of corticosteroids or generalized inanition. The static expiratory lung compliance was reduced in all patients (55 +/- 18 percent predicted), but normalized immediately following passive inflation of the lungs to transpulmonary pressures of more than 30 cm H2O in two of the three subjects tested. The volume restriction was not progressive over a period of 38.5 patient-years.