A re-evaluation of effects of acute central congestion on pulmonary compliance in normal subjects

¹ Department of Physiology, Harvard School of Public Health, Department of Pediatrics, Harvard Medical School; and Children's Medical Center, Boston, Massachusetts

In a re-examination of the effects on lung compliance of acute central vascular engorgement produced in normal subjects by inflation of a ‘G suit’ it was found that the reduction in complicance, previously reported, during suit inflation was in part due to artifactual changes in esophageal pressure. When the esophageal balloon used for pressure recording was positioned higher on the esophagus than in the previous study, and when decreases in mid-position, which usually accompany the abdominal compression associated with suit inflation, were prevented, the complicance reductions in a small group of subjects were approximately one-half as great as those obtained with the balloon low in the esophagus and with the mid-position uncontrolled. Extrinsic pressures from distended mediastinal structures, greater in the distal esophagus, and greater at low lung volumes are thought to be responsible. Additional observations are presented which support this possibility. It is concluded that respiratory esophageal pressure change may not be a valid index of lung surface pressure change in the presence of central vascular congestion. Those measurements of pulmonary compliance during clinical and experimental central vascular engorgement which have used esophageal pressure must be accepted with this reservation.

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