The Journal of Thoracic and Cardiovascular Surgery, Vol 74, 396-402, Copyright © 1977 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Regional pulmonary function during experimental unilateral pneumothorax in the awake state
JF Moran, RH Jones and WG Wolfe
This study examines changes in regional pulmonary function during
unilateral pneumothorax, immediately after, and 2 hours following re-
expansion in awake dogs. Respiratory rate, tidal volume, physiologic dead
space, arterial blood gases, and pulmonary shunt fraction were determined
at each stage. Cardiac output (thermodilution), vascular pressures, and
regional ventilation and perfusion (133Xe scans) were also measured. Chest
roentgenogram confirmed the presence of UP. Respiratory rate increased 124
percent (p less than 0.01) during UP while alveolar ventilation remained
unchanged. Pulmonary shunt fraction rose 93 percent (p less than 0.01)
during UP, causing PaO2 to fall from 86 to 51 mm. Hg (p less than 0.01).
PaCO2, pH, and cardiac output were not altered by UP. UP caused a relative
underventilation of the collapsed lung (V/Q = 0.73 (p less than 0.01)) and
an overventilation of the contralateral lung (V/Q = 1.74) (p less than
0.01). Immediately after re-expansion of the collapsed lung, all the above
changes reverted to the control values. All variables remained unchanged 2
hours following complete re-expansion.