VALIDATION OF ESOPHAGEAL PRESSURE OCCLUSION TEST AFTER PARALYSIS

Measurements of respiratory mechanics are frequently made in ventilate d infants and children. Esophageal pressure measurements (P-es) using a balloon on a catheter have been used to partition the respiratory me chanics into lung and chest wall components. Appropriate positioning o f this balloon is crucial to obtain accurate estimates of pleural pres sure. Traditionally, in spontaneously breathing subjects the balloon p osition is assessed with an occlusion test. In ventilated subjects, it is not always possible to perform an occlusion test prior to paralysi s, and even if such a test is performed it may not be relevant under c onditions of positive pressure ventilation. We have assessed a positiv e pressure occlusion test that is suitable for paralyzed subjects. By occluding the airway opening and applying gentle pressure to the abdom en or rib cage, positive swings in pressure can be measured by both P- es and airway opening pressure (P-ao). We compared traditional occlusi on tests measured in 16 spontaneously breathing puppies to the positiv e pressure occlusion test performed after paralysis. In 2 pups we were unable to obtain a reasonable traditional occlusion test (> 15% diffe rence between P-es and P-ao) but we obtained 10 traditional occlusion tests in each of the remaining 14 pups (2.1-14 kg). In 11 of these ani mals Delta P-es was within 10% of Delta P-ao. This compared well to po sitive pressure occlusion test using abdominal pressure performed afte r paralysis, where Delta P-es was within 10% of Delta P-ao in 10 anima ls. In 9 of these pups occlusion tests were also performed by applying pressure on the rib cage, where Delta P-es was within 10% of Delta P- ao in 6 animals. These results suggest that it is possible to perform accurate occlusion tests in paralyzed subjects by abdominal or rib cag e compression with the airway occluded. (C) 1994 Wiley-Liss, Inc.