In 5 anesthetized pigs the interdependence between an obstructed posterior basilar segment and its surrounding tissue was measured during spontaneous and positive pressure ventilation when the segment was both inferior and superior to the contralateral lung. These manipulations caused diaphragmatic excursions to differ when tidal volumes were similar. Diaphragmatic excursion was measured radiographically by the caudal movement of the catheter which obstructed the lung region. Tracheal pressure (Ptr), airway pressure in the obstructed segment (Pseg) and esophageal pressure in the upper half of the esophagus (Pes) were measured at end expiration and end inspiration. Interdependence was expressed in terms of an index K(= -Δ(Pseg-Pes)/Δ(Ptr-Pes)) where K = 0 in the absence of interdependence and increases when interdependence increases. The authors found that K varied directly with diaphragmatic excursion. The greatest K (1.17) and diaphragmatic motion (6.8 mm) occurred with the segment inferior during spontaneous ventilation. Both these values were least with positive pressure ventilation in both the inferior and superior lung regions and intermediate with spontaneous ventilation in the superior lung region. Because diaphragmatic motion was less with positive pressure breathing for the same tidal volume, ribcage motion must have been greater. These data suggest that for lung regions having large diaphragmatic surface areas, interdependence is greater the greater the diaphragmatic motion.
|Original language||English (US)|
|Number of pages||1|
|Journal||American Review of Respiratory Disease|
|Issue number||4 II|
|State||Published - Jan 1 1976|
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine