The effects of changes in pulmonary vascular pressure and flow on collateral flow resistance (Rcoll) were studied in anesthetized dogs prepared with a right heart bypass. A peripheral bronchus was obstructed and Rcoll measured by infusing air (V) and measuring the pressure distal to the point of obstruction (Ps) relative to alveolar pressure of the surrounding lung (Palv). When blood flow into the pulmonary artery was stopped (stop flow), pulmonary artery pressure (PPA) decreased from a control of 18.5 to 8.3, 7.0 and 5.0 mmHg at 3, 6, and 12 sec. Left atrial pressure decreased from a control of 6.1 to 2.5, 0.9, and 0.3 mmHg at 3, 6, and 12 sec. (Ps Palv)/V was not significantly different from control under stop flow conditions at 3 sec., but was 5.2 and 15.6% greater at 6 and 12 sec. Thus under stop flow conditions Rcoll progressively increased with time; however, the fall in pulmonary vascular pressures preceeded the change in Rcoll. Furthermore, Rcoll increased with stop flow with control PPA ranging from 9.8 to 37.0 mmHg and Ps ranging from 2.8 to 19.0 mmHg. This suggests that the state of distention of pulmonary vessels surrounding collateral ventilatory channels was not the primary determinant of the change in Rcoll. Other factors which might be responsible for this change include changes in PaCO2 and changes in the elastic properties of the lungs.
|Original language||English (US)|
|State||Published - Jan 1 1976|
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