Journal of Applied Physiology, Vol 56, Issue 5 1289-1293, Copyright © 1984 by American Physiological Society
Positive end-expiratory pressure decreases bronchial blood flow in the dog
E. M. Baile, R. K. Albert, W. Kirk, S. Lakshaminarayan, B. J. Wiggs and P. D. Pare
Positive end-expiratory pressure (PEEP) increases pulmonary vascular
resistance, but its effect on the bronchial circulation is unknown. We have
compared two techniques for measuring bronchial blood flow in anesthetized,
open-chest, ventilated dogs at varying levels of PEEP. Bronchial blood flow
( Qbr ) to the left lower lobe (LLL) and trachea was measured with
radiolabeled microspheres. Total Qbr was partitioned into tracheal,
bronchial, and parenchymal fractions. We also measured the bronchopulmonary
anastomotic flow ( Qbra ) by attaching cannulas from the lobar pulmonary
artery and vein to reservoirs, interrupting the LLL pulmonary blood flow
and collecting the flow going into the reservoirs. We measured Qbr and Qbra
in 10 animals ventilated with varying levels of PEEP (3, 10, and 15 cmH2O)
applied randomly. Pulmonary venous pressure was kept at 0 cmH2O. There was
no difference observed between Qbr and Qbra at PEEP 3 and 10 cmH2O, but at
PEEP 15 cmH2O, Qbr was greater than Qbra , suggesting that at low left
atrial pressures bronchial blood flow drains mainly to the left atrium,
whereas at elevated alveolar pressures a larger fraction empties into the
right side of the heart. PEEP decreased LLL Qbr and Qbra (P less than
0.01). That fraction of Qbr going to the trachea did not change with PEEP.
However, the bronchial and parenchymal fractions decreased.
