Micropuncture measurement of lung microvascular pressure profile during hypoxia in cats.

Abstract

To determine the lung microvascular pressure profile during hypoxia, we micropunctured the subpleural microcirculation of isolated perfused cat lungs. Our procedures involved exsanguinating a cat, then cannulating its pulmonary artery, left atrium, and trachea. Using the cat's own blood, we perfused the lungs at pulmonary artery and left atrial pressures of 18 and 9 cm water, respectively, to obtain lung blood flow of 81 +/- 29 ml/(kg body weight x min), which we held constant throughout the experiment. We stabilized the lung surface with a vacuum ring and micropunctured 30- to 50-micrometers arterioles and venules to measure microvascular pressure by the servo-null method. During micropuncture, we held the lungs at constant inflation using airway pressure of 8 cm water. We varied the oxygen concentration of the inflation gas from 30% during baseline to 2% during hypoxia. We studied groups with high (more than 7.5) or normal pH. During normoxia, 27, 44, and 29% of the pressure drop occurred in the arterial, capillary and venous segments, respectively. During hypoxia, the increase in pulmonary vascular resistance, which was marked in both groups, was significantly greater in the normal pH group. All segmental pressure drops increased significantly during hypoxia. However, the predominant increase occurred in the arteries where segmental pressure drop increased by 148% and 210%, respectively, in the high and normal pH groups. We conclude that the major site of hypoxic vasoconstriction is in the pulmonary arteries.

Pathophysiology and Treatment of High-Altitude Pulmonary Vascular Disease

“…9 Ventilation of intact lungs with a hypoxic gaseous mixture (eg, fraction of inspired oxygen=0.10) leads to acute pulmonary vasoconstriction throughout the pulmonary vascular bed, including nonmuscular arterioles, capillaries, and veins, but is most pronounced in small pulmonary arterioles. [10][11][12][13] That said, HPV is not distributed evenly throughout the lung and lung perfusion is inhomogeneous during hypoxia.…”

Intrinsic Microbicidal Activity and Pulmonary Hypertension in Isolated Newborn Piglet Lungs

“…Because of the close agreement Drzcgs and che/nicals. The following drugs and chemicals were between Pdo and microvascular pressure determined by microused: DMTU (Aldrich Chemical Co., Milwaukee, WI) was dis-puncture (10) or by the isogravimetric technique (1 I), Pdo is solved in sterile isotonic saline on the day of each experiment. taken as an estimate of microvascular pressure.…”

Effects of Water Deprivation and Morphine Administration on Atrial Natriuretic Peptide mRNA Levels in Rat Auricles

“…On the other hand, it has been reported that exposure of animals to chronic or acute hypoxia increases plasma ANP concentration up to 2 10-fold (20,21) and that chronic hypoxia decreases the left atrial ANP mRNA level (13). Although the mechanism of hypoxia-induced release of ANP is unclear, pulmonary hypoxic vasoconstriction and change in the pulmonary circulation may be implied (22)(23)(24). From these findings, we consider that the morphine-induced increase in plasma ANP concentration is most likely re lated to respiratory depression and possibly a change in pulmonary circulation, and that in creased ANP release may secondarily enhance the ANP gene expression in the right auricle.…”