Effects of unilateral hypoxia and hypercapnia on pulmonary blood flow distribution in the dog.

BORST,HANSG.,JAMES L. WHTTTENBERGER,ERIKBERGLUNDANDMAURICE MCGREGOR. Effects of unilateral hypoxia and hypewapnia on pulmonary blood $0~ distribution in the dog. Am. J. Physiol. 191(3): 446-452. q57.-Effects of hypoxia and of hypercapnia on pulmonary blood flow distribution were examined in 19 dogs. The blood flow through each lung was continuously recorded; the test gas was administered to one lung, and the other lung was used as the control. Low oxygen gas mixtures were administered to one lung for periods of z-47 minutes. When constriction occurred, it began within onehalf minute after the gas administration was started and reached a plateau within S-20 minutes. Vasodilation was never observed. In most animals no vasomotor effect of hypoxia was found early in the experiment (less than 6 hr. after induction of anesthesia), but seven of the early nonreactors became positive later in the experiment. After 6-8 hours from induction of anesthesia, all animals tested showed a vasoconstrictor response to hypoxia. The administration to one lung of 5 or 10% carbon dioxide for 2-10 minutes was always accompanied by vasoconstriction in that lung. In dogs that showed unilateral pulmonary vasoconstriction during hypoxia, further vasoconstriction was produced by adding 5% carbon dioxide. Some of the contradictory results of other investigators may be explained by the refractory period observed in these experiments. I N 1946 von Euler and Liljestrand reported that respiratory hypoxia and hypercapnia produced an elevation of the pulmonary artery pressure in the cat (I). They suggested, as Beyne had (2), that this was due to a local vasoconstrictor response in the lung. Subsequent investigations on this subject have given conflicting results (see 3, 4). Both hypercapnia and hypoxia may produce reactions of the organism as a whole which Received for publication June 28, 1957. 1 Supported by grants from the Life Insurance Medical Research Fund, New York, N. Y., and the National Heart Institute, National Institutes of Health, Bethesda, Md. 2 Present address : Chirurgische UniversitaetsKlinik, Marburg/Lahn, Germany. 3 Present address : Renstromska S jukhuset , Giiteborg, Sweden. 4 Eli Lilly Research Fellow (South Africa). Present address: McGill University, Montreal, Quebec, Canada. could influence pulmonary vascular pressures and resistance, e.g., changes in cardiac output and left atria1 pressure. In testing for the presence of a local vasoconstrictor mechanism, it is therefore desirable to supply the stimulus to one lung only and use the other lung as a control. The necessity of using the Fick method, with either estimates of pulmonary venous oxygen content or attempts at blood sampling from the pulmonary veins, can be avoided by direct and continuous measurement of the blood flow to each lung. In the present study the problem has been reinvestigated, using the methods mentioned above. The results to be described indicate that another hitherto neglected factor has to be considered, namely the time interval between the onset of the experiment and the exposure to the test gas. 446 by 10.0.33.5 on Jne 9, 2017 http://ajple.physiology.org/ D ow nladed fom HYPOXIA AND HYPERCAPNIA ON PULMONARY BLOOD FLOW 447