Effect of acute pulmonary hypertension on pressure/flow in the canine pulmonary vascular bed.
The relationship of pulmonary blood flow and vascular resistance to pulmonary artery pressure was examined in pentobarbital-anesthetized open-chest dogs. The pulmonary artery perfusion pressure was varied in the range 0-100 mm Hg. This was achieved by perfusion of the lobar artery supplying the left upper lobe of the lung from the subclavian artery. Perfusion pressure was varied by a clamp on the external shunt. The relationship was rectilinear in the lower pressure range, from zero flow at 5 mm Hg, to 45-55 mm Hg. Above this, curvilinearity developed, concave toward the pressure axis. Possible participation of the autonomic nervous system (ANS) in the P/F relationship was examined by treatment with the ganglionic blocking agent, hexamethonium. Although the drug was successful in lowering systemic arterial pressure, it had no effect on the pulmonary P/F relationship. Possibly, the sympathetic nervous system (SNS) tone to pulmonary vessels was low or absent in our preparation. Changes in compliance of the pulmonary arterial supply, resulting from changes in transmural pressure, may explain the results. A myogenic type of response is favored.
D000208:Acute Disease; D000818:Animals; D001340:Autonomic Nerve Block; D001794:Blood Pressure; D004285:Dogs; D006801:Humans; D006976:Hypertension, Pulmonary / Q000503:physiopathology*; D008297:Male; D011651:Pulmonary Artery / Q000503:physiopathology; D011652:Pulmonary Circulation; D014655:Vascular Resistance