We have examined the effect of acute
hypoxemia and hypercarbia on bronchial blood flow (
Qbr) in 10 anesthetized, ventilated, open-chest dogs using a modification of the radioactive
microsphere technique. After surgery, dogs were divided into two groups of five. Group 1 was ventilated for 30 min with each of the following gas mixtures: 1) room air; 2) 15% O2-85% N2; 3) 10% O2-90% N2, and group 2 with 1) room air; 2) 5% CO2-30% O2-65% N2; 3) 10% CO2-30% O2-60% N2. Measurements of pulmonary arterial, left atrial and aortic pressures, cardiac output, and blood
gases were made before injection of 46Sc-, 153Gd-, and 103Ru-labeled
microspheres into the left atrium as a marker of
Qbr. After the final measurements, dogs were killed and the lungs removed and the parenchyma stripped off the large and small airways of the left lung. Knowing the radioactivity in the trachea, bronchi, parenchyma, and in the blood from the reference-flow sample and also the aortic and left atrial pressures, total and regional
Qbr, and bronchovascular resistance (BVR) were calculated. Results showed that acute
hypoxemia (10% O2) caused a significant (P less than 0.05) decrease in
Qbr and increase in BVR and acute hypercarbia (10% CO2) caused a significant (P less than 0.05) increase in
Qbr and decrease in BVR.