Hempleman S C, Powell F L
Respir Physiol. 1986 Mar;63(3):285-92. doi: 10.1016/0034-5687(86)90096-4.
O2 diffusing capacity (DO2) was measured in anesthetized, unidirectionally ventilated ducks during hypercapnic hypoxia. DO2 averaged 78.2 mumol X (min X Torr)-1. This value increased to 97.3 mumol X (min X Torr)-1 after correction for ventilation-perfusion inequality. DO2 increased when pulmonary O2 exchange (MO2) and pulmonary blood flow (Q) were increased by either 2,4 dinitrophenol (DNP,ca. 5 mg/kg i.v.) or temporary unilateral pulmonary artery occlusion (TUPAO). DO2 increased with MO2 42.4 mumol X (mmol X Torr)-1 (R = 0.664), and with Q 80.3 mumol X (L X Torr)-1 (R = 0.895). Since there is evidence against expansion of membrane diffusing capacity through recruitment and distention of pulmonary capillaries in avian lungs, we suggest that the close coupling of DO2 to Q reflects a reduction of functional lung heterogeneity at higher blood flows, perhaps due to better matching of V to D, or D to Q.
