Use of nitrous oxide to measure mammary blood flow in anesthetized lactating goats

¹ Laboratories of Physiology, Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania

The N₂O diffusion method has been adapted to measure blood flow in anesthetized lactating goats. The partition coefficient for N₂O between blood and mammary tissue was found to be 1.008 (se 0.008). N₂O concentrations, determined during gas inhalations in all four mammary veins simultaneously, were found to be the same provided the catheter was placed deeply in the subcutaneous abdominal vein. Thirty minutes was required for venous N₂O concentration to reach 0.15 vol % of arterial concentration, which was 97% of true equilibrium. Flow values obtained by the N₂O method differed from those obtained by the Shipley-Wilson rotameter method by 6%. The N₂O method yields results accurate to within 7% of the measured value and is satisfactory for measuring an average mammary blood flow for a 30-min period. Blood flow obtained from ten experiments averaged 32.8 ± 5.1 ml/min per 100 g tissue.

Key Words: circulation, mammary • nitrous oxide, mammary blood flow

Submitted on April 3, 1963