Residence at 3,800-m altitude for 5 mo in growing dogs enhances lung diffusing capacity for oxygen that persists at least 2.5 years

1 Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas; and 2 Department of Medicine, University of California, San Diego, La Jolla, California Submitted 3 September 2006 ; accepted in final form 15 November 2006 Mammals native to high altitude (HA) exhibit larger lung volumes than their lowland counterparts. To test the hypothesis that adaptation induced by HA residence during somatic maturation improves pulmonary gas exchange in adulthood, male foxhounds born at sea level (SL) were raised at HA (3,800 m) from 2.5 to 7.5 mo of age and then returned to SL prior to somatic maturity while their littermates were simultaneously raised at SL. Following return to SL, all animals were trained to run on a treadmill; gas exchange and hemodynamics were measured 2.5 years later at rest and during exercise while breathing 21% and 13% O 2 . The multiple inert gas elimination technique was employed to estimate ventilation-perfusion ( A / ) distributions and lung diffusing capacity for O 2 (D L O 2 ). There were no significant intergroup differences during exercise breathing 21% O 2 . During exercise breathing 13% O 2 , peak O 2 uptake and A / distributions were similar between groups but arterial pH, base excess, and O 2 saturation were higher while peak lactate concentration was lower in animals raised at HA than at SL. At a given exercise intensity, alveolar-arterial O 2 tension gradient (A-aD O 2 ) attributable to diffusion limitation was lower while D LO 2 was 12–25% higher in HA-raised animals. Mean systemic arterial blood pressure was also lower in HA-raised animals; mean pulmonary arterial pressures were similar. We conclude that 5 mo of HA residence during maturation enhances long-term gas exchange efficiency and D L O 2 without impacting A / inequality during hypoxic exercise at SL. hypoxia; ventilation-perfusion distribution; multiple inert gas elimination technique; oxygen diffusing capacity; exercise Address for reprint requests and other correspondence: R. L. Johnson, Jr., Dept. of Internal Medicine, Univ. of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9034