Indexed on: 04 Feb '16Published on: 04 Feb '16Published in: American journal of respiratory and critical care medicine
Adults born and raised at high altitudes have larger lung volumes and greater pulmonary diffusion capacity compared with adults at low altitude; however, it remains unclear whether the air and tissue volumes have comparable increases, and whether there is a difference in airway size.To assess the effect of chronic hypoxia on lung growth using in vivo high resolution computed tomography measurements.Healthy adults born and raised at Moderate Altitude (2000 meters above sea level; n=19) and at Low Altitude (400 meters above sea level; n=23) underwent high resolution computed tomography. Differences in total lung, air, and tissue volume, mean lung density, as well as airway lumen and wall areas in anatomically matched airways were compared between groups.No significant differences for age, sex, weight or height were found between the two groups (p>0.05). In a multivariable regression model, altitude was a significant contributor for total lung volume (p=0.02), air volume (p=0.03) and tissue volume (p=0.03), whereby the volumes were greater for the Moderate vs. Low Altitude group. However, altitude was not a significant contributor for mean lung density (p=0.35), or lumen and wall areas in anatomically matched segmental, subsegmental and subsubsegmental airways.Our findings suggest that the adult lung did not increase lung volume later in life by expansion of an existing number of alveoli, but rather from increased alveolarization early in life. In addition, chronic hypoxia accentuates dysanaptic lung growth by increasing the lung parenchyma, but not the airways.