Individual Susceptibility to High Altitude and Immersion Pulmonary Edema and Pulmonary Lymphatics

Background: High-altitude pulmonary edema (HAPE) and immersion pulmonary edema (IPE) are potentially life-threatening conditions that affect athletes, including high-altitude climbers, long-distance swimmers, and underwater divers. The objectives of this study were to measure lung density (before and after exercise) and quantify the pulmonary lymphatic network in individuals susceptible and resistant to HAPE/IPE. Methods: Eighteen male (N = 10) and female (N = 8) subjects were recruited. Based on medical histories, nine subjects were susceptible to HAPE/IPE, and nine were resistant. Subjects were matched for gender, age, height, weight, and cold-water diving or high-altitude trekking experiences. Lung mass and density (at three slice locations) were determined using computed tomography at rest and after intense exercise. Lung mass and density were calculated from X-ray attenuation values. Two blinded investigators counted interlobular septal lines according to criteria established by the research group. Results: At rest, susceptible subjects had a lower lung density [Susceptible: 0.192 (0.035 SD) g center dot ml(-1); Resistant: 0.22 (0.029 SD) g center dot ml(-1))], a significantly lower lung mass [Susceptible: 132.1 (24.16 SD) g; Resistant: 156.1 (19.19 SD) g], and significantly fewer interlobular septa [Susceptible: 17 (4.5 SD); Resistant: 23 (7.1 SD)] compared to resistant subjects. The differences in density and mass were not affected by intense exercise. Discussion: Subjects susceptible to HAPE/IPE had lower lung density, significantly lower lung mass, and fewer interlobular septa than subjects resistant to HAPE/IPE, suggesting a smaller pulmonary lymphatic network. The observed differences in lymphatics could represent either predisposing factors to, or sequelae of, these potentially lethal conditions.