Suggested predictive indices for high altitude pulmonary oedema

A study was conducted to evaluate the responses of chemoreceptors and pulmonary vascular bed to hypoxia, on two groups of soldiers exposed to similar altitudes, one group which did not suffer from high altitude (HA) maladies (Gp A) and the other when exposed to similar altitudes suffered from HA maladies (Gp B high altitude pulmonary edema--susceptible group (HAPE-S). Aim of this study was to find out whether these two tests could be used as a screening test for soldiers and sojourners proceeding to HA. Chemoreceptor responses were evaluated by hypoxic ventilatory response (HVR) test and the pulmonary vascular responses were studied by recording pulmonary artery pressure (PAP) changes under simulated hypoxia by breathing hypoxic gas mixtures (HGM) in both the groups. It was observed that HAPE-S subjects showed a reduced HVR response and an increase in PAP (systolic, diastolic, and mean). While Gp A subjects showed an increase in ventilation of 11.39 +/- 3.36 L, the same in Gp B subjects was 3.51 +/- 2.65 L. Thus, the comparison of increase in ventilation following HVR test between the two groups was highly significant. Under hypoxic gas mixture (HGM) breathing, systolic pressure of 28.2 +/- 6.9 and 52.6 +/- 11.0 mm Hg; diastolic pressure of 11.4 +/- 3.8 and 23.6 +/- 5.8 mm Hg and mean pressure of 17.6 +/- 4.3 and 35.0 +/- 7.4 mm Hg were recorded in pulmonary arteries in Gp A and Gp B subjects, respectively. Gp B subjects showed a highly significant increase in all the three pulmonary pressures under HGM breathing.