Changes of oscillatory resistance and reactance at high altitude and during a simulated ascent in hypobaric chamber

High altitude (HA) exposure can change airway and lung mechanical properties: the decreased air density is expected to reduce airway resistance, whereas extra vascular lung fluid accumulation should change the elastic properties. Aim: to measure airway resistance (Ros) and reactance (Xrs) by means of oscillometric technique during both simulated ascent (S) in the hypobaric chamber of Italian Air Force (90 minutes exposure) and the trekking to the Pyramid Lab in Nepal (HA) (7 days exposure). Methods: 6 subjects (4M, 2F; age 32-64 yr.) performed oscillometric technique (Quark i2M, Cosmed, Italy) at sea level (SL), 3500m, 5050m in both conditions. Values at 5Hz, which are expected to better define the presence of peripheral obstruction, are reported in the table. The values at SL did not differ significantly. During S, Ros significantly decreased while Xrs did not show any significant changes. At HA: Ros showed a significant decrement at 3500m while at 5050m the value increased again; Xrs significantly decreased at both 3500m and 5050m. The lack of a decrease of Ros at 5050m HA and the decrease of Xrs already at 3500m HA are suggestive of peripheral airways obstruction and changes in elastic properties of the lung probably due to intersititial lung edema induced by the prolonged exposure HA hypoxia. The oscillometric technique seems to be an accurate tool to identify changes in the respiratory system at HA.