The Multiple Inert Gas Elimination Technique (MIGET) by Susan R. Hopkins & Peter D. Wagner

Author:Susan R. Hopkins & Peter D. Wagner
Language: eng
Format: epub
Publisher: Springer US, Boston, MA

7.2.6.2 Exercise in Hypoxia/High Altitude

As previously mentioned, MIGET studies have shown that mismatch increases with increasing exercise intensity in normoxia [162] and is also further increased by exercise in hypoxia [101, 116, 401]. Thus, ventilation-perfusion inequality as a contributor to inefficient gas exchange is likely present in most individuals exercising at altitude. However, since the net effect of ventilation-perfusion inequality on the AaDO2 depends on the overall of lung units on the oxygen hemoglobin dissociation curve, although the extent of ventilation-perfusion inequality increases markedly, the effect on the AaDO2 decreases to an even greater extent. Thus, MIGET has shown that, in contrast to the resting data, mismatch plays a minor role in gas exchange inefficiency during hypoxic exercise. Conversely, as seen in Fig. 7.5, MIGET studies suggest that diffusion limitation becomes an increasingly larger contributor to the AaDO2 during exercise at altitude, despite an overall increase in [116, 183, 265]. The exception to this is at extreme simulated altitude [412], where Wagner and coworkers showed larger amount of inequality at rest and during exercise consistent with the development of pulmonary edema as discussed below.

Fig. 7.5The effect of maximal exercise at simulated altitude on the AaDO2 and the relative contributions to the AaDO2 from diffusion limitation and ventilation-perfusion mismatch. With increasing altitude the contribution of mismatch to the AaDO2 decreases and the AaDO2 decreases. However, diffusion limitation becomes more pronounced. Data from [412]

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