ABSTRACT

Introduction: The impact of the main pulmonary and extra-pulmonary variables affecting gas exchange was analyzed in the sixties in computer models of the lung. The objective was to analize similarly gas exchange but at 2,240 m of altitude (Mexico City) and compare it with that estimated for sea level. Methods: We utilized West pulmonary gas exchange model, originally programmed in Fortran language. Results:The pattern of response to changes in typical variables: cardiac output, alveolar ventilation, shunt, V’/Q’ heterogeneity, inspired fraction of oxygen, hemoglobin, estimated for Mexico City are in general parallel to those found for sea level. However is more accurate to utilize specific estimations for the altitude than to those described usually in texbooks assuming sea level. Conclusions: Gas exchange models allow to predict lung performance under controlled situations, but it is important to clarify than in vivo, additional adjustments occur, often several at the same time, circumstances not considered in the models, and therefore results have to be taken with reserve, searching always for empirical documentation.

KEYWORDS

Gas exchange, shunt, oxygenation index, altitude.

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