[Ventilation and gas exchange in the lungs during physical exertion in patients following the correction of mitral stenosis].

During rehabilitation of 40 patients after correction of mitral stenosis, a study was made of ventilation and gas exchange in the lungs under spirometric bicycle ergometry according to the "standard protocol" until the maximal oxygen consumption (MOC) was attained. The patients were examined 20-30 days, 3 and 6 months after operation. In accordance with the magnitude of the MOC expressed in metabolic equivalents (MET), all the patients were divided into 3 functional classes which corresponded roughly to the NYHA classification. It was revealed that with the same magnitude of the MOC the patients of the worst functional class had a lower production of CO2, a greater volume of the dead space and a higher level of minute ventilation. It is supposed that the described respiratory abnormalities are connected with enhanced ventilation of the poorly perfused alveoli, apparently because of venous congestion in the pulmonary capillaries. The characteristics of gas exchange and ventilation in the lungs investigated under the conditions of the "standard protocol" of spirometric bicycle ergometry objectively mark pump function of the heart and respiratory potentialities of the cardiorespiratory system, which might be the basis for the functional classification of the patients after cardiosurgical interventions.