Distribution of Inspired Gas and Pulmonary Diffusing Capacity at Rest and During Graded Exercise in Patients with Mitral Stenosis

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Abstract
In 12 patients with tight mitral stenosis and in 10 normal subjects the pulmonary diffusing capacity (steady state method) and the distribution of inspired gas (lung clearance index) were studied in sitting position both at rest and during graded exercise. There were no differences between the both groups in the pulmonary diffusing capacity related to oxygen consumption and the 2 groups did not differ in the distribution of inspired gas. The functional residual capacity and the lung clearance index did not change from rest to exercise. The pulmonary diffusing capacity is positively related to the work load, tidal volume and oxygen pulse in both groups of subjects. Patients with mitral stenosis show higher values of ventilation equivalent (VE/Vo2) and higher respiratory frequency. In another session the patients were subjected to right heart catheterization in supine position. In spite of the fact that during exercise the pressures in pulmonary capillaries exceeded the values of oncotic pressure, the patients did not develope clinical signs of pulmonary edema and the PaO2 remained within normal limits. It may be concluded that the pulmonary capillary hypertension in patients with mitral stenosis of short duration of symptoms does not necessarily lead to the impairment of pulmonary gas exchange and does not result in ventilation/perfusion disturbances.

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