THE PULMONARY DIFFUSING CAPACITY AND VENTILATORY CAPACITY BEFORE AND AFTER MITRAL VALVOTOMY

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Abstract
Pre-and post-operative studies in 40 patients with mitral stenosis have been presented. All underwent mitral valvotomy, and pulmonary function has been correlated with the pressure in the pulmonary circulation and the size of the mitral orifice as determined at operation. In early cases and those with minimal obstruction of the mitral valve (as exemplified by the absence of significant pulmonary hypertension and a mitral orifice measuring 2.5 cm or more in its longest diameter) tests of both ventilation and diffusion capacities were virtually normal before valvotomy and were almost identical afterwards. In more severe obstruction, particularly in the presence of pulmonary hypertension, DLCO was impaired before operation, while ventilatory function was encroached upon. Reasons for these effects such as pulmonary congestion and narrowing of pulmonary capillary bed are put forward. While the majority had both objective and subjective improvement after operation, there was little change in either ventilation or diffusion. It is postulated that the principal reason is irreversible lung damage, not only from pulmonary endarteritis but due to thickening of the alveolar membrane. An additional factor is possibly pleural thickening, the consequence of thoracotomy.