PULMONARY DIFFUSING CAPACITY IN MITRAL VALVE DISEASE

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Abstract
The results of tests of both ventilatory and diffusing capacities in 53 patients with mitral valve disease are presented and correlated with the size of the mitral orifice found at operation and with the pulmonary arterial pressure. The tests were also performed in 7 normal subjects as controls and in 11 patients with no cardiac disease but with severe pulmonary emphysema, to indicate how severely the DCo [diffusing capacity] could be reduced. The present study confirms that in early mitral disease with no rise in pulmonary arterial pressure and no demonstrable pulmonary congestion, ventilation is normal as is the DCO at rest and on exercise. With the onset of pulmonary hypertension and consequent reduction in pulmonary blood flow, the DCO fails to show the normal physiological increase with exercise. At a more advanced stage of the disease, when definitive pulmonary vascular changes are present, which may or may not be reversible, the DCO is also low at rest. In addition, the impaired ventilatory capacity reflects the loss of compliancy by the lungs.