Disturbance of Pulmonary Diffusing Capacity in Mitral Stenosis

　For purposes of elucidating the pathophy—siology of mitral stenosis and determining the　indication of commissurotomy, remarks have　been made regarding the method of measuring—the disturbance of pulmonary diffusion and its　clinical significance.

　The alveolar-arterial oxygen pressure gradi—ent has hitherto been used as an index of the　disturbance of pulmonary diffusion.　Changes　in this gradient due to a mixture of the　membrane component, the venous admixture　component and hyperventilation were studied　in our cases.　Investigations into the A-a　gradient on the basis of the diffusing capacity　measured by an CO analyser disclosed that　the cases of disturbance of pulmonary diffu—sion due chiefly to the membrane component　by the D_LCO　(eases of the increased A-a gradi—ent)　were irreversible after commissurotomy,　while the cases of the high D_LCO due to the　venous admixture component or hyperventila—tion were reversible postoperatively.

　On electron microscopy of the alveolar　membrane, a marked hypertrophy was observ—ed in the basement membrane of the blood—air pathway in all the cases if the low D_LCO,　and this condition suggested the disturbance　of pulmonary diffusion.

　The pulmonary pressure, the pulmonary　capillary pressure, the pulmonary vascular re—sistance or the alveolar-arterial oxygen pres—sure gradient has hitherto been taken as an　index to the indication of an operation for　mitral stenosis.　From the standpoint of　pulmonary physiology, the pulmonary diffus—ing capacity and the basement membrane of　the alveolar membrane are of great signifi—cance in the prognosis of this disease after　commissurotomy.