Studies on the Cardio-pulmonary Function in Tuberculosis (3) Studies on the Disturbance of the Alveolar Gas Exchange in Patients with Pulmonary Tuberculosis

Abstract

Krogh and Roughton have estimated the pulmonary diffusing capacity using the carbonmonooxide technique. Recently Rilely et al designed a new procedure to estimate both pulmonary diffusing capacity and venous admixture. Mc Clement et al, Anderson et al have reported, using Riley's method, studies on various pulmonary diseases including tuberculosis.Estimation of both pulmonary diffusing capacity and venous admixture of patients with pulmonary tuberculosis, with the method of Riley et al, was made by the author in an attempt to answer their significance relating to the pulmonaty circulatory and ventilatory functions.Materials and Method : 15 patients with pulmonary tuberculosis, three being minimal, seven moderately advanced, three far advanced and two pneumonectomized cases, were studied by the right heart catheterization technique in ambient air breathing 12 to 15 percent oxygen gas mixture. Expired gas, arterial blood, and mixed venous blood were taken from the patients in both ambient air and low oxygen breathing. Blood gas tension was measured by the method of Riley et al, using the Roughton-Scholander's syringe. pH of the blood was determined by the method of Singer-Hastings. Alveolar gas tension was calculated from the alveolar equation ; effective alveolar carbon-dioxide tension being assumed to be equal to carbon-dioxide tension of the arterial blood. Respiratory dead space was calculated by the Bohr's equation.Results Three minimal, four moderately advanced, and one pneumonectomized cases showed the normal diffusing capacity, but other cases, depressed diffusing capacity. The diffusing capacity, in average, of the minimal cases fell into a normal range, and that of the moderately advanced cases was at the lower level of a normal range, and that of the far advanced was surely under this range. Venous admixture was normal in two minimal and one pneumonectomized cases but was increased in the order cases. The venous admixture in average was increased in the other of the minimal, moderately advanced, and far advanced cases. Among two pneumonectomized cases, one showed normal venous admixture and depressed diffusing capacity, and the other increased venous admixture and normal diffusing capacity. Respiratory dead space was found to be over normal in one minimal, two moderately advanced, and three far advenced cases. It was apparently increased, in average, in far advanced cases. The respiratory dead apace ratio was negatively related to the carbon-dioxide tension of the arterial blood.Alveolar-arterial oxygen tension gradient (A-a gradient) was within normal limit in one minimal case; but was over normal in all other cases. Its average values were increased in the order of the minimal, moderately advanced, and far advanced cases.So far as the high level of oxygenation of the arterial blood was concerned, the A-a gradient was much closely related to the venous admixture and that in the low level of oxygenation was related to the diffusing capacity. When the A-a gradient was divided into the diffusion gradient and the venous admixture gradient, in the high level of oxygenation a very intimate correlation between venous admixture gradient was demonstrated, and in the low level of oxygenation, a similar correlation between diffusing capacity and diffusion gradient was found.No significant correlation was noted among diffusing capacity, venous admixture and respiratory dead space, or between diffusing capacity and oxygen removal. On the contrary, a positive correlation between vital capacity, percent of predicated, and a negative correlation between vital capacity, percent of predicted, and respiratory dead space were found.No correlation between vital capacity, percent of predicted, and venous admixture was found.Discussion and Summary In fifteen patients with pulmonary tuberculosis, disturbance of the pulmonary alveolar gas exchange was studied by the method of Riley et al. The diffusing capacity in average was decreased in th