[The thymothoracic index and its usefulness in the diagnosis of newborn infants with respiratory distress syndrome].

In order to evaluate the use of the thymothoracic index (TTI) in the diagnosis of the respiratory distress syndrome (RDS), 51 newborn infants were studied and divided into two groups: group A included 30 patients with RDS and group B, 21 infants with lung pathology other than RDS. The diagnosis in both groups was based on clinical, radiological and anatomopathological grounds. The TTI is obtained by dividing the diameter of the cardiothymic shadow at the carina level between the chest diameter at the costophrenic angles, using a simple chest radiography. In both groups, the height, weight and gestational age were similar; the only difference was the time when the X-Ray was taken; in group A the average time was 11.5 hours after birth and group B, 17.1 hours. The TTI was greater in group A (0.44 +/- 0.09) than in group B (0.30 +/- 0.08) with a significant difference. In conclusion the TTI is a simple and practical method that can be useful in the diagnosis of RDS.