The Nitrous Oxide Test

The diagnosis of a left-to-right shunt generally depends upon the demonstration of significant differences in oxygen content among the venae cavae, the chambers of the right heart, and the pulmonary artery. The inconclusive or misleading results sometimes obtained with this method have stimulated interest in improved technics. The wide arteriovenous difference that normally exists during the inhalation of nitrous oxide has been studied in the development of a more accurate diagnostic approach. The superiority of the nitrous oxide test over the oxygen method is demonstrated.