To the Editor.
—In the article on permissive hypercapnia in the September 28,1994, issue of The Journal,1 the first two equations are incorrect and make the third incorrect also. The correct equations are as follows:This equation tells the user that the exchange ratio (R) effects the result only when inert gas (1—FIO2) is present.This equation shows that the alveolar carbon dioxide partial pressure (PACO2) is independent of the barometric pressure (PB). I point these things out for the sake of accuracy of concept. However, this does not in any way materially change the conclusions reached in the article in question. The animal body is very tolerant of hypercapnia, and prevention of pulmonary barotrauma is indeed important. The subject procedure deserves further study.
Helmholz HF. Permissive Hypercapnia: Some Equations. JAMA. 1995;273(10):775. doi:10.1001/jama.1995.03520340029024