To the Editor.
—Arterial blood gas study results, as indicated by Stein and Willis,1 are of limited value in the diagnosis of pulmonary embolism. This is not to say, however, that they may not be diagnostic under some circumstances. In two previously well patients with acute massive embolism, the initial Pco2 was in excess of 50 mm Hg, despite minute ventilation volumes of more than 20 L/min. Their massive dead-space ventilation, in the context of their clinical manifestation, admitted of no other explanation and made immediate specific therapy possible.The only reference in the literature to this (admittedly uncommon) situation that I have come across is in Clinical Application of Blood Gases by Shapiro et al.2I hope that the authors' comment may be of general interest.