ARTERIOVENOUS CARBOXYHEMOGLOBIN DIFFERENCE SUGGESTS CARBON-MONOXIDE PRODUCTION BY HUMAN LUNGS

Carbon monoxide is hypothesized to be produced by the enzyme heme oxyg enase predominantly in liver and spleen, bound to hemoglobin, and excr eted by the lungs. Thus, venous carboxyhemoglobin is expected to be hi gher or equal to arterial carboxyhemoglobin. Unspecific inflammatory s timuli have been shown to induce heme oxygenase in lung tissue possibl y leading to pulmonary carbon monoxide production. Arterial and centra l venous carboxyhemoglobin levels were measured in critically ill pati ents on the third day of ICU stay (n = 59) as well as in otherwise hea lthy humans prior to orthopedic surgery (n = 29). Arterial and central venous carboxyhemoglobin were higher in ICU patients than in healthy humans, respectively. In both groups, arterial carboxyhemoglobin was s ignificantly higher than central venous carboxyhemoglobin. The arterio venous carboxyhemoglobin differences were similar in both groups. The data suggest (a) increased GO-generation in critical illness and (b) p ulmonary GO-production in healthy and critically ill humans. (C) 1998 Academic Press.