TITLE: INCREASED CARBON MONOXIDE (CO) IN EXHALED AIR OF CRITICALLY ILL PATIENTS

AUTHORS: Marion Scharte, MD, A. Ginski, MD, H. Van Aken, MD, PhD, H. G. Bone, MD, U. R. Jahn, MD, J. Meyer, MD
AFFILIATION: Westfälische Wilhelms-Universität, Muenster, Germany.

INTRODUCTION: Heme oxygenase produces carbon monoxide (CO) during breakdown of heme molecules primarily in liver and spleen. CO is excreted by exhalation via the lungs. Recent data suggest that CO is also produced in the lungs. A number of inflammatory agents induce the expression of heme oxygenase, possibly leading to increased CO production. We investigated whether critical illness results in increased CO concentration in exhaled air.
METHODS: Exhaled CO concentrations were measured on a CO monitor in critically ill patients (n=30) and in healthy controls (n=6). Arterial and venous blood samples were drawn as part of the routine diagnostic procedure in critically ill patients.
RESULTS: Critically ill patients showed significantly higher CO concentrations in exhaled air compaired to healthy controls. There was no correlation between CO concentration in exhaled air and carboxyhemoglobin in arterial and central venous blood of critically ill patients. Carboxyhemoglobin in arterial blood was significantly higher compaired to carboxyhemoglobin in central venous blood (p<0.05). Data in the figure are shown as median, 25^th and 75^th (box), 10^th and and 90^th (whiskers), and 5^th and 95^th percentiles (dots).
CONCLUSION: The present data showed an elevation in CO concentration in exhaled air in critically ill patients. This suggests an induction of inducible heme oxygenase (HO-1). Increased concentration of CO in exhaled air might reflect the severity of illness. The difference in arterial and venous carboxyhemoglobin supports the hypothesis of pulmonary CO production.