Exhaled nitric oxide as a marker of lung injury in coronary artery bypass surgery

Background. Exhaled nitric oxide (NO) concentrations have been suggested as a marker of disease onset and severity in a number of inflammatory conditions such as acute asthma. Known markers of the onset of acute lung injury require invasive tests and laboratory based analysis and have limited clinical applicability. We performed a study of the use of exhaled NO as a marker of developing acute lung injury during and after coronary artery bypass grafting in patients requiring cardiopulmonary bypass.

Methods. Mixed expired air samples were taken from the patient breathing system and analysed for exhaled NO using chemiluminescence analysis.

Results. Exhaled nitric oxide concentrations in expired gas correlated with the Pa-O2/Fi(O2) ratio (r=0.23, P<0.01). There was a non-significant trend towards a reduction in exhaled NO levels from after induction of anaesthesia to post-bypass time points, with the lowest exhaled NO concentrations occurring at this time (P=0.07). There was no correlation between mean arterial pressure (r=-0.1, P=0.54) or mean pulmonary artery pressure (r=-0.1, P=0.67) and expired NO levels.

Conclusions. Further work is required to test whether exhaled NO concentration may be useful in diagnosing the onset of acute lung injury in patients undergoing coronary artery bypass grafting.