Elevated alveolar nitric oxide is linked to poor aerobic capacity and chronotropic incompetence in liver transplant candidates

Background & Aims. Increased nitric oxide is involved in abnormal hemodynamic parameters and respiratory function of cirrhotic patients. We aimed to quantify partitioning exhaled nitric oxide measurements in exhaled air in liver transplantation (LT) candidates and evaluate their relationships with chronotropic incompetence and aerobic capacity. Methods. We compared exhaled nitric oxide (NO) measurements, heart rate response and peak oxygen uptake during incremental exercise in liver transplantation candidates to those of controls. Results. As opposed to healthy control subjects, LT candidates displayed elevated alveolar NO, blunted chronotropic response and reduced V′O2 at maximal exercise. In LT candidates, median peak V′O2 was 18.7 ml kg−1 min−1 (interquartile range (IQR) 16.2; 21.8), corresponding to 65% (IQR 57; 72) of the predicted value. Compared with controls, LT candidates had increased levels of alveolar NO (median (IQR) 2.0 (1.2; 2.2) versus 3.1 (2.3; 4.5), p < 0.001). In controls, no relations were found between alveolar NO and V′O2 peak or heart rate reserve whereas in cirrhotic patients, negative correlations and negative slopes were found between alveolar NO and V′O2 peak and heart rate reserve decrease. Conclusions. Increasing alveolar NO could be a specific pathophysiological condition limiting aerobic capacity in LT candidates.