Gas exchanges and pulmonary vascular abnormalities at different stages of chronic liver disease

Background: It is unclear whether and to which extent respiratory function abnormalities may complicate the earliest stages of chronic liver disease (CLD). Aim of this study was to compare pulmonary capillary volumes and gas exchange efficiency of CLD patients with and without cirrhosis.

Methods: Sixty-seven participants (mean age 56.5 years; women 22.4%) were divided into three groups (matched by age, sex, smoking) according to the baseline CLD stage as follows: (a) healthy controls (Group A, n=20); (b) non-cirrhotic CLD patients (Group B; n=23); (c) cirrhotic CLD patients (Group C; n=24). All participants underwent clinical assessment, respiratory function tests, gas exchange estimation by the alveolar diffusion of carbon monoxide (TLCO) measurement and 6-min walking test. Groups were compared by chi-square and one-way anova tests.

Results: Chronic liver disease patients had significantly lower levels of TLCO (Group B=17.7 ml/min mmHg, and Group C=14.2 ml/min mmHg) compared with healthy controls (Group A=24.4 ml/min mmHg). Consistent results were obtained when analyses were performed using TLCO expressed as percentage of the predicted value. TLCO adjusted for the alveolar volume was lower in cirrhotic patients compared with both controls and non-cirrhotic CLD patients (P<0.001 and P=0.035 respectively). Group C participants presented blood gas parameters tending to a compensated chronic respiratory alkalosis status compared with the other groups.

Conclusions: Pulmonary microvascular and gas exchange modifications are present at early stages of CLD. Future studies should be focused at evaluating the pathophysiological mechanisms underlying this relationship.