Gas exchanges and pulmonary vascular abnormalities at di¡erent stages of chronic liver disease

AbstractBackground: It is unclear whether and to which extent respiratory functionabnormalities may complicate the earliest stages of chronic liver disease(CLD). Aim of this study was to compare pulmonary capillary volumes andgas exchange efficiency of CLD patients with and without cirrhosis.Methods: Sixty-seven participants (mean age 56.5 years; women 22.4%) weredivided into three groups (matched by age, sex, smoking) according to thebaseline CLDstage asfollows:(a)healthycontrols(GroupA, n=20);(b) non-cirrhotic CLD patients (Group B; n=23); (c) cirrhotic CLD patients (GroupC;n=24).Allparticipantsunderwentclinicalassessment,respiratoryfunctiontests, gas exchange estimation by the alveolar diffusion of carbon monoxide(TLCO) measurement and 6-minwalking test. Groups werecompared bychi-square and one-way ANOVA tests. Results: Chronic liver disease patients hadsignificantly lowerlevelsofTLCO(GroupB=17.7ml/minmmHg,andGroupC=14.2ml/minmmHg) compared with healthy controls (Group A=24.4ml/minmmHg). Consistent results were obtained when analyses were performedusingTLCOexpressedaspercentageofthepredictedvalue.TLCOadjustedforthe alveolar volume was lower in cirrhotic patients compared with bothcontrols and non-cirrhotic CLD patients (Po0.001 and P=0.035 respec-tively). Group C participants presented blood gas parameters tending to acompensated chronic respiratory alkalosis status compared with the othergroups. Conclusions: Pulmonary microvascular and gas exchange modifica-tions are present at early stages of CLD. Future studies should be focused atevaluating the pathophysiological mechanisms underlying this relationship.The presence of respiratory symptoms and lung functionabnormalities (i.e. hypoxaemia, ventilatory restriction)in patients with chronic liver disease (CLD) was de-scribed for the first time in 1884 by Fluckinger (1). It hasbeen estimated that pulmonary function test abnormal-ities and dyspnoea are present in about 50 and 70% ofpatients with advanced CLD respectively (2).The hepatopulmonary syndrome (HPS), defined by aclinical triad consisting in CLD (usually, but not necessa-rily, cirrhosis), increased alveolar–arterial oxygen gradi-ent [Pa(A-a)O