Sustained low diffusing capacity in hepatopulmonary syndrome after liver transplantation

Abstract

AIM: To study the presence of sustained low diffusing capacity (DL_CO) after liver transplantation (LT) in patients with hepatopulmonary syndrome (HPS).

METHODS: Six patients with mild-to-severe HPS and 24 without HPS who underwent LT were prospectively followed before and after LT at mid-term (median, 15 mo). HPS patients were also assessed at long-tem (median, 86 mo).

RESULTS: Before LT, HPS patients showed lower PaO₂ (71 ± 8 mmHg), higher AaPO₂ (43 ± 10 mmHg) and lower DL_CO (54% ± 9% predicted), due to a combination of moderate-to-severe ventilation-perfusion (V_A/Q) imbalance, mild shunt and diffusion limitation, than non-HPS patients (94 ± 4 mmHg and 19 ± 3 mmHg, and 85% ± 3% predicted, respectively) (P < 0.05 each). Seven non-HPS patients had also reduced DL_CO (70% ± 4% predicted).

At mid- and long-term after LT, compared to pre-LT, HPS patients normalized PaO₂ (91 ± 3 mmHg and 87 ± 5 mmHg), AaPO₂ (14 ± 3 mmHg and 23 ± 5 mmHg) and all V_A/Q descriptors (P < 0.05 each) without changes in DL_CO (53% ± 8% and 56% ± 7% predicted, respectively). Post-LT DL_CO in non-HPS patients with pre-LT low DL_CO was unchanged (75% ± 6% predicted).

CONCLUSION: While complete V_A/Q resolution in HPS indicates a reversible functional disturbance, sustained low DL_CO after LT also present in some non-HPS patients, points to persistence of sub-clinical liver-induced pulmonary vascular changes.

Keywords: Carbon monoxide diffusing capacity; Multiple inert gas elimination technique; Pulmonary gas exchange; Pulmonary vascular disorders; Ventilation-perfusion relationships