Attenuated Exercise Capacity And Pulmonary Capacitance In Patients With Non-alcoholic Steatohepatitis (nash)

PURPOSE: Reduced pulmonary function is often found in patients with non-alcoholic steatohepatitis (NASH) linked to increased metabolic complications and inflammatory processes. However, the change in exercise capacity and pulmonary vascular capacitance in NASH are not clearly understood. Accordingly, the present retrospective study was to investigate alterations in exercise capacity (VO2peak) and pulmonary capacitance (GXcap), which is an estimate of pulmonary vascular capacitance, in patients with NASH. METHODS: This study utilized a database of patients with NASH (n = 26, male/female = 18/8, 58.9 ± 4.3 years) and healthy individuals (n = 23, male/female = 12/11, 58.6 ± 7.9 years) who underwent cardiopulmonary exercise tests (CPET) on a recumbent cycle ergometer (Corival, Lode, Netherlands) in our laboratory. The exercise protocol included 2 min of resting phase and incremental exercise phase. The wattage was increased by 25 W every 2 min until volitional fatigue. During CPET, breathing patterns and respiratory gas exchange including breathing efficiency (VE/VCO2) and end-tidal CO2 (PETCO2) were measured, and heart rate (HR) was monitored via electrocardiograph (ECG). To determine peak exercise capacity, VO2peak was obtained via averaging the last 30 sec at peak level. In addition, GXcap was obtained by calculation [GXcap = oxygen pulse (O2 pulse) x PETCO2]. RESULTS: There was no significant difference in age between the NASH and the healthy groups (p > 0.05), however, the NASH group had a higher body mass index (BMI) than the healthy group (p < 0.05). The NASH group demonstrated reduced VO2peak relative to the healthy group (17.5 ± 8.4 vs. 34 ± 10.2 ml/kg/min, respectively, p < 0.05). In addition, there was a higher VE/VCO2 relationship in the NASH group relative to the healthy group (34.9 ± 5.5 vs. 32.2 ± 4.0, respectively, p < 0.05) and lower PETCO2 in the NASH group compared to the healthy group (32.8 ± 4.0 vs. 35.3 ± 3.8 mmHg, respectively, p < 0.05). Furthermore, the NASH group showed lower GXcap than the healthy group (456 ± 150 vs. 551 ± 202, respectively, p < 0.05). CONCLUSION: Patients with NASH had reduced exercise capacity and pulmonary vascular capacitance relative to age-matched healthy adults and this may contribute to pulmonary pathophysiology in this type of liver disease.