Portal hypertension is a typical complication of end-stage liver disease (ESLD). Beta-blockade is used as prophylaxis to minimize the risk of gastroesophageal variceal haemorrhage. The use of beta-blockers may negatively impact peak oxygen uptake (V̇ O2peak) and ventilatory threshold (VT) by reducing cardiac output. V̇ O2peak and VT have shown to predict short- and long-term complications after liver transplantation but may be limited by peripheral fatigue due to beta-blockade. The oxygen uptake efficiency slope (OUES) represents the effectiveness of the body to extract oxygen from ventilation and may offer an effort-independent measure of cardiorespiratory fitness (CRF) in patients with ESLD. PURPOSE: To determine whether OUES is influenced by beta-blocker therapy compared to V̇ O2peak and VT in patients with ESLD. METHODS: Participants completed a symptom-limited cardiopulmonary exercise test (CPX) as part of pre-liver transplant risk stratification. Those who reached a respiratory exchange ratio (RER) ≥ 1.05 were included in the analysis. V̇ O2peak was determined as the highest 30-second average values during the test. VT was measured using the Vslope method. OUES [VO2 (L/min) = m(log10VE) + B, where m = OUES] was calculated at 50% (OUES50), 75% (OUES75) and 100% (OUES100) of the test. Independent t-tests and Mann-Whitney U tests compared the mean difference in CPX variables between participants on and off beta-blockade. RESULTS: Sixty-three participants [age 55.9 (interquartile range 51.4-59.5); model of end-stage liver disease score 15.5±4.7; male 85.7%] were included. Twenty-six participants (41%) were receiving beta-blockade at the time of CPX. Compared to those off beta-blockers, patients taking the medication demonstrated significantly (p<0.05) reduced VO2peak (3.9±3.7 vs. 16.1±2.6 ml.kg-1.min-1) and VT (10.7±2.6 vs. 12.6±2.1 ml.kg-1.min-1). However, there were no significant differences (p>0.05) at OUES100 (1.59± 0.48 vs. 1.76±0.51), OUES75 (1.61±0.43 vs. 1.72±0.52) and OUES50 (1.24±0.52 vs. 1.54±0.66) between beta-blocked and non-beta-blocked cohorts. CONCLUSION: Unlike traditional CRF measures, the OUES does not appear to be influenced by beta-blocker in patients with ESLD. The OUES may therefore have utility as an effort-independent measure of CRF in this patient cohort.
|Publication status||Published - 3 Jun 2016|
|Event||American College of Sports Medicine's 63rd Annual Meeting - |
Duration: 1 Jan 2016 → …
|Conference||American College of Sports Medicine's 63rd Annual Meeting|
|Period||1/01/16 → …|