PURPOSE: Poor cardiorespiratory fitness is associated with increased all cause morbidity and mortality. In children with obesity, maximum oxygen uptake (VO2max) may not be achieved due to reduced motivation and peripheral fatigue. We aimed to identify a valid submaximal surrogate for VO2max in children with obesity. METHODS: Ninety-two children with obesity (7-16 years) completed a maximal exercise treadmill test and entered a three-month exercise and/or nutrition intervention after which the exercise test was repeated (n=63). Participants were required to reach VO2max to be included in this analysis (n=32 at baseline and n=13 at both time-points). The oxygen uptake efficiency slope (OUES) was determined as the slope of the line when VO2 (L/min) was plotted against logVE. Associations between the maximal OUES, submaximal OUES (at 3, 4, 5 and 6 minutes of the exercise test) and VO2max were calculated. RESULTS: In the cross-sectional analysis, VO2max (L/min) was strongly correlated with 5-min OUES independent of Tanner puberty stage and sex (R2=0.80, P<0.001). Longitudinal changes in VO2max were closely reflected by changes in 5-min OUES independent of change in percent body fat (R2=0.63, P<0.05). CONCLUSIONS: The 5-min OUES is a viable alternative to VO2max when assessing children with obesity.
Summary Background: Patients with advanced liver disease may develop portal hypertensionthat can result in variceal haemorrhage. Beta-blockers reduce portal pressure andminimise haemorrhage risk. These medications may attenuate measures of car-diopulmonary performance, such as the ventilatory threshold and peak oxygenuptake measured via cardiopulmonary exercise testing. Aim: To determine the effect of beta-blockers on cardiopulmonary exercise testingvariables in patients with advanced liver disease. Methods: This was a cross-sectional analysis of 72 participants who completed acardiopulmonary exercise test before liver transplantation. All participants remainedon their usual beta-blocker dose and timing prior to the test. Variables measuredduring cardiopulmonary exercise testing included the ventilatory threshold, peakoxygen uptake, heart rate, oxygen pulse, the oxygen uptake efficiency slope and theventilatory equivalents for carbon dioxide slope. Results: Participants taking beta-blockers (n = 28) had a lower ventilatory threshold(P <.01) and peak oxygen uptake (P = .02), compared to participants not takingbeta-blockers. After adjusting for age, the model of end-stage liver-disease score,liver-disease aetiology, presence of refractory ascites and ventilatory thresholdremained significantly lower in the beta-blocker group (P = .04). The oxygen uptakeefficiency slope was not impacted by beta-blocker use. Conclusions: Ventilatory threshold is reduced in patients with advanced liver dis-ease taking beta-blockers compared to those not taking the medication. This mayincorrectly risk stratify patients on beta-blockers and has implications for patientmanagement before and after liver transplantation. The oxygen uptake efficiencyslope was not influenced by beta-blockers and may therefore be a better measureof cardiopulmonary performance in this patient population.