Prediction of oxygen uptake at peak exercise in patients with inflammatory bowel disease using submaximal cardiopulmonary exercise testing and the steep ramp test as a practical field test

Purpose: To develop predictive equations for oxygen uptake at peak exercise (VO2peak) measured during a cardiopulmonary exercise test (CPET) for patients with inflammatory bowel disease (IBD) using submaximal CPET-derived parameters and the steep ramp test, along with demographic and clinical characteristics. Methods: This study included patients with IBD in remission or with mild-to-moderate disease activity who performed a CPET and a steep ramp test within 14 days. Submaximal CPET-derived parameters included oxygen uptake (VO2) at the ventilatory anaerobic threshold (VAT) and oxygen uptake efficiency slope (OUES), while the outcome of the steep ramp test was the work rate achieved at peak exercise (WRpeak). Results: Predictive regression equations with submaximal VO2 at the VAT and with OUES, when combined with age and body fat percentage, explained >89% of the variance in VO2peak (optimism-adjusted R2 = 0.895 and 0.938). Predictive capacity increased when both VO2 at the VAT and OUES were combined in a predictive regression equation, together with age, body fat percentage, and clinically active disease (optimism-adjusted R2 = 0.951). Steep ramp test WRpeak explained 89% of the variance in VO2peak (optimism-adjusted R2 = 0.892). Conclusion: The highly predictive equations developed in this study support the use of the submaximal CPET and the steep ramp test as alternatives for assessing VO2peak in patients with IBD in remission or with mild-to-moderate disease activity in clinical and research settings.