Oxygen consumption as a measure of metabolic demand during early rehabilitation and bedside activity in critically ill adults receiving invasive mechanical ventilation: A systematic review and meta-analysis

Purpose: Early rehabilitation and bedside activity can increase oxygen demand during invasive mechanical ventilation (IMV), but the magnitude and variability of this response remain uncertain. To quantify acute changes in oxygen consumption (VO₂) during rehabilitation and bedside activity in adults receiving IMV and compare intervention domains. Methods: PubMed/MEDLINE, Scopus, and Web of Science were searched from inception through July 6, 2026. Activity-related percentage changes in VO₂ were pooled using random-effects models. Risk of bias was assessed using revised Joanna Briggs Institute tools. Results: Twenty studies were included, and 11 contributed 14 estimates to the primary meta-analysis. VO₂ increased by 29.2% from baseline (95% CI, 16.2%–43.6%; I 2 = 96.2%; 95% prediction interval, −9.7% to 84.7%). All 14 point estimates were above baseline (+3.1% to +66.3%), although not all were individually statistically significant. Pooled estimates were higher for respiratory physiotherapy (43.3%; 95% CI, 32.3%–55.2%) than for other rehabilitation and bedside interventions (18.4%; 95% CI, −0.2%–40.5%), although this domain comparison was exploratory and confounded by study era and case mix. Mean arterial pressure and cardiac output showed pooled increases; other secondary analyses included few comparable studies. Conclusion: Oxygen consumption was above baseline in all 14 point estimates, with a pooled increase of 29.2% and estimates ranging from 3.1% to 66.3%. Responses did not follow a simple passive-to-active pattern, showing that clinically indicated bedside care and rehabilitation can impose markedly different metabolic loads. When perceived exertion cannot be assessed, VO₂ offers an objective measure of session-specific metabolic demand that can be interpreted alongside the patient's cardiorespiratory reserve.