Accepted for/Published in: JMIR Research Protocols
Date Submitted: Feb 15, 2026
Open Peer Review Period: Feb 17, 2026 - Apr 14, 2026
Date Accepted: Jun 2, 2026
(closed for review but you can still tweet)
Protocol for Standardized Single-Session Cardiopulmonary Exercise Test for Measuring Peak Oxygen Uptake, Oxygen On/Off Kinetics, and Skeletal Muscle Oxygenation in ICU survivors: ICU Combined Assessment of Cardio-Respiratory Exercise (ICU-CARE) Study
ABSTRACT
Background:
ICU-acquired weakness (ICU-AW) research focuses predominantly on intrinsic muscle pathology rather than integrated systemic interactions, commonly studied in exercise science. Peak oxygen uptake (V ̇O_2peak), V ̇O_2 on/off kinetics, and skeletal muscle oxygenation provide quantitative evaluation of exercise capacity, and are infrequently measured in ICU survivors. Routine cardiopulmonary exercise test (CPET) research separates V ̇O_2peak and V ̇O_2 kinetics assessments into multiple sessions. Yet, a combined experimental approach may enhance diagnosis, follow-up retention, and mechanistic insight for patients with ICU-AW.
Objective:
This prospective cross-sectional observational study aims to develop a standardized, single-session CPET protocol for combined assessment of V ̇O_2peak, V ̇O_2 kinetics, and skeletal muscle microvascular oxygenation in ICU survivors, enabling quantitative and integrated assessment of ICU-AW.
Methods:
Adults mechanically ventilated ≥ 7 days will be recruited to participate 6 months post-ICU discharge, in a modified CPET exercise session on an upright cycle ergometer. The proposed standardization will involve (i) the estimation of V ̇O_2peak using a priori formulae with a V ̇O_2peak correction factor for the ICU population, (ii) V ̇O_2 on-kinetics (constant-work-rate [CWR]) targeting relative 30% V ̇O_2reserve, (iii) an incremental ramp exercise based on self-reported functional status, and (iv) a 10-minute recovery to quantify V ̇O_2 off-kinetics. In addition, near-infrared spectroscopy (NIRS) will be placed on the vastus lateralis muscle to simultaneously collect tissue saturation index (TSI) and deoxy-hemoglobin (HHb) during each phase of the protocol.
Results:
Recruitment is anticipated to begin in June 2026, and is expected to be completed in 2029/2030. Anticipated sample size will be approximately 48 participants based on feasibility of recruitment of 1 participant per month and a sample size calculation based on Bland-Altman limits of agreement between predicted and measured V ̇O_2peak.
Conclusions:
The ICU-CARE CPET protocol will enable the quantitative evaluation of V ̇O_2peak, V ̇O_2 on/off kinetics, and local microvascular skeletal muscle oxygenation during a single exercise session, facilitating the integrated physiological study of ICU-AW. Clinical Trial: Registered at clinicaltrials.gov under the clinical study ID NCT06193980
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Copyright
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