Currently submitted to: JMIR Research Protocols
Date Submitted: Feb 15, 2026
Open Peer Review Period: Feb 17, 2026 - Apr 14, 2026
(currently open for review)
Warning: This is an author submission that is not peer-reviewed or edited. Preprints - unless they show as "accepted" - should not be relied on to guide clinical practice or health-related behavior and should not be reported in news media as established information.
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 2028. Anticipated sample size will be approximately 25 participants based on convenience sampling and recruitment of 1 participant per month.
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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