PMID 33527199

Research
All papers

The Feasibility of High-Intensity Interval Training in Patients with Intensive Care Unit-Acquired Weakness Syndrome Following Long-Term Invasive Ventilation

Wernhart S, Hedderich J, Wunderlich S, Schauerte K, Weihe E, Dellweg D, Siemon K

Question

Is a HIIT bicycle-ergometer protocol feasible and safe in early rehabilitation patients with ICU-acquired weakness after long-term invasive ventilation, and how do outcomes compare with moderate continuous training?

Summary

This retrospective rehabilitation study compared two bicycle-ergometer training protocols in patients recovering from long invasive ventilation with ICU-acquired weakness. Patients trained five days per week for three weeks in an early rehabilitation facility. The HIIT-style protocol used five cycles inside a 14-minute session with hard phases rated 7/10 and active recovery rated 4/10 on the Borg CR10 scale. No major adverse events were observed, and both HIIT and moderate continuous training improved walking distance, lung function, inspiratory pressure, and functional status. HIIT showed a trend toward greater six-minute-walk improvement, but group assignment was not randomized and the authors caution that the protocol may have been moderate rather than truly high intensity.

Methodology

  • Post-ICU patients with ICU-acquired weakness after at least 7 days of invasive ventilation.
  • 46 participants.
  • Bicycle ergometry.
  • Work intervals: High-intensity phases at Borg CR10 7/10; exact interval duration not extracted.
  • Recovery: Active recovery/cool-down phases at Borg CR10 4/10; exact duration not extracted.
  • Intensity: Borg CR10 7/10 hard phases.
  • 14 min.
  • 5 days/week.
  • 3 weeks.
  • Retrospective non-randomized comparison of two established rehabilitation training protocols.
  • Six-minute walk test, Vital capacity and FEV1, Maximal inspiratory pressure, and Functional status were tracked.

Outcomes

Six-minute walk test

Both groups improved, with a trend toward greater improvement in HIIT.

HIIT +159.5 m (SD 64.9) vs MCT +120.4 m (SD 60.4); p=0.057 by Mann-Whitney, ANCOVA group effect p=0.055.

Improved

Secondary respiratory and functional outcomes

VCmax, FEV1, PImax, FIM/FAM, and Barthel improved in both groups without significant between-group differences.

Between-group p values reported as nonsignificant.

Improved

Safety

No major adverse events occurred, but five sessions were terminated early for dizziness.

Two dizziness terminations in HIIT and three in MCT.

Mixed

Insights

  • Clinical HIIT can be feasible even in very fragile populations when intensity is Borg-guided and medically monitored.
  • For safety-sensitive users, readiness checks and explicit stop criteria may matter as much as interval structure.
  • The HIIT label needs verification: perceived hard intervals may not equal objective high-intensity work in severely deconditioned patients.

Limitations

  • Retrospective non-randomized design.
  • Selection bias from clinician-assigned groups.
  • No no-exercise control group.
  • Semi-quantitative Borg intensity without CPET thresholds.
  • Short intervention duration.
  • Heterogeneous diagnoses and comorbidities.

Safety

  • No major adverse events.
  • Five premature exercise terminations due to dizziness; symptoms resolved within minutes.
  • Strict session exclusion and termination criteria were used.