The sit-to-stand test as a patient-centered functional outcome for critical care research: a pooled analysis of five international rehabilitation studies.

BACKGROUND

With ICU mortality rates decreasing, it is increasingly important to identify interventions to minimize functional impairments and improve outcomes for survivors. Simultaneously, we must identify robust patient-centered functional outcomes for our trials. Our objective was to investigate the clinimetric properties of a progression of three outcome measures, from strength to function.

METHODS

Adults (≥ 18 years) enrolled in five international ICU rehabilitation studies. Participants required ICU admission were mechanically ventilated and previously independent. Outcomes included two components of the Physical Function in ICU Test-scored (PFIT-s): knee extensor strength and assistance required to move from sit to stand (STS); the 30-s STS (30 s STS) test was the third outcome. We analyzed survivors at ICU and hospital discharge. We report participant demographics, baseline characteristics, and outcome data using descriptive statistics. Floor effects represented ≥ 15% of participants with minimum score and ceiling effects ≥ 15% with maximum score. We calculated the overall group difference score (hospital discharge score minus ICU discharge) for participants with paired assessments.

RESULTS

Of 451 participants, most were male (n = 278, 61.6%) with a median age between 60 and 66 years, a mean APACHE II score between 19 and 24, a median duration of mechanical ventilation between 4 and 8 days, ICU length of stay (LOS) between 7 and 11 days, and hospital LOS between 22 and 31 days. For knee extension, we observed a ceiling effect in 48.5% (160/330) of participants at ICU discharge and in 74.7% (115/154) at hospital discharge; the median [1st, 3rd quartile] PFIT-s difference score (n = 139) was 0 [0,1] (p < 0.05). For STS assistance, we observed a ceiling effect in 45.9% (150/327) at ICU discharge and in 77.5% (79/102) at hospital discharge; the median PFIT-s difference score (n = 87) was 1 [0, 2] (p < 0.05). For 30 s STS, we observed a floor effect in 15.0% (12/80) at ICU discharge but did not observe a floor or ceiling effect at hospital discharge. The median 30 s STS difference score (n = 54) was 3 [1, 6] (p < 0.05).

CONCLUSION

Among three progressive outcome measures evaluated in this study, the 30 s STS test appears to have the most favorable clinimetric properties to assess function at ICU and hospital discharge in moderate to severely ill participants.