Analysis of mobility level of COVID-19 patients undergoing mechanical ventilation support: A single center, retrospective cohort study

Abstract

Background: Severe coronavirus disease 2019 (COVID-19) patients frequently require mechanical ventilation (MV) and undergo prolonged periods of bed rest with restriction of activities during the intensive care unit (ICU) stay. Our aim was to address the degree of mobilization in critically ill patients with COVID-19 undergoing to MV support.

Methods: Retrospective single-center cohort study. We analyzed patients' mobility level, through the Perme ICU Mobility Score (Perme Score) of COVID-19 patients admitted to the ICU. The Perme Mobility Index (PMI) was calculated [PMI = ΔPerme Score (ICU discharge-ICU admission)/ICU length of stay], and patients were categorized as "improved" (PMI > 0) or "not improved" (PMI ≤ 0). Comparisons were performed with stratification according to the use of MV support.

Results: From February 2020, to February 2021, 1,297 patients with COVID-19 were admitted to the ICU and assessed for eligibility. Out of those, 949 patients were included in the study [524 (55.2%) were classified as "improved" and 425 (44.8%) as "not improved"], and 396 (41.7%) received MV during ICU stay. The overall rate of patients out of bed and able to walk ≥ 30 meters at ICU discharge were, respectively, 526 (63.3%) and 170 (20.5%). After adjusting for confounders, independent predictors of improvement of mobility level were frailty (OR: 0.52; 95% CI: 0.29-0.94; p = 0.03); SAPS III Score (OR: 0.75; 95% CI: 0.57-0.99; p = 0.04); SOFA Score (OR: 0.58; 95% CI: 0.43-0.78; p < 0.001); use of MV after the first hour of ICU admission (OR: 0.41; 95% CI: 0.17-0.99; p = 0.04); tracheostomy (OR: 0.54; 95% CI: 0.30-0.95; p = 0.03); use of extracorporeal membrane oxygenation (OR: 0.21; 95% CI: 0.05-0.8; p = 0.03); neuromuscular blockade (OR: 0.53; 95% CI: 0.3-0.95; p = 0.03); a higher Perme Score at admission (OR: 0.35; 95% CI: 0.28-0.43; p < 0.001); palliative care (OR: 0.05; 95% CI: 0.01-0.16; p < 0.001); and a longer ICU stay (OR: 0.79; 95% CI: 0.61-0.97; p = 0.04) were associated with a lower chance of mobility improvement, while non-invasive ventilation within the first hour of ICU admission and after the first hour of ICU admission (OR: 2.45; 95% CI: 1.59-3.81; p < 0.001) and (OR: 2.25; 95% CI: 1.56-3.26; p < 0.001), respectively; and vasopressor use (OR: 2.39; 95% CI: 1.07-5.5; p = 0.03) were associated with a higher chance of mobility improvement.

Conclusion: The use of MV reduced mobility status in less than half of critically ill COVID-19 patients.

Fig 1. Perme score over the first 27 days of ICU admission.

Circles are mean and error bars are 95% confidence interval. P value from a mixed-effect generalized linear model with Gaussian distribution, with group and time, and a group x time interaction as fixed effect, and the patients as random effect to account for repeated measurements. The number of patients with available data decreases over successive study days due to deaths and discharges. *Perme ICU mobility score ranges from 0 to 32, with higher scores indicating better mobility level.

Fig 2. Kaplan-Meier curves of time until the first day the patient got out of bed.

Definition of abbreviations: HR = Hazard ratio; MV = mechanical ventilation; SAPS III = simplified acute physiology score; BMI = body mass index; CCI = Charlson comorbidity index; MFI = Modified Frailty Index. Unadjusted hazard ratio calculated with a Cox proportional hazard model. To account for the competing risk of death, patients who died without achieving the event of interest were assigned the worst time possible. a) mechanical ventilation, with groups required (MV = yes) or not required (MV = no); b) simplified acute physiology score (SAPS III score); c) body mass index (BMI) calculated by weight in kilograms divided by the square of the height in meters (Kg/m²), categorized into groups normal or healthy weight (BMI ≤25·0), overweight (BMI = 25·0–29·9), and obese (BMI ≥30·0); d) age (<65 or ≥65); e) Charlson comorbidity index with groups <1 or ≥ 1; and f) Modified Frailty Index at the admission, with groups non-frail (MFI = 0), pre-frail (MFI = 1–2) and frail (MFI ≥3).