COURSE OF RECOVERY OF RESPIRATORY MUSCLE STRENGTH AND ASSOCIATIONS WITH PHYSICAL FUNCTIONING: A PROSPECTIVE COHORT STUDY AMONG CRITICAL ILLNESS SURVIVORS

M. Major¹, M. van Egmond¹, R. Engelbert², D. Dettling-Ihnenfeldt², S. Ramaekers¹, M. Van der Schaaf²

¹Amsterdam University of Applied Sciences, Physical Therapy, Amsterdam, Netherlands, ²Amsterdam University Medical Centers (AMC), Rehabilitation Medicine, Amsterdam, Netherlands

Background: Mechanical ventilation affects the respiratory muscles, but little is known about long-term recovery of respiratory muscle weakness (RMW) and potential associations with physical functioning in survivors of critical illness.

Purpose: The aim of this study was to investigate the course of recovery of RMW and its association with functional outcomes in patients who received mechanical ventilation.

Methods: We conducted a prospective cohort study with 6-month follow-up among survivors of critical illness who received ≥ 48 hours of invasive mechanical ventilation. Primary outcomes, measured at 3 timepoints, were maximal inspiratory and expiratory pressures (MIP/MEP). Secondary outcomes were functional exercise capacity (FEC) and handgrip strength (HGS). Longitudinal changes in outcomes and potential associations between MIP/MEP, predictor variables, and secondary outcomes were investigated through linear mixed model analysis.

Results: A total of 59 participants (male: 64%, median age [IQR]: 62 [53-66]) were included in this study with a median (IQR) ICU and hospital length of stay of 11 (8-21) and 35 (21-52) days respectively. While all measures were well below predicted values at hospital discharge (MIP: 68.4%, MEP 76.0%, HGS 73.3% of predicted and FEC 54.8 steps/2m), significant 6-month recovery was seen for all outcomes. Multivariate analyses showed longitudinal associations between older age and decreased MIP and FEC, and longer hospital length of stay and decreased MIP and HGS outcomes. In crude models, significant, longitudinal associations were found between MIP/MEP and FEC and HGS outcomes. While these associations remained in most adjusted models, an interaction effect was observed for sex.

Conclusions: Respiratory muscle weakness was observed directly after hospital discharge while 6-month recovery to predicted values was noted for all outcomes. Longitudinal associations were found between MIP and MEP and more commonly used measures for physical functioning, highlighting the need for continued assessment of respiratory muscle strength in deconditioned patients who are discharged from ICU. The potential of targeted training extending beyond ICU and hospital discharge should be further explored.

Implications: To our knowledge, this is the first study presenting longitudinal data up to 6 months after hospital discharge on the course of recovery of MIP and MEP in patients who received mechanical ventilation in the intensive care unit. Respiratory muscle weakness was present directly after hospital discharge and MIP remained marginally impaired at 3 months, approaching reference values at 6 months after hospital discharge. As RMW was associated with decreased exercise capacity and handgrip strength, we recommend ongoing assessment of MIP/MEP in deconditioned and weakened patients who are discharged from ICU and hospital and in need of follow-up interventions. More studies are needed to investigate pathophysiological mechanisms explaining associations between RMW, ICU-AW and decreased exercise capacity. For severely deconditioned patients, potential benefits of the addition (or continuation) of inspiratory muscle training as a component of post-ICU exercise programs should be investigated further.

Funding acknowledgements: Mel Major received a Dutch Research Council grant (NWO, 023.007.006). Partly funded by Taskforce for Applied Research (SIA, RAAK.PUB04.037).

Keywords:
Respiratory Muscle Strength
Mechanical Ventilation
Critical Illness

Topics:
Critical care
Cardiorespiratory
Primary health care

Did this work require ethics approval? Yes

Institution: Amsterdam University Medical Centers (location AMC)

Committee: Medical Ethics Committee

Ethics number: 2019_012, ABR NL 68475.018.19