Risk factors for physical impairment after acute lung injury in a national, multicenter study

Abstract

Rationale: Existing studies of risk factors for physical impairments in acute lung injury (ALI) survivors were potentially limited by single-center design or relatively small sample size.

Objectives: To evaluate risk factors for three measures of physical impairments commonly experienced by survivors of ALI in the first year after hospitalization.

Methods: A prospective, longitudinal study of 6- and 12-month physical outcomes (muscle strength, 6-minute-walk distance, and Short Form [SF]-36 Physical Function score) for 203 survivors of ALI enrolled from 12 hospitals participating in the ARDS Network randomized trials. Multivariable regression analyses evaluated the independent association of critical illness-related variables and intensive care interventions with impairments in each physical outcome measure, after adjusting for patient demographics, comorbidities, and baseline functional status.

Measurements and main results: At 6 and 12 months, respectively, mean (± SD) values for strength (presented as proportion of maximum strength score evaluated using manual muscle testing) was 92% (± 8%) and 93% (± 9%), 6-minute-walk distance (as percent-predicted) was 64% (± 22%) and 67% (± 26%), and SF-36 Physical Function score (as percent-predicted) was 61% (± 36%) and 67% (± 37%). After accounting for patient baseline status, there was significant association and statistical interaction of mean daily dose of corticosteroids and intensive care unit length of stay with impairments in physical outcomes.

Conclusions: Patients had substantial impairments, from predicted values, for 6-minute-walk distance and SF-36 Physical Function outcome measures. Minimizing corticosteroid dose and implementing existing evidence-based methods to reduce duration of intensive care unit stay and associated patient immobilization may be important interventions for improving ALI survivors' physical outcomes.

Figure 1.

Patient flow diagram. *One site joined the follow-up study late; hence, 27 patients enrolled into the ALTA and/or EDEN/OMEGA trials from that site were ineligible for follow-up.

Figure 2.

Scatterplot of the physical outcomes versus mean corticosteroid dose. The solid line in each panel represents the change in mean value of the physical outcome measure as a function of mean daily dose of corticosteroid (prednisone-equivalent dose in milligrams) using locally weighted scatterplot smoothing (LOWESS). The x axis of each panel is truncated at 300 mg, excluding a single patient with an average dose greater than 300 mg. 6MW = 6-minute-walk test; MRC = Medical Resource Council.