Muscle Power is Related to Physical Function in Patients Surviving Acute Respiratory Failure: A Prospective Observational Study

Background: Up to 66% of patients admitted to the intensive care unit (ICU) for acute respiratory failure (ARF) develop ICU-acquired weakness, which is diagnosed by muscle strength testing. Muscle power, different from strength, is an important determinant of function that is not a common focus in patients surviving critical illness. Therefore, the purpose of this study is to assess muscle power in survivors of ARF.

Methods: A cross-sectional observational study performed with survivors of ARF. Muscle power, strength and physical function were assessed 4-8 weeks post-hospital discharge. Cross sectional area and echogenicity of rectus femoris and tibialis anterior muscles were assessed using ultrasonography. Healthy community-dwelling adults were included for comparison.

Results: 12 survivors of ARF mean age of 55.6 ± 17.1 (66% male) and 12 healthy adults mean age of 51.6.1 ± 10.3 (66% male) participated in this study. Patients in the post-ARF group had a mean muscle power of 9.9 ± 3.5 W and 63.7 ± 31.6 W for 2-lb and 10% of body-weight loads, respectively. Compared to matched controls, power in ARF group was reduced by 43%. Muscle power in post-ARF group had moderate correlations with 5-times sit-to-stand testing (r = -0.644, P = 0.024), 4-m habitual gait speed (-0.780, P = 0.002), and 6-min walk distance (r = 0.589, P = 0.044).

Conclusions: Muscle power is significantly reduced in survivors of critical illness and associated with deficits in physical function. These preliminary findings may support therapeutic interventions aimed at improving muscle power to potentially increase functional benefit.