Diaphragm and Skeletal Muscle Changes During Intensive Care: Association With Patient Outcomes (DRASTIC): Observational Study

Background Intensive care unit‐acquired limb and diaphragm weakness contributes to delays in weaning from mechanical ventilation. Purpose To determine the associations between measures of diaphragm excursion and thickness and rectus femoris/vastus intermedius thickness during an ICU admission and patient outcomes such as ICU‐AW, mechanical ventilation duration and length of stay in ICU. Methods Single‐centre prospective cohort study undertaken in a tertiary referral metropolitan Australian mixed medical‐surgical ICU of St Vincent's Hospital Sydney Australia. Inclusion of critically ill adult patients who were expected to remain mechanically ventilated for more than 48 h. Ultrasound measurements of right rectus femoris thickness, vastus intermedius thickness, and right hemidiaphragm thickness/excursion were taken on ICU admission and upon liberation from mechanical ventilation, in addition to Manual muscle strength (MRC‐SS), the ICU mobility scale, and the Chelsea Critical Care Physical Assessment score on awakening and ICU discharge. Results Forty‐three participants were enrolled. Study participants were predominantly male (34, 79%) with a median (IQR) age of 55 (40.5–67.5) years, with a mean (SD) APACHE II score of 17.5 ± 6.2. There were reductions (median (IQR)) from ICU admission to liberation from ventilation in the thickness of the R rectus femoris and vastus intermedius by −17% (−37.1% to −4.2%) and −19.7% (−35.1% to −11.2%), respectively. The (R) end‐expiratory diaphragm muscle thickness decreased, increased and remained unchanged after ventilator liberation in 19/34 (56%), 8/34 (24%) and 7/34 (20%), respectively. Multiple linear regression demonstrated that ICU discharge MRC‐SS and (R) diaphragm excursion on ICU admission were associated with the ICU length of stay. The fitted regression model was ICU length of stay = 24.18 − (4.14 × cm of (R) diaphragm excursion) − (0.19 × ICU DC MRC‐SS score). Discussion Diaphragm excursion and muscle strength during ICU admission may be associated with ICU LOS. Further studies are needed to clarify their prognostic value.