Protein provision and associations with changes in skeletal and diaphragm muscle during COVID-19 critical illness

During COVID-19 critical illness, both muscle mass and muscle strength decline. Protein provision is one of the factors influencing changes in muscle mass and may therefore also play a role in diaphragm atrophy. The aim of this study was to investigate whether protein provision is related to changes in skeletal muscle and diaphragm muscle mass and quality in critically ill COVID-19 patients during the first 30 days of ICU admission. We studied skeletal muscle area (SMA) and diaphragm volume (DV) as markers of muscle mass. As indicators of muscle quality, skeletal muscle density (SMD) and diaphragm density (DD) were studied.

This is a retrospective cohort study including adult critically ill COVID-19 patients who were mechanically ventilated for ≥48 hours and had at least two available computed tomography (CT) scans. SMA (cm²) and DV (cm³) were segmented, and quality (Hounsfield Units, HU) was assessed. Linear mixed-model analysis was performed to study the association between both average weight-based protein provision (g/kg /day) and average adequate or low protein provision (≥1.2 vs. <1.2 g/kg/day) with SMA, DV, SMD and DD. Sensitivity analyses were conducted to rule out potential effects from non-physiological influences like edema or scan protocol variability.

A total of 93 patients with available data on skeletal muscle were included. Diaphragm data were available in a subgroup of 28 patients. Protein provision (g/kg/day) was not significantly related to changes in SMA, DV, SMD and DD. SMD decreased significantly over time (-0.3 HU per day, 95% CI -0.4 to -0.2, p <0.001), whereas SMA, DV and DD did not significantly change during the first 30 days of ICU admission.

There was no clear relationship between the amount of protein administered and changes in SMA, DV, SMD and DD. Skeletal muscle quality decreased over time, but skeletal muscle mass, diaphragm volume and quality appeared to remain stable during the first 30 days of ICU admission.