Bedside examination of alterations is of importance since prolonged breathing in COVID-19 patients might lead to atrophy and contractile weakening of respiratory muscle fibers. Therefore, the purpose of the research was to track the ultrasound-measured thickness of respiratory muscles over time. 

Patients older than 18 years old who tested positive for SARS-CoV-2 and required mechanical ventilation for more than 24 hours were included in this study. Within 24 hours following intubation, a baseline ultrasound examination (of the diaphragm, rectus abdominis, and lateral abdominal wall muscles) was done. Exams continued the next day, up to a total of 8 per topic.

Of the 30 participants, 11 had a more than or equal reduction in diaphragm thickness of at least 10% from baseline, 10 had less than a change of 10%, and 9 had an increase. The least improvement group had the shortest time between symptoms and intubation (12 [11-14] days, P =.03). For the first 7 days, the increasing group required the least amount of ventilation time (156 [129-172] h, P =.03). The average thickness of the diaphragm at the beginning of the study was 1.4 (1.1-1.6) mm, and it did not change significantly by the end (1.3 [1.1-1.5] mm, P =.54). There were no statistically significant changes in the rectus abdominis, although the thickness of the lateral abdominal wall reduced from 14 [10-16] mm at baseline to 11 [9-13] mm on the last day of mechanical breathing (P =.08). The usage of neuromuscular blocking agents (NMBAs) has been linked to wasting away of muscle, as shown by mixed-effects linear regression (P= .01). 

Subjects with COVID-19 who were ventilated showed no significant increase or decrease in diaphragm thickness. Shorter ventilation times were seen in subjects whose thickness was either stable or reduced, while longer times were seen in those whose thickness was raised. Thinner people reported using NMBA. There was no change in the thickness of the rectus muscle, and there was a small but non-significant decrease in the thickness of the lateral abdominal muscle.