Mortality is higher in patients with severe Covid-19 who have respiratory muscle wasting, suggests a study published in the journal Critical Care Medicine. The findings of the study were also presented at the Society of Critical Care Medicine Congress.^1,2

This retrospective single-center study analyzed data from 99 lab-confirmed Covid-positive patients hospitalized in ICU between March 2020 and December 2020 to evaluate the extent of respiratory muscle wasting and its influence on patient outcomes. Their mean age was 64 years; the median BMI was 30.3 kg/m2 and the median SOFA score was 4. They underwent chest CT within 2 days of admission. A cross-sectional area of respiratory skeletal muscle at the level of fifth thoracic vertebra was examined with the help of a software that analyzed medical images (Slice-O-Matic® software) to calculate the respiratory muscle index. Patients were grouped into two, one with the lowest gender-specific quartile of respiratory muscle index and the other with second to fourth gender-specific respiratory muscle index quartiles. There were 31 deaths and 43 patients were on invasive mechanical ventilation.

Nineteen patients were found to have respiratory muscle wasting. These patients were older in age (71.5 years) than those who did not have respiratory muscle wasting (60.2 years). They also had lower mean respiratory muscle index (26.8 vs 39.2 cm2/m2) and lower BMI (26.4 vs 32.1 kg/m2).

Mortality during hospitalization was higher in patients with respiratory muscle wasting (53% vs 27%, respectively) on univariate analysis. Mortality was also found to be higher for patients with baseline thrombocytopenia. But, after adjusting for admission platelet count on multivariate logistic regression analysis, a significant association was seen between respiratory muscle wasting and in-hospital mortality with odds ratio of 3.3.

No differences were observed between the two groups of patients with regard to CRP, ferritin, platelet count and LDH. But the mean creatine kinase levels were much lower in patients who had respiratory muscle wasting. The rates of mechanical ventilation also were comparable between patients with nonrespiratory muscle wasting and those with respiratory muscle wasting (44% vs 53%) as were the tracheostomy rates (6% vs 5%). Similarly, the duration of mechanical ventilation (5.4 vs 5 days) and ICU admission (11.3 vs 9.9 days) did not differ significantly between the two groups.

Sarcopenia or generalized muscle wasting is generally age-related. But it is also associated with other health conditions such as type 2 diabetes and in patients receiving intensive care and is associated with adverse outcomes. This study has demonstrated that respiratory muscle wasting is significantly associated with poor prognosis in patients with severe Covid-19. Hence, examining critically ill Covid-19 patients for respiratory muscle wasting can help in their risk stratification.

References

1. Wakefield C, et al. 21: Respiratory muscle wasting is associated with mortality in ICU covid-19 patients, Critical Care Medicine. 2022 Jan;50(1):11. doi: 10.1097/01.ccm.0000806552.67328.39.
2. https://www.healio.com/news/pulmonology/20220420/respiratory-muscle-wasting-associated-with-mortality-in-patients-with-severe-covid19.