Respiratory muscle wasting associated with mortality in patients with severe COVID-19
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The presence of respiratory muscle wasting in patients with severe COVID-19 was associated with increased in-patient mortality, according to a study presented at the Society of Critical Care Medicine Congress.
“Sarcopenia, or the state of generalized muscle wasting and dysfunction, has been demonstrated to be associated with poor outcomes across various patient populations,” Connor J. Wakefield, MD, resident physician in the department of internal medicine at the Brooke Army Medical Center in Fort Sam Houston, Texas, said during a presentation. “There is a lack of research investigating the role of thoracic sarcopenia in critical illness and COVID-19 outcomes.”
Wakefield and colleagues aimed to implement a new technique to assess degree of respiratory muscle wasting through the use of CT and body composition analysis and also to investigate the impact of respiratory muscle wasting on the outcomes of patients with severe COVID-19.
The retrospective single-center cohort study included 99 adults (median age, 64 years; 67% men) admitted to the ICU with confirmed COVID-19 from March to December 2020 . All patients received chest CT within 2 days of admission. Using medical image analysis software, researchers assessed a cross-sectional area of respiratory skeletal muscle at the fifth thoracic vertebral level and calculated respiratory muscle index. Patients were categorized into the lowest gender-specific quartile of respiratory muscle index and the second to fourth gender-specific respiratory muscle index quartiles.
The primary outcome was mortality. Secondary outcomes included mechanical ventilation duration, tracheostomy and hospital length of stay.
Researchers observed respiratory muscle wasting in 19 patients. These patients were older (71.5 vs. 60.2 years), had lower BMI (26.4 vs. 32.1 kg/m2) and had lower mean respiratory muscle index (26.8 vs. 39.2 cm2/m2).
Levels of C-reactive protein (P = .55), ferritin (P = .79), platelet count (P = .33) and lactate dehydrogenase count (P = .15) were all similar between patients with respiratory muscle wasting and nonrespiratory muscle wasting.
Compared with nonrespiratory muscle wasting, patients in the respiratory muscle wasting group had significantly decreased mean creatine kinase (586 vs. 536.2 U/L; P = .003).
The researchers reported no difference in COVID-19-targeted therapies received between the groups.
Results showed no significant differences in rates of mechanical ventilation (44% vs. 53%; P = .563), mechanical ventilation duration (5.4 vs. 5 days; P = .729), rates of tracheostomy (6% vs. 5%; P = .972) or ICU length of stay (11.3 vs. 9.9 days; P = .761) between patients with nonrespiratory muscle wasting and those with respiratory muscle wasting, respectively.
However, the presence of respiratory muscle wasting was associated with increased in-patient mortality compared (53% vs. 27%; P = .019). In addition, respiratory muscle wasting was associated with in-hospital mortality after adjusting for admission platelet level in multivariate models (OR = 3.3; 95% CI, 1.02-10.46; P = .047).
Wakefield highlighted several limitations of the study, including its retrospective single-center design and lack of CT scan early after admission for all patients with COVID-19. He said this may represent a cohort with increased recombinant thoracic processes, such as pulmonary embolism, although the rate of PE in this cohort was low (10%).
“Future directions include performing serial analysis of CT scans over time in patients with mechanical ventilation dependence as a way to predict ventilator weaning,” Wakefield said. “Prospective studies are also needed to investigate the effects of various therapies including respiratory muscle training, and ventilation modes on the impact on ventilation we need success.”