Low skeletal muscle area as a prognostic marker for chronic obstructive pulmonary disease in elderly patients admitted to ICU

www.nature.com/scientificreports OPEN Low skeletal muscle area as a prognostic marker for chronic obstructive pulmonary disease in elderly patients admitted to ICU Jiehua Zhi1,4, Qing Shan2,4, Lanyu Liang2*, Han Liu2 & Hua Huang3 Low L3 skeletal muscle area (SMA), which is assessed on computed tomography (CT) images, has been reported to indicate poor clinical outcomes of patients with acute exacerbation of chronic obstructive pulmonary disease (COPD). The dorsal muscle group area at the T12 vertebral level (T12DMA) was used as an alternative to L3 SMA. This study aimed to investigate whether T12DMA could be used as a predictor of in-hospital mortality and long-term survival in elderly patients with COPD admitted to the intensive care unit (ICU). This single-center retrospective case–control study was performed by analyzing the clinical information and measuring T12DMA on chest CT images of elderly patients with COPD admitted to the ICU between May 2013 and May 2018. This study included 136 patients. The multivariate logistic regression analysis showed that T12DMA, neutrophil–lymphocyte ratio, invasive mechanical ventilation, and systemic steroid therapy were independent risk factors for predicting the hospital mortality. The median survival was significantly higher in the high-T12DMA group (214 days) than in the low-T12DMA group (32 days). Chronic obstructive pulmonary disease (COPD) represents a major public health problem worldwide due to increasing prevalence, morbidity, and mortality. It was ranked the eighth among the causes of disease burden worldwide measured by disability-adjusted life-years in 20151. It was also the fourth leading cause of years of life lost in China in 20172. The prevalence of COPD was 14% in patients aged ≥65 years, with a fold increase for every 10–year increment of age3. COPD often presents in aging patients as a component of multimorbidity. Sarcopenia was one of the common comorbidities4. Sarcopenia, which is defined as age-associated loss of muscle mass and strength, is highly prevalent among patients with COPD and is associated with a worse prognostic index4–6. The prevalence of sarcopenia was reported to be 24% among patients with COPD based on a cross-sectional study of a Southeast Asian population. It was associated with age and Global Initiative for Chronic Obstructive Pulmonary Disease (GOLD) stage7. Patients with COPD worsened by respiratory failure requiring mechanical ventilation (MV) were more likely to be admitted to the intensive care unit (ICU). Sarcopenia was a strong predictor of mortality among patients with COPD or other diseases requiring MV in the ICU8–11. Meanwhile, muscle wasting, as a major contributor to ICU-acquired weakness, occurred early and rapidly during the first week of critical illness12. It was associated with short-term and long-term mortality, as a driver of long-term functional disability after discharge from the ICU13–15. Therefore, the diagnosis of sarcopenia might help in preventing the mortality of these patients. In 2018, the European Working Group on Sarcopenia in Older People (EWGSOP) revised the diagnostic criteria for sarcopenia, which is now determined by both low muscle quantity and quality. The EWGSOP recommends the area measurement on a single cross-section computed tomography (CT) image at the level of the third lumbar (L3) vertebra as an alternative tool, since this area accurately represents the whole-body muscle. Thus, this method may serve as an alternative tool for assessing muscle quantity16. The quantification of L3 skeletal muscle area (SMA) using a single transverse CT slice showed that more than 56% of patients with respiratory failure had comorbidity of sarcopenia8. However, abdominal CT is not a routine examination for patients with COPD. 1 Department of Gastroenterology, The Affiliated Hospital of Yangzhou University, Yangzhou University, Yangzhou, China. 2Department of Gerontology, The Affiliated Hospital of Yangzhou University, Yangzhou University, Yangzhou, China. 3Department of Radiology, The Affiliated Hospital of Yangzhou University, Yangzhou University, Yangzhou, China. 4These authors contributed equally: Jiehua Zhi and Qing Shan. *email: Scientific Reports | (2019) 9:19117 | https://doi.org/10.1038/s41598-019-55737-z 1 www.nature.com/scientificreports/ www.nature.com/scientificreports Chest CT scanning is a conventional assessment of muscle mass and is easy to acquire for patients with COPD. The examination of T12, T11, and T10 may serve as an alternative strategy when L3 is unavailable17. Moreover, the decline in paravertebral muscle size and attenuation at T12 on CT images has been reported to be associated with mortality among patients with hip fracture18 and those undergoing liver transplantation19 and general and vascular surgery20. The relationship between the T12 vertebral level (T12DMA) and the mortality related to the acute exacerbation of COPD (AECOPD) remains unclear. This study retrospectively investigated clinical parameters, including T12DMA, dorsal muscle group (DMG) density at the T12 vertebral level (T12DMD), and other risk factors, to evaluate whether these parameters might serve as prognostic markers for in-hospital mortality among elderly patients with AECOPD requiring ICU admissions for ventilation support. It also explored whether the level of T12DMA at admission might be a predictor of long-term survival among patients with COPD after ICU admission. Materials and Methods Population cohort and design. This was a retrospective case–control study conducted by the Affiliated Hospital of Yangzhou University, a Chinese tertiary teaching hospital, between February 2013 and May 2018. Patients diagnosed with AECOPD based on the International Classification of Diseases, Tenth Revision codes, including J44.000, J44.101, and J44.100, were consecutively enrolled. All patients were previously diagnosed with COPD based on the GOLD 2017 recommendations. Patients had dyspnea with or without unconsciousness when admitted to the ICU directly from the emergency department or during hospitalization. The inclusion criteria were as follows: (1) age ≥60 years; (2) invasive mechanical ventilation (IMV) or noninvasive mechanical ventilation (NIMV) during the ICU stay; and (3) chest CT scan performed at admission or within 48 h after admission. The exclusion criteria were as follows: (1) discharge within 24 h; (2) no adequate imaging within 48 h after admission; (3) patients admitted to the ICU due to other diseases and suffering from comorbidity of COPD; (4) tumor history; (5) an ICU admission history; and (6) more than 90 days of ICU stay. A total of 136 patients were eligible for this study. They were divided into two groups based on their survival when discharged from the hospital. All enrolled patients were followed up until October 31, 2019. Demographic and clinical information. Data on demographic statistics, comorbidities, clinical information, la (...truncated)