The product of trunk muscle area and density on the CT image is a good indicator of energy expenditure in patients with or at risk for COPD

Toru Shirahata,Machika Soma,Satoshi Nakae,Makoto Nagata,Yuki Nishida,Shigeho Tanaka,Fuminori Katsukawa,Kaiji Inoue,Hidetoshi Nakamura,Sanehiro Yogi,Hideaki Sato,Tomohiko Mio,Mamoru Niitsu,Tomoe Akagami

doi:10.1186/s12931-021-01621-2

Abstract

BackgroundPhysical inactivity due to cachexia and muscle wasting is well recognized as a sign of poor prognosis in chronic obstructive pulmonary disease (COPD). However, there have been no reports on the relationship between trunk muscle measurements and energy expenditure parameters, such as the total energy expenditure (TEE) and physical activity level (PAL), in COPD. In this study, we investigated the associations of computed tomography (CT)-derived muscle area and density measurements with clinical parameters, including TEE and PAL, in patients with or at risk for COPD, and examined whether these muscle measurements serve as an indicator of TEE and PAL.MethodsThe study population consisted of 36 male patients with (n = 28, stage 1–4) and at risk for (n = 8) COPD aged over 50 years. TEE was measured by the doubly labeled water method, and PAL was calculated as the TEE/basal metabolic rate estimated by the indirect method. The cross-sectional areas and densities of the pectoralis muscles, rectus abdominis muscles, and erector spinae muscles were measured. We evaluated the relationship between these muscle measurements and clinical outcomes, including body composition, lung function, muscle strength, TEE, and PAL.ResultsAll the muscle areas were significantly associated with TEE, severity of emphysema, and body composition indices such as body mass index, fat-free mass, and trunk muscle mass. All trunk muscle densities were correlated with PAL. The product of the rectus abdominis muscle area and density showed the highest association with TEE (r = 0.732) and PAL (r = 0.578). Several trunk muscle measurements showed significant correlations with maximal inspiratory and expiratory pressures, indicating their roles in respiration.ConclusionsCT-derived measurements for trunk muscles are helpful in evaluating physical status and function in patients with or at risk for COPD. Particularly, trunk muscle evaluation may be a useful marker reflecting TEE and PAL.

Highlights

Physical inactivity due to cachexia and muscle wasting is well recognized as a sign of poor prognosis in chronic obstructive pulmonary disease (COPD)
The physical activity level (PAL) was calculated using the following equation: PAL = (TEE estimated by doubly labeled water (DLW) method)/ (BMR measured by indirect calorimetry) [35]
Almost all of the areas and densities of trunk muscles such as the pectoralis muscle (PM), rectus abdominis muscle (RAM), and erector spinae muscle (ESM) were significantly associated with total energy expenditure (TEE) and PAL

Summary

Introduction

Physical inactivity due to cachexia and muscle wasting is well recognized as a sign of poor prognosis in chronic obstructive pulmonary disease (COPD). Increasing physical activity is expected to improve prognosis, and measurement of energy expenditure is considered to be very important to assess physical activity levels (PALs) In this respect, a number of studies on the energy expenditure of COPD patients have been documented. The DLW method is the gold standard for TEE assessment because it is the most accurate method to measure total energy expenditure in daily life, which is essential to determine the energy requirement and avoid weight loss in COPD patients. This method is quite demanding since it requires significant technical expertise for implementation and analysis and involves high costs and thorough patient compliance to facilitate collection of urine samples. Studies using the DLW method have been limited to small-sized populations

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