Impaired skeleton muscle high quality is a major risk element for adverse outcomes in acute respiratory failure. However, conventional methods for skeletal muscle assessment space inapplicable in the critical care setting. This research aimed to identify the prognostic worth of computed tomography (CT) fat muscle portion (FMF) together a biomarker the muscle top quality in patient undergoing extracorporeal membrane oxygenation (ECMO). To calculation FMF, paraspinal skeleton muscle area was obtained from clinical CT and also separated into areas of fatty and also lean muscle based on densitometric thresholds. The cohort to be binarized follow to average FMF. Patients with high FMF displayed significantly increased 1-year mortality (72.7% versus 55.8%, P = 0.036) ~ above Kaplan–Meier analysis. A multivariable logistic regression version was developed to test the affect of FMF ~ above outcome. FMF was established as a far-ranging predictor that 1-year mortality (hazard ratio per percent FMF, 1.017 <95% confidence interval, 1.002–1.033>; P = 0.031), elevation of anthropometric characteristics, Charlson Comorbidity Index, simplified Acute Physiology Score, respiratory tract Extracorporeal Membrane Oxygenation survival Prediction Score, and also duration that ECMO support. Come conclude, FMF guess 1-year mortality separately of developed clinical prognosticators in ECMO patients and also may have the potential to end up being a brand-new muscle top quality imaging biomarker, i beg your pardon is accessible from clinical CT.

You are watching: What are the fractions of muscle and fat in the leg?


In patients with major acute respiratory fail (ARF), extracorporeal membrane oxygenation (ECMO) might be taken into consideration as a treatment option1. ECMO to be reported to achieve remarkable success for circumstances in influenza A (H1N1) connected ARF2 and within a huge randomized managed trial3. Consequently, the consumption of ECMO for treatment of ARF is boosting worldwide4. Breakthroughs in an essential care medicine, including progress in the ar of ECMO, have actually led to improved survival prices in this patients1,5,6. However, early its ongoing high incidence, ARF is still taken into consideration a significant health issue5,7. Except that, ARF survivors were commonly observed to suffer from persistent sequelae such together physical impairment and also reduced mobility, causing dismal outcomes8,9. To some extent, this may be explained by the fact that intensive treatment unit (ICU) acquired muscle weak was shown to it is in frequent amongst those patients and is related to enhanced morbidity and mortality on long-term follow up10,11. Consequently, the skeleton muscle device is considered a major target and also primary determinant of sensible recovery and thereby outcome in these patients. Amongst factors such together age, nutritional status, comorbidities, and administered medications, the baseline muscle sensible status is taken into consideration to be of an essential importance for permanent outcome in ARF12. However, together patients with ARF are frequently admitted as emergencies, the baseline muscle condition is almost always unknown.

Conventional techniques for evaluate of bones muscle duty such together measurement of hands-on grip strength or electromyography13,14 call for patient cooperation. Therefore, these tests may be thought about impractical for skeletal muscle evaluate in the ECMO setting. Also, activities markers such together albumin15 might be minimal to evaluate skeletal muscles in ECMO patients, as laboratory values may be distorted by concomitant disorders or alterations in hydration status. Ultrasound may be supplied as a bedside imaging modality because that skeletal muscle assessment in critically ok patients16,17,18. However, it requires a specialized examination and measurements might be influenced by examiner-related components such as transducer positioning. Although factors such as transforms in hemodynamics complicate conduction that CT in ECMO patients, numerous clinical scenarios exist which do CT examinations crucial in these patients19,20. Bones muscles might be assessed from CT for determination of body composition13. For instance, in a recent report fat muscle fraction (FMF), opportunistically acquired from pre-interventional CT, was proposed together an objective measure up of muscle top quality in patient receiving endovascular aortic valve replacement21. Therefore, in this study we aimed to discover whether clinical CT examinations in ECMO may also be exploited for determination of human body composition and if the acquired measurements may additionally be regarded outcome in these patients.


Study population

Patients who obtained vv-ECMO for ARF between December 2014 and also August 2018 in ~ our tertiary scholastic center to be retrospectively evaluate (Fig. 1). Patient who had diagnostic CT scans in ~ 4 days the initiation that ECMO support were identified. In this patients, the superior mesenteric artery essential to be extended by the field-of-view, as this level offered as the anatomical landmark for conduction that muscle measurements. Clinical records to be reviewed to retrieve clinical variables and also baseline physical attributes of included patients.


*

Study consists flowchart. Patients who received venovenous ECMO for significant acute respiratory tract failure in between December 2014 and also August 2018 in ~ our center were screened because that eligibility (n = 306). Patients to be excluded if no CT scan in ~ 4 days that ECMO initiation was available (n = 176), if they got previous ECMO assistance (n = 22), or if CT scans were no applicable (n = 21). CT Computed tomography, ECMO Extracorporeal Membrane Oxygenation.


Image analysis

Skeletal muscle measurements were performed in ~ the level of the beginning of the premium mesenteric artery, as this level is frequently covered additionally in chest CT protocols. For each patient, a single axial cross-sectional image at the source of the superior mesenteric artery was retrieved. Tissue locations at this level were formerly demonstrated to be highly associated with total compartment volumes and also corresponding dimensions were presented to be highly reproducible22,23. CT exams were exported native the institutional picture archiving and also communication system (IMPAX, Agfa Healthcare, Belgium), de-identified, and also transferred to a typical radiological workstation for picture analysis. Image analysis was performed utilizing an in-house software written in MATLAB (Mathworks, Natick, MA, USA) v details of the software application reported elsewhere23. All muscle measurements were perform by one radiologist (AF) through 3 years of suffer in human body composition analysis, who was blinded to patience data, not affiliated in patience treatment and unaware of result parameters. For segmentation the the complete skeletal muscle compartment, the thoracolumbar fascia was carefully traced bilaterally, separating both the left and right paraspinal bones muscle compartment from surrounding tissues24,25. Within the total skeletal muscle compartment, skeleton muscle organization was figured out by one attenuation threshold range − 29 to 100 HU26,27. Because that calculation the paraspinal skeletal muscle area, pixels in ~ the identified attenuation threshold range were counted up and also multiplied through the particular pixel surface area. Next, come quantify skeleton muscle fat infiltration, the paraspinal bones muscle area to be separated into locations of fatty and lean muscle based on commonly accepted attenuation thresholds26. Accordingly, fatty and also lean muscle were identified by attenuation threshold arrays of short (− 29 come 29 HU) and normal muscle attenuation (30 to 100 HU), respectively. Fatty Muscle fraction (FMF) to be then calculated together the area of short attenuation muscle tissue referred to the skeleton muscle area21 (Fig. 2).

See more: Which Of The Following Is Not A Characteristic Of The Accrual Basis Of Accounting?


*

The concept of FMF. (A) skeletal muscle fat infiltration is considered an indicator of muscle quality. Based on densitometric thresholds and accepted cut-off values of lean and also fatty skeleton muscle, muscle compartments might be be separated into areas of fatty and lean muscle. The FMF is calculated as the area of fatty muscle tissue regarded the complete skeletal muscle area, leading to a relative and comparable measure of muscle quality. This biomarker deserve to be opportunistically acquired from clinical CT scans. (B) skeleton muscle area was obtained as the bilateral compartment area the paraspinal skeletal muscles at the level the the remarkable mesenteric artery. In ~ the skeleton muscle area, muscle tissue is identified by an attenuation threshold selection of 100 come − 29 HU. Median Radiodensity was highlighted come visualize overall muscle fat infiltration (myosteatosis). Based on thresholds ranges of − 29 come 29 HU for fatty muscle and also 30 to 100 HU for skinny muscle, FMF was calculated. CT Computed tomography, FMF fatty muscle fraction, HU Hounsfield units.


Statistical analysis

SPSS Statistics 24 (IBM, Armonk, NY, USA) and Prism 8 (GraphPad Software, La Jolla, CA, USA) were supplied for statistical analysis. Data ware checked for normal circulation using the Shapiro–Wilk test. If generally distributed, continuous variables room expressed as method with typical deviation and also otherwise are given as medians with 25th and 75th interquartile ranges (IQR). Categorical data are presented as pure frequencies. For survive analysis, the cohort was binarized based on median FMF v a cutoff worth of > 44% to define high FMF. The Kaplan–Meier technique with log-rank test was provided to compare survival in between these two groups. For group comparison of consistent variables, unpaired t-test and also Mann Whitney U test were offered for parametric and also nonparametric testing, respectively. Categorical data were compared using one of two people χ2 check or Fisher’s precise test, together appropriate. A multivariable logistic regression version was developed to recognize the affect of FMF and also clinical variables top top 1-year mortality. Covariates were selected a priori, including FMF together a continuous variable alongside v a collection of routinely accessible factors that were judged to have actually a potential affect on outcome based upon clinical judgement. These components were the respiratory ECMO survival Prediction (RESP) score as it was formerly proposed together a validated measure up to predict survival in ECMO patients1, the Charlson Comorbidity table of contents (CCI) together an indicator of severe comorbidities, the simplified Acute Physiology Score II (SAPS II) as an indicator of an illness severity, the expression of ECMO support as well as baseline anthropometric features such as the body mass index (BMI). Outcomes of the cox regression analysis are presented as readjusted hazard ratio (HR) through 95% confidence interval (CI). Spearman correlation coefficient was calculated to check the correlation in between FMF and consistent clinical determinants within the model. The level of statistical meaning was set to P 
Full size table

*


*