Relation Between Bioelectrical Impedance Analysis (BIA) and CT-scan Analysis in the ICU

Study Overview
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Brief Summary
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Aim of the present study is to determine whether muscle mass as assessed by bioelectrical impedance analysis correlates with and corresponds to muscle mass as assessed by CT scan analysis in critically patients admitted to the intensive care unit.

Detailed Description
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BIA measurements are performed in critically ill patients admitted to the ICU or MC, within 72 hours before or after CT scanning. The BIA measurements are taken with the BIA 101 ASE, manufactured by Akern, Florence-7 Italy. This device is phase sensitive and injects an alternating current of 400 µA at 50 kHz. Measurements were performed while patients lay in supine position with a pillow supporting the head. The resistance, reactance, body weight and length are entered in the BIA algorithm, using BodyGram PRO. This algorithm calculated the body composition, with muscle mass being reported in kilogram (kg). Abdominal CT scans are analyzed using the computer program SliceOmatic® version 4.3 and 5.0 (TomoVision, Montreal, QC, Canada) at the level of the third lumbar vertebra (L3). The muscle tissue was identified by using boundaries in Hounsfield Units (grayscale) set of -29 to +150(23). The program computes muscle surface area in cm2, by multiplying the pixel area by the amount of pixels identified as muscle. For a direct comparison with the BIA-derived muscle mass, the CT-derived muscle area is converted to kg. This is done by following two steps. Firstly, the Shen equation is used for the conversion to litres.Secondly, the muscle volume is multiplied by its density, resulting in muscle mass expressed in kg.

Official Title
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Relation Between Bioelectrical Impedance-derived Muscle Mass and CT-derived Muscle Area in Critically Ill Patients

Conditions
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Muscular Atrophy

Intervention / Treatment
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* Other: BIA


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Abdominal CT-scan made for diagnostic reasons Exclusion Criteria: CT-scan not analysable Internal or external metal devices active pacemaker

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| BIA and CT<br>Patients who had a CT-scan made for diagnostic reasons. | Other: BIA<br>* Bioelectrical impedance analysis was performed within 4 days after a CT-scan was made<br>* Other names: Bioelectrical impedance analysis;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Agreement between BIA-derived muscle mass and CT-derived muscle mass | Agreement will be calculated using a Bland-Altman plot | Patient's data from the ICU-stay will be used, an average of one week | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Sensitivity of BIA to identify low muscle patients | Using CT-derived cut-off points, sensitivity of BIA to identify the same patients as having low muscle will be calculated | Patient's data from the ICU-stay will be used, an average of one week | 
| Specificity of BIA to identify low muscle patients | Using CT-derived cut-off points, specificity of BIA to identify the same patients as having low muscle will be calculated | Patient's data from the ICU-stay will be used, an average of one week | 
| Correlation between BIA-derived muscle mass and CT-derived muscle mass | Correlation will be calculated using Pearson's r | Patient's data from the ICU-stay will be used, an average of one week | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Muscles, Intensive Care, Tomography, X-Ray Computed, Electric Impedance