Obesity By Subjective Physician Identification Can Serve As A Substitute For Anthropometric Calculation

Body mass index (BMI) is widely used to characterize adiposity and indicate disease risk. In trauma and emergency settings, many patients are unable to provide height and weight. In these situations, it is important to understand the effect of subjective assessment on treatment outcomes. PURPOSE: To compare objective BMI measurement to subjective obesity classification on patient outcomes. METHODS: We analyzed 1,344 thoracic trauma patients from the registry of a Level 1 trauma center. Independent variables were objective BMI by height-weight assessment and subjective physician-identified obesity. Dependent variables were systolic blood pressure (SBP), diastolic pressure (DBP), duration in the intensive care unit (ICU), and days on mechanical ventilation. Blood pressure was analyzed using linear regressions and duration of care was analyzed with negative binomial regressions. Potential confounding variables were held constant. RESULTS: Subjective obesity status was documented in all applicable patients. Objective BMI was measured in 61.6% of patients (n = 828). Patient age was 55.5 ± 20.3 yr, BMI was 28.3 ± 6.6 kg/m2, SBP was 132.8 ± 30.4 mmHg, and DBP was 80.7 ± 17.0 mmHg. Mechanical ventilation was used in 320 patients (23.9%) for a duration of 10.0 ± 10.9 days, and 669 patients (49.8%) were admitted to the ICU for a mean duration of 7.2 ± 9.2 days. Holding age and injury severity constant where significant, physician identification of obesity predicted 2.5 mmHg higher SBP (p = 0.259; 95% CI of β: -1.9 to 7.0), 1.5 mmHg higher DBP (p = 0.264; 95% CI of β: -1.1 to 4.1), 5.5-fold longer duration in the ICU (p = 0.018; 95% CI of IRR: 1.4 to 39.9), and 52.9-fold longer duration on ventilation (p = 0.045; 95% CI of IRR: 1.1 to 2,562.4). Anthropometric classification of obesity predicted 3.8 mmHg higher SBP (p = 0.050; 95% CI of β: -0.0 to 7.7), 2.6 mmHg higher DBP (p = 0.034; 95% CI of β: 0.2 to 5.0), 4.4-fold longer duration in the ICU (p = 0.044; 95% CI of IRR: 1.0 to 18.4), and 68.1-fold longer duration on ventilation (p = 0.024; 95% CI of IRR: 1.8 to 2,635.3). CONCLUSION: Obesity predicted higher blood pressure and worse outcomes in thoracic trauma patients. If height and weight are inaccessible, a physician's estimation of body composition may serve as a relatively accurate substitute for calculating BMI using anthropometric measurements.