HSC Section 6 Nov2016 Green Book

Reprinted by permission of Laryngoscope. 2015; 125(5):1093-1097.

The Laryngoscope V C 2014 The American Laryngological, Rhinological and Otological Society, Inc.

Does Body Mass Index Predict Tracheal Airway Size?

Brian D’Anza, MD; Jesse Knight, MD; J. Scott Greene, MD, FACS

Objectives/Hypothesis: To determine the relationship between body mass index along with other anthropomorphic variables as they relate to tracheal airway dimensions. Study Design: Retrospective case series. Methods: This was a radiographic study of 123 consecutive hospitalized patients undergoing tracheotomy over a 4-year period (2007–2011). We measured airway dimensions in axial computed tomography imaging and made comparisons with height, weight, body mass index, gender, and age. Measurements were taken at the first tracheal ring level including anterior- posterior length, width, and calculated area. We expected higher body mass index not to be a good predictor of larger airway dimensions. Results: The linear regression model showed body mass index was significantly inversely related to tracheal width after controlling for gender and age ( P 5 .0389). For every 1 kg/m 2 increase in body mass index, the tracheal width decreased by 0.05 mm. There was a trend for airway area to diminish with increasing body mass index. Conclusions: These results are consistent with the hypothesis that obese patients do not have larger airways. Our study indicated a trend toward smaller airways as body mass index increased. Specifically, as body mass index increases, tracheal width appears to decrease. This information should help medical professionals avoid the tendency to use a larger tube to secure the airway of an obese patient. Hopefully, this will result in further research into the field and may prevent future air- way injuries in a society where obesity has become epidemic. Key Words: Tracheal airway size, endotracheal tube size, obesity. Level of Evidence: 4 Laryngoscope , 125:1093–1097, 2015

INTRODUCTION General guidelines exist for endotracheal tube (ETT) size selection in adults. 1,2 Variations in the choice of tube selection are influenced by factors such as patient age, gender, and body habitus. Generally speak- ing, a larger diameter tube is used for adult males and those with larger body habitus when compared to females or smaller individuals. Tracheostomy tube selec- tion follows similar decision making algorithms in the adult population. 3 Due to normal anatomical variability, it is difficult to standardize recommendations for endo- tracheal and tracheostomy tube sizes for adults. 4 On a case-by-case basis, considerations for choosing a tube size might include those mentioned previously. Body dimensions that could be used to predict airway sizes include body mass index (BMI). A literature review From the Department of Otolaryngology, Head and Neck Surgery, Facial Plastic Surgery ( B . D ., J . S . G ), Geisinger Medical Center, Danville, Pennsylvania; and the ENT Associates of Los Alamos, PLLC ( J . K .), Los Alamos, New Mexico, U.S.A. Editor’s Note: This Manuscript was accepted for publication September 3, 2014. Presented at the 2013 American Academy of Otolaryngology–Head and Neck Surgery National Meeting, Vancouver, British Columbia, Can- ada, September 30, 2013. The authors have no funding, financial relationships, or conflicts of interest to disclose. Send correspondence to Brian D’Anza, MD, Department of Otolar- yngology, Head and Neck Surgery, Facial Plastic Surgery, Geisinger Medical Center, 100 N. Academy Ave., Danville, PA 17822. E-mail: bddanza@geisinger.edu

shows the lack of a study comparing BMI with airway dimensions. Larger-than-necessary ETTs are known to cause laryngeal or tracheal trauma and are to be avoided. Common problems can include laryngeal webs, vocal cord ulcerations, vocal cord paralysis or paresis, subglot- tic stenosis, and tracheal stenosis among others. 5,6 How- ever, our experience has shown the tendency of emergency medical providers and critical care physicians to place a larger tube in a larger patient. Based on our observations at time of tracheotomy, we have found that it is common to find a smaller than anticipated trachea in an obese patient. Based on this experience, we hypothesize that higher BMI is not a good predictor of larger airway size. The purpose of our study was to eval- uate the airway dimensions and identify anatomical con- cerns for the use of relatively oversized ETTs in an obese population. We measured airway dimensions in axial computed tomography (CT) imaging of 123 patients who underwent tracheotomy and made comparisons with their height, weight, BMI, gender, and age. MATERIALS AND METHODS The Geisinger Medical Center Office of Research Compli- ance and Institutional Review Board approved the retrospective electronic chart case series titled Predictors of Airway Size. The study was performed reviewing the information on 123 patients who underwent tracheotomy surgery by the otolaryngology department over a 4-year period (2007–2011) and who also had CT imaging of the trachea within the previous 3 months. Anthropomorphic measurements were taken from the time of

DOI: 10.1002/lary.24943

Laryngoscope 125: May 2015

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