Pediatric Sex-Differences in Large Conducting Airway Anatomy

Abstract

Background: The cross-sectional area of airways is the main determinant of resistance to airflow in the respiratory system. Recently, we showed the large conducting airways to be larger in height matched men. In pediatric patients, existing data for sex-differences in airway size is limited to indirect measurements, cadaveric studies involving a small number of subjects, only reporting tracheal data, and with a narrow spectrum of pediatric ages. There are no studies that compare sex-differences in airway size in pediatric population without respiratory comorbidities. We sought to assess sex-differences in luminal area of large conducting airways in pediatric patients with no history of respiratory comorbidities. Methods: Retrospective study of 225 pediatric patients who underwent a chest computed tomography (CT) scan in the emergency department as part of the trauma protocol between 03/13/2009-03/13/2019 at Mayo Clinic, Rochester MN. Using three-dimensional reconstructions from lowdose high-resolution CT-scans, we assessed the airway luminal area in healthy pediatric males (n=128) and females (n=97) and over a wide range of ages (1-17 yr). The luminal areas of large conducting airways were measured at three discrete points. A multivariable analysis was used to provide an estimate of the variance attributable specifically to sex differences. Results: No differences between the sexes were noted in the luminal airway areas of the youngest (age 1-12 yr.) children. However, in older (≥13 years old) the luminal areas were larger in males compared to females. On average, the luminal area of the trachea was 25% (218± 44 vs. 163±24 mm 2 , P<0.01) larger in males compared to females among older subjects (ages 14-17). Moreover, the difference in the luminal area of the left main bronchus, left upper lobe, and left lower lobe between sexes for these age groups were 24% (110±29 vs. 83±15 mm 2 , P<0.01), 20% (71±19 vs. 57±15 mm 2 , P<0.01), and 22% (63±15 vs. 49±10 mm 2 , P<0.01), respectively. Lastly, the sex-differences on the luminal airway size of the right main bronchus, bronchus intermedius, and right upper lobe were 20% (154±34 vs. 123±20 mm 2 , P<0.01), 18% (89±20 vs. 73±12 mm 2 , P<0.01), and 20% (59±15 vs. 47±11 mm 2 , P<0.01). These sex-airway differences were attenuated but persisted in the height adjusted analysis (Figure 1). Conclusions: Airways size is determined by height but also independently by biological sex. The sexdifferences are the result of hormonal changes during puberty and are not innate.