Tracheal Size and Morphology on the Reconstructed CT Imaging*

Abstract

Objectives: To characterize the real size and morphology of tracheas in childhood for the optimal selection of endotracheal tube. Design: A retrospective cohort study of pediatric patients who received CT scan of the cervical spine from July 2011 to March 2018. Cross-sectional CT images vertical to trachea were reconstructed and the accurate tracheal diameters were measured. The validity of the traditional age-based formula for predicting the endotracheal tube size was assessed for the best fit to trachea. Setting: Tertiary Emergency and Critical Care Center of Kyushu University Hospital. Patients: Children, who are 1 month to 15 years old, received CT scan of the cervical spine. Interventions: None. Measurements and Main Results: We enrolled 86 children with median age of 53 months. The cross-sectional shape of pediatric trachea was circular at the cricoid level and elliptical at the infraglottic level. The narrowest part of pediatric trachea was the transverse diameter at the infraglottic level at any age. Significant positive correlation between age and the narrowest diameter was observed. When compared the transverse diameter at the infraglottic level with the outer diameter of endotracheal tubes, uncuffed endotracheal tubes selection based on the traditional age-based formula ran a significant risk of oversized endotracheal intubation until 10 years old compared with cuffed endotracheal tubes selection (60.0% vs 23.8%; p < 0.05). Conclusions: These findings indicate the safety and efficacy of cuffed endotracheal tubes in infants and children and the reconsideration for the airway management in pediatric anesthesia and intensive care.

Cuffed vs Uncuffed Endotracheal Tubes for Pediatric Patients: A Review

“…Based on plaster molds of the pediatric airway in cadaveric studies, the funnel-shaped larynx was understood to transition towards a more cylindrical adult airway around 8 years of age. Recent CT, MRI, and video laryngoscopy studies have shown that the narrowest part of the pediatric airway is actually at the infraglottic level with an elliptical form of anteriorposterior greater than transverse diameter; although, the rigid cricoid ring is still functionally the narrowest part of the larynx [6][7][8][9]. The newly appreciated elliptical shaped airway at the level of the cricoid cartilage is potentially vulnerable to damage even from a properly sealed uncuffed tube.…”

Airway Management in Pediatric Patients: Cuff-Solved Problem?

“…The epiglottis is longer and U-shaped. The narrowest part of the pediatric airway seems to be the subglottic area [ 11 ], However, Dalal et al described the rima glottidis (as in adults) as the narrowest part [ 27 ]. The difference probably lies in the distensibility of these areas.…”

“…The subglottic area at the level of the cricoid ring is stiff and nondistendable, while the glottis area is distendable manually and even pharmacologically (muscle relaxation). After a detailed computed tomography evaluation of the pediatric airway, significant differences between the infraglottic area and the airway area at the level of cricoid were found [ 11 ]. These levels were traditionally defined as one, but according to Mizuguchi et al, the pediatric airways at the level of cricoid are indeed circular, as described previously [ 1 , 2 ]; however, the narrowest part of the airway lies at the infraglottic level (slightly above the cricoid cartilage) [ 11 ].…”

“…After a detailed computed tomography evaluation of the pediatric airway, significant differences between the infraglottic area and the airway area at the level of cricoid were found [ 11 ]. These levels were traditionally defined as one, but according to Mizuguchi et al, the pediatric airways at the level of cricoid are indeed circular, as described previously [ 1 , 2 ]; however, the narrowest part of the airway lies at the infraglottic level (slightly above the cricoid cartilage) [ 11 ]. The infraglottic area was elliptical in all analyzed patients (n = 86), with a short transverse diameter.…”

“…In the recent two decades, several articles revealing the lower incidence of postextubation stridor with cuffed tubes have been published [ 5 , 6 , 7 ]. Extensive anatomical research (real-time bronchoscopy, computed tomography and magnetic resonance imaging) revealed that the originally thought circular-shaped subglottic area is in reality elliptical, with a wide anteroposterior diameter and narrow transverse diameter [ 8 , 9 , 10 , 11 ]. These findings could explain the risk of postextubation stridor even with the properly placed uncuffed tube, which could severely damage the mucosa in the transverse edges of the subglottic region.…”