Neonates With Tracheomalacia Generate Auto-Positive End-Expiratory Pressure via Glottis Closure

Area of Science:

• Neonatal respiratory physiology
• Pediatric airway disorders
• Medical imaging and computational modeling

Background:

• Tracheomalacia is a pediatric airway condition causing tracheal lumen collapse during breathing, potentially requiring respiratory support.
• Adults with tracheomalacia can self-generate positive end-expiratory pressure (PEEP) by narrowing the glottis to prevent airway collapse.
• The phenomenon of auto-PEEP in newborns with tracheomalacia has not been previously investigated.

Purpose of the Study:

• To measure the glottis cross-sectional area throughout the breathing cycle in neonates.
• To quantify the total pressure difference through the glottis in neonates with and without tracheomalacia.
• To investigate the potential for auto-PEEP in neonates with tracheomalacia.

Main Methods:

• Ultrashort echo time MRI was performed on 21 neonatal ICU patients (11 with tracheomalacia, 10 without).
• MRI scans were reconstructed at four breathing phases; computational fluid dynamics simulations were used for patient-specific airway models.
• The study quantified glottis cross-sectional area and total pressure difference through the glottis and trachea.

Main Results:

• Neonates with tracheomalacia exhibited a mean glottis cross-sectional area less than half that of controls at peak expiration (4.0 vs 10.3 mm²; P=.002).
• The mean total pressure difference through the glottis at peak expiration was over 10 times higher in neonates with tracheomalacia (2.88 vs 0.26 cm H₂O; P=.005).
• These findings indicate significant glottic narrowing in neonates with tracheomalacia during expiration.

Conclusions:

• Neonates with tracheomalacia actively narrow their glottises during expiration.
• This glottic narrowing generates increased pressure in the trachea, functioning as a form of auto-PEEP.
• This mechanism may help prevent tracheal collapse in neonates with tracheomalacia.