NeoQuest February 2023: A Preterm Infant with Unexpected Congenital Airway Anomaly

A 2-kg male infant with prenatally diagnosed right pulmonary agenesis was delivered at 34 weeks’ gestation due to maternal pre-eclampsia with severe features. He was admitted to the NICU in room air, but at 25 days of age, he develops acute respiratory failure with biphasic stridor requiring emergent intubation. Only a size 2.5-mm endotracheal tube can be placed without meeting resistance. Flexible bronchoscopy is performed with the findings (white arrows) shown in Figure 1A and 1B.

Figure 1A-B: Endoscopic images of the infant’s airway. From: Flemming B, Savioli K, Burruso L, Perkins J, Curtis J. Respiratory failure in an infant with known congenital anomalies and novel genetic defect. Neoreviews. 2023;24(2):e107–e111. neo.24-2-e107

What is the most appropriate ventilatory management strategy for this diagnosis?

1. Increase positive end expiratory pressure
2. Maintain a fraction of inspired oxygen (FiO₂) close to 1.0
3. Place a tracheostomy tube
4. Utilize a prolonged inspiratory time and low respiratory rate

Explanation:

Answer: D. Utilize a prolonged inspiratory time and low respiratory rate

The endoscopic images obtained from this patient demonstrate complete tracheal rings in the mid-trachea and severe distal tracheal stenosis consistent with congenital tracheal stenosis (CTS) (Figure 1A–B).¹ The infant’s CTS caused symptomatic airway obstruction and subsequent hypoxic and hypercarbic respiratory failure requiring intubation.

The anterior aspect of the trachea is typically composed of incomplete C-shaped rings of hyaline cartilage, which are connected posteriorly by the trachealis muscle (Figure 2).² CTS is hypothesized as a defect in embryogenesis of the primitive foregut around the 8^th week of gestation, causing complete, circumferential tracheal cartilage formation with absent posterior muscle tissue.² CTS has 3 distinct morphologic types: 1) generalized hypoplasia; 2) funnel-like stenosis; and 3) segmental stenosis (Figure 3).³ There is a spectrum of clinical presentations ranging from asymptomatic incidental findings to respiratory failure in the neonatal period. Infants with CTS may also be asymptomatic at birth and later develop respiratory failure when their physical growth surpasses the anatomical limitation of their trachea.¹ Operative repair is typically indicated in patients who present with significant respiratory symptoms.⁴ Given the prematurity and small size of the patient described in the vignette, intubation and mechanical ventilation are necessary temporizing measures while awaiting surgical repair. Depending on a patient’s CTS morphology, surgical options include primary reconstruction with end-to-end anastomosis in short segment stenosis, the slide tracheostomy technique, and tracheal reconstruction with autologous or heterologous graft material (Figure 4).^3,4

Figure 2: Endoscopic views of a normal larynx at the level of the subglottis (C) and midtrachea (D). From: Gallant JN, Ransom M, Kaspar A, Wilcox LJ, Whigham AS, Engelstad HJ. Neonatal laryngotracheal anomalies. Neoreviews. 2022;23(9):e615

Figure 3: Anatomic classification of CTS from Cantrell and Guild. Type 1 is generalized hypoplasia, type 2 is funnel-like stenosis, and type 3 is segmental stenosis. Affected areas are highlighted. From: Hofferberth SC, Watters K, Rahbar R, Fynn-Thompson F. Management of congenital tracheal stenosis. Pediatrics. 2015;136(3):e661

Figure 4: Slide tracheoplasty technique. The stenosed tracheal area is identified and transversely divided at the midpoint (A). Then, the upper stenotic segment is incised posteriorly, and the lower stenotic segment is incised anteriorly (B). Then, the ends of the two segments are brought together and sutured (C). The tracheal circumference is now doubled, and the cross-sectional area is quadrupled (D and E). From: Hofferberth SC, Watters K, Rahbar R, Fynn-Thompson F. Management of congenital tracheal stenosis. Pediatrics. 2015;136(3):e665

The infant’s CTS is causing increased airway resistance and turbulence, thereby decreasing airflow past the point of obstruction. His CTS also prevents effective lung emptying during exhalation, causing hypercarbia. Utilizing a prolonged inspiratory time with a low respiratory rate (Option D) allows for improved lung aeration and adequate time for expiration to decrease air trapping.⁵

The differential diagnosis for an infant presenting with increased work of breathing, stridor, and a persistent need for respiratory support should include a diagnosis of subglottic stenosis (SGS). SGS is defined as a narrowing of the airway to less than 4 mm at the level of the cricoid and is often seen in infants who have had a history of intubation.⁶ To diagnosis SGS, a rigid airway evaluation and measurement of the degree of stenosis are needed. The first-line treatment for SGS includes serial endoscopy with scar division, steroid injection, and balloon dilation. If first-line treatment fails or if the stenosis is severe, the infant may require a tracheostomy with tube placement (Option C) while awaiting definitive airway reconstruction.⁶ In our patient with CTS, a tracheostomy is not possible due to the presence of complete tracheal rings. If an endotracheal tube is unable to be placed in an infant with CTS, a laryngeal mask airway may be considered to maintain airway ventilation as a temporary measure.⁷

Increasing positive end expiratory pressure (Option A) helps increase functional residual capacity (FRC) and improves oxygenation. Per Poiseuille’s law, a decrease in airway radius results in an exponential increase in airway resistance, thus requiring a greater pressure gradient to maintain adequate airflow.⁶ In premature infants with respiratory distress syndrome (RDS), surfactant deficiency causes decreased FRC. In these patients, providing positive end expiratory pressure (PEEP) helps stabilize and recruit collapsed alveoli.⁸ RDS is not the cause of this infant’s respiratory distress because of the late presentation of respiratory distress. In our patient with CTS, increasing PEEP may result in increased barotrauma proximal to the level of the obstruction.⁵ Therefore, increasing PEEP should be utilized with caution and is not an ideal ventilatory management strategy in infants with CTS.

Maintaining a fraction of inspired oxygen (FiO₂) close to 1 (Option B) could be used to improve oxygenation in infants with respiratory distress but would not help improve ventilation. Infants who have congenital pulmonary abnormalities, such as pulmonary hypoplasia, are at risk for developing pulmonary hypertension. In infants with pulmonary hypertension, increasing FiO₂ may help with oxygenation, as oxygen is a potent pulmonary vasodilator. However, recent animal studies have shown that even brief exposure to a FiO₂ of 1.0 in newborn lambs result in increased contractility of the pulmonary arteries, reduced response to inhaled nitric oxide, and increased risk of oxidative stress.⁹ Adverse events stemming from hyperoxia in the neonatal period include increased airway reactivity and inflammation, a higher risk for retinopathy of prematurity, and hematologic cell abnormalities.¹⁰ While increasing FiO₂ may help with acute hypoxia, maintaining the FiO₂ close to 1 as a long-term management strategy would likely be both ineffective and potentially damaging for patients with CTS awaiting surgical correction.

Did you know?
Approximately 50% of patients with CTS can present with a congenital cardiac anomaly, including left pulmonary artery sling, patent ductus arteriosus, ventricular septal defect, and double aortic arch.¹¹ CTS has also been reported to occur with gastrointestinal, renal, and skeletal system anomalies.¹¹

What are the indications and contraindications for initiating extracorporeal membranous oxygenation in a neonate presenting with respiratory failure?
To find the answer, please refer to the following article: Parga J, Garg M. Extracorporeal membrane oxygenation in neonates: history and future directions. Neoreviews. 2017;18(3):e166-e172

February NeoQuest Authors
Angelina June MD, University of Virginia Children’s Hospital
Faith Kim, MD, Columbia University Medical Center

References:

1. Flemming BC, Savioli KA, Borruso LA, Perkins JN, Curtis J. Respiratory failure in an infant with known congenital anomalies and novel genetic defect. 2023;24(2):e107–e111
2. Sengupta A, Murthy RA. Congenital tracheal stenosis and associated cardiac anomalies: operative management & techniques. J Thorac Dis. 2020;12(3):1184–1193
3. Hofferberth SC, Watters K, Rahbar R, Fynn-Thompson F. Management of congenital tracheal stenosis. Pediatrics. 2015;136(3):e660–669
4. Dodge-Khatami A, Tsang V, Roebuck D, Elliott M. Management of congenital tracheal stenosis: a multidisciplinary approach. Images Paediatr Cardiol. 2000;2(1):29–39
5. Lodha R, Guglani L, Sharma SC, Kabra SK. Ventilatory management of severe tracheal stenosis. Indian J Pediatr. 2006;73(5):441–444
6. Gallant JN, Ransom M, Kaspar A, Wilcox LJ, Whigham AS, Engelstad HJ. Neonatal laryngotracheal anomalies. Neoreviews. 2022;23(9):e613–624
7. Nelson J, Lee H, Sinha P, Deutsch N. Management of complete tracheal rings in a neonate with tetralogy of Fallot. BMJ Case Rep. 2018;2018:bcr2018225392
8. Warren JB, Anderson JDM. Core concepts: respiratory distress syndrome. Neoreviews. 2009;10(7):e351–e361
9. Lakshminrusimha S, Keszler M. Persistent pulmonary hypertension of the newborn. Neoreviews. 2015;16(12):e680–692
10. Perrone S, Bracciali C, Di Virgilio N, Buonocore G. Oxygen use in neonatal care: a two-edged sword. Front Pediatr. 2017;9;4:143
11. Herrera P, Caldarone C, Forte V, Campisi P, Holtby H, Chait P, Chiu P, Cox P, Yoo SJ, Manson D, Kim PC. The current state of congenital tracheal stenosis. Pediatr Surg Int. 2007;23(11):1033–1044