Acquired subglottic cysts: a case-control study

Background: Subglottic cysts (SGCs) are rare but important causes of stridor in infants. They may cause significant upper airway obstruction and potentially lethal consequences, particularly when exacerbated by upper respiratory tract infections. Although typically seen in preterm infants, there is a lack of literature regarding their aetiology apart from the common finding of preterm birth and intubation. Previous studies have reported series of cases without control groups. We aimed to determine the risk factors in patients with SGCs compared to a matched cohort of intubated patients who did not develop cysts. Methods: A retrospective case-control study was conducted, reviewing reports of all microlaryngoscopies and bronchoscopies conducted in a tertiary paediatric hospital from January 2009 to 2014. The cases were matched to controls based on gestational age, birth weight, and age. The medical records of the patients and controls were reviewed to identify the possible risk factors, including gestational age, weight, suction frequency, duration of intubation, number of re-intubations, and size of the endotracheal tube (ETT). Results: SGCs were identified in 15 of the 1,095 microlaryngoscopies and bronchoscopies performed. Of the 15 patients, 14 were born premature. All patients with SGCs were ventilated, and 13 of the 15 controls were ventilated. The overall duration of ventilation and frequency of re-intubation were similar between the two groups; however, patients with SGCs had a higher frequency of ETT suction (P=0.002). Conclusions: This study demonstrated an association between SGCs in preterm infants and previous intubation. SGCs are associated with an increased suction frequency in intubated infants. The increased suction frequency may be due to conditions that increase secretion, such as infection or acid reflux, which are considered risk factors for subglottic stenosis. However, it is likely that infants with repeated or multiple manipulations of the airway may be at a higher risk of developing SGCs and should be followed up closely to avoid potentially life-threatening complications.