Methods
We performed a prospective cohort study from July 2018 to April 2020 in children from 0-2 years with physician suspected airway anomalies. We suspected airway anomalies in the presence of either persistent (more than two weeks) inspiratory or biphasic (both inspiratory and expiratory) stridor or children with persistent (more than two weeks) barking or brassy cough or children with unexplained wheezing that is not responding to inhaled steroids for 4-8 weeks with proper compliance and technique or choking while feeding without significant developmental delay. We excluded children with hypoxia (SpO2 <92%), hemodynamic instability, naso-facial deformities, tracheostomy and pulmonary bleed. We recorded detailed history, physical examination and baseline data of all enrolled children. Then these children underwent IPFT and bronchoscopy. The two investigations were done within a week of each other. The person doing the IPFT was not aware of bronchoscopy findings if bronchoscopy was done earlier.
The IPFTs (TBFVL) were done during sleep or light sedation by trichlophos single dose of 50 mg/kg. TBFVL was performed in the pulmonary function test lab with EXHALYZER-D equipment (ECO MEDICS, Duernten, Switzerland) having Spiroware-1 software. Bronchoscopy was performed as per unit protocol under conscious sedation. Three observers (SKK, KRJ, AP) independently reported abnormalities and severity after seeing the saved bronchoscopy video. IPFT were also reported by three observers blindly, and in case of discrepancy, the final diagnosis was made by discussion.
Patterns and parameters of IPFT were compared with findings of bronchoscopy. We categorized the IPFT curve into the following five patterns, as shown and explained in Figure 1, modified from the study by Filippone et al. (5).