Trends in Pediatric Hypoxia Altitude Simulation Testing (HAST): Data from a Pediatric Referral Center

Abstract

Rationale: Hypoxia altitude simulation tests (HASTs) simulate changes in physiology that occur during commercial air flight (FiO2 16% in cabin pressurized to 8,000 ft) and help identify patients who may need additional respiratory support during flight. There is a paucity of literature regarding pediatric HAST studies. The purpose of this study is to identify patient characteristics, indications, and results of HAST studies at a pediatric tertiary care referral center. Methods: This IRB-exempt, retrospective chart review examined HAST studies over 5 years (2017-2021) at Nemours Children's Hospital (Wilmington, Delaware, USA). HAST studies were performed by respiratory therapists, supervised by pulmonologists, in the PFT laboratory. Standard protocol for the studies was performed including administration of 16% oxygen while monitoring SpO2 and heart rate for 10 minutes and administration of supplemental oxygen as indicated. Patient information collected included: demographic and anthropometric data, primary indication for HAST, baseline respiratory support, co-morbidities, reported prior difficulty with air travel, and results. Descriptive statistics were calculated. Results: 22 studies were ordered, and 12 were completed. Characteristics of patients who completed testing (N=12) are as follows: Mean age 77.0 (range 1.4-216) months, mean weight 21.7 kg, 58% male, 75% white, 8.3% with baseline tracheostomy/ventilatordependence, and 16.7% with baseline supplemental oxygen dependence. 25% reported history of difficulty with air flight. The most common primary indications included chronic lung disease of prematurity (41.7%), followed by restrictive lung disease (50%), followed by sickle cell disease (8.3%). Of the 12 patients who completed testing, 4 had abnormal results. Of those, the mean age was 45.6 months, mean weight 12.6 kg, 75% were male, and 50% on supplemental oxygen at baseline. The most common indications were chronic lung disease of prematurity (50%) followed by restrictive lung disease (50%). The most common co-morbidity was asthma (75%). See Table 1. Compared to patients who had normal results, patients with abnormal testing had a greater change in SpO2 (10.8 vs 4.9%) with lower mean SpO2 nadir of 87% compared to 93.6%. Discussion: The most common indications for HAST studies in this pediatric study include chronic lung disease of prematurity, restrictive lung disease, and sickle cell disease. Many studies were not completed, likely due to decrease in air travel during the Covid-19 pandemic. Patients with abnormal results were younger and more likely to have baseline oxygen requirements. Further research is needed to better understand which pediatric patients are at risk for cardiorespiratory compromise during flight or at altitude.