101 - Relationships Between Lung Volume Measurements and Sleep Study Abnormalities in Adolescents with Severe Obesity

Poster Number: 101
Publication Number: 101.3272

Background: Severe obesity (BMI ≥ 35 kg/m2) is highly prevalent in pediatric patients and is associated with respiratory compromise. The relationships between lung volumes measured by pulmonary function tests (PFT) and polysomnography (PSG) in this group have not been well-studied; PFT variables may provide important data regarding sleep apnea risk.

Objective: To analyze the relationships between PFT and PSG in a cohort of youth with severe obesity and measure the impact of PFT on PSG parameters.

Design/Methods: This IRB-approved, retrospective review consists of pediatric patients ages 12-17 years who had both PSG and PFT performed between 2014-2018 at Nemours Children’s Hospital in Wilmington, Delaware. Patients completed upright, seated PFT and overnight PSG within the same 23-hour period for clinical purposes. The following data were collected from chart review: age, sex, insurance status, BMI, BMI Z-score, PFT lung volume data (TLC, RV, ERV and DLCO measured as % predicted for age/sex/height/ethnicity) and PSG data (OAHI, AHI, SpO2 nadir, peak EtCO2). Descriptive statistics were calculated. After Spearman rank correlations were calculated, multiple regression analysis was performed to explore the relationships between PFT variables on PSG variables, controlling for BMI, sex, insurance status.

Results: 215 patients [mean age 15.2(±1.7) years, 66.5% female, mean BMI 50.1(±7.2) kg/m2] were included in our analysis. There were high rates of sleep apnea (64.7%) with mean AHI 16.3±21.1 events/hour, mean OAHI 2.1(±7.3) events/hour, mean SpO2 nadir 87.8 ±7.2%, and mean peak EtCO2 of 50.6±3.9 mmHg. Lung volumes were notable for overall normal mean TLC (101.54±16.4)% and DLCO (93.5±17.2) but low-normal mean RV (82.1±39.3)% and decreased mean ERV (70.2±25.6)%. In multiple regression analysis, when controlling for BMI, sex, and insurance status, TLC was associated with peak EtCO2 (β= -0.04, p=0.02), OAHI (β= -0.006, p=0.09), AHI (β= -0.013, p=0.02), SpO2 nadir (β=0.08, p=0.01); DLCO was associated with peak ETCO2(β= -0.016, p< 0.001); ERV was associated with peak EtCO2(β= -0.03, p=0.02); RV was associated with OAI(β= -0.003, p=0.005).

Conclusion(s): In this cohort of youth with severe obesity, there were frequent respiratory abnormalities on PSG with high rates of sleep apnea. PFT abnormalities were less common, but there were multiple associations between PFT parameters (especially TLC) and PSG values, even when performed in seated, upright position. Pulmonary function testing, including lung volumes, may provide important data to determine which patients are most at risk of nocturnal respiratory compromise.