Interpreting CPAP device respiratory indices in children

Study Objectives: An increasing number of children with obstructive sleep apnea (OSA) require treatment with continuous positive airway pressure (CPAP). This study aimed to determine whether automatic respiratory indices from a CPAP device accurately predict manually determined respiratory indices derived from overnight polysomnography (PSG) in children. Methods: Consecutive children undergoing manual CPAP titration PSG using a ResMed VPAP ST-A (S9) were included. The apnea-hypopnea index (AHI), apnea index (AI), and hypopnea index (HI) from automatic analysis of the CPAP device for that night (AHI_CPAP, AI_CPAP, and HI_CPAP) were compared with manually derived respiratory indices (RDI_PSG, OAHI_PSG, AI_PSG, and HI_PSG) using the Wilcoxon matched-pairs signed-ranks test. Results: Forty-six children (32 boys; median age, 13.5 years; range, 4.6–20.0 years) were included. There was no difference between RDI_PSG and AHI_CPAP (P = .6) nor between HI_PSG and HI_CPAP (P = .2). AI_PSG was significantly lower than AI_CPAP (mean difference −1.3 events/hr, P < .001). AI_PSG and AI_CPAP were strongly correlated (r² = .72, P <.01), but the CPAP machine overestimated the number of apneas at higher AIs. OAHI_PSG was significantly lower than AHI_CPAP (P =.003) but strongly correlated (r² = .87, P < .01). The CPAP device significantly underestimated the number of hypopneas at higher indices. Using the manually scored OAHI_PSG of ≥5 events/hr to define significant residual OSA, the AHI_CPAP had a high specificity (0.95) but low sensitivity (0.20). Conclusions: The ResMed S9 respiratory indices are not accurate enough to guide treatment decisions in children; in particular, they do not rule out the presence of residual OSA in children that remain symptomatic on CPAP. A low AHI_CPAP is reassuring in the context of a stable patient but may miss ongoing hypopneas.