0480 Less Is More? A Study Comparing Outcomes Between 4% vs 3% Hypopnea Scoring Rules

Abstract Introduction The definition of respiratory events has evolved over decades. The current American Academy of Sleep Medicine scoring manual recommends hypopneas be defined by a ≥ 30% airflow reduction with either ≥ 3% desaturation or an arousal, while the prior “recommended” criteria of a ≥ 30% airflow reduction and associated ≥ 4% oxygen desaturation (with no requirement of arousal) was changed to “optional”. Consequently, events previously characterized as a respiratory effort related arousal (RERA) may now be defined as a 3% hypopnea. We hypothesized that while the 3% apnea-hypopnea index (3%AHI) will be higher than the 4%AHI, the 3%AHI will be similar to the 4% respiratory disturbance index (4%RDI), and that the measurement of RERAs under 3% scoring criteria will be clinically insignificant. Methods We prospectively collected 70 consecutive in-lab polysomnography results in 4 adult age groups. We re-scored the respiratory events utilizing the 3% hypopnea rule, and compared the differences between 3% and 4% scoring criteria. Results Among the 70 studies (mean age 50, males 46%), the 3%AHI was significantly higher than the 4%AHI (+9.247 ± 1.161, p< 0.001). This was mainly due to increased hypopnea events (+10.313 ± 1.617, p< 0.001). The 3%AHI was significantly different from the 4%RDI (+7.096 ± 1.133, p< 0.001). There were no significant differences between the 3% and 4% RERA indices, with both values being minimal. Results were similar in both diagnostic and titration phases of testing. Conclusion As previously shown, utilizing the 3% hypopnea rule results in an increased AHI. Most of this difference is related to hypopneas with negligible influence of RERAs. This may lead to increased diagnosis and severity of sleep-disordered breathing in the adult population, and potentially be associated with payer ramifications. Our findings demonstrated negligible RERA indices on average with either rule, thus calling into question the clinical significance of this index in most patients. Support (if any) NA