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Are scoring respiratory effort-related arousals worth the effort? --A study comparing outcomes between 4 % vs 3 %
Xinhang Tu1, Timothy I Morgenthaler2, Julie Baughn2
1Center for Sleep Medicine, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, USA.
Study Objectives:
The respiratory effort-related arousal (RERA) has been combined with apneas and hypopneas into the respiratory disturbance index (RDI). RERAs are characterized by ≥ 10 s of increasing upper airway effort terminating in arousal without meeting hypopnea criteria. The recent change to hypopnea definitions now includes a ≥30 % reduction in airflow for 10 s with EITHER a 3 % oxygen desaturation OR an arousal. Consequently, many events previously categorized as RERAs will now be included in the 3 % hypopneas, likely reducing the number of events scored as RERAs. We hypothesized that the 3 % apnea-hypopnea index (3%AHI) would approximate the 4%RDI, with the number of 3 % RERAs being negligible.
Research Question:
How does the transition from the 4 % to the 3 % hypopnea rules impact the significance of RERAs in clinical practice, and how we should relate the AHI and RDI using the different hypopnea rules?
Methods:
We prospectively collected 76 consecutive polysomnography results in 4 adult age groups. We re-scored the respiratory events utilizing both the 3 % and the 4 % hypopnea rules and compared the outcomes.
Results:
Among 76 diagnostic studies (mean age 47.5 years, males 47.4 %), the 3 % RERA index [0.8 (0.0, 3.1)] [median (Q1, Q3)] was significantly lower than the 4 % RERA index [3.5 (1.0, 7.3)]. The 3%AHI was 3.07 ± 9.23 (mean ± SD) higher than the 4%RDI (p = 0.005). The 3%AHI was 8.63 ± 8.86 higher than the 4%AHI in all age groups (p < 0.001). This was mainly due to an increased hypopnea index (+8.51 ± 9.03, p < 0.001). In patients with obstructive sleep apnea (OSA), the 3%RERA contributes 4.3 % to the 3%RDI, while the 4%RERA contributes 27.7 % to the 4%RDI.
Interpretations:
Both 3%RDI and 3%AHI are higher than the 4%RDI, primarily due to identification of more hypopnea events, resulting in more patients being classified as having OSA. This change in criteria complicates the comparison of hypopnea and RERA contributions between sleep studies scored using the different hypopnea rules.
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