Abstract

NIGRO, C. A.  and  RHODIUS, E. E.. Effect of the definition of hypopnea on apnea/hypopnea index. Medicina (B. Aires) [online]. 2003, vol.63, n.2, pp.119-124. ISSN 0025-7680.

The objective of this study was to determine whether different decreases in oxygen saturation (SaO₂) or the presence of electroencephalographic arousals (EEGA) in the definition of hypopnea modify hypopnea index and apnea/hypopnea index and the prevalence of obstructive sleep apnea/hypopnea syndrome (OSAHS). A total of 20 polysomnographies performed in patients with OSAHS were analyzed. There are four different definitions of hypopnea: > 30% reduction in airflow or 50% decrease in abdominal movement associated with ¯SaO₂ > 3% (type 1); ¯ SaO₂ > 3% or EEGA (type 2); ¯ SaO₂ > 4% (type 3); ¯ SaO₂ > 4% or EEGA (type 4). The prevalence of OSAHS was calculated for an apnea/hypopnea index (AHI) > 10 and > 15. Hypopnea index (HI) and AHI types 2 and 4 were higher than type 3 (HI: type 2: 20±10.6, type 4: 18.6±10, type 3: 11.4±10, p < 0.001; AHI: type 2: 23.3±11.6, type 4: 21.4±11.2, type 3: 14.7±11.6, p < 0.001). No differences were observed between HI and AHI types 1 and 2 (HI: type 1: 17.4±10, type 2: 20±10.6; AHI: type 1: 20.6±11.8, type 2: 23±11.6, p > 0.05). The prevalence of OSAHS was 30-55% in type 3, 70-85% in type 4 (p < 0.05), and 70-85% in types 1 and 2 (p > 0.05). In our patient´s population, the presence of EEGA in the definition of hypopnea significantly increased the HI, the AHI and the prevalence of OSAHS when associated with a > 4% decrease in SaO₂.

Keywords : Diagnosis; Hypopnea; Sleep apnea syndrome.

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