Heart rate variability (HRV) during Decreases in the Amplitude fluctuations of Pulse Photopletysmography signal events (DAP) is studied. The DAP duration and the time span of the polysomnography (PSG) recording under study are also considered for identification of Obstructive Sleep Apnea events in children. Oxygen desaturation is used as reference. The study involves recordings of 21 children. Periods of time associated with a drop in SaO2 of 3% from baseline during at least 5% of the time were labeled as pathologic. DAP events were detected using an automatic detector, HRV signal processing using the Smooth Pseudo Wigner-Ville Distribution was carried out in order to obtain several time and frequency HRV indexes. T-test was used to analyze differences between groups. The results show discrimination power between groups that increases as the duration of the time period under analysis, becomes shorter, and so more tune to the apneic episodes. Also HRV increase the discrimination power helping in discriminating DAP event non related to apnea.