Background: Near infrared spectroscopy (NIRS) has been used to assess the impact of obstructive sleep apnea-hypopnea syndrome (OSAHS) on cerebral oxygenation. However the relationship between the variations in the cerebral tissue oxygen saturation (ΔTOI) and the variations in pulse oximetry (ΔSpO2) has not been addressed in children with OSAHS.Aims and objectives: To assess the relationship between ΔTOI and ΔSpO2 in children with OSAHS.Methods: Consecutive clinically stable children with severe OSAHS (apnea-hypopnea index (AHI) >15 events/h) diagnosed during a nighttime polygraphy with simultaneous recording of cerebral oxygenation with NIRS (NIRO-200NX, Hamamatsu Photonics KK) were included. Maximal ΔSpO2 (SpO2 drop from the value preceding desaturation to nadir) and concomitant variations in transcutaneous carbon dioxide (ΔPtcCO2), maximal ΔTOI and maximal variations in cerebral oxygenated (O2Hb) and deoxygenated (HHb) hemoglobin were reported. The relationships between ΔSpO2, ΔPtcCO2 and ΔTOI, ΔO2Hb and ΔHHb were investigated.Results: The data from 5 children (age 9.6±6.7 years, AHI 16-91 events/h) were analyzed. Strong correlations were found between ΔSpO2 and ΔTOI (r=0.887, p<.001), and with ΔO2Hb and ΔHHb. Mean ΔSpO2 was 20±17% and mean ΔTOI was 8±7%. Maximal ΔSpO2 of about 70% were coupled with ΔTOI of no more than 35%. ΔPtcCO2 correlated only weakly with the cerebral oxygenation indexes.Conclusions: This pilot study shows a strong relationship between pulse oximetry and cerebral oxygenation in children with OSAHS, with lower changes in TOI as compared to SpO2. Future studies should address the clinical impact of respiratory events on cerebral oxygenation and its consequences.