Hello everyone.
From a pathophysiologic point of view, how long is it reasonable to look back in the nasal flow signal of OSA patients to see whether a desaturation episode is related to a previous nasal flow reduction? The delay amount might depend on specific patient's characteristics. In that case, are there phenotypes of patients with obstructive sleep apnoeas that take such delay variability into account?
Thank you in advance.
Hello Matteo,
Here is the study that might be helpful:
Ng AS, Wong TK, Gohel MD, Yu WW, Chung JW, Fan KL. Using pulse oximetry level to indicate the occurrence of sleep apnoea events. Stud Health Technol Inform. 2006;122:672-5.
In brief, this research on ten people ( all men, mean age 45 /SD 8.9, body mass index 27/SD 3.3, apnea/hypopnea index 47/SD 15) attempted to select pulse oximetry (SpO2) level as an alternative parameter to indicate the occurrence of sleep apnoea. Time differences were compared between the "onset of nasal airflow cessation" and the "onset of three percent oxygen desaturation from the baseline" during sleep apnoea events. The results of this study showed there was around a twenty second delay after the onset of the cessation of nasal airflow. The paper provides results for each individual patient: the lowest time, in second (mean/SD) is 19.5/5.8, and the highest is 27.3/7.74.
These researchers concluded that the SpO2 level is not immediately sensitive to the occurrence of sleep apnea, where the time delay may be caused by: i) time utilized by the devise to process the signal, ii) time needed to carry deoxygenated blood to the finger, or iii) the desaturating of SpO2 level, which is affected by the last sleep apnea event and during the occurrence of repetitive events.
Hope this helps. Best wishes with your study,
Tatyana
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