It is important to observe sleep in both the supine and decubitus postures, as obstruction occurring in the supine posture can be simply relieved by position training. Failure to observe apnoeas during a short period of sleep does not of course exclude OSA syndrome. Modern equipment enables the arterial oxygen saturation and pulse rate to be recorded for at least 8 hours overnight and can be used at home. Overnight arterial oxygen saturation monitoring. A patient with severe obstructive sleep apnoea.
Recording shows multiple dips in oxygen saturation.
Overnight arterial oxygen saturation monitoring. The same patient while receiving continuous positive airway pressure via a nasal mask throughout the night. The recording shows the abolition of dips and is essentially a normal tracing. Figure 5a shows a recording of the SaO2 characteristic of OSA syndrome. A totally flat trace in a patient who says he slept well virtually excludes the diagnosis.