Middle latency auditory evoked potentials in sleep apneics during waking and as a function of arterial oxygen saturation during apneas.

In adults with obstructive sleep apnea middle latency auditory evoked responses were recorded as a function of apnea-related arterial oxygen desaturation both before sleep onset and during nocturnal sleep. In waking, wave Pa latency was normal in five of six subjects, and Pa amplitude was normal in all. During sleep apneas, wave Pa remained stable even during intervals of severe oxygen desaturation (e.g., 45-90% and 50-84% saturation in two subjects). Furthermore, wave Pa recorded immediately on awakening in the morning was unaltered compared with the response recorded just prior to sleep onset, despite a high frequency of nocturnal apneas in all subjects. These data indicate that repetitive nocturnal oxygen desaturation associated with severe obstructive sleep apnea syndrome has neither immediate nor cumulative measureable effects on the functioning of neurons that subserve the middle latency evoked response. These findings are discussed in relation to a possible cortical contribution to the middle latency response.