When would you expect to see the highest concentration of respiratory events in a patient with REM-related apnea?

The highest concentration of respiratory events in a patient with REM-related apnea is typically observed during the last third of the study. This is primarily due to the normal sleep architecture, where REM sleep periods become more prolonged and frequent as the night progresses.

During the latter part of the sleep cycle, specifically in the last third, patients tend to experience longer episodes of REM sleep. REM sleep is characterized by atonia and a lack of respiratory drive, making individuals more susceptible to apneic events. As such, if a patient is experiencing REM-related apnea, the likelihood of these events increases significantly during this phase of sleep.

In contrast, the first third of the sleep study is predominantly composed of non-REM sleep stages, particularly stages 1 and 2, which are generally associated with a lower incidence of respiratory events. Similarly, the middle section may include transitions between sleep stages but does not yet reach the longer periods of REM that are characteristic of the final third of the study. An even distribution of events throughout the study is not expected due to the inherent nature of the sleep cycle and the specific characteristics of REM sleep.