CPAP washout prior to reevaluation polysomnography: a sleep surgeon's perspective.

PURPOSE: Obstructive sleep apnea (OSA) is characterized by repetitive upper airway collapse during sleep, leading to decreased oxygen blood levels and arousal from sleep. The gold standard treatment option for moderate to severe OSA is considered continuous positive airway pressure (CPAP). In case primary treatment with CPAP fails, a reevaluation of disease severity [by means of the apnea/hypopnea-index (AHI)] can be required. A subset of patients that prefer a CPAP alternative is still using CPAP until the reevaluation polysomnography (PSG), and a so-called washout effect is not ruled out. The purpose of this study is to evaluate the evidence on the existence and duration of this washout effect and its clinical relevance for current practice. METHODS: To identify papers for this review, an extensive literature search was run electronically through MEDLINE and EMBASE databases. RESULTS: An overview of currently available literature on this washout effect and the findings of 13 studies on this topic are discussed. CONCLUSION: There is some evidence that CPAP washout exists in patients with a stable BMI throughout the follow-up period. However, the intensity and duration of this effect remains unclear. Within the limitations of the present study, it seems reasonable to maintain a washout period of 1 week, in case alternative treatments options are considered and especially when a baseline PSG (and subsequent repeat PSG after treatment) is needed in case of clinical trials.

Inhibition of projections from the basolateral amygdala to the entorhinal cortex disrupts the acquisition of contextual fear.

The development of excessive fear and/or stress responses to environmental cues such as contexts associated with a traumatic event is a hallmark of post-traumatic stress disorder (PTSD). The basolateral amygdala (BLA) has been implicated as a key structure mediating contextual fear conditioning. In addition, the hippocampus has an integral role in the encoding and processing of contexts associated with strong, salient stimuli such as fear. Given that both the BLA and hippocampus play an important role in the regulation of contextual fear conditioning, examining the functional connectivity between these two structures may elucidate a role for this pathway in the development of PTSD. Here, we used optogenetic strategies to demonstrate that the BLA sends a strong glutamatergic projection to the hippocampal formation through the entorhinal cortex (EC). Next, we photoinhibited glutamatergic fibers from the BLA terminating in the EC during the acquisition or expression of contextual fear conditioning. In mice that received optical inhibition of the BLA-to-EC pathway during the acquisition session, we observed a significant decrease in freezing behavior in a context re-exposure session. In contrast, we observed no differences in freezing behavior in mice that were only photoinhibited during the context re-exposure session. These data demonstrate an important role for the BLA-to-EC glutamatergic pathway in the acquisition of contextual fear conditioning.