The Effects of Continuous Positive Airway Pressure (CPAP) Treatment on Fear Learning in Veterans with Obstructive Sleep Apnea with and without Co-morbid Posttraumatic Stress Disorder (PTSD) Open Access
Kantarovich, Diana (2017)
Abstract
Posttraumatic stress disorder (PTSD) is a debilitating neurological condition that results from exposure to an extremely stressful and dangerous event. Primarily, this disorder is characterized by three major symptom clusters: re-experiencing, avoidance, and physiological alterations. Intrusive nightmares as well as co-morbid breathing impairments during sleep, such as obstructive sleep apnea (OSA), lead to sleep disruptions. Sleep has been widely associated with memory consolidation and learning. Considering patients diagnosed with PTSD have an impaired ability to discriminate between danger and safety cues, we propose that these impairments might be enhanced by reductions in sleep, more specifically, by disruptions in rapid eye movement (REM) sleep. Our study identified 41 veterans from the Sleep Clinic (Veterans Affairs Long Beach Healthcare System, Long Beach, CA). Twenty-three were diagnosed with OSA and were treated using continuous positive airway pressure (CPAP) for approximately eight weeks. We used a protocol where conditioned fear was acquired throughout the AX+/BX- Discrimination paradigm. During Acquisition, two shapes were presented together and paired with an aversive airblast to the larynx (AX+) and another set of shapes were presented and not reinforced by the unconditioned stimulus (BX-). Stimuli A and B were presented together to measure the inhibition of conditioned fear. Additionally, participants underwent Extinction Learning, where the conditioned stimulus was no longer reinforced, and after 24 hours they underwent the Recall of Extinction Test. These assessments were conducted both pre- and post-CPAP treatment. All patients showed a robust fear-potentiated startle to the reinforced stimulus. Our results demonstrated that CPAP treatment enhanced the ability to inhibit fear responses in patients with OSA. Additionally, participants with OSA showed rapid extinction of the previously conditioned stimulus both prior and after CPAP treatment. However, patients with OSA and co-morbid PTSD had an impaired ability to extinguish prior to the CPAP treatment. Our study advocates for further research in this group of veterans in order to better understand the underlying neurobiology leading to the results found in our study and to improve current protocols for treatment in patients with these disorders.
Table of Contents
Introduction……………………………………………………………………………………………………………………1
Methods………………………………………………………………………………………………………………………… 8
Results…………………………………………………………………………………………………………………...…….14
Discussion……………………………………………………………………………………………………………………..18
Figures and Tables…………………………………………………………………………………………………………26
Figure 1. AX+/BX- Discrimination Paradigm………………………………………………………...…….26
Figure 2. Diagram of the Trials During AX+/BX- Session…………………………………..........27
Figure 3. Fear Acquisition: Fear-Potentiated Startle.…………………………………………….…….28
Figure 4. Fear Acquisition: CS Discrimination and Transfer of Inhibition Test…...…....29
Figure 5. Extinction Learning and Extinction Recall Test………………………………………….….30
Figure 6. Fear Acquisition (OSA and PTSD): Fear-Potentiated Startle………………….…….31
Figure 7. Fear Acquisition (OSA and PTSD):
CS Discrimination and Transfer of Inhibition Test………..............………………………………..32
Figure 8. Extinction Learning and Extinction Recall Test (OSA and PTSD)…………..…….33
Table 1. Retrospective Chart Review of Patients with OSA……………………………............34
Table 2. Demographic and Clinical Information…………………………………………………………...34
References………………………………………………………………………………………………………………………35
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