Sleep respiratory concomitants of comorbid panic and nightmare complaint in post-traumatic stress disorder

Posttraumatic stress disorder (PTSD) patients with comorbid panic disorder (PD) may express additive symptoms of central fear system disturbance. They endorse elevated levels of sleep and nightmare disturbance [Leskin GA, et al., J Psychiatr Res 2002;36:449-452], and demonstrate movement suppression during laboratory sleep [Woodward SH, et al., Sleep 2002;25:681-688]. We estimated respiratory rate and rate variability separately for rapid-eye movement (REM) and non-rapid-eye movement (NREM) sleep. Subjects were 49 Vietnam combat-related PTSD inpatients (11 with comorbid PD and 38 without) and 15 controls. Computer-based estimates of respiratory rate and variability were derived from 10 to 18 hr of baseline sleep collected over two or three nights. Neither rate nor rate variability distinguished PTSD patients with comorbid PD from those without, or PTSD patients from controls; however, PTSD patients failed to exhibit the expected differences between REM and NREM respiratory rates. Moreover, the difference between REM and NREM respiratory rate was inversely related to a continuous measure of PTSD severity. PTSD patients with trauma-related nightmare complaint exhibited higher sleep respiration rates over both REM and NREM sleep. Conversely, in addition to slowed respiration, nightmare-free patients exhibited reduced respiratory rate variability in REM relative to NREM sleep, which was a reversal of the normal pattern. These finding are discussed in light of known telencephalic regulatory influences upon respiration rate.