Quantifying Posttraumatic Stress Disorder Symptoms During Traumatic Memories Using Interpretable Markers of Respiratory Variability

Background: Posttraumatic stress disorder (PTSD) causes heightened fight-or-flight responses to traumatic memories (i.e., hyperarousal). Although hyperarousal is hypothesized to cause irregular breathing (i.e., respiratory variability), no quantitative markers of respiratory variability have been shown to correspond with PTSD symptoms in humans. Objective: In this study, we define interpretable markers of respiration pattern variability (RPV) and investigate whether these markers respond during traumatic memories, correlate with PTSD symptoms, and differ in patients with PTSD. Methods: We recruited 156 veterans from the Vietnam-Era Twin Registry to participate in a trauma recall protocol. From respiratory effort and electrocardiogram measurements, we extracted respiratory timings and rate using a robust quality assessment and fusion approach. We then quantified RPV using the interquartile range and compared RPV between baseline and trauma recall conditions, correlated PTSD symptoms to the difference between trauma recall and baseline RPV (i.e., <inline-formula><tex-math notation="LaTeX">$\Delta$</tex-math></inline-formula>RPV), and compared <inline-formula><tex-math notation="LaTeX">$\Delta$</tex-math></inline-formula>RPV between patients with PTSD and trauma-exposed controls. Leveraging a subset of 116 paired twins, we then uniquely controlled for factors shared by co-twins via within-pair analysis for further validation. Results: We found RPV was increased during traumatic memories (p <inline-formula><tex-math notation="LaTeX">$&lt;$</tex-math></inline-formula> .001), <inline-formula><tex-math notation="LaTeX">$\Delta$</tex-math></inline-formula> RPV was positively correlated with PTSD symptoms (p <inline-formula><tex-math notation="LaTeX">$&lt;$</tex-math></inline-formula> .05), and patients with PTSD exhibited higher <inline-formula><tex-math notation="LaTeX">$\Delta$</tex-math></inline-formula> RPV than trauma-exposed controls (p <inline-formula><tex-math notation="LaTeX">$&lt;$</tex-math></inline-formula> . 05). Conclusions: This paper is the first to elucidate RPV markers that respond during traumatic memories, especially in patients with PTSD, and correlate with PTSD symptoms. Significance: These findings encourage future studies outside the clinic, where interpretable markers of respiratory variability are used to track hyperarousal.