Posttraumatic Stress Disorder Is Associated With a Decrease in Anaerobic Threshold, Oxygen Pulse, and Maximal Oxygen Uptake

Background: Posttraumatic stress disorder (PTSD) has been linked to respiratory symptoms and functional limitations, but the mechanisms leading to this association are poorly defined. Research Question: What is the relationship between PTSD, lung function, and the cardiopulmonary response to exercise in combat veterans presenting with chronic respiratory symptoms? Study Design and Methods: This study prospectively enrolled military service members with respiratory symptoms following deployment to southwest Asia. All participants underwent a comprehensive evaluation that included pulmonary function testing and cardiopulmonary exercise testing. Pulmonary function test variables and cardiopulmonary response to exercise were compared in subjects with and without PTSD by using multivariable linear regression to adjust for confounders. Results: A total of 303 participants were included (PTSD, n = 70; non-PTSD, n = 233). Those with PTSD had a greater frequency of current respiratory symptoms. There were no differences in measures for airway disease or lung volumes, but patients with PTSD had a reduction in diffusing capacity that was eliminated following adjustment for differences in hemoglobin levels. Participants with PTSD had a lower anaerobic threshold (23.9 vs 26.4 cc/kg per minute; P = .004), peak oxygen pulse (19.7 vs 18.5 cc/beat; P = .03), and peak oxygen uptake (34.5 vs 38.8 cc/kg per minute; P < .001). No significant difference was observed in gas exchange, respiratory reserve, or effort at peak exercise between participants with and without PTSD. Interpretation: A diagnosis of PTSD was associated with a reduced anaerobic threshold, oxygen pulse, and peak oxygen uptake. This objective reduction in cardiopulmonary work is independent of baseline lung function, was not associated with abnormalities in gas exchange or respiratory reserve, and may be related to deconditioning.