Cardioventilatory Impairments in Deployed Post-9/11 Veterans: 3645 Board #84 June 4, 9: 30 AM - 11: 00 AM.

Following deployments to Iraq or Afghanistan (post-9/11), military veterans have reported exercise intolerance, dyspnea and other symptoms that may be associated with exposure to deployment-related airborne hazards (e.g., burn pit smoke, particulate matter air pollution). While veterans may be more susceptible or vulnerable to the harmful effects of air pollution and other hazardous agents, very little is known about their functional health status post-deployment. PURPOSE: To compare cardioventilatory responses to exercise and paced breathing in deployed post-9/11 veterans and non-deployed controls. METHODS: 32 deployed veterans (6 women; 35.4±8.2 years) and 18 controls (5 women; 33.2±9.7 years) underwent a maximal, symptom-limited cardiopulmonary exercise test (Bruce) on a motorized treadmill and performed a paced breathing protocol at a fixed rate (6 breaths·min-1). Cardioventilatory and electrocardiographic signals were collected continuously throughout each protocol. In addition, health-related questionnaires and symptoms were assessed for all participants. RESULTS: Peak oxygen consumption relative to body mass was similar between-groups (deployed, controls: 33.7±8.3, 34.5±10.4 ml/kg/min), but deployed veterans had an earlier ventilatory threshold onset (5.6±1.1 vs. 7.3±1.9 min; p<0.001), more severe dyspnea (5.1±1.8 vs. 3.4±1.4; p<0.001) and slower heart rate recovery (42.9±13.7 vs. 53.3±18.5 bpm; p=0.03). Heart rate variability indices derived from paced breathing indicated reduced total power (5154.0±4529 vs. 10529.9±10211.3 ms2; p=0.02) and amplitude of respiratory sinus arrhythmia (9.4±4.9 vs. 14.1; p=0.01). CONCLUSIONS: Despite similar levels of cardiorespiratory fitness, deployed veterans reported more severe dyspnea and demonstrated a slower post-exercise heart rate recovery than non-deployed controls. Blunted heart rate recovery along with reduced heart rate variability during paced breathing may suggest impaired cardiac autonomic control in deployed veterans with respiratory symptoms.