METHODS: All military personnel referred for deployed-related pulmonary symptoms underwent a standardized evaluation. Studies included allergy testing, HRCT imaging, ECG, and echocardiography. Pulmonary function testing consisted of full PFTs with LV, DLCO; post-BD testing, impulse oscillometry (IOS), and exhaled nitric oxide. Further diagnostic tests also included methacholine, laryngoscopy, cardiopulmonary testing, and bronchoscopy with bronchoalveolar lavage. Impulse oscillometry measures resistance (R5 and R20) and reactance (X5) using non-effort dependent sound wave frequencies.