Inclusion Criteria:  clinically stable CTED or post-PE syndrome patients, as defined by stable hemodynamic status, optimized medical treatment, no changes in medication dosage or frequency of administration with no hospital admissions in the preceding 6 weeks; a diagnosis of persistent, moderate to severe exertional dyspnea ≥ 6 months following PE as confirmed by study physician at time of enrollment by a modified Medical Research Council (mMRC) dyspnea scale =2, or Baseline Dyspnea Index (BDI) focal score <=6; male or female non-pregnant adults >20 years of age; ability to perform all study procedures ability to provide informed consent  Exclusion Criteria:  women of childbearing potential who are pregnant or trying to become pregnant; echocardiographic evidence of pulmonary hypertension prior history of unstable pulmonary thromboembolism or systemic connective tissue vasculopathy, active cardiopulmonary disease or other comorbidities that could contribute to dyspnea and exercise limitation; history/clinical evidence of asthma, atopy and/or nasal polyps; history of hypercapnic respiratory failure or a clinical diagnosis of sleep disordered breathing; important contraindications to clinical exercise testing, including inability to exercise because of neuromuscular or musculoskeletal disease(s); body mass index (BMI) <18.5 or ≥35.0 kg/m2; use of daytime oxygen or exercise-induced O2 desaturation (<80% on room air).