The purpose of this monocentric, preliminary study is to assess the evolution of pulmonary capillary blood volume (Vc), measured by the double diffusion nitric oxide/carbon monoxide (NO/CO) method (Guenard et al.; Respir Physiol 1987), from the starting of the anticoagulant therapy to 6 months after, and to search correlations with the evolution of clinical (dyspnea and results of the 6 minutes walking test), biological (BNP; Troponin), echocardiographic (right ventricular dysfunction, pulmonary arterial pressure) and ventilation/perfusion lung scan data.

Inclusion Criteria:

• Patient with a first episode of symptomatic pulmonary embolism, treated with anticoagulant
• Age from 18 to 75 years-old

Exclusion Criteria:

• Confirmed pulmonary embolism in the past
• Massive pulmonary embolism, thrombolytic treatment
• Confirmed left heart systolic dysfunction
• Confirmed asthma, chronic obstructive pulmonary disease or pulmonary fibrosis
• Expected life below 6 months
• Pleural effusion with indication of evacuation
• Bronchopulmonary cancer
• Pulmonary surgery with resection of two lobes minimum
• Predictable incapacity to complete the 6 minutes walking test

Patient with a first episode of symptomatic pulmonary embolism