Our patient's pulmonary function tests revealed restrictive lung disease, as evidenced by modest reduction in lung volumes and normal airway flows. These findings may be consistent with interstitial lung disease. However, in the presence of clear lung fields on physical examination and chest X ray, idiopathic pulmonary arterial hypertension should be considered the more likely cause.
Ventilation perfusion scan
The next laboratory evaluation that should be carried out in our patient is a ventilation perfusion lung scan. This can rule out the presence of chronic thromboembolic disease as the cause of our patient's pulmonary hypertension.
Pulmonary function tests - examples
These are perfusion scans from our patient, a patient with chronic thromboembolic disease and a normal patient. The perfusion lung scan on the upper left, from our patient, shows diffuse patchy irregularity of perfusion throughout the lungs and is characteristic of patients with severe pulmonary hypertension from many causes, but represents a low probability for pulmonary embolism. The perfusion lung scan on the upper right is from another patient with pulmonary hypertension from chronic thromboembolism. Note the large bilateral lobar and segmental perfusion defects, most common in the right lower lobe. This pattern represents a high probability for pulmonary embolism. The lowermost perfusion scan is normal, with homogeneous distribution of the isotope throughout both lung fields.
Our patient's ventilation scan
The ventilation scan from our patient was normal, a finding that may be seen with both idiopathic pulmonary arterial hypertension and chronic thromboembolic disease.
You may now choose further discussion of thromboembolic pulmonary hypertension or proceed to the next section.