Lung function and blood gas testing

Functional studies of the lungs and analysis of blood gas composition are conducted to diagnose the extent of ventilation and respiratory failure, as well as to specify the nature of the disorders (obstructive, restrictive). In pulmonary hypertension, there is a reduction in the diffusing capacity of carbon monoxide (40–80% of the normal value), a decrease in PaO2, and typically a decrease in PaCO2 due to alveolar hyperventilation. A decline in lung volumes and speed indicators of ventilation function, along with hypoxemia, is identified in severe pulmonary hypertension during the early stages of the disease.

Ventilation-Perfusion Scintigraphy

Ventilation-perfusion lung scintigraphy is the most informative method for diagnosing clinical class 4 - chronic thromboembolism of the pulmonary artery and its branches.

In patients with pulmonary hypertension, one may observe an entirely unaltered image or minor peripheral subsegmental perfusion defects without impaired ventilation. In this scenario, perfusion defects are identified in the lobar and segmental zones. In the differential diagnosis of pulmonary hypertension and chronic thromboembolism, the sensitivity of ventilation-perfusion lung scintigraphy ranges from 90-100%, and the specificity is between 94-100%. In patients with parenchymal lung disease, perfusion defects align with ventilation defects.