Non-invasive methods for determining the pulmonary blood pressure using ultrasonics in patients with chronic respiratory diseases

Ultrasound techniques and especially Doppler echocardiography offer several approaches to non-invasive assessment of pulmonary arterial pressure. The method based on the measurement of the velocity of the jets of tricuspid or pulmonary regurgitation is the most straightforward one, in most cases allowing for reliable quantitative assessment of pulmonary hypertension and thus should be applied as a method of choice whenever possible. Unfortunately, its application in patients with lung hyperinflation is limited by topographic factors. Short acceleration time of flow velocity in the right ventricular outflow tract (AcT less than 70-75 msec), especially accompanied by midsystolic deceleration occurring at end-expiration, is a strong evidence of severe pulmonary hypertension. Long AcT (above 115-120 msec) is virtually diagnostic of normal pulmonary arterial pressure. If high speed Doppler tracings of both pulmonary and tricuspid valve flow are available right ventricular isovolumic relaxation time may be used for estimation of pulmonary systolic pressure. However, the elaboration of the laboratory's own regression formula rather than application of Burstin nomogram seems more advisable in such cases. The future of non-invasive assessment of pulmonary hemodynamics will depend on the reliability to monitor acute and chronic changes not only in pulmonary arterial pressure, but also in flow and resistance. At present, echocardiography should be considered as a good screening test allowing also to stratify moderate and severe pulmonary hypertension. The exact assessment of pulmonary hemodynamics, especially in patients with chronic respiratory disease, when needed for important therapeutic decisions, should in most cases rely on right heart catheterization.