Transpulmonary Gradient Measurement and Clinical Significance

Measurement Procedure

The American College of Cardiology states that the transpulmonary gradient (TPG) is measured as the difference between mean pulmonary artery pressure and mean pulmonary capillary wedge pressure, with units of measurement being millimeters of mercury (mm Hg) 1
TPG is obtained during right heart catheterization, which requires insertion of a pulmonary artery catheter (PAC) to measure pulmonary artery pressure (PAP) and measurement of pulmonary artery occlusion pressure (PAOP), also known as pulmonary capillary wedge pressure (PCWP) 3, 4

The European Heart Journal recommends calculating TPG using the formula TPG = mean PAP - mean PCWP, with units of millimeters of mercury (mm Hg) 1, 5
Normal TPG values are typically less than 12 mm Hg, according to the European Heart Journal 5, 6

The Intensive Care Medicine journal states that TPG helps assess the degree of pulmonary vascular abnormality, particularly in contexts where pulmonary hypertension may be present 3, 4
A TPG > 12 mm Hg has traditionally been used to identify "reactive" or "out of proportion" pulmonary hypertension in patients with left heart disease, as noted in the European Heart Journal 5
TPG is particularly valuable in evaluating patients with ARDS (Acute Respiratory Distress Syndrome) 3, 4
TPG is useful in differentiating between passive and reactive post-capillary pulmonary hypertension, according to the European Heart Journal 5, 6

The Intensive Care Medicine journal notes that during ventilation with high PEEP (Positive End-Expiratory Pressure), calculating the transmural value of PCWP allows estimation of true left ventricular filling pressure 3
In cases of tricuspid regurgitation with right ventricular dilatation, cardiac output measurements can be erroneous, affecting derived values, as stated in the Intensive Care Medicine journal 3