Pulmonary artery diastolic pressure is a reasonable surrogate for PAOP
(when you don’t want to wedge for whatever reason.)
- PADP is usually within about 5mmHg of PAOP
- PADP will be more than 5mmHg different if the patient is tachycardic or there is a condition which increases pulmonary vascular resistance
- The relationship between PAOP and PADp is stable:
- If the PAOP is 5mmHg below the PADP, you can expect that to stay that way for at least a few hours; so you don’t need to keep wedging
The PADP is usually higher than the PAWP.
- The diastolic pressure in the pulmonary arteries is higher because of the resistance to flow in the pulmonary arterial network;
- Thus if the flow is abolished (by occluding the artery) the pressure drops.
- If the PADP is LOWER than the PAWP, the PAWP measurement is probably wrong.
- It may mean your catheter tip position needs to be changed.
PADP is a measure of pulmonary hypertension
- As said before, the diastolic pressure in the pulmonary arteries is higher because there is flow, and resistance to this flow.
- Once you abolish flow, you also abolish resistance, and the pressure drops.
- Thus, the difference between PADP and PAOP is a surrogate measure of pulmonary vascular resistance
Thus: If the PADP is SIGNIFICANTLY HIGHER than the PAWP, there is probably pulmonary hypertension.
How much higher? 6mmHg is the usually quoted number.