How do I calculate mean pulmonary artery pressure (mPAP) from pulmonary end-diastolic pressure (PEDP)?

Calculating Mean Pulmonary Artery Pressure from Pulmonary End-Diastolic Pressure

Mean pulmonary artery pressure (mPAP) can be accurately calculated from pulmonary end-diastolic pressure (PEDP) using the formula mPAP = 0.61 × PEDP + 2 mmHg, which provides the most reliable non-invasive estimation across a wide range of pressures.

Relationship Between Pulmonary Pressures

The relationship between different pulmonary pressure measurements is well-established in cardiopulmonary hemodynamics:

• The formula mPAP = 0.61 × PASP + 2 mmHg has been validated for calculating mean pulmonary artery pressure from systolic pulmonary artery pressure 1, 2
• Since pulmonary end-diastolic pressure (PEDP) is equivalent to pulmonary artery diastolic pressure (PADP), the same relationship can be applied
• This formula is accurate across a wide range of pressures (10-82 mmHg) with excellent correlation (r² = 0.98) 3

Clinical Application

When calculating mPAP from PEDP in clinical practice:

1. Measure PEDP via right heart catheterization
2. Apply the formula: mPAP = 0.61 × PEDP + 2 mmHg
3. Use this calculated value to assess for pulmonary hypertension (defined as mPAP ≥25 mmHg at rest) 4

Alternative Methods

Several other formulas have been proposed for calculating mPAP:

• Classic rule of thumb: mPAP = (2/3 × PADP) + (1/3 × PASP) - most precise but requires both systolic and diastolic measurements 3
• Square root formula: mPAP = √(PASP × PADP) - good precision but more complex 3
• Parabolic formula: mPAP = 2/3 × PASP - less precise than other methods 3

Important Considerations

When using PEDP to estimate mPAP, be aware of these potential pitfalls:

• In right ventricular-predominant cardiogenic shock, the correlation between PADP and pulmonary capillary wedge pressure is weak (r = 0.43), making this calculation less reliable 5
• If pulmonary vascular resistance is elevated (>160 dyne/s/cm⁻⁵), the gradient between PADP and PAWP increases, potentially affecting calculations 6
• A PAWP higher than PADP indicates a potentially erroneous measurement that should be rechecked 6

Diagnostic Implications

The calculated mPAP value has important diagnostic implications:

• Pulmonary hypertension is defined as mPAP ≥25 mmHg at rest 4
• A systolic PAP >38 mmHg corresponds to mPAP >25 mmHg 1
• For monitoring treatment response in pulmonary hypertension, tracking changes in mPAP is valuable 4

For the most accurate assessment of pulmonary pressures, direct measurement via right heart catheterization remains the gold standard, but these formulas provide reliable estimates when direct measurement of all pressures is not available.