Chest
Volume 126, Issue 4, October 2004, Pages 1313-1317
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Clinical Investigations in Critical Care
New Formula for Predicting Mean Pulmonary Artery Pressure Using Systolic Pulmonary Artery Pressure

https://doi.org/10.1378/chest.126.4.1313Get rights and content

Study objectives:

Mean pulmonary artery pressure (MPAP) and systolic pulmonary artery pressure (SPAP) are used interchangeably to define pulmonary hypertension (PH). We tested the hypothesis that the measurement of MPAP and SPAP is redundant in resting humans over a wide pressure range.

Design:

Prospective, observational study.

Setting:

Catheterization laboratory in a university hospital.

Patients:

This study involved 31 patients, as follows: primary PH, nine patients; chronic pulmonary thromboembolism, seven patients; venous PH, six patients; and control subjects with normal pulmonary artery pressure, nine patients.

Interventions:

None.

Measurements and results:

High-fidelity pulmonary artery pressures were obtained when patients were at rest. Over the wide MPAP range that was under study (10 to 78 mm Hg), MPAP and SPAP were strongly related (r2 = 0.98). Regression analysis performed on the first 16 subjects (test sample) allowed us to propose a formula (MPAP = 0.61 SPAP + 2 mm Hg), the accuracy of which was confirmed in the remaining 15 subjects (validation sample bias, 0 ± 2 mm Hg). If PH was defined by an SPAP in excess of 30 or 40 mm Hg, this corresponded to an MPAP in excess of 20 or 26 mm Hg. If PH was defined by an MPAP of > 25 mm Hg, this corresponded to an SPAP of > 38 mm Hg.

Conclusions:

In resting humans, MPAP can be accurately predicted from SPAP over a wide pressure range. The new formula may help to refine the threshold pressure values used in the diagnosis of PH. Further studies are needed to test the hypothesis that our formula may allow the noninvasive prediction of MPAP from Doppler-derived SPAP values.

Section snippets

Patients

The prospective study was approved by the ethics board of Paris-Sud 11 University, and informed consent was obtained for all patients. The study involved 31 patients (23 men and 8 women) who had been referred to our catheterization laboratory either for severe PH or for the investigation of chest pain, heart failure, or other cardiovascular disorders. PH was defined by an MPAP of > 25 mm Hg at rest while the patient was breathing room air. Precapillary (ie, arterial) and postcapillary (ie,

Results

In the overall population (31 patients), there was a positive linear relationship between MPAP and SPAP (r2 = 0.982), DPAP (r2 = 0.958), and pulmonary artery pulse pressure (r2 = 0.900). Individual pressure values are given in Table 2. When SPAP was considered as the independent variable in the test sample, MPAP and SPAP were linearly related according to the following equation: MPAP = 0.61 SPAP + 2 mm Hg (r2 = 0.979; 16 patients) [Fig 1].

When the MPAP formula that was obtained in the test

Discussion

The present prospective study demonstrates that MPAP can be accurately predicted from SPAP according to the following formula:

MPAP=0.61SPAP+2mmHg

In their pioneer study, Laskey et al9 provided individual high-fidelity pressure values in 10 normotensive subjects and 8 PPH patients (see Tables 1 and 2 in Laskey et al9). The MPAP vs SPAP relationship that we have calculated from their data9 is as follows: MPAP = 0.61 SPAP + 1 mm Hg (r2 = 0.99; MPAP range, 9 to 67 mm Hg). The equation calculated

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