A New Corrected Formula for Correct Estimation of Mean Central Aortic Pressure from Peripheral Cuff Measurements.

BACKGROUND: Mean arterial pressure (MAP) has critical importance in tissue perfusion. In clinical practice, the most used formula was suggested by Gauer, which uses systolic (SBP), diastolic (DBP), and pulse (PP) pressures gathered via the iliac artery (MAP = DBP + 0.333 x PP). However, its results are not reliable for noninvasive recordings as blood pressures are higher. OBJECTIVES: We derived a corrected formula for the correct calculation of MAP from the noninvasive cuff blood pressure recordings: MAP = DBPcuff + [0.33 + (0.43 - 0.0038 x DBPcuff)] x PPcuff. METHODS: 149 patients were included in this study. Intra-aortic and cuff blood pressure tracings were obtained simultaneously. The PP coefficient of the standard formula is 0.333 for all calculations. The PP coefficient deviation of the standard formula was calculated with the formula of PP coefficient - 0.333. These two formulas were compared using linear regression analysis and Akaike information criterion (AIC). The level of significance was set at 5% in the statistical analysis. RESULTS: The measured intra-aortic mean pressure was 111.5±13.0 mmHg. The calculated intra-aortic mean pressure by the standard formula and the corrected formula was 105.8±13.5 and 111.3±12.1, respectively. The R, R2, and AIC of the corrected formula were better than the standard formula [(0.905 vs 0.887), (0.818 vs 0.787), and (858.9 vs 1002.7), respectively]. CONCLUSION: To the best of our knowledge, this is the first study for the calculation of the MAP from cuff measurements, and the corrected formula has better accuracy than the standard formula for estimation of the MAP.