Predictive equations for CPAP titration in OSAS patients

Continuous positive airway pressure (CPAP) is the elective treatment of obstructive sleep apnea. The therapeutic level of CPAP is generally established by manual titration or an auto CPAP device, but an alternative way involves the use of predictive formulas. The aim of the present study was to test the difference between mathematical equations and CPAP or auto CPAP in terms of therapeutic pressure. A retrospective analysis of 197 subjects with a diagnosis of obstructive sleep apnea needing a CPAP treatment was performed. The patients were divided into two groups: the first one included patients who had received CPAP after manual titration and the second one included patients who had received auto CPAP titration. The therapeutic CPAP pressure was then compared to the pressure calculated by three different equations: Eq. A by Stradling, Eq. B by S,riSs, and Eq. C by Hoffstein. One hundred ninety-seven patients were included in the study, 110 were titrated by auto CPAP and 87 by manual titration. There was a positive correlation between the pressure defined by the three equations and both titration methods, but each equation usually gave a higher pressure with patients needing CPAP < 8 and lower for patients needing CPAP > 11. Equation C normally gave a lower result than the other two equations. Manual or auto CPAP titration remains the best way to define the appropriate CPAP. However, predictive formulas can be useful if used with caution and always after verifying the real efficacy, particularly for patients needing higher pressure.