Background: Obstructive Sleep Apnea (OSA) is a form of sleep-disordered breathing, which can be diagnosed by clinical history, physical exam, and confirmatory test such as polysomnography. After a patient is diagnosed with OSA, the current standard of practice involves continuous positive airway pressure (CPAP) titration. This study aims to determine the factors related to starting CPAP level among Filipino patients with obstructive sleep apnea who achieved optimal CPAP titration during polysomnography and developed a predictive formula based on the determine factors that were not included in the existing calculation by Oliver and Hoffstein. This formula will be used as starting pressure during CPAP titration in order to hasten and allow the optimal CPAP to be reached sooner and minimize the risk of running out of time during titration.
Methods: A retrospective, cross-sectional study conducted among Filipino patients aged more than 19 years old who were diagnosed by polysomnography with OSAand underwent CPAP titration (therapeutic or split-night study) with starting pressure at 4 cm H2O at PHC Sleep Laboratory from January 1, 2012 to December 31, 2014. There were2 phases in this study: (1) The PHC Sleep Questionnaire was retrieved to gather all the factors related to OSA and CPAP titration; and (2) after significant factors were identified, the coefficients of these factors were used to developed the predictive formula of starting CPAP for Filipino patients with OSA.
Results: A total of 108 patients were enrolled in the study with mean age of 51 years with male (71%) predominance, obese (BMI of 34.4±12.6), and 76% were diagnosed with severe OSA. These patients had higher neck circumference with Mallampati score at 3.6±0.7. Immediately prior to polysomnography, these patients complained of mild to moderate daytime sleepiness with comorbidities observed such as hypertension (n72), diabetes mellitus (n=37), and coronary artery disease (n=28). Total cholesterol and LDL levels of the patients were unremarkable. FBS was elevated. Only mild hypoxemia was recorded as the as the lowest oxygen saturation achieved during diagnostic study. The patients slept for a total of 7 to 8 hours, with approximately 4 hours allotment for titration study.
Conclusion: After multiple linear regression analysis, the factors related to starting CPAP level among Filipino patients with obstructive sleep apnea who achieved optimal CPAP titration during polysomnography were age, BMI,neck circumference, and AHI during diagnostic study. The coefficients of these factors were used to develop the predictive formula for starting pressure during CPAP titration as follows: Starting CPAP level = (0.046 x age) + (0.0 x BMI) +(0.119 x NC) + (0.034 x AHI dx)- 5.3