Respiratory Center Function and Its Impact in Obesity Hypoventilation Syndrome Treatment.

Introduction: Patients with obesity hypoventilation syndrome (OHS) need treatment with positive pressure either with continuous (CPAP) or double pressure (NIV). The apnea-hypopnea index (AHI) is considered a key data for making therapeutic decisions. We hypothesized that HR may be an useful tool to establish different phenotypes and individualize treatment in patients with OHS. Our objective was to analyze the role of the respiratory center response to hypercapnia (HR) in the adequacy of positive airway pressure therapy.

Method: We included subjects with OHS treated with CPAP or NIV according to AHI and baseline pCO. We analyzed therapeutic effectiveness and treatment changes prioritizing CPAP if AHI>30/h. Therapy was considered adequate if it was effective after two years. HR was measured with the p0.1/pEtCO ratio and its capability to select therapy was analyzed. The statistical study was performed by means comparison (Student's t) and multivariate analysis (logistic regression).

Results: 67 subjects were included of 68(11) years old, 37 (55%) males, initially 45 (67%) treated with NIV and 22 (33%) with CPAP, one case was excluded and in 25 (38%) the treatment was changed. Finally, CPAP was adequate for 29 subjects (44%) and NIV for 37 (56%). The CPAP group showed AHI 57/h (24) and p0.1/pEtCO 0.37cmHO/mmHg (0.23), NIV group AHI 43/h (35) and p0.1/pEtCO 0.24 (0.15) with p=0.049 and 0.006. In multivariate analysis, p0.1/pEtCO (p=0.033) and AHI>30 (p=0.001) were predictors of adequate therapy.

Conclusion: Measuring the RH of the respiratory center helps to select the most appropriate treatment for patients with OHS.