Effect of positive pressure therapy on endothelial dysfunction, blood pressure and renal fuctions in patients with obstructive sleep apnea syndrome

Introduction and Aim: Sleep, constituting about one-third of our daily life, is an essential process for a healthy life. An important group of sleep-related disorders observed during sleep is respiratory disorders. Among these, most commonly seen is obstructive sleep apnea syndrome (OSAS). Depending on the pathologies of the airway obstruction and the response given by the organism against this pathologies, foremost cardiovascular, affecting many organs and systems constitutes. In this study, we aimed to show the renal functions, ambulatory blood pressure measurements (ABPM), serum asymmetric dimethyl arginine (ADMA) levels as an indicator of endothelial dysfunction and the difference in blood chemistry and complete blood count between healthy volunteers (HV) as well as the change in the parameters with continuous positive airway pressure (CPAP) therapy in patients whom polysomnography (PSG) performed for the first time due to OSAS symptoms and diagnosed as OSAS. Materials and Methods: 233 adults patients who received diagnostic PSG for the first time in Duzce University Faculty of Medicine Hospital Sleep Laboratory between September 2013 and January 2015 were evaluated. 54 patients who were diagnosed OSAS according to the results of PSG, scheduled for CPAP therapy were included in the study. 54 patients were divided into 3 groups according to their AHI, position and REM rates; 25 Positional/Rem dependent (Group 1), 7 medium (Group 2), 22 severe (Group 3). 39 patients who completed the study [Group 1 (n = 17), group 2 (n = 7), Group 3 (n = 15)] were included in the statistical evaluation. In addition, 15 healthy volunteers without apnea were enrolled in the study as the control group. Renal function tests, ABPM, ADMA levels, complete blood count and routine biochemistry tests were performed to all patients and healthy volunteers. After three months of CPAP treatment, tests were repeated and compared with pre-treatment results. Results: Creatinine levels were significantly higher in patients compared to HVs, but no change was observed with CPAP therapy. Patient groups were similar with healthy volunteers in terms of proteinuria and remained same after CPAP therapy. Group 3 patients being within the normal range of ALT and AST levels were significantly higher than HVs, but did not show significant change with CPAP therapy. Patient groups were similar in terms of bilirubin levels with HVs and secondary to treatment with CPAP, significant decrease in unconjugated bilirubin levels were seen in Group 1 and Group 2. Cystatin C levels of Group 3 were significantly higher than healthy volunteers before treatment and significant decrease was seen with CPAP therapy. Patient groups were similar in baseline serum ADMA levels and did not show change with treatment. Creatinine-based estimated glomerular filtration rate eGFRcr levels of patients were lower than healthy volunteers before treatment and no change was observed with CPAP treatment. Cystatin C-based estimated glomerular filtration rate (eGFRcyc) levels of Group 3 were significantly lower than healthy volunteers before treatment but increased significantly after CPAP therapy. Pre-treatment average daytime mean arterial blood pressure and average daytime systolic blood pressure of Group 3 was significantly higher than healthy volunteers and showed meaningful decline with CPAP treatment. When the patient groups were evaluated, non-dipper blood pressure was 64.7%. 72% of non-dippers had dipper blood pressure after treatment. Conclusion: OSAS is a systemic disease that affects many organs and systems, impairs quality of life, and reduces the daily performance and increases morbidity and mortality. In this study, we found out lower eGFRcr levels in patients with OSAS, increase in Cystatin C levels in severe OSAS group, high non-dipper hypertension prevalence in OSAS patients and deterioration in liver function tests. In addition, CPAP treatment did not influence eGFRcr, lowered Cystatin C levels, increased eGFRcyc and improved non-dipper blood pressure.