Validação de sistema portátil de monitorização respiratória para o diagnóstico de apneia obstrutiva do sono em pacientes com doença arterial coronariana / Validation of portable respiratory monitoring system for the diagnosis of obstructive sleep apnea in patients with coronary artery disease

Naury de Jesus Danzi Soares

Introduction: Obstructive sleep apnea (OSA) is characterized by repeated episodes of partial or complete collapse of the upper airway during sleep, resulting in respiratory events characterized by hypopnea or apnea, respectively. Respiratory events may result in sleep fragmentation, hypoxemia and recurrent generation of negative intrathoracic pressure. All these mechanisms are potentially harmful to the cardiovascular system. OSA is common among patients with cardiovascular disease, but is still poorly recognized. The gold standard for diagnosis of OSA is polysomnography (PSG). Access to full PSG is limited, contributing to the under diagnosis of OSA. The polygraph nocturnal of respiratory variables (PGR) is a simplified method, being a promising alternative for the diagnosis of OSA. However, validation studies of PGR only included populations pre-selected or referred to sleep laboratories and excluded patients with significant comorbidities. Currently the American Academy of Sleep Medicine recognizes the use of PGR for the diagnosis of OSA in patients with high pretest probability of moderate to severe OSA and in patients without significant comorbidities. Objective: Validate the PGR for the diagnosis of OSA among consecutive patients evaluated for coronary artery bypass grafting (CABG), therefore with Coronary Artery Disease (CAD). To assess the prevalence of OSA and to evaluate the usefulness of clinical symptoms for diagnosis of OSA among patients with CAD. Methods: Patients with indication of CABG were evaluated by clinical examination and routine laboratory, the scale of daytime sleepiness (Epworth) and clinical risk of sleep apnea (Berlin questionnaire), echocardiogram, PSG and PGR. The PGR use is classified as type 3, with the following channels: airflow, respiratory effort, pulse oximetry, pulse rate, snoring and position sensor, (Stardust II ®). Results: We studied 70 consecutive patients (76% male); age (mean SD) = 58 ± 7 years; body mass index (BMI), [median (25-75%)] = 27,6 (25,8 to 31,1) kg/m2. Twenty patients (29%) had left ventricular ejection fraction (LVEF) 45%. The PSG of population showed apnea-hypopnea index (AHI) = 23 20 events / h. The prevalence of OSA with an AHI 5, 15 and 30 events / h was 87%, 54% and 27%, respectively. Daytime sleepiness measured by Epworth Sleepiness Scale and the clinical risk of OSA verified by the Berlin questionnaire were poor predictors of OSA. The sensitivity and specificity to detect OSA (AHI 5 events / h) and severe OSA (AHI 30 / events) of the PGR were 0,92/0,67% and 0,42/0,92%, respectively. The average difference in AHI between the two diagnostic methods presented in Bland-Altman was + 5,3, indicating that the values of the AHI of the PGR were on average lower than the PSG. The standard deviation of the difference was 14,6 events / hour, presenting a considerable agreement between the AHI of PSG and the PGR. Conclusion: This study validates the use of PGR for the diagnosis of OSA in a population of consecutive patients evaluated for CABG, in whom heart disease is significant. The prevalence of OSA among patients with CAD is high reaching over 50% of this population. However, the clinical symptoms are not adequate predictors of OSA in this population. Due to the high prevalence of OSA and low specificity of clinical symptoms, our data suggest that the PGR is a promising tool for the assessment of CAD patients evaluated for surgery for the CABG

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