Using respiratory sinus arrhythmia to detect obstructive sleep apnea

Abstract

There is a strong relationship between sleep apnea, hypertension and cardiovascular disease. Traditionally, sleep apnea is diagnosed by overnight sleep study performed in a certified sleep laboratory, which is both costly and inconvenient. As a result, 100,000 s of adults with sleep apnea go undiagnosed each year at an annual estimated economic cost of $165 billion dollars in the United States alone. In this study, we explored sleep apnea related cardiorespiratory variability with the objective of devising a novel tool that could be used to detect sleep apnea in the very early stages of the disease well before progression to hypertension. Respiration-related expansion of the chest wall and heart rate were recorded during rest breathing in subjects diagnosed with moderate obstructive sleep apnea (n = 9) and in healthy aged matched adults (n = 11). Using a correlation between the chest wall motion and heart rate variability, we were able to detect marked differences in sleep apnea patients relative to healthy aged matched adults (P < 0.001). We developed a novel means of detecting OSA using standard measures of heart rate (ECG) and respiration (chest wall motion traces) performed by clinical personnel with standardly available monitoring equipment. Most importantly, we wanted to devise a tool that could detect OSA in awake individuals in <10 min. Diagnosis of sleep apnea and cardiorespiratory variability typically depend on time consuming measurements obtained during sleep. In this case we used RR variability and the correlation between the chest wall trace and heart rate variability to test the hypothesis that these measures could differentiate between subjects with sleep apnea and non-OSA healthy adults of the same age. Using these parameters, we were able to detect differences between healthy and OSA subjects in very short time windows (~ 2 min) during rest breathing in wakefulness and using vital signs monitoring devices available in most hospitals.

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