Home recording for pre-phase sleep apnea diagnosis by Holter recorder using MMC memory

Long time data recordings by ambulatory devices became common today with widespread use of high capacity memories. In this study, this technology is used on home recording device especially designed for the pre-phase sleep apnea analysis at home before having certain diagnosis by proper polysomnographic examination in a hospital. Designing a portable recording system for clinically significant signals and analyzing an associated apnea detection algorithm are two significant and complementary studies carried out and reported in this paper. According to our aim, the Holter device discussed here is capable of recordings from many channels simultaneously but specifically for this study we consider just three signals namely ECG, breathing activity and oxygen saturation which are all significant for apnea detection in polysomnographic diagnostic phase. In apnea detection part we have initially studied the algorithm based on Hilbert Transform of ECG signal. The study also includes the comparison of three selected QRS detection algorithms (digital filter based, differentiation based and higher order statistics based) for ECG processing required for the Hilbert transform based apnea detection algorithm. Differentiation based QRS algorithm is preferred over other two due to its better performance on noisy ECG signals.

I. INTRODUCTION

Sleep Apnea is reported to be an important risk factor for many health problems ranging from daily life troubles like drowsiness, depression, irritability, loss of memory, lack of energy to more serious problems like development of cardiovascular diseases [1], [2]. The subjects prone to sleep apnea are usually diagnosed at the overnight clinical research through polysomnographic data. This is a complicated procedure and generally evaluates those records for many other sleep disorders. Polysomnography (PSG) based diagnosis is certain and reliable way of assessing the sleep apnea problem and it requires an expert decision in final phase. However, it is also an expensive diagnostic routine and causes some physical and psychological difficulties to the patients when they are monitored over eight hours in a sleep room of the hospital generally with a technical attendance. Thus, organizing home care units for pre-phase sleep apnea analysis becomes quite advantageous for raising the awareness to this problem and scanning the population in this pre-phase analysis with sparing time and energy of the hospital resources. The main aim in our study is to design a relatively low cost portable device for home record as an alternative and reliable way to monitor the presence of obstructive sleep apnea (OSA) but this is of course not a claim for having certain apnea diagnosis.