Wireless Point-of-Care Diagnosis for Sleep Disorder With Dry Nanowire Electrodes

Abstract

Currently, available sleep monitoring systems use electrical recording where the electrodes make contact with the patient’s skin using a conducting gel. The electrode wires are connected to a processing recording system. The subject has to be in close proximity of these machines due to the direct electrical connections with the body and the machine. The conductive gel along with many wires connected to the biopotential electrodes makes them uncomfortable for the subject, with the result that recording and monitoring of the patient’s sleep patterns can become very difficult. The patient has to be in a sleep lab and/or a hospital at all times and at least one technician needs to watch the patient’s sleep behavior via video. The patient may not experience normal sleep patterns under such environments and as such, the diagnostic results are not really very conclusive. The commonly monitored biopotential electrodes are electrocardiogram, electroencephalogram, electromyogram, and electrooculogram. The electrodes used for monitoring these signals are Ag/AgCl and gold, which require skin preparation by means of scrubbing to remove the dead cells and application of electrolytic gel to reduce the skin contact resistance. The gel takes a role of reducing skin contact impedance in the conventional Ag/AgCl electrode and its usage is directly related to the sensitivity. However, the wet conventional Ag/AgCl electrode has some drawbacks such as difficulty in long time monitoring because the gel dries out after few hours and skin irritations. Usually, physiological parameters are monitored over an extended period of time during the patient’s normal daily life to diagnose a disease. In this case, the wet conventional Ag/AgCl cannot be used because of the dry-out of gel. The dry-out of gel increases the impedance between skin and electrode and it is reflected in the poor signal sensitivity. Also noises, such as motion artifact and baseline wander, are added to the biopotential signals as the electrode floats over the electrolytic gel during monitoring. To overcome these drawbacks, dry nanoelectrodes are proposed in this paper where the electrodes are held against the skin surface to establish contact with the skin without the need for electrolytic fluids or gels. The results are presented along with a wireless communication such that the proposed system is ideal for point-of-care diagnosis of the patient at home.