Computer simulated assessment of radio frequency electromagnetic waves for the detection of obstructive sleep apnea

Abstract

Obstructive sleep apnea/hypopnea syndrome (OSAHS) is the most common form of sleep-disorder breathing (SDB). Recurring restriction or occlusion of the upper airway throughout the night concurrent with continued respiratory efforts lasting more than 10 s characterizes the disorder. Prevalence of OSAHS is increasing globally, with a high association with obesity, hypertension, and heart failure. Nocturnal polysomnography (NPSG), which is the gold standard for OSAHS diagnosis, is scarce, expensive, and cumbersome. Methods for home screening and diagnosis of the disorder, directly and indirectly, are highly sought after to amend or replace NPSG. Well-established norms and procedures for electromagnetic (EM) antenna design, radiation pattern and characterization, and signal reception and measurements can be employed for the direct detection of upper airway occlusion. The utilization of radio-frequency (RF) EM antennas is desirable, as it is inexpensive, and simple to design and implement. In this paper, a computerized simulation of a new EM sensing system for direct detection of the occlusion in the upper airway is presented. Electromagnetic, anatomical, and RF safety constraints are taken into consideration. The theoretical basis of EM, antenna design, and physiological interactions with EM waves are presented. The proposed methodology for creating an anatomically-correct neck and airway simulated phantoms to test the hypothesis and the results of the tests are presented. Hypothesis: Radio-frequency electromagnetic waves transmitted through an open airway will have different energy levels at the distal side of the neck compared to those associated with a fully occluded airway. Methodology: A system is designed comprising a simulated phantom model of the upper airway and neck with the approximate anatomical dimensions and dielectric properties of homogenous neck tissue. Additionally, an RF patch antenna is designed and matched to the phantom neck. An iterative process is developed and implemented for the patch antenna design and coupling with a tissue. Simulation of the EM wave propagation and dissipation throughout the neck in the open and closed airway cases is provided and calculated based on the specific absorption ratios (SAR). The results of several permutations of antenna orientation with respect to the neck and several gaps between the antenna and the neck are provided. Results: the Computer simulations for all antenna orientation and location have shown that the EM energy levels recorded from open airway phantom models are statistically different and lower than those recorded from the occluded airway phantom models. Conclusions: The results of this study support the hypothesis that it is theoretically feasible to use electromagnetic energy to distinguish between open and occluded upper airway. keywords: Biological system modeling, Biomedical signal processing, Sleep apnea, Computer-aided diagnosis, Electromagnetic radiation, Antenna design