AUTHOR=Han Hyewon , Kim Dongsin , Kim Jin Seok , Kwac Lee Ku , Hyeon Janghun , Oh Junhyoung 

TITLE=A novel sleep aid device to reduce sleep latency using air–CO2 mixed gas

JOURNAL=Frontiers in Neurology

VOLUME=Volume 14 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2023.1163904

DOI=10.3389/fneur.2023.1163904

ISSN=1664-2295

ABSTRACT=Introduction: Sleep is an indispensable element of human life. However, in modern times, the number of people suffering from insomnia and sleep deprivation has increased significantly. Therefore, sleeping pills and various sleep aids are being released and used. However, sleeping drugs are limitedly prescribed due to side effects and resistance to drugs, and sleep aids have only the majority of scientific groundless products. This study aims to develop a device that induces sleep by spraying a mixed gas of carbon dioxide and air to create an environment that could induce sleep like inside of a sealed vehicle to control oxygen saturation in the body. 
Methods: Based on safety standards and human tidal volume, the target concentration was determined to be three types: 15,000 ppm, 20,000 ppm, and 25,000 ppm. After analyzing diverse structures for safely mixing gases, the most appropriate shape, the reserve tank, was selected. Various variables such as spraying angle and distance, flow rate, atmospheric temperature, and nozzle length were comprehensively tested, and based on this, diffusion simulation of carbon dioxide concentration and actual experiments were conducted. To secure the stability and reliability of the developed product, an accredited test to investigate the error rate of carbon dioxide concentration was performed, and clinical trials consisting of polysomnography and questionnaires confirmed its effectiveness in not only reducing sleep latency but also in overall sleep quality. 
Results: When the developed device was used, sleep latency was decreased by 29.01% on average for those with a sleep latency of 5 minutes or more compared to when the device was not in use. Moreover, total sleep time was increased by 29.19 minutes, WASO was decreased by 13.17%, and sleep efficiency was increased by 5.48%. We also affirmed that ODI and 90% ODI did not decrease when using the device. Although questions may be raised about the safety of CO2, the result that ODI was not reduced shows that sleep aids using CO2 mixtures do not adversely affect health. 
Discussion: The results of this work may suggest a new method that can be used to treat sleep disorders including insomnia.