Audiovisual stimulation with synchronized pulsed tones and flickering lights set at a delta frequency can induce a sedative effect

Corresponding author: Jong-Man Kang, M.D., Ph.D., Department of Anesthesiology, Kyung Hee University Hospital at Gangdong, 149, Sangildong, Gangdong-gu, Seoul 134-090, Korea. Tel: 82-2-440-6193, Fax: 82-2-440-7808, E-mail: [email protected] This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http:// creativecommons.org/licenses/by-nc/3.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. CC The perioperative period is a source of significant fear and anxiety for patients. Therefore, anxiolytic and sedative drugs are administered routinely, before and during surgery [1]. However, a larger dose of sedatives can delay the recovery in the ambulatory setting and be associated with an increased risk for complications. Nonpharmacologic methods can be alternatives for the relief of patient discomfort and anxiety under regional anesthesia. There exist some studies on the sedative effect of binaural auditory beats and music [1,2]. MC square (GEOMC CO, LTD, Seoul, Korea) is a portable audiovisual device for inducing synchronized pulsed tones and flickering lights set at a delta frequency [3]. Eleven healthy participants (6 males and 5 females, ages from 24 to 44 years) without otological or neurological disease in their histories were recruited for this experiment. Participants had enough sleep the previous night and the test was performed in the daytime. Each participant lay supine on an operating table with a pillow under the head. We applied the “sleep mode” (synchronized pulsed tones and flickering lights set at a delta frequency) of MC square with a headset and an eye goggle device to participants and other stimuli were absent during the test. The test was performed for 40 minutes; we monitored basic vital signs (electrocardiogram, non-invasive blood pressure and pulse oximeter) and the degree of sedation by the bispectral index (BIS) every 5 minutes. The BIS score showed a steady decline as time passed (Fig. 1). Vital signs were maintained within normal limits. None of the volunteers had any discomfort or complaints. Brain electrical activity is largely composed of oscillations at characteristic frequencies. These rhythms are thought to perform important pathological and physiological functions. There are two kinds of sleep characterized as non-rapid eye movement and rapid eye movement sleep and they have different brain wave patterns. Non-rapid eye movement sleep brain waves typically have taller and slower delta waves (1-4 Hz).