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© 2022, BioSelf Technology, Ltd., a subsidiary of Sensate, Inc. London, United Kingdom. All Rights Reserved. 1
Sensate® Somacoustics: A New Wave for Stress Management. Volume I
By, Scott McDoniel, Ph.D., M.Ed.1 & Stefan Chmelik, M.Sc. 2
1. Faculty; College of Health Professions, Walden University, Minneapolis, MN
2. BioSelf Technologies, Ltd, London, UK
Societal Stress
The human population has endured much stress since
the turn of the century. Stress is both positive (eustress) and
negative (distress). However, distress appears to represent the
majority of human stress. In fact, before the Covid-19
pandemic, most adults reported elevated amounts of distress
(Clay, 2011; Ray, 2019). For example, nearly 50% of American
adults reported a moderate to high-stress level (Clay, 2011).
Leading causes of distress were related to finances, job security,
and economic concerns (Clay, 2011; Ray, 2019). Distress levels
have only increased due to the unpredictability of COVID-19
and its future implications. The leading causes of distress are
the same as in prior years. However, additional stressors have
increased for parents and caregivers. Parents report more stress
than non-parents (Stress in America™, 2020: Stress in the Time
of COVID-19, Volume One, 2020). Leading parental stressors
extend to their children's daily lives. Over 70% of parents report
significant stress managing their children's online learning, and
nearly 75% of parents report disrupted routines or adjustment to
new routines as stressful. In addition, there are concerns about
the physical and mental health implications of COVID-19
(Stress in America™, 2020: Stress in the Time of COVID-19,
Volume One, 2020).
Continued distress negatively affects mental and
physical health. The central nervous system responds to
physical and psychological stressors through the autonomic
nervous system (ANS). The ANS is divided into the
sympathetic and parasympathetic systems. Both systems work
to stimulate and relax critical physiological systems when
stressed. The sympathetic nervous system is activated by
releasing critical hormones such as cortisol and adrenaline,
increasing heart rate, blood pressure, and respiration rate
(Godoy et al., 2018; Gordan et al., 2015). There are three stages
of stress response within the body; Alarm, Resistance, &
Exhaustive (Selye, 1950). The initial stressor leads to the alarm
phase, which is the body's "flight or fight" response. The alarm
phase is intended to be short-lived by providing the energy
needed to respond to the stressor. The second phase of stress is
resistance when the body attempts to repair itself by activating
the parasympathetic nervous system (Selye, 1950).
This is when the body attempts to self-regulate by
reducing stress hormones and allowing the body and mind to
return to baseline or homeostasis with heart, respiration rate,
and blood pressure. However, if the stressor is not removed,
then the body will stay in the alert stage, never allowing the
body to recover during the resistance stage. Individuals cannot
return to homeostasis due to prolonged stress and can develop
irritability, sleeplessness, headaches, suppressed immune
function, and hypertension (Godoy et al., 2018; Won & Kim,
2016). The final phase of stress is the exhaustion stage. This is
when the body has depleted its mental, emotional, and physical
resources to recover from stress (Selye, 1950). This is the stage
when an individual is no longer able to cope, and symptoms of
individuals in this stage include burnout, fatigue, anxiety,
feeling of hopelessness, and depression (Won & Kim, 2016).
Unfortunately, according to Selye's theory, many
individuals appear stuck in a stress response's second and third
stages. According to the (2011) Stress in America report, nearly
50% of adults indicate stress fatigue and lack of
interest/motivation in doing things. Moreover, approximately
45% of respondents indicate heightened anxiety and feelings of
sadness/depression (Clay, 2011). These have worsened since
the pandemic. Approximately 50% of adults demonstrate
anxiety traits, and nearly 60% exhibit depression (Shah et al.,
2020). According to America's State of Mind report, there was
a 20 % increase in anti-anxiety, anti-depressant, and anti-
insomnia medications during the initial phase of the pandemic.
The most significant increase was in anti-anxiety medications at
34% compared from early February 2019 to mid-March 2019.
Equally alarming is that nearly 80% of anti-anxiety, anti-
depressant and anti-insomnia medications were new
prescriptions (America's State of Mind Report, 2020).
Unfortunately, these medications do not help with positive
behavior change. One year into the pandemic suggests adults
have either gained or lost an undesired amount of weight as a
result of negative eating behaviors, increased consumption of
alcohol to assist with coping, and are not getting adequate sleep
due to insomnia (Stress in America™ One Year Later, A New
Wave of Pandemic Health Concerns, 2021). Individuals need
positive coping mechanisms to assist with anxiety, insomnia,
and other stress-related symptoms.
Several self-help methods for positive stress
management include physical exercise, setting a sleep schedule,
deep breathing exercises, eating healthy, and reducing alcohol
intake. However, applying these skills requires motivation, self-
determination, and self-discipline. The motivation to apply
these self-help options can be inconsistent with increased
anxiety, fatigue from the lack of sleep, and depressive
tendencies. One of the easiest methods for managing stress-
related symptoms is deep breathing exercises.
Deep breathing techniques are postulated to stimulate
the vagus nerve (Gerritsen & Band, 2018), the tenth cranial
nerve representing the primary component of the
parasympathetic nervous system influencing mood, heart, and
respiration rate (Breit et al., 2018). The vagus nerve is a mixed
nerve composed of 20% "efferent" fibers (i.e., sending signals
from the brain to the body) and 80% "afferent" fibers (i.e.,
carrying information from the body to the brain) (Howland,
2014). Theoretical mechanisms of how deep breathing
stimulates the vagus nerve to improve parasympathetic function
2
are complex and may be attributed to indirect and direct
respiratory patterns such as a slower respiratory rate, the ratio
between inhalation and exhalation, "O.M." chanting, and
diaphragmatic breathing, (i.e., deep abdominal breathing)
Gerritsen & Band, 2018; Kalyani et al., 2011; Stancák et al.,
1993; Stancák et al., 1991).
Vagus Nerve Stimulation
Vagus nerve stimulation (VNS) can be defined as a
"technique or method" that creates an action potential on
afferent nerve fibers leading to the vagus nerve. The earliest
recorded example of vagus stimulation was with massage in the
late 1800s. The carotid sinus baroreceptors in the artery are
innervated by the carotid sinus nerve branch leading to the
vagus nerve. It was observed that compressing and massaging
the cervical region of the carotid artery could suppress seizures
(Lanska, 2002). In addition, we know massaging the carotid
artery can lead to decreased heart rate and blood pressure.
VNS is not new, and research on the efficacy of
stimulating the vagus nerve with electrical currents is well
documented and understood in the medical community
(Howland, 2014). Electrical stimulation (eVNS) can be
achieved by a surgically implanted device that emits an
electrical current to the right or left cervical vagus nerve. A
transducer emits a volt to the nerve, and the membrane potential
of the nerve cell becomes more positive than when at rest
(Purves et al., 2001a). This creates an action potential sending
the signal to the brain. The voltage will not influence the
intensity of the action potential. Instead, the electrical current's
voltage or intensity will increase the action potential's
frequency (Purves et al., 2001a). In addition, electrical currents
may be applied transcutaneously to specific nerve endings, such
as through the auricular branch of the vagus nerve (Howland,
2014). Prior research has suggested that electrical stimulation of
the vagus nerve may be efficacious for reducing anxiety and
improving depression (Aaronson et al., 2017; Breit et al., 2018;
George et al., 2008; Noble et al., 2017; Rong et al., 2016; Rush
et al., 2005).
Another possible mechanism is mechanical wave (i.e.,
acoustic wave or soundwave) vibrations (aVNS). Mechanical
waves need a medium to travel, such as air or liquid, compared
to electrical waves. Soundwaves include audible (20hz-20Khz)
and subaudible (0-20hz and >20Khz) vibrations. Ultrasound
(>20Khz) vibrations have been commonly used in medical
diagnostics and physical therapy (Carovac et al., 2011; Miller et
al., 2012). In addition, infrasound vibrations influence the
human body. There is debate on the adverse effects of
environmental infrasound from wind turbines on human health
(Knopper et al., 2014). However, there is research supporting
improved cell metabolism from infrasound, and the effect of
infrasound depends on the applied frequency, duration of
exposure, and amplitude (Vahl et al., 2021). Nonetheless, sound
waves are pressure waves that create a physiological response,
and it is believed this can also occur in the central nervous
system. The body's mechanoreceptors can respond to a broad
frequency of sound vibrations (Persinger, 2013). One of the
most sensitive mechanoreceptors to sound vibrations are
pacinian corpuscles. These are located throughout the body,
below the skin, joint spaces, thoracic cavity, and organs
(Iheanacho & Vellipuram, 2021; Purves et al., 2001b). When
vibratory pressure is detected, a compression force is
transmitted to the central nerve fiber via fluid in the corpuscle.
This deformation opens specific sodium channels in the nerve
fiber, generating a receptor potential. This action potential
sends the signal along the sensory nerve and is carried to the
brain (Figure 1) (Purves et al., 2001b; Sigurdardóttir et al.,
2019). The possible mechanisms for the actional potential and
transmitting the signal to the brain is likely the result of
acoustic resonance (fluid, organs, and cavity) within the body
(Persinger, 2013). It is theorized that the amplified sound wave
directly influences the vagus nerve's sub-branches. Soundwaves
travel faster and further through the water compared to air. The
human body is composed mainly of water, and the speed of
sound is similar in many of the body's soft tissues (1500-1600
meters/sec) (Lloyd; Shin et al., 2010). The amplified sound
waves from the abdominal cavity likely create the action
potential to stimulate the vagus nerve. Initial research using
High Amplitude Low Frequency–Music Impulse Stimulation
(HALF‐MIS) targeting the abdominal part of the vagal nerve
and its afferent branches suggests a positive response
(Sigurdardóttir et al., 2019).
Researchers conducted a pilot study utilizing eight
HALF-MIS sessions for 20 minutes per time in combination
with pharmacotherapy for depression over a period of 3-4
weeks. Results demonstrated a significant improvement in
depressive ratings when comparing HALF‐MIS as an add‐on
treatment to standard pharmacotherapy options (Sigurdardóttir
et al., 2019). However, a 2021 study attempted to assess the
vagus nerve response in chronic pain patients over three weeks.
With this technology, researchers questioned the ability to
stimulate the vagus nerve (Eshuis et al., 2021). Eshuis and
colleagues applied various frequency therapeutic sessions of
MAHL-MIS therapy (20-100 Hz) with music or higher
frequency (200-300 Hz) music through randomized means in
60 patients. Eight treatment sessions were 24 minutes in
duration per session. Researchers utilized self-reported
questionnaires (Numeric Pain Rating Scale (NSR) and health-
related quality of life (EQ05D-3L) Pain Disability Index (PDI))
before and following the last session. However, no biometric
data was obtained for a parasympathetic response.
3
Figure 1. Pacinian corpuscles transfer afferent action potentials through the vagus nerve to the
brainstem and subsequent areas of the brain implicated for mood (Sigurdardóttir et al., 2019).
Results suggest in both treatment groups that the
average NRS score per patient after treatment was significantly
lower than the average NRS per patient before treatment. There
was no difference between groups, and there was no difference
over time with EQ-5D-3L and PDI. Researchers suggest
various reasons for pain improvement immediately following
each treatment; rest, placebo, music, gate control theory, and
VNS (Eshuis et al., 2021). However, the researchers reported
that VNS on nociception is conflicting and depends upon the
individual. Moreover, the researchers failed to monitor a proxy
of vagal activity, and the sample size was smaller than
anticipated due to the COVID-19 pandemic (Eshuis et al.,
2021). Therefore, results from this study should be cautioned
given these limitations. Yet, it does offer a possible immediate
benefit following treatment.
Olav Skille initially suggested vibroacoustic
stimulation as a mechanism for whole body vibration (WBV).
Early reports suggest vibroacoustic stimulation may improve
stress-induced depression, anxiety, tension, and fatigue (Skille,
1989). These findings, along with results from Sigurdardóttir et
al. (2019), may support the use of aVNS as a feasible, effective
modality for individuals being treated for stress-related
symptoms.
Neurological effects from VNS
The U.S. Food and Drug Administration approved
VNS as a long-term adjunctive treatment for chronic recurrent
depression in patients over the age of 18 years (Carreno &
Frazer, 2017). The vagus nerve efferent component originates
in the brainstem. In comparison, the initial termination point of
its afferent fibers is primarily the nucleus solitarius, located in
the medulla (Figure 1). As mentioned earlier, 80% of the vagus
nerve is afferent, meaning information is sent from the body to
the brain. eVNS, through functional magnetic resonance,
demonstrates changes in various regions of the brain and
brainstem (Carreno & Frazer, 2017). More specifically, 4-
weeks of VNS were found to alter the resting state functionality
between the right amygdala and left dorsolateral prefrontal
cortex and enhancement of the left insula, which propagate
improvement in depressive symptoms (Fang et al., 2017; Liu et
al., 2016).
VNS is also believed to enhance the neurotransmission
of the non-androgenic and serotonergic systems associated with
anxiety and depression. Several eVNS studies have
demonstrated improved dopamine, norepinephrine, and
serotonin response within the brain (Carreno & Frazer, 2017).
Albeit there are no studies on the use of aVNS and its effect on
neurochemicals, there are several studies on whole-body
vibrations (WBV). Results from low-amplitude WBV suggest
increased dopamine in the striatum and dopaminergic neurons
in the brain (Zhao et al., 2014). In addition, whole body
vibration between 20-30 Hz significantly increases brain
secretion levels, increases proteins for required neural plasticity
(Ariizumi & Okada, 1983; Boerema et al., 2018), and reduces
anxiety-related behavior (Oroszi et al., 2021). However, the
latter may be related more to the effects of physical exercise,
given that WBV is defined as passive physical exercise
(Boerema et al., 2018).
VNS and WBV have limitations as the long-term
therapeutic effects are not the result of acute use. Like anti-
depressants, the benefits will be over time as it may take
between 1 to 12 months to see improvements based on
depression and anxiety severity (Carreno & Frazer, 2017).
However, Eshuis et al. (2021) noted that there were immediate
benefits following a MAHL-MIS therapy session, such as
relaxation and decreased pain perception. Therefore, benefits
might be acute and long-term, dependent upon the individuals'
severity and duration of stress-related symptoms.
Sensate® Device
Sensate® (Sensate Inc/BioSelf Technology Ltd of
USA/London, UK) is a non-electrical, vibrotactile device for
stress management (Figure 2). Sensate® is one component of a
complex, cross-modal (acoustic and aural) sensory experience
(i.e., Sensate® Somacoustics) that supports relaxation and
positive affect. The device utilizes low-frequency technology
(<50 Hz) to improve the parasympathetic nervous system's
(PNS) response to chronic stress. Two theoretical concepts of
the Sensate® device are Bone Conduction and Thoracic
Resonance.
Bone conduction is commonly used for patients with
hearing abnormalities. Bone conduction hearing is the
placement of a vibrating transducer in contact with the skin of
the head (Lenhardt et al., 2007). Sound waves in a human move
much faster through bone when compared to soft tissue. For
example, soundwaves can travel up to 2814 m/sec in the
human skull and up to 3515 meters/sec in cortical regions of the
bone (Lloyd, 2022).
4
Figure 2. Sensate® device applies infrasonic sound technology for improved parasympathetic
response to stress.
Cortical regions of the bone are primarily located in the
outer layer of the long bones forming the shaft. A study by
Lenhardt et al. 2007 demonstrated that the placement of a
transducer on various regions of the body could result in
Ultrasonic detection (25 kHz and 62.5 kHz). However, further
placement of the transducer from the ear must have greater
energy as it takes approximately 5 dB more energy to detect
ultrasound in distant regions from the head except for the neck
and thorax (Lenhardt, 2007). Researchers were surprised by the
sternum's sensitivity as the vibrating transducer's placement at
the sternum is similar to the mastoid bone in sensitivity. Curved
bones (e.g., rib bones) produce greater electrical energy,
according to Lendardt (2007). Therefore, the sternum can easily
be displaced due to more significant bone movement, leading to
greater amplification. In addition, additional energy may result
from resonant properties within the thorax (Lenhardt, 2007).
Thoracic amplification can be supported by the results
from Lenhardt (2007) and research on chest percussion (Peng et
al., 2014). Percussion is a common component of clinical chest
physical examinations where the objective is to assess if an area
is an air, fluid, or solid-filled (Peng et al., 2014). Peng et al.
(2014) evaluated the percussion of high and low frequency (50-
200 Hz) sound waves when placed on the chest using computed
tomography. Their research supports that low-frequency sound
waves (60 Hz) travel a longer distance around the internal
organs, and the internal organs' structural changes have a
negligible effect on the transmission of low-frequency waves
(Figure 3).
The afferent nerve branches that innervate to the vagus
nerve are located throughout the thoracic cavity. The cross-
section of the C.T. image supports possible afferent aVNS with
lower frequency soundwaves given the proximity of the
transducer, resonant properties of the sternum/ribs (Lenhardt,
2007; Lloyd, 2022), and resonance of the thoracic cavity (Peng
et al., 2021; Peng et al., 2014). As a result, the Sensate® device
may be a novel aVNS modality that improves PNS function. An
improved PNS response from Sensate® may result in lower
anxiety, insomnia, and other stress-related symptoms leading to
improved well-being.
Figure 3. Simulation of 60 Hz (A & B) and 120 Hz (C&D) excitation frequency cross-section of
the torso presenting displacement in the anterior to posterior direction. The color bar shows
displacement in [um](Pen et al., 2014).
Biographical Note
Dr. Scott McDoniel has over 15 years of clinical research
experience in health and wellness and over 20 years of clinical
experience in integrated healthcare.
Stefan Chmelik, M.Sc., inventor, and founder of Sensate®,
provided technical and clinical information on the Sensate®
device. Stefan has over 30 years of clinical experience and is a
pioneer in technology-assisted relaxation.
Conflict Statement
Dr. Scott McDoniel is an independent research consultant for
BioSelf Technology, Ltd. Dr. McDoniel has no ownership of
patents, stock, or equities to Sensate®.
For more information about Sensate®, visit
www.getsensate.com
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