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Effects of earplugs and eye masks on nocturnal sleep, melatonin and cortisol in a simulated intensive care unit environment

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  • The Second Affiliated Hospital of Fujian Medical University

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Environmental stimulus, especially noise and light, is thought to disrupt sleep in patients in the intensive care unit (ICU). This study aimed to determine the physiological and psychological effects of ICU noise and light, and of earplugs and eye masks, used in these conditions in healthy subjects. Fourteen subjects underwent polysomnography under four conditions: adaptation, baseline, exposure to recorded ICU noise and light (NL), and NL plus use of earplugs and eye masks (NLEE). Urine was analyzed for melatonin and cortisol levels. Subjects rated their perceived sleep quality, anxiety levels and perception of environmental stimuli. Subjects had poorer perceived sleep quality, more light sleep, longer rapid eye movement (REM) latency, less REM sleep when exposed to simulated ICU noise and light (P < 0.05). Nocturnal melatonin (P = 0.007) and cortisol secretion levels (P = 0.004) differed significantly by condition but anxiety levels did not (P = 0.06). Use of earplugs and eye masks resulted in more REM time, shorter REM latency, less arousal (P < 0.05) and elevated melatonin levels (P = 0.002). Earplugs and eye masks promote sleep and hormone balance in healthy subjects exposed to simulated ICU noise and light, making their promotion in ICU patients reasonable.
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RESEARC H Open Access
Effects of earplugs and eye masks on nocturnal
sleep, melatonin and cortisol in a simulated
intensive care unit environment
Rong-fang Hu
1
, Xiao-ying Jiang
1*
, Yi-ming Zeng
2
, Xiao-yang Chen
2
, You-hua Zhang
3
Abstract
Introduction: Environmental stimulus, especially noise and light, is thought to disrupt sleep in patients in the
intensive care unit (ICU). This stud y aimed to determine the physiological and psycho logical effects of ICU noise
and light, and of earpl ugs and eye masks, used in these conditions in healthy subjects.
Methods: Fourteen subjects underwent polysomnography under four conditions: adaptation, baseline, exposure to
recorded ICU noise and light (NL), and NL plus use of earplugs and eye masks (NLEE). Urine was analyzed for
melatonin and cortisol levels. Subjects rated their perceived sleep qu ality, anxiety levels and perception of
environmental stimuli.
Results: Subjects had poorer perceived sleep quality, more light sleep, longer rapid eye movement (REM) latency,
less REM sleep when exposed to simulated ICU noise and light (P < 0.05). Nocturnal melatonin (P = 0.007) and
cortisol secretion levels (P = 0.004) differed significantly by condition but anxiety levels did not (P = 0.06). Use of
earplugs and eye masks resulted in more REM time, shorter REM latency, less arousal ( P < 0.05) and elevated
melatonin levels (P = 0.002).
Conclusions: Earplugs and eye masks promote sleep and hormone balance in healthy subjects exposed to
simulated ICU noise and light, making their promotion in ICU patients reasonable.
Introduction
Sleep disruption is common in ICU patients and has
been characterized by several studies using polysomno-
graphy (PSG) [1-3]. Adverse consequences of sleep dis-
ruption include impaired immune function, decreased
inspiratory muscle endurance, negatively affec ted wean-
ing fr om mechanical ventil ation, and a possible associa-
tion with delirium and severe morbidity [4,5]. The
causes of sleep disruption in the ICU are multifactorial.
The ICU environment is thought to be an important
factor in sleep disruption [6].
Numerous studies have fo und excessive noise levels in
the ICU, often with nighttime peaks of more than 80 dB
(A) [5,7]. In a ddition, subjective and objective studies
both demonstrate that patients have been disturbed by
ICU noise [1,8-10]. Light ex posure is another important
sleep dis ruptor in ICU settings. Reported nocturnal illu-
mination in ICUs varies widely, with mean m aximum
levels of 5 to 1400 lux [5,11]. Light exposure is the pri-
mary external cue for circadian rhythm. In addition,
nocturnal melatonin secretion can be acutely suppressed
by light, and 100 lux is sufficient to impact nocturnal
melatonin secretion [12]. Throughout the past decade,
evidence has been accumulating for the altered secretion
of melatonin in ICU patients. ICU patients suffer from a
severe lack of sleep associated with loss of the nocturnal
melatonin secretion pattern [13,14]. Therefor e, effective
interventions to promote sleep in ICU patients are
urgently needed.
Despitemanyclaimsthattheuseofnoisereduction
and lighting practice in an intensive care environment
may improve the patients sleep quality, there have been
few objective studies to evaluate the effects of these
interventions [15-17]. Most research in this area has
focused purely on noise reduction and not explored the
combined effects of ICU noise and light factors on
* Correspondence: xiaoyj320@163.com
1
School of Nursing, Fujian Medical University, Jiaotong Road 88, Fuzhou,
350004, PR China
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any medium, provid ed the original wor k i s properly cited.
physiological and psychological outcomes, including
sleep architecture, perceived sleep quality and hormone
secretion (melatonin and cortisol). No studies have yet
evaluated the effects of earplugs and eye masks on the
sleep of ICU patients as measured by PSG and hormone
secretion.
We hypothesized that patients sleep is disrupte d by
the noise and light in the ICU, accompanied by
impaired nocturnal melatonin secretion and elevated
cortisol secretion. Earplugs and eye masks worn during
exposure to a sim ulated ICU environment may improve
sleep and protect nocturnal melatonin and cortisol
secretion. To test this hypothesis, an experimental study
was conducted in a sleep laboratory.
Materials and methods
Research design
This study used a repe ated measures design. Four noc-
turnal nine-hour (10:00 p.m. to 7:00 a.m.) periods of
sleep were measured, including adaptation, baseline,
exposure to recorded ICU noise and light (NL), and NL
plus use of earplugs and eye masks (NLEE). All subjects
(n = 14) underwent a total of four overnight PSG.
To minimize order effects, earplugs and eye masks
were randomly worn on either the third ( n = 7) or
fourth (n = 7) night (Figure 1). For each subject, study
nights were spaced one day apart to avoid delay effects.
Subjects were asked to keep a sleep diary to record their
rest, activity and diet during the study period.
Subjects were asked to provide two nocturnal (10:00 p.m.
to 7:00 a.m.) urine samples, during base, NL and NLEE
nights. Urine levels of melatonin sulfate and cortisol were
determined by ELISA and radioimmunoassay (RIA),
respectively.
All s ubjects completed a sleep scale and the Chinese
version of the Spielberger State Anxiety I nventory (SAI)
[18] at 7:30 a.m. after every experimental night to record
perceived sleep quality and anxiety levels, respectively.
The study was performed at the Sleep-breath D isor-
ders Center at the Second Affiliated Hospital, Fujian,
China. The study design was approved by the research
ethics boards of the hospital and the Fujian Medical
University.
Subjects
Subjects were in cluded in the study if they were non-
smokers, older than 18 years of age, had no hearing pro-
blem as determined by a hearing screening t est , had no
sleep disorders, scores of 7 or less on the Pittsburgh
Sleep Quality Index (PSQI), had no history of night-shift
work i n the past three years and agreed t o abstain from
caffeine and alcohol for 12 h ours prior to each study
night. All provided written informed consent before
being enrolled in the study.
Figure 1 Study design.
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Subjects were excluded if PSG on the adaptation night
found any sleep disorder including s leep apnea, narco-
lepsy, chronic insomnia or restless leg syndrome. Female
subjects were excluded while they were menstruating.
Subjects were recruited by advertisements posted at
the Second Affiliated Hospital. Fourteen subjects were
enrolled in the study. Each was paid 200 Yuan Renminbi
at the end of the study.
Instruments
Recorded ICU noise
ICU noi se was cont inuously monitored for 24 hours
using a sound meter, model AWA5610D (AWAI, Hang-
zhou, China) i n five ICU environments: a surgical ICU
(SICU), a coronary care unit (CCU), a cardiac surgical
ICU (CSICU) and two medical ICUs (MICU). All had
noise levels far exceeding the 20 dB(A) at nighttime
recommended by the Guidelines of the Chinese Associa-
tion of Critical Care Medicine (2006)[19]. The SICU was
the loudest. The mean (standard deviation) noise value
in the SICU was 70.1 ± 11.9 dB(A), the peak noi se level
recorded was 95.3 dB(A), and the minimal noise value
was 51.4 dB(A) . Thereafter, ambient noise of the SICU
and CSICU were recorded digitally during a typical
weeknig ht shift and stored on computer for playback in
the sleep laboratory. The sound recording equipment,
modelICD-P320(SonyInc.,Tokyo,Japan)wasposi-
tioned at the bed of patients receiving mechanical venti-
lation. Simultaneous sound meter readings were taken
to ensure similar noise levels during playback in the
sleep laboratory.
Lighting conditions
Nighttime illum ination in fiv e ICU settings and the
sleep laborat ory were monitored by a light det ector,
model TES1332 (Taiwantes, Shenzen, China). In all set-
tings, light was provided by ceiling fluorescent lights.
The light detector was placed as close as possibl e to the
head of the bed of a patient receiving mechanical venti-
lation, but not so as to interfere with patient car e. L ight
measurements were taken every hour for 24 hours. Fi ve
ICUs maintained high mean night l ight levels ranging
between 50 and 238.6 lux, with highest mean nighttime
light levels in the SICU and CSICU. Mean nighttime
light levels in the sleep laboratory measured 100 lux
with the light on, and 5 lux with it off and the door to
the hallway shut. Therefore, the study used 100 lux to
simulate the ICU lighting condition.
Earplugs and eye masks
Subjects were instructed to wear earplugs with 29 d B
noise reduction rating (3 M Corporation, Beijing,
China) and eye masks during experimental night
NLEE. Subjects chose from three types of e ye masks
provided.
Polysomnography
Sleep was assessed by PSG using the Polysmith 2003
sleep acquisition and analysis system (Neurotronics, Gai-
nesville, FL, USA). The standard proc edure for sleep
measur ement described by Rechtschaffen and Kales [20]
was followed. Subjects were hooked up to record elec-
troencephalogram (EEG), eye movement and sub-mental
electromyogram (CHin EMG) in t he sleep lab oratory.
During NL and NLEE nights, recorde d ICU noise was
played and fluorescent lights turned on. A sound meter
wasplacedattheheadofthesubjects bed and the
recording time synchronized with t he sound meter to
ensure playback in a similar range of decibels to that
recorded. Electrode impedances were w ithin acceptable
limits (<10kQΩ). PSG equipment was located outside
the subjects room. Sleep variables (sleep period time,
sleep efficiency index, sleep onset latency, rapid eye
movement (REM) lat ency, arousa l index and percentage
of sleep in REM, stage one, two and three) were scored
manually by two scorers independently who were una-
ware of the experimental conditions, according to stan-
dardized criteria [20,21].
Melatonin and cortisol
Nocturnal urine was collected between 10 p.m. and
7 a.m. on baseline, NL and NLEE nights. The containers
were wrapped with black plastic t o protect the urine
from light. The amount was recorded and two samples
of each 2 ml were frozen to -20°C for later analysis.
Concentrations of 6-sulphatoxymelatonin (6-SMT), the
stable metabolite o f melatonin, were measured by
enzyme-linked immunometric assay (IBL, Hamburg,
Germany) in duplicate. Concentration of cortisol, a
stress-related hormone, was measured in another urine
sample b y RIA (Beijing North Instit ute of Biological
Technology, Beijing, China).
Subjective measurements
Subjective sleep quality was assessed by a visual analog
scale developed by the researchers based o n previous
scales [22]. Subjects evaluated their sleep quality on a
scale of 0 to 10 (0 = e xcellent, 10 = poor) at 7:30 a.m.
on the morning after every experimental night, with a
higher score indicating poorer habitual sleep quality.
State anxiety level was assessed at 7:30 a.m. on the
morning after every experimental nights. In our study,
Spielberger State Anxiety Inventory (SAI) was chosen
because it provides evaluation of state anxiety levels,
nam ely a temporary unpleasant emotional arousal in the
face of threatening demands or dangers [23]. Subjects
rated their feelings of anxiety on a four-point scale ranging
from one (almost never anxious) to four (almost always
anxious), a higher score indicating a higher anxiety level.
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On the morning after the NL night, subjects were
asked to assess the effects of simulated ICU noise and
light on sleep disruption, using a five-point scale ranging
from one (no disruption) to five (significant disruption).
Subjec ts were asked to evaluate the comfort, effective-
ness and ease o f use of e arplugs and eye masks on the
morning after the NLEE night, using a five-point scale
ranging from one (very uncomfortable, very unhelpful,
very awkward) to five (very comfortable, very helpful,
very ea sy to use) with low scores indicating a less plea-
sant experience.
Statistical analysis
Data were analyzed using SPSS version 16.0 (SPSS Inc.,
Chicago, IL, USA). Data for the adaptation night were
excluded from analysis bec ause the first night of sleep in
a sleep laboratory room with unfamiliar surroundings dif-
fers from sleep on subsequent nights [24]. All data were
expressed as mean ± standard deviation. One-way
repeated measures analysis of variance (ANOVA) were
used to determine differences in sleep variables, 6-SMT
and cortisol c oncentrations, perceived sleep quality and
anxiety levels during the three nights of the experiment.
Paired students t-test or non-parametric Wilcoxons
rank sum test were performed to evaluate the effect of
earplugs and eye mas ks on sleep variables and hormones
secretion during exposure to simulated ICU sound and
light where appropriate. Paired sample test was also used
to analyze differences in sound levels between NL and
NLEE nights. An alpha of 0.05 was considered significant.
Results
Fifteen healthy volunteers were recruited. One was
excluded due to evidence of significant insomnia.
A total of 14 subjects (8 females and 6 males, aged 21
to 70 years, mean 31.07 ± 15.64 years) completed the
study. The earplugs and eye masks were applie d easily
and remained intact during NLEE nights.
Sleep architecture
Results of sleep variables during basel ine, NL and NLEE
nights are shown in Table 1. Repeated measures
ANOVA showed that sleep architecture changed signifi-
cantly in percentage of REM sl eep (P =0.03),REM
latency (P = 0.02) and arousal index (P = 0.03) by condi-
tion. Contrast of sleep variables during exposure to
simulated ICU environment indicated tha t use of ear-
plugs and eye masks resulted in more REM sleep
(P = 0.005), shorter REM latency (P = 0.013) and fewer
arousals (P = 0.04; Figure 2).
Urinary excretion of 6-SMT and cortisol
Subjects urinary excretion during baseline, NL
and NLEE nights of 6-SMT and cortisol is shown in
Figures 3 and 4, respectively. Dif ferences in nocturnal
urinary secretion levels of 6-SMT (F =7.84,P =0.007)
and cortisol (F = 9.26, P = 0.004) were both significant.
Wilcoxons rank sum test showed significant differ-
ences in urine 6-SMT levels for NL and NLEE nights
(Z = -3.17, P = 0.002). But no difference was found in
urine cortisol levels for NL an d NLEE nights (Z = -1.47,
P = 0.14).
Subjective sleep quality and anxiety levels
The results of repeated measures ANOVA for subjective
sleep quality were significant (F = 20.6, P =0.00),but
those for anxiety levels (F =3.55,P =0.06)werenot
(Table 2).
Paired co ntrast showed use of earplugs and eye masks
improved perceived sleep quality notably (P = 0.001).
No difference was founded in anxiety levels between
the NL and NLEE nights (P = 0.28) by paired contrast,
although SAI scores showed interesting trends that
scores for NL night were highest.
Subjective perception of ICU environment and
interventions
On baseline, NL and NLEE nights, sound levels averaged
34 ± 0.6, 66.1 ± 4.2 a nd 66 ± 5.3 dB(A), respectively.
Paired contrast revealed no significant d ifference in the
noise l evel for NL a nd NLEE nights (P = 0.94). Table 3
shows t he subjective percept ion of t he effect of nois e
and light stimuli on sleep disruption on the NL night.
Eleven subjects perceived noise factor as a l ittle disrup-
tion but were able to fall asleep, two perceived n oise as
some disruption and were sometime s unable to fall
sleep, and one perceived light sleep and was easily awa-
kened by noise. There were eight, one and five subjects
perceived a little disruption but were a ble to fall asleep,
some disruption and was sometimes unable to f all
asleep, and light sleep and were easily awakened by con-
stant lighting, respectively.
Subjects evaluation of earplugs and eye masks is listed
in Table 4. Overall, they rated the devices highly, as very
comfortable, very helpful and very easy to use.
Discussion
These results support the notion that sleep and hor-
mones are both disturbed w ith exposure to simulated
ICU noise and light in healthy subjects. Use of earplugs
and eye masks improve subjective sleep quality
noticeably.
Our results confirm that subjects not only have poorer
perceived sleep quality, but also suffer from sleep dis-
ruption, measured as more light sleep, longer REM
latency and less REM sleep, with exposure to simulated
ICU noise and light levels. The results are similar to
those reported by Topf and Davis [25] and Wall ace and
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Table 1 Sleep architecture and study condition for subjects (n = 14)
Variable Baseline NL NLEE ANOVA P Contrast P
Time in bed (min) 539.7 ± 1.7 536.0 ± 15.9 536.0 ± 13.7 0.48 ——
Total sleep time (min) 456.0 ± 39.9 454.7 ± 41.8 475.1 ± 33.4 0.20 0.06
Sleep efficiency
Index
0.8 ± 0.1 0.8 ± 0.1 0.9 ± 0.0 0.12 0.09
REM% 10.9 ± 5.9 9.3 ± 4.3 12.9 ± 4.3 0.03 0.005
S1% 21.8 ± 10.4 23.4 ± 11.9 22.5 ± 9.7 0.80 0.67
S2% 43.9 ± 10.2 45.6 ± 10.3 43.5 ± 6.9 0.57 0.20
S3% 14.0 ± 6.8 11.6 ± 6.5 13.9 ± 5.6 0.30 0.11
Sleep onset latency (min) 22.3 ± 13.1 23.4 ± 16.6 15.4 ± 16.4 0.46 0.055
REM latency (min) 121.8 ± 47.0 146.9 ± 56.2 105.7 ± 47.0 0.02 0.013
Arousals index 13.0 ± 4.7 15.1 ± 6.2 12.2 ± 6.5 0.03 0.04
ANOVA, repeated measures analysis of variance; Contrast, paired students test or wilcoxons rank sum test of simulated ICU environment with and without
earplugs and eye masks; NL, recorded ICU noise and light exposure; NLEE, recorded ICU noise and light, subjects wore earplugs and eye masks; REM, rapid eye
movement.
Figure 2 Example of sleep histograms from the same subject.Lessrapideyemovement(REM)time,longerREMlatencyasexposure
to recorded ICU noise and light. NL, recorded ICU noise and light exposure; NLEE, recorded ICU noise and light, subjects wore earplugs
and eye masks.
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Figure 3 Urinary excretion of 6-SMT for different study conditions . Nocturnal urine 6-SMT concentration dur ing baseline, NL and NLEE
nights were 26.5 ± 20.0, 15.1 ± 13.6, and 22.3 ± 22.9 μg/kg, respectively. 6-SMT, 6-sulphatoxymelatonin; NL, recorded ICU noise and light
exposure; NLEE, recorded ICU noise and light, subjects wore earplugs and eye masks.
Figure 4 Urinary excretion of cortisol for different study conditions. Nocturnal urine cortisol concentration during baseline, NL and NLEE
nights were 2.0 ± 1.6, 4.0 ± 2.4, and 3.2 ± 2.1 μg/kg, respectively. NL, recorded ICU noise and light exposure; NLEE, recorded ICU noise and
light, subjects wore earplugs and eye masks.
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colleagues [16]. However, our study differs in that we
combined levels of noise and light i n a simulated ICU
environment in a sleep laboratory.
The I CU environment is not conducive to sleep. Sur-
vey studies showed that ICU patients co nsidered exces-
sive noise and bright lights noxious and disrupti ve [26].
Freedman and colleagues reported that nurse interven-
tions were mo re disrupt ive than noise or light [8].
Gabor and colleagues found that noise, light and patient
care activities accounted for less than 30% of nocturnal
arous als and awakenings [10]. Recently Cabello and col-
leagues reported noise accounte d for less than 15% o f
arousals and awakenings in mechanical ventilation
patients [27]. Therefore, noise has proved to be an
important sleep-disruptive factor and has negative phy-
siological and psychological effects on patients, although
it may not be responsible for the majority of the sleep
fragmentation. Recent emphasis has been on noise
reduction and encouraging the dimming of lights over-
night in ICU settings, but control of noise is not always
possible and light s are always present in critical care for
patient observations and patient care ac tivities. There-
fore, we hypothesized t hat use of earplugs and eye
masks may have benefits in some ICU patients with
regards to sleep disturbances.
The tolerability of these interventions is critical. Most
healthy subjects rated earplugs as comforta ble and easy
to use [16]. In our study, six subjects rated earplugs as
comfortable and 10 rated eye masks as comfortable, and
allsubjectsusedthemeasilyandkeptthemintactdur-
ing the study nights. However, previous studies showed
that some ICU patients were unwilling to use the ear-
plugs and/or eye masks because they found the inter-
ventions uncomfortable [28]. Some patients commented
that there was a feeling of heat, tightness, sore ears,
claustrophobia and still being a ble to hear when using
earplugs [15,29]. The reasons for this may include
improper inse rtion, individu al var iability in sensitivity or
anatomy of the ears, unsuitable type of earplugs and eye
masks and the a nxious state of patients. Future studies
should consider the sleep intervention according to
patients tolerability and explore other methods when
patients can not tolerate the devices. Light disturbances
may be blocked by other means and exclusion of blue
light at night by pat ients wearing g lasses that filter out
this light wavelength or nocturnal lighting sources with-
out blue light may be alternatives with regard to mini-
mizing adverse effects on the nocturnal melatonin surge.
In addition, critical care nurses should patiently provide
accurate instruction and assistance for use of earplugs
and eye masks, which may help mor e patients to benefit
from the use of the earplugs and eye masks to promote
better sleep [29].
Previous studies consistently found ICU patients suf-
fered from severe sleep disruption, with a n increased
percentage of wakefulness and stage 1 sleep and a
decrease or absence of both slow wave sleep and REM
sleep [1-3]. Our study indicates a significant difference
in PSG of percentage of REM sleep, REM latency and
arousal index b etween NL and NLEE. Although percen-
tage of REM sleep (12.9%) was statistically significantly
higher in the NLEE period, t he absolute figure in NL
(9.3%) period is still high compared with that frequently
reported in ICU patient PSG studies in which REM per-
centage is often less than 5% [1,2]. Our study cannot
completely simulate the ICU scenario; the healthy
volunteers slept relatively well in a sleep laboratory
while ICU patients are exposed to many other physical
and psychological stressors during their acute illness,
which may also contribute to their sleep disturbance.
Table 3 Subjective perception of sleep disruption (n = 14)
No disruption A little disruption but able to
fall asleep
Sometimes unable to
fall sleep
Light sleep, easy be
awakened
Significant disruption, awake
all night
Noise 0 11 2 1 0
Light 0 8 1 5 0
Table 4 Evaluation of earplugs and eye masks (n = 14)
Helpful to sleep promotion Comfortable Effective for noise/light reduction Easy to apply
Earplugs 6 6 10 11
Eye masks 8 10 13 14
Table 2 Subjective assessment of sleep quality and state anxiety by condition
Baseline night NL night NLEE night ANOVA P Contrast P
State anxiety 28.7 ± 6.3 32.5 ± 5.6 29.8 ± 6.4 0.06 0.28
Sleep quality 1.7 ± 1.3 4.1 ± 1.7 2.3 ± 1.3 0.00 0.001
ANOVA, repeated measures analysis of variance; Contrast, paired students test or wilcoxons rank sum test of simulated ICU environment with and without
earplugs and eye masks; NL, recorded ICU noise and light exposure; NLEE, recorded ICU noise and light, subjects wore earplugs and eye masks.
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Melatonin is the key circadian regulatory hormone in
humans. Cortisol is an important stress hormone. Mela-
tonin se cretion normally increases at night and decreases
in the early morning hours. In contrast, cortisol secretion
falls. Both are biological markers of the circadian rhythm.
Melatonin therapy has been shown to be ef fective in the
resetting of sleep-wake cycles, the entrainment of circa-
dian rhythms and the treatment of ch ronic insomnia
[30,31]. The melatonin secretion pattern has been related
to the sleep disturbances observed in the ICU [13,14].
Recently there has been some evidence that exogenous
melatonin is effective in improving s leep in ICU patients
[28,32]. Sleep intervention should be extended to a coor-
dinated exogenous melatonin therapy with bright light
[28]. Friese suggested that lighting could be coupled with
shielding o f patients eyes to allow for a sufficiently lit
environment so ICU staff could carry out necessary
nighttime activit ies and minimize retinal stimulation for
the patients [33]. Most previous studies evaluated the
effects of earplugs, and recently two studies indicated
that earplugs and eye ma sks w ere a relatively che ap wa y
to improve sleep quality in critically ill patients [15,34].
In fact, our study found that subjects disliked light as
much as noise and eye masks are better than ear plugs in
terms of the subjects tolerability.
In addi tion, our finding of significantly higher co rtisol
levels when exposure to ICU noise and light agreed with
previous results that acute noise stress invokes the stress
response and high levels of stress hormones [35].
Limitations of the study and suggestions for future
studies
Our study design has a number of limitations, which
should be reviewed. First, the study w as performed in a
sleep laboratory with healthy subjects rather than in an
ICU set ting of critically ill patients, and therefore could
not completely simulate the full auditory and visual
experience of the ICU. Second, the study was only per-
formed for a nine-hour nocturnal period rather than
over 24 hours. T he ICU pat ients experienc e circadian
rhythm disturbances with sleep traversing the day and
night. Therefore, an ideal study should measure the
sleep in healthy volunteers lying recumbent over a 24-
hour period to completely simulate the ICU scenario.
Our study combined noise and light as e nvironmental
stimuli and used earplugs and eye masks as intervention,
so we were unable to measure the effect of each one
separately on sleep and hormones secretion. Further stu-
dies are needed to elucidate the separate mechanisms of
ICU noise and light on sleep disturbance and hormones
secretion. In addition, our sample sizes were small,
which limited the power of our statistical analyses.
Future studies with larger and more diversity of the par-
ticipants would likely support these recommendations.
Conclusions
In summary, our results found that use of earplugs and
eye masks in subjects not only improves subjective sleep
quality, but also incr eases the amount of REM sleep and
nocturnal melatonin levels in a simulated ICU environ-
ment. Our pilot study provides a reasonable basis for
promoting the use of earplugs and eye masks for ICU
patients. Sleep is a b asic human need, sleep disruption
may contribute to patient morbidity and degenerate
quality of life [4,5]. Therefore, we recommend the rou-
tine use of earplugs and eye masks in all ICU patients
even though some patients may b e undergoing o ngoing
disease processes. Future studies should be designed to
determine if t he use of earplugs and eye masks will
improve the sleep quality and ultimately benefit the clin-
ical outcome of critically ill patients.
Key messages
Subjects had poorer perceived sleep quality, more
light sleep, longer REM latency, and less REM sleep
when exposed to simulated ICU noise and light.
Nocturnal melatonin and c ortisol secretion levels
differed significantly by experimental condition.
Use of earplugs and eye masks r esulted in more
REM time, shorter REM latency, less arousal and an ele-
vation of nocturnal melatonin levels.
Abbreviations
6-SMT: 6-sulphatoxymelatonin; ANOVA: analysis of variance; CCU: coronary
care unit; CHin EMG: sub-mental electromyogram; CSICU: cardiac surgical
ICU; EEG: electroencephalogram; ELISA: enzyme-linked immunosorbent assay;
MICU: medical ICU; NL: recorded ICU noise and light exposure; NLEE: NL plus
use of earplugs and eye masks; PSG: polysomnography; PSQI: Pittsburgh
Sleep Quality Index; RAI: radioimmunoassay; REM: rapid eye movement; SICU:
surgical ICU; STAI: Spielberger State-Trait Anxiety Inventory.
Acknowledgements
Thanks are due to Ms Wang Wanyu, Ms Lin yuanjian, Ms Zeng jing, Zhang
Yixiang MD, and Li Yueping MD for their support to the study. The authors
also thank the referees for their careful review of the manuscript.
Author details
1
School of Nursing, Fujian Medical University, Jiaotong Road 88, Fuzhou,
350004, PR China.
2
Sleep-Breath Disorders Center, Second Affiliated Hospital,
Zhongshan Road 34, Quanzhou, 362000, PR China.
3
Department of Nuclear
Medicine, Fujian Province Hospital, East Street 134, Fuzhou, 350001,
PR China.
Authors contributions
JX and ZY designed the study, and participated in the coordination and
writing of the manuscript. HR performed data collection, data entry,
statistical analysis and wrote the manuscript. CX participated in the data
collection, data entry, and statistical analysis. ZY was responsible for analysis
of the levels of 6-SMT and cortisol.
Competing interests
The authors declare that they have no competing interests.
Received: 2 October 2009 Revised: 23 December 2009
Accepted: 18 April 2010 Published: 18 April 2010
Hu et al. Critical Care 2010, 14:R66
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doi:10.1186/cc8965
Cite this article as: Hu et al.: Effects of earplugs and eye masks on
nocturnal sleep, melatonin and cortisol in a simulated intensive care
unit environment. Critical Care 2010 14:R66.
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... Patient information form prepared by the authors [19,20], Visual Analogue Scale (VAS) to evaluate pain [21], Morningness-Eveningness Questionnaire (MEQ) to determine the chronotypes of patients [22][23][24], Sleep Quality Scale in Coronary Intensive Care Patients (SQ-CC) developed by the authors to determine the patients' sleep quality [25], Hospital Anxiety and Depression Scale (HADS) to evaluate anxiety [26,27], Intensive Care Delirium Screening Checklist (ICDSC) to calculate delirium scores [28] were applied to both intervention and control groups to obtain data in line with the purpose of the study. Permission was obtained by e-mail for the scales used in the study. ...
... This form, which the researcher prepared in the light of the literature [19,20], consists of 9 questions including demographic characteristics such as age, gender, marital status, educational status, family structure, income, comorbidities, smoking habit and alcohol use. ...
... However, over time, melatonin levels increased and cortisol levels decreased in both groups. The literature presents contradictory findings: some studies report an increase in melatonin with no change in cortisol [19], others report no changes in either hormone [43], while others observe positive changes in both [44]. One study found variations depending on measurement timing but no differences at similar times, consistent with the present study's findings [45]. ...
Article
Full-text available
Aim This study carried out to examine the effects of nursing care given to coronary intensive care patients according to their circadian rhythms on sleep quality, pain, anxiety, and delirium. Study Design This study was designed as a randomised controlled, clinical investigation. The study population consisted of patients treated in the coronary care unit of a training and research hospital between September 2022 and February 2023. Total of 44 participants were included. The included participants were followed up for 3 days in the coronary intensive care unit. Data were collected using “Patient Information Form, Sleep Quality Scale in Coronary Intensive Care Patients (SQ-CC), Visual Analogue Scale (VAS), Morningness-Eveningness Questionnaire (MEQ), Hospital Anxiety and Depression Scale (HADS), Intensive Care Delirium Screening Checklist (ICDSC).” In addition, melatonin and cortisol measurements were made, and sleep data were taken with a smartwatch. Patients with intermediate chronotype, delirium, on ventilator support, or using sedative drugs were excluded. The chronotypes of the participants were determined, and the patients in the intervention group were given nursing care by their circadian rhythms. No intervention was made to the control group, and their routine care was continued in accordance with intensive care unit functioning. Frequency distribution, dependent and independent sample t-test, Wilcoxon test, repeated measures analysis of variance, Mann Whitney U, and chi-square analysis were used to evaluate the data. The study has been registered in ClinicalTrials.gov (Identifiers: NCT04934436). During statistical analysis, the groups were coded as Group A and Group B, ensuring blinding for the statistician. Results The intervention group’s sleep quality increased compared to the control group (post-test SQ-CC total scores: intervention group 22.41 ± 6.67 vs. control group 50.45 ± 10.63, p < 0.001). Although no significant difference was found between the groups as a result of the study, there was a significant decrease in the pain score in the intervention group (VAS pre-test: 1.55 ± 2.15, post-test: 0.68 ± 2.21, p = 0.036). The anxiety of the intervention group decreased significantly compared to the control group (post-test HADS-Anxiety scores: intervention group 3.18 ± 3.29 vs. control group 8.50 ± 5.66, p = 0.001). The post-test delirium score was higher in the control group compared to the intervention group (post-test ICDSC scores: intervention group 0.32 ± 0.48 vs. control group 1.18 ± 0.50, p < 0.001). Melatonin increased and cortisol decreased in both groups without statistically significant differences between them (melatonin and cortisol levels: p > 0.05). Considering the sound levels in the environment, the first-night decibel mean was significantly higher in the intervention group than in the control group (first-night decibel mean: intervention group 56.58 ± 2.43 dB vs. control group 54.51 ± 2.41 dB, p < 0.05). Finally, the smartwatch data show no significant difference in sleep times between groups (p < 0.05), but the intervention group had more deep and total sleep, while the control group had less deep sleep. Conclusions Nursing care given in accordance with the circadian rhythm increases sleep quality and reduces the risk of delirium and anxiety in patients followed up with acute coronary syndrome in the coronary intensive care unit.
... Multiple studies indicate that the sleep quality of ICU nurses is generally poor. For instance, research has found that compared to the general population, ICU nurses have signi cantly higher rates of sleep disorders, characterized by di culties falling asleep, sleep interruptions, and poor sleep quality [6]. These issues primarily stem from the irregularity of their work schedules and high levels of stress, such as long hours of night shifts and frequent rotation shifts. ...
... Sleep disorders not only diminish the personal life quality of ICU nurses but may also signi cantly affect their job performance. Studies indicate that inadequate sleep and fatigue can reduce nurses' work e ciency, increase the risk of medical errors, and potentially affect patient safety and treatment outcomes [6,11].Latent Class Analysis (LCA) is a method that utilizes Latent Class Models (LCM) to explore the relationships between manifest categorical variables [12]. ...
Preprint
Full-text available
Objective This study aims to identify the potential classifications of sleep disturbances within the ICU nurse population, and to compare the between-group differences in demographic data and sleep characteristics. Methods Through convenience sampling, ICU nurses from three tertiary A-level hospitals in China were selected as research subjects from March to May 2024. A survey was conducted using a demographic data questionnaire, the PSQI scale, the DASS-21 scale, and the BPS scale, and the data on the sleep quality of ICU nurses was collected via electronic questionnaires. This research also utilized latent class analysis to examine the symptomatic traits of sleep quality in ICU nurses. Additionally, it applied univariate analysis and unordered multinomial logistic regression models to determine the factors influencing the various categories of their sleep quality. Results A total of 545 questionnaires were distributed, of which 522 were validly returned, yielding an effective response rate of 95.7%. Four potential sleep quality profiles were identified, including "high sleep quality - no sleeping pills," "medium sleep quality - low sleeping pills," "medium sleep quality - medium sleeping pills," and "low sleep quality - high sleeping pills," with proportions of 43.7%, 40.6%, 10.5%, and 5.2%, respectively. Unordered multinomial logistic regression analysis indicated that the number of night shifts per week, marital status, BPS scores, FSS scores, and DASS-21 scores were key factors affecting the sleep quality classification of ICU nurses(P < 0.05). Conclusion The sleep quality characteristics of ICU nurses are diverse and can be divided into four different categories. Therefore, nursing managers should be aware of this heterogeneity and take corresponding intervention measures based on the classification of nurses to ensure their sleep quality and promote psychological health.
... The light level of indoor ceiling lights usually ranges between 300 and 500 lux, which is enough to disturb the body production of melatonin (Pisani et al., 2015;Simons et al., 2019). By wearing eye masks, patients can effectively block excess light at night, facilitate melatonin secretion, obtain more rapid eye movement sleep and improve overall sleep quality (Hu et al., 2010). On the contrary, although sleep-inducing drugs can also facilitate sleep, they may introduce side effects such as cognitive impairment, drug tolerance or dependency, hypopnea and adversely affected sleep physiology (Devlin et al., 2018;Hu, Jiang, Chen, et al., 2015). ...
... Eye masks can increase the melatonin level by blocking lights and consequently enhance the sleep quality (Hu et al., 2010). The I 2 of the 13 selected studies was 94%, but dropped to 64% for the standalone use of eye masks. ...
Research
Aims: To evaluate the effect of earplugs and eye masks on the sleep quality of patients in intensive care unit (ICU). Design: Systematic review and meta-analysis. Data Sources: Randomized controlled trial studies conducted before May 5, 2020 were searched for in Embase, MEDLINE, Cochrane Library, CINAHL and Index to Taiwan Periodical Literature System databases. Review Methods: Analyses in this study were according to the PRISMA statement. The heterogeneity of the data was investigated through subgroup analysis while a meta-analysis was performed using the Review Manager 5.3 software. Results: A total of 797 patients from 13 studies were included in this study. Without considering alone or combined use of earplugs and eye masks, the meta-analysis supported that there was a significant effect on self-reported sleep quality. The overall standardized mean difference of the effect size was 1.44 (95% confidence interval [CI]: [0.80, 2.09]). Subgroup analysis indicated that the use of earplugs alone had no significant effect on sleep quality (effect size: 0.07, 95% [CI]: [−0.50, 0.64]). The use of eye masks alone had a significant effect on sleep quality (effect size: 1.56, 95% [CI]: [1.08, 2.05]). The use of both earplugs and eye masks proved to have the largest effect size on sleep quality (effect size: 2.08, 95% [CI]: [0.95, 3.21]). Conclusion: The combined use of earplugs and eye masks or the standalone use of eye masks is a non-invasive, economical and effective way to promote sleep quality in adult ICU patients. Impact: Clinical nurses could use this meta-analysis as it recommends that nurses provide adult ICU patients with either one or both earplugs and eye masks to improve the patients' sleep quality. Study Registration: The review protocol was registered a priori and published on-line in the PROSPERO database of systematic reviews (www.crd.York.ac.uk/Prospero with the registration number # CRD42021221185). K E Y W O R D S earplugs, eye masks, intensive care, meta-analysis, nursing, sleep quality, systematic review
... Moreover, individuals with delirium commonly display disrupted sleep-wake cycles. Exposure of subjects to simulated ICU noise and light environments often leads to sleep deprivation and fragmentation; however, when noise and light levels are reduced, their sleep patterns tend to normalize (Hu et al., 2010). In the ICU, the administration of sedatives, particularly benzodiazepines, can disrupt the regular sleep-wake cycle by promoting lighter sleep and reducing slow-wave and REM sleep stages (Devlin et al., 2018). ...
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Delirium is an acute, global cognitive disorder syndrome, also known as acute brain syndrome, characterized by disturbance of attention and awareness and fluctuation of symptoms. Its incidence is high among critically ill patients. Once patients develop delirium, it increases the risk of unplanned extubation, prolongs hospital stay, increases the risk of nosocomial infection, post-intensive care syndrome-cognitive impairment, and even death. Therefore, it is of great importance to understand how delirium occurs and to reduce the incidence of delirium in critically ill patients. This paper reviews the potential pathophysiological mechanisms of delirium in critically ill patients, with the aim of better understanding its pathophysiological processes, guiding the formulation of effective prevention and treatment strategies, providing a basis for clinical medication.
... Because of these noted benefits, more studies have been using sleep masks in medical settings, such as in the Intensive Care Unit (ICU), to help patients sleep better. Because ICU patients are exposed to constant light and noise, they may experience sleep disruption, which can affect the recovery process (Hu et al., 2010). In studies within a simulated ICU environment, patients had their arousal index and other sleep parameters measured by polysomnography when they were wearing sleep masks and when they were not. ...
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For reasons we only partially understand, sleep is vitally necessary to human well-being. As such, factors that influence sleep quality have garnered increased attention in recent years. One such factor is the use of sleep masks. In general, sleep masks are used to block out light, as therapeutic masks to promote relaxation and treat illness, and as fashion accessories. This essay reviews the existing literature on the use of sleep masks. It also includes a preliminary survey that addresses the attitudes and habits of individuals who use sleep masks.
... In a study conducted on 14 adult volunteers in intensive care unit, it was reported that using eye mask patches and earplugs increased the level of urinary 6-sulfatoxymelatonin [34]. Eye masks for babies are used during phototherapy. ...
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Background/aim The aim of this study was to investigate the effect of phototherapy treatment on serum melatonin levels in term newborn infants. Material and methods This study was planned as a single-center, prospective, observational, case-control study. Term infants (gestation week ≥37 weeks) who received at least 6 h of phototherapy due to jaundice constitute the phototherapy group, while the term infants without jaundice and who were exclusively breastfed constitute the control group. Melatonin levels were examined by taking blood samples from babies in both groups at 02:00 at night. Melatonin values were compared between groups. The effect of phototherapy on serum melatonin levels was investigated. The relationship between the duration of phototherapy and maximum serum bilirubin values on melatonin values was investigated. Results Seventy term infants (64.3% girls) were included in the study. Mean gestational week was 38.3 ± 1.1 weeks, mean birth weight was 3295 ± 434 g. There was no statistically significant difference between the phototherapy group and the control group in terms of sex, type of delivery, gestational week, birth weight, height, and head circumference (all p > 0.05). Serum melatonin level was 20.3 ± 5.9 pg/mL (range: 8.7–36.6 pg/mL) in the phototherapy group and 19.9 ± 4.38 pg/mL (range: 9.9–26.3 pg/mL) in the control group. There was no significant difference between the two groups in terms of serum melatonin levels (p = 0.155). The mean total bilirubin value was 17.65 ± 1.48 mg/dL, and the average duration of phototherapy application was 13.94 ± 7.64 h in the babies in the phototherapy group. No correlation was found between the duration of phototherapy application and serum melatonin levels (p = 0.791). Conclusion It was determined that there was no significant difference in serum melatonin levels in term newborn babies who received phototherapy for at least 6 h due to jaundice. No correlation was found between the duration of phototherapy application and the serum melatonin level of the maximum bilirubin values.
... To minimize circadian disruptions without compromising critical care, adopting strategies like cycle lighting and light-blocking at night can be beneficial, drawing from successful approaches used in human critical care units. This includes implementing a "chronobundle" of interventions (Scotto et al., 2009;Xie et al., 2009;Hu et al., 2010;Patel et al., 2014;McKenna et al., 2018), potentially employing specific light spectra, such as blue-poor light during sleep time to limit light-induced melatonin suppression (Souman et al., 2018). These strategies, proven to reduce sleep disruptions and delirium in human hospitals (Engwall et al., 2015(Engwall et al., , 2017Ruben et al., 2019a), may offer similar benefits to animal patients. ...
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Circadian biology’s impact on human physical health and its role in disease development and progression is widely recognized. The forefront of circadian rhythm research now focuses on translational applications to clinical medicine, aiming to enhance disease diagnosis, prognosis, and treatment responses. However, the field of circadian medicine has predominantly concentrated on human healthcare, neglecting its potential for transformative applications in veterinary medicine, thereby overlooking opportunities to improve non-human animal health and welfare. This review consists of three main sections. The first section focuses on the translational potential of circadian medicine into current industry practices of agricultural animals, with a particular emphasis on horses, broiler chickens, and laying hens. The second section delves into the potential applications of circadian medicine in small animal veterinary care, primarily focusing on our companion animals, namely dogs and cats. The final section explores emerging frontiers in circadian medicine, encompassing aquaculture, veterinary hospital care, and non-human animal welfare and concludes with the integration of One Health principles. In summary, circadian medicine represents a highly promising field of medicine that holds the potential to significantly enhance the clinical care and overall health of all animals, extending its impact beyond human healthcare.
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To determine the effectiveness of using earplugs and eye masks on the melatonin and cortisol levels of patients hospitalized in cardiac critical care units (CCUs). The research population of this study included all patients with acute coronary syndrome hospitalized in the CCU of Shahid Rajaei Hospital affiliated with to Alborz University of Medical Sciences. A total of 60 patients were selected by the available sampling method based on the inclusion criteria and then were divided into 2 control and intervention groups by block randomization method with blocks of 4 (n = 30 in the intervention group, and n = 30 in the control group). Patients in the intervention groups used blindfolds and earmuffs during the night sleep for 3 nights, but patients in the control group received the routine care. Cortisol and melatonin levels of both groups were measured at 8 am, using the urine samples. The findings of the 2 groups were compared and statistically analyzed by SPSS software version 16. The findings showed no significant difference between the 2 groups in terms of demographic characteristics and clinical variables. The intervention had no effect on the cortisol level of patients in the intervention group ( P = .24). After the intervention, a statistically significant difference was observed between the control and intervention groups in terms of the melatonin level in the nocturnal urine ( P ≤ .001). A statistically significant difference was also observed between the 2 groups in terms of the time taken for patients to fall asleep ( P ≤ .001) and the number of times waking up at night ( P ≤ .001). The use of earplugs and eye masks had no impact on the level of cortisol hormone, but it affected the level of melatonin hormone and the sleep quality of patients hospitalized in the CCU.
Article
BACKGROUND: Sleep deprivation may contribute to impaired immune function, ventilatory compromise, disrupted thermoregulation, and delirium. Noise levels in intensive care units may be related to disturbed sleep patterns, but noise reduction has not been tested in this setting. OBJECTIVE: To measure the effect of a noise reduction intervention on the sleep of healthy subjects exposed to simulated intensive care unit noise. METHODS: After digital audiotape recording of noise and development of the noise reduction intervention, 5 nocturnal 8-hour periods of sleep were measured in 6 paid, healthy volunteers at 7-day intervals in a sleep disorders center. Polysomnographic data were collected by experienced sleep disorders technicians and scored by certified raters. After the first 3 quiet nights, earplugs were randomly assigned to be worn on the fourth and fifth nights during exposure to the recorded noise. Sound pressure levels were measured during all 5 nights. RESULTS: Sleep architecture and sound measurements on quiet nights did not differ significantly. Sound levels were significantly lower on quiet nights than on noise nights. Exposure to the noise increased the number of awakenings, percentage of stage 2 sleep, and rapid eye movement latency and decreased time asleep, sleep maintenance efficiency index, and percentage of rapid eye movement sleep. Earplugs worn during exposure to the noise produced a significant decrease in rapid eye movement latency and an increase in the percentage of rapid eye movement sleep. CONCLUSION: The results provide a reasonable basis for testing the effects of earplugs on the sleep of critically ill subjects.
Article
Sleep deprivation and fragmentation occurring in the hospital setting may have a negative impact on the respiratory system by decreasing respiratory muscle function and ventilatory response to CO2. Sleep deprivation in a patient with respiratory failure may, therefore, impair recovery and weaning from mechanical ventilation. We postulate that light, sound, and interruption levels in a weaning unit are major factors resulting in sleep disorders and possibly circadian rhythm disruption. As an initial test of this hypothesis, we sampled interruption levels and continuously monitored light and sound levels for a minimum of seven consecutive days in a medical ICU, a multiple bed respiratory care unit (RCU) room, a single-bed RCU room, and a private room. Light levels in all areas maintained a day-night rhythm, with peak levels dependent on window orientation and shading. Peak sound levels were extremely high in all areas representing values significantly higher than those recommended by the Environmental Protection Agency as acceptable for a hospital environment. The number of sound peaks greater than 80 decibels, which may result in sleep arousals, was especially high in the intensive and respiratory care areas, but did show a day-night rhythm in all settings. Patient interruptions tended to be erratic, leaving little time for condensed sleep. We conclude that the potential for environmentally induced sleep disruption is high in all areas, but especially high in the intensive and respiratory care areas where the negative consequences may be the most severe.
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This study aimed to determine the effects of earplug use on the subjective experience of sleep for patients in critical care. The negative effects of noise in critical care include sleep disturbances, increased stress response, and reduced patient satisfaction. The nature of critical care often precludes quiet time protocols. Previous studies indicated that earplugs can improve REM sleep and sleep efficiency. This study examined the effects of earplugs as a non-invasive method for improving the subjective sleep experience and increasing patient satisfaction. Quasi-experimental intervention study with random assignment of subjects. Subjects were non-ventilated, non-sedated adults admitted to critical care. The intervention group used earplugs during nighttime sleep hours allowing short term removal during patient care. Participants completed the Verran-Snyder-Halpern Sleep Scale, an 8-question visual analogue scale, to describe their subjective response to sleep. Two sample T-tests were used to detect differences between the group scores. 88 participants (49 intervention/39 control) completed the study. Mean age 63, 56% males, 93% Caucasian. Total sleep satisfaction scores were significantly better for the intervention group (p = .002). Seven of the subjective categories were independently significant (p = .005-.044). One category, satisfaction with the amount of time needed to fall asleep, was not significant (p = .111). Earplug use improved the subjective experience of sleep for un-medicated critical care patients without interfering with care delivery. The negligible cost and low level of invasiveness of earplugs makes this preferable as a primary intervention to promote sleep while avoiding unnecessary sedating medications.