ArticlePDF Available

Light affects heart rate's 24‐h rhythmicity in intensive care unit patients: an observational study



Background Intensive care unit (ICU) patients experience two affronts to normal 24‐h rhythms: largely internal events such as medication and external factors such as light, noise and nursing interventions. Aims and objectives We investigated the impact of light variance within an ICU on 24‐h rhythmicity of three key physiological parameters: heart rate (HR), mean arterial blood pressure (MAP) and body temperature (BT) in this patient population. Design Patients were assigned to beds either in the ‘light’ or ‘dark’ side within a single ICU. An actigraph continuously recorded light intensity for a 24–72‐h period. Methods Measurements of HR, MAP and BT were recorded every 30 min. Results HR, MAP and BT did not follow 24‐h rhythmicity in all patients. Higher light exposure in the Light Side of the ICU (122·3 versus 50·6 lx) was related to higher HR (89·4 versus 79·8 bpm), which may translate to clinically relevant outcomes in a larger sample. Duration of stay, the one clinical outcome measured in this study, showed no significant variation between the groups (p = 0·147). Conclusions ICU patients are exposed to varying light intensities depending on bed positioning relative to natural sunlight, affecting the 24‐h rhythm of HR. Larger, well‐controlled studies also investigating the effect of relevant light intensity are indicated. Relevance to clinical practice Light is a variable that can be manipulated in the constrained environment of an ICU, thus offering an avenue for relatively unobtrusive interventions.
doi: 10.1111/nicc.12433
Light affects heart rate’s 24-h rhythmicity in
intensive care unit patients: an observational
Anna Korompeli
, Nadia Kavrochorianou
, Lubos Molcan, Olav Muurlink, Eleni Boutzouka, Pavlos Myrianthefs
and Georgios Fildissis
Intensive care unit (ICU) patients experience two affronts to normal 24-h rhythms: largely internal events such as medication and external factors such as light, noise
and nursing interventions.
Aims and objectives:
We investigated the impact of light variance within an ICU on 24-h rhythmicity of three key physiological parameters: heart rate (HR), mean arterial blood
pressure (MAP) and body temperature (BT) in this patient population.
Patients were assigned to beds either in the ‘light’ or ‘dark’ side within a single ICU. An actigraph continuously recorded light intensity for a 24– 72-h period.
Measurements of HR, MAP and BTwere recorded every 30 min.
HR, MAP and BT did not follow 24-h rhythmicity in all patients. Higher light exposure in the Light Side of the ICU (122
6 lx) was related to higher HR (89
versus 79
8 bpm), which may translate to clinically relevant outcomes in a larger sample. Duration of stay, the one clinical outcome measured in this study, showed no significant
variation between the groups (p
ICU patients are exposed to varying light intensities depending on bed positioning relative to natural sunlight, affecting the 24-h rhythm of HR. Larger, well-controlled
studies also investigating the effect of relevant light intensity are indicated.
Relevance to clinical practice:
Light is a variable that can be manipulated in the constrained environment of an ICU, thus offering an avenue for relatively unobtrusive
Key words:
24-h rhythm
The internal states of patients in an intensive
care unit (ICU), because of medication (seda-
tion, opioids) and physiological parameters
(organ dysfunction and failure), tend
to result in distorted 24-h rhythms (Paul
and Lemmer, 2007; McKenna et al., 2018).
On the other hand, external cycles (light,
environmental noise, medical and nursing
interventions) tend towards 24-h activity
(Weiss et al., 2016; Korompeli et al., 2017;
McKenna et al., 2017). Articial lighting
afforded to patients, however, only loosely
These authors contributed equally to this study.
Authors: A Korompeli, National and Kapodistrian University of Athens, University ICU, Ag. Anargyroi General Hospital, Athens, Greece; N Kavrochorianou, National and
Kapodistrian University of Athens, University ICU, Ag. Anargyroi General Hospital, Athens, Greece; L Molcan, Department of Animal Physiology and Ethology, Faculty of Natural
Sciences, Comenius University, Bratislava, Slovakia; O Muurlink, Central Queensland University, Brisbane, Griffith Institute of Educational Research, Brisbane, Queensland, Australia;
E Boutzouka, National and Kapodistrian University of Athens, University ICU, Ag. Anargyroi General Hospital, Athens, Greece; P Myrianthefs, National and Kapodistrian University of
Athens, University ICU, Ag. Anargyroi General Hospital, Athens, Greece; G Fildissis, National and Kapodistrian University of Athens, University ICU, Ag. Anargyroi General Hospital,
Athens, Greece
Address for correspondence: N Kavrochorianou, National and Kapodistrian University of Athens, University ICU, Ag. Anargyroi General Hospital, Noufaron & Timiou Stavrou,
Kaliftaki, Nea Kifissia 14564, Athens, Greece
conforms to ‘normal’ light/dark cycles, and
nursing rosters are structured to respond
to staff availability and capability. The mis-
match between internal states and external
cycles in the ICU environment thus offers
a unique challenge to circadian timing. In
addition, Durrington et al. (2017) report that
ICUs offer a paradoxical mixture of subop-
timal light and bursts of bright light during
night time, representing a major challenge
to good-quality sleep. Moreover, admission
for acute illness is itself a major risk factor
for rest– activity rhythm disturbance, and
the illness prole may impact meals and
daily physical activity (Sunderram et al.,
2014). Thus, the illness, its direct treatment
and the context in which it is treated may
collectively disturb the circadian timing
system. The rhythm abnormalities are often
expressed in ICU patients through altered
rhythmic 24-h proles of physiological
parameters such as sleep/wake cycles,
mean arterial blood pressure (MAP), heart
rate (HR), body temperature (BT), sponta-
neous motor activity and levels of melatonin
and cortisol (Engwall et al., 2017).
© 2019 British Association of Critical Care Nurses
Vol 2 4 N o 5
Light affects heart rate’s 24-h rhythmicity of ICU patients
Bright light treatment during daytime has
been found to adjust sleep– wakefulness
cycles and reduce postoperative delir-
ium (Taguchi et al., 2007; Ono et al., 2011;
Taguchi, 2013; Simons et al., 2016). On the
other hand, light at night (LAN) affects the
circadian system, diminishes light/dark
(L/D) differences and can be harmful to
other physiological systems (Fonken and
Nelson, 2014; Gaston et al., 2015). Patients
in ICUs demonstrate dampened L/D dif-
ferences, possibly because of LAN in ICUs;
however, pain and acute inammation can
also alter 24-h oscillations (Touitou et al.,
2017). There is currently limited evidence on
the therapeutic implications of ICU lighting.
Data from previous studies indicate that
patients assigned to well-lit positions in car-
diac ICUs had shorter lengths of stay, lower
mortality rates (Vinzio et al., 2003) and better
outcomes (lower pain and stress); however,
the current study offers greater control and
makes use of a more homogenous sample
than previous studies (Ritchie et al., 2015).
The purpose of the present study was
to examine the impact of light exposure, as a
function of bed positioning relative to natu-
ral light, over a continuous 24– 72-h period
on the 24-h rhythmicity of three key physio-
logical parameters: HR, MAP and BT. These
parameters are continuously measured
and monitored during the normal course
of operation of most ICUs and are used
as predictors of mortality rates in patients
in ICUs. Their 24-h rhythm can be altered
by the inuence of light (Bourcier et al., 2016;
McKenna et al., 2017). This study investi-
gated the potential role differential exposure
to natural light in an ICU setting may play.
ICU design
This observational study was conducted
in a small, single-ward University ICU at a
Greek general hospital in Athens. Generally,
total admissions to this ICU are low because
the study site is a training hospital without
a high-dependency unit (HDU), with HDU
patients instead assigned to the ICU, result-
ing in a long mean length of stay. The
windows in the ICU offered access to nat-
ural lighting. Articial lighting, consisting
of overhead panels containing bright white
uorescent lights, illuminated the ICU.
The arrangement of beds in the ICU led
to a distinction between an array of three
fully equipped beds close to the windows
on the ‘light’ side and six otherwise iden-
tical beds bounded by a corridor on the
‘dark’ side in the same large room. Patients
were assigned to a bed on either side of the
ICU (Durrington et al., 2017) depending
on bed availability. Although not random,
the assignment was not based on patients’
clinical condition. The same nursing staff
attended both sets of patients. Notably, this
study did not manipulate light exposure
but took advantage of natural uctuations
of light within the existing ICU design.
‘Daytime’ was set from 8 a.m. to 8 p.m., and
‘nighttime’ was set from 8 p.m. to 8 a.m.
Eligibility criteria
The study site was a general ICU; thus, it
included critically ill patients with respi-
ratory and cardiovascular disease, as well
as surgical patients. To ensure a high degree
of homogeneity, patients were enrolled
according to the following inclusion crite-
ria, which had to be met at least 24 h prior
to study entry and maintained throughout
the whole 24– 72 h of the study period:
18– 87 years of age, afebrile (BT <383C),
cessation of analog sedation and mechan-
ical ventilation and/or other disturbance
necessitating analog sedation.
The exclusion criteria of patients were:
participation in another clinical study
in the past 30 days, use of glucocorti-
coid medication during the last 14 days,
use of b-adrenergic receptor blockers or
monoamine oxidase inhibitors less than 1
week before study entry, delirium, sleep
disorders, clinical depression, craniocere-
bral injury, thyroid disorders, liver cirrhosis,
renal failure, haemodialysis, coronary heart
disease, sepsis, multi-organ failure or severe
coagulopathy. All patients were evaluated
within 24 h of admission by calculating
the Acute Physiology and Chronic Health
Evaluation II score, a severity-of-disease
classication system, and the sequential
organ failure assessment score, used to pre-
dict hospital mortality based on six organ
dysfunction factors. To avoid implications
of hormonal changes in female participants,
only post-menopausal female patients were
Activity and light parameters
Light exposure (lux levels) and rest– activity
rhythm of the patients were monitored
for 24– 72 consecutive hours and anal-
ysed separately for daytime and nighttime
using the MotionWatch actigraphy sys-
tem (MW8, CamNtech, Cambridge, UK).
Activity and light data were recorded
with a 1-minute epoch and tracked
with MotionWare 1.1.20 software (Cam-
Ntech, Cambridge, UK).
Physiological parameters
The physiological parameters HR (beats per
minute, bpm) and mean arterial pressure
(MAP) (millimetre of mercury, mmHg) were
recorded automatically every 30 min with a
Philips IntelliVue MP60 Monitor. In addi-
tion, BT (C) was measured automatically
with a body thermometer every 30 min
(Motohashi et al., 1987). All parameters
(HR, MAP and BT) were measured at the
same time for each patient and at the same
interval of 30 min for a 24–72-h period.
Data analysis
As the length of the data collection period
varied between patients, HR, MAP and BT
data of each patient were integrated for anal-
ysis purposes into a single 24-h period,
and the signicance of this period using
the cosinor model (Renetti et al., 2007) was
evaluated a priori. Specically, if patient
data exceeded the minimum 24-h period,
rather than discarding the data or choos-
ing a 24-h period from a longer period for
these patients, full patient data was inte-
grated into a single 24-h unit. Because of the
absence of 24-h rhythms in some patients
and some parameters, we further anal-
ysed only the mesor (average value around
which the variable oscillates), as well as day-
time and nighttime mean values and their
differences (delta) in all measured variables.
Statistical analysis
SPSS Statistics 22 (IBM, Armonk, New
York) was used for all analyses. The
Shapiro– Wilk test of normality was applied,
the independent two-group t-test was
used for comparison of normally dis-
tributed data. Otherwise, a non-parametric
Mann-Whitney U-test was used for the
comparison of non-normally distributed
data. The statistical tests were considered
statistically signicant if the pvalue was
less than 005. Data in the text are expressed
as the arithmetic mean ±standard error of
mean (SEM). The distribution of data is
demonstrated by box plots, with the box
© 2019 British Association of Critical Care Nurses
Light affects heart rate’s 24-h rhythmicity of ICU patients
representing the range from the rst to third
quartiles; the band near the middle of the
box is the median, and the lines above and
below the box indicate the locations of the
minimum and maximum value.
The study was conducted in full accordance
with ethical principles of the World Medi-
cal Association Declaration of Helsinki (ver-
sion, 2002), followed the protocols set out
by Portaluppi et al. (2010) and was indepen-
dently reviewed and approved by the ethical
committee of the hospital. Informed consent
forms were signed by all patients, or when
patients were unable to sign, consent was
obtained from their legal representatives.
Patients’ characteristics
A total of 86 subjects were admitted to the
ICU during the period between May
and November 2016. Of the 86 admitted
patients, 51 were ineligible because of the
exclusion criteria. The remaining 35 eligible
ICU patients were divided into ‘Light Side’
(n=9, 257%) and ‘Dark Side’ (n=26, 743%)
groups. Of the 35 eligible patients, 13 were
removed from the study post-hoc because
of missing data relating to light exposure.
Specically, because of actigraph sensors
being obscured by clothes and bed linen,
signicant light data were absent. In order
to ensure proper light recording and data
validity, we chose to attach the actigraph to
the bed (not the wrist), and only data from
the subsequent 22 patients were retained for
As patients were treated exclusively in
bed during the study period, the measured
Table 1
Patients’ characteristics and group assignment (mean
Total ICU Dark Side Light Side
Number of patients (n)22175
Male (n, %) 14 (63
6) 10 (58
8) 4 (80)
Female (n, %) 8 (36
4) 7 (41
2) 1 (20)
Age (years) 71
APACHE-II score 21
SOFA score 8
Length of ICU stay (days) 17
Length of ICU stay before inclusion to the study (days) 16
Light exposure during 24-h period (lx) 66
Daytime light exposure (lx) 108
2 233
Nighttime light exposure (lx) 31
APACHE, Acute Physiology and Chronic Health Evaluation; ICU, intensive care unit; SOFA, Sequential Organ Failure Assessment.
activity levels of these patients were below
the detection limit of the actigraph; thus,
activity measurement was discontinued.
Table 1 illustrates the characteristics of the
22 enrolled patients, showing that the base-
line values of all variables, including the
length of stay in the ICU, were comparable
between the groups. On conclusion of the
recording period, the patients continued to
be treated in the ICU or were transferred
Light exposure of patients in the
‘Light Side’ and ‘Dark Side’ of the
In order to investigate the difference
in exposure to light between the ‘Light
Side’ and ‘Dark Side’ groups of patients
at ICU, we measured light intensity (lx)
and compared the mean values for the
whole 24-h period, daytime and nighttime
between the ‘Light Side’ and ‘Dark Side’
groups. As anticipated a priori, average
light intensity was higher during the whole
24-h period in the ‘Light Side’ group than
in the ‘Dark Side’ group of patients in the
ICU, a result that approached statistical
signicance (mean difference: 717±278lx
[95% CI =(12, 1447); p=0053] (Table 1).
Moreover, average light intensity was statis-
tically higher during daytime in the ‘Light
Side’ group compared with the ‘Dark Side’
group of patients in the ICU (mean differ-
ence: 1544±34 lx [95% CI =(594, 2494);
p=0011] (Table 1). Similarly, average light
intensity was signicantly higher during
nighttime in the ‘Light Side’ group com-
pared with the ‘Dark Side’ group of ICU
patients (p=0009) (Table 1). Notably, the
ratio between daytime and nighttime light
intensity (relative intensity) was found to be
similar between the ‘Dark Side’ (34±03lx)
and ‘Light Side’ (42±07 lx) groups (mean
difference: 076 ±08 [95% CI=(14, 29);
p=039] (data not shown).
Clinical variables
We a priori intended to use cosinor analy-
sis to explore the impact of light exposure
on 24-h rhythmicity HR, MAP and BT. How-
ever, because of the small number of patients
in both ‘Light Side’ and ‘Dark Side’ groups
demonstrating signicant 24-h rhythms of
HR, MAP and BT (data not shown), we
decided to further investigate other out-
puts independent of 24-h rhythm presence
(curve tting). For the subsequent analyses,
we evaluated the mean values of all mea-
sured variables for daytime and nighttime
separately and their difference (delta) in the
‘Light Side’ and ‘Dark Side’ groups.
Light impact on HR, MAP and BT
of ICU patients
In order to investigate the effect of light
on the measured physiological parame-
ters, we evaluated and compared mean
values of HR, MAP and BT for the whole
24-h period, daytime and nighttime sep-
arately, as well as and their difference
(delta) between the ‘Light Side’ and ‘Dark
Side’ groups. Signicantly higher HR
values were observed during daytime
(Figure 1A) in patients allocated to the
‘Light Side’ (894±28 bpm) in compari-
son with patients in the ‘Dark Side’ of the
ICU (798±22 bpm), with a mean differ-
ence of 96±36 bpm [95% CI =(16, 176);
p=0024]. However, the light did not signif-
icantly affect HR during nighttime (mean
difference: 45±49 bpm [95% CI =(74,
© 2019 British Association of Critical Care Nurses
Light affects heart rate’s 24-h rhythmicity of ICU patients
Figure 1
Average heart rate (beats/min, bpm) of patients during daytime (A) and nighttime (B) of the 24-h period by
allocation to the Light (n
17) or Dark (n
5) Sides of the ICU. The difference of daytime and nighttime for each ICU
group is expressed as delta (C). Mesor represents the middle value of the whole 24-h period (D).
164); p=04] (Figure 1B). In addition,
mean MAP did not differ between ‘Light
Side’ (865±39 mmHg) and ‘Dark Side’
(826±16 mmHg) groups (mean differ-
ence: 4 ±42 mmHg [95% CI =(67, 148);
p=038]. Similarly, mean values of BT did
not differ between ‘Light Side’ (368±01C)
and ‘Dark Side’ (366±01C) groups (mean
difference: 023 ±015C [95% CI =(01,
06); p=015] (data not shown).
This study demonstrates that ICU bed posi-
tioning relative to natural sunlight may have
direct measurable impacts on a BTpatient’s
24-h rhythms. A signicantly lower HR was
observed during daytime in the ‘Dark Side’
group compared with the ‘Light Side’ group
of ICU patients. In contrast, such differences
did not emerge during nighttime or in other
parameters such as mean arterial pressure
or BT.
Despite tight inclusion parameters result-
ing in a relatively small sample for analysis,
this study provides evidence of 24-h rhyth-
micity disruption in a cohort of patients in
an ICU, in line with studies over the past
three decades examining circadian deregu-
lation in ICU patients (Brainard et al., 2015;
Madrid-Navarro et al., 2015). Indeed, the
rhythms of the parameters included in this
study are used as predictors of mortality
rates in patients in the ICU (Bourcier et al.,
2016). The timing of exposure, as well as
the quantum and rhythm of exposure, has
been shown in previous studies to be key.
For example, a shorter duration of light
exposure prior to stress has been shown to
promote survival (Castro et al., 2012).
Our observational study demonstrates
no signicant difference between the ‘Light
Side’ and ‘Dark Side’ groups in terms of
duration of stay in the ICU. This nding
does not agree with previous evidence
showing that patients assigned to well-lit
positions in cardiac ICUs experience a
shorter stay (Vinzio et al., 2003), and this
inconsistency may be attributed to the small
number of patients in the current study and
unbalanced allocation to the ‘Light Side’
and ‘Dark Side’ groups.
In this ICU, illumination levels dur-
ing daytime (115 ±29 lx) and nighttime
(35 ±7 lx) were within the normal range
(Engwall et al., 2017) in contrast to other
previous studies showing a greater range in
ICU lighting. For example, Hu et al. (2016)
recorded levels ranging from 62 to 790lx
during daytime, 15 to 489 lx during the
evening and 10 to 239 lx during nighttime,
while Elliott et al. (2014) observed median
daytime levels of 74 lx and nighttime levels
of 2 lx. Another study reported that 522% of
the assessed hospitals had illumination lev-
els below the 2011 recommended European
Standards, ranging from 100 lx for general
lighting to 100 000 lx for some operating
areas (Dianat et al., 2013).
Our data importantly demonstrate that,
inside a single small ICU, critically ill
patients can be exposed to signicantly
varying light intensities depending on bed
© 2019 British Association of Critical Care Nurses
Light affects heart rate’s 24-h rhythmicity of ICU patients
positioning. The ‘Light Side’ group was
exposed to signicantly higher average
light intensity all day in comparison with
the ‘Dark Side’ group. When examined
separately, mean light exposure was higher
in the ‘Light Side’ group versus ‘Dark Side’
group during daytime, as well as during
nighttime. The nding of overall higher
mean illumination in the ‘Light Side’ group
of patients in the ICU is consistent with
previous studies (Durrington et al., 2017;
Fan et al., 2017) and can be explained to an
extent by the fact that, besides articial ICU
lighting, beds near the windows are further
exposed to natural sunlight during daytime
and to street light and moonlight at night.
Besides the light intensities, physiologi-
cal variables such as HR, its variability, BT
(Litscher et al., 2013), MAP, arterial stiffness
and endothelial function (Stern et al., 2018)
can be affected by coloured light exposure.
It is interesting to note that, despite the
difference in absolute values of daytime
and nighttime light intensity in ‘Light Side’
and ‘Dark Side’ groups, the relative light
intensity (daytime/nighttime ratio) was
very similar between the two groups. This
nding indicates that not only the absolute
value of light but also its relative nighttime
decrease may be of signicant importance,
but this remains open for further explo-
ration. If relative light intensity is proven
important for circadian rhythm normaliza-
tion, relative light offers a new avenue for
intervention. As nighttime articial light in
a working ward cannot easily be reduced
below current levels, clinically signicant
outcomes may be achieved by increasing
daytime light. In favour of this speculation,
increased daytime light is proposed to result
in improvement in circadian modulated
physiological parameters in both transla-
tional and human studies (Fan et al., 2017).
The results of this study need to be
considered in the context of several lim-
itations. Clearly, the sample size was small,
with unbalanced allocation to the ‘Light
Side’ and ‘Dark Side’ groups because
of fewer beds in the ‘Light Side’ of this
ICU. Overnight light interruptions were not
recorded, although those interruptions were
likely to have been distributed randomly
between patients and conditions. Bright
LAN can eliminate 24-h rhythms (Durring-
ton et al., 2017), although such high-intensity
light interruptions are necessary to enable
the delivery of 24-h care to critically ill
patients. It is worth noting that patients
were monitored with the MotionWatch
actigraphy system. While this system did
not interfere with intravascular lines, the
data showed no meaningful activity vari-
ation (Mistraletti et al., 2009), with patients
largely immobile. Finally, BT was used as
a proxy for what is the ‘gold standard’ of
establishing core BT but probably offers a
good approximation as a circadian marker
(Motohashi et al., 1987). However, it would
have been valuable to include cortisol
and melatonin measurements (Van Dycke
et al., 2015).
Critically ill patients are clearly an
unusual subject pool for circadian studies.
They were partly chosen for this study to
ensure that the differences in their responses
as patients could be, to a signicant degree,
attributed to differences in bed position-
ing as other aspects of their cases were
controlled. Cardiovascular variables may
change because of differences in diagnoses,
smoking history, level of tness etc. between
groups. As another limitation, such differ-
ences were not considered in this study.
While larger trials are needed to estab-
lish the parameters, studies with relatively
more homogenous samples, such as the cur-
rent study, can begin to address the ques-
tion of the role of light in the critically
ill patients. In particular, a larger sample,
as well as the analysis of the main circa-
dian biomarker melatonin, will offer greater
insight into the impact of relatively minor
changes of lighting on outcomes (such as
time to discharge) in this highly vulnerable
Light intensity appears to have implications
for physiological variables. This study high-
lights the inuence on HR, pointing towards
a need to better simulate daily variability
of light in the ICU setting.
Differential light exposure depending
on ICU bed positioning seems to have
a signicant impact on HR in patients.
Decreased light intensity was associated
with decreased HR. Light exposure is one
factor present in the highly structured
and constrained environment of hospi-
tals that can be relatively easily modulated
and is thus a promising avenue for relatively
unobtrusive interventions. Further study
of the importance of relative light intensity is
We express many thanks to Professor Arne
Lowden, Stockholm University, Stress
Research Institute for assisting with the
MotionWatch actigraphy system (MW8,
ICU patients often exhibit dysregulated 24-h profiles of physiological parameters such as sleep/wake cycles, mean arterial blood pressure, heart rate and spontaneous motor
activity; moreover, acute illness is itself a major risk factor for 24-h rhythm.
Although there is limited evidence of therapeutic implications of ICU lighting, evidence from previous studies suggests that patients assigned to well-lit positions in cardiac
ICUs had shorter lengths of stay and lower mortality rates.
ICU patients were exposed to varying light intensities depending on bed positioning.
Bed positioning relative to natural sunlight affects the 24-h rhythm of heart rate.
Apart from the absolute levels of light, its relative nighttime decrease may be important.
Light levels can be modulated as an intervention for circadian rhythm normalization.
© 2019 British Association of Critical Care Nurses
Light affects heart rate’s 24-h rhythmicity of ICU patients
Bourcier S, Pichereau C, Boelle PY, Nemlaghi S,
Dubée V, Lejour G, Baudel JL, Galbois A,
Lavillegrand JR, Bigé N, Tahiri J, Leblanc G,
Maury E, Guidet B, Ait-Oufella H. (2016).
Toe-to-room temperature gradient corre-
lates with tissue perfusion and predicts out-
come in selected critically ill patients with
severe infections. Annals of Intensive Care;6:
Brainard J, Gobel M, Scott B, Koeppen M,
Eckle T. (2015). Health implications of dis-
rupted circadian rhythms and the potential
for daylight as therapy. Anesthesiology;122:
1170– 1175.
Castro RA, Angus DC, Hong SY, Lee C, Weiss-
feld LA, Clermont G, Rosengart MR. (2012).
Light and the outcome of the critically ill: an
observational cohort study. Critical Care;16:
Dianat I, Sedghi A, Bagherzade J, Jafarabadi
MA, Stedmon AW. (2013). Objective and
subjective assessments of lighting in a
hospital setting: implications for health,
safety and performance. Ergonomics;56:
1535– 1545.
Durrington HJ, Clark R, Greer R, Martial FP,
Blaikley J, Dark P, Lucas RJ, Ray DW. (2017).
“In a dark place, we nd ourselves”: light
intensity in critical care units. Intensive Care
Medicine Experimental;5:9.
Elliott R, Rai T, McKinley S. (2014). Factors
affecting sleep in the critically ill: an obser-
vational study. Journal of Critical Care;29:
859– 863.
Engwall M, Fridh I, Jutengren G, Bergbom I,
Sterner A, Lindahl B. (2017). The effect of
cycled lighting in the intensive care unit
on sleep, activity and physiological param-
eters: a pilot study. Intensive & Critical Care
Nursing;41: 26– 32.
Fan EP, Abbott SM, Reid KJ, Zee PC, Maas
MB. (2017). Abnormal environmental light
exposure in the intensive care environment.
Journal of Critical Care;40: 11–14.
Fonken LK, Nelson RJ. (2014). The effects
of light at night on circadian clocks and
metabolism. Endocrine Reviews;35: 648– 670.
Gaston KJ, Visser ME, Hölker F. (2015). The bio-
logical impacts of articial light at night: the
research challenge. Philosophical transactions
of the Royal Society of London. Series B;370:
Hu R, Hegadoren KM, Wang X, Jiang X. (2016).
An investigation of light and sound levels
on intensive care units in China. Australian
Critical Care;29: 62– 67.
Korompeli A, Muurlink O, Kavrochorianou N,
Katsoulas T, Fildissis G, Baltopoulos G.
(2017). Circadian disruption of ICU
patients: a review of pathways, expres-
sion, and interventions. Journal of Critical
Care;38: 269– 277.
Litscher D, Wang L, Gaischek I, Litscher G.
(2013). The inuence of new colored light
stimulation methods on heart rate variabil-
ity, temperature, and well-being: results of a
pilot study in humans. Evidence-based Com-
plementary and Alternative Medicine;2013:
McKenna HT, Reiss IK, Martin DS. (2017). The
signicance of circadian rhythms and dys-
rhythmias in critical illness. Journal of the
Intensive Care Society;18: 121– 129.
McKenna H, van der Horst GTJ, Reiss I,
Martin D. (2018). Clinical chronobiol-
ogy: a timely consideration in critical care
medicine. Critical Care;22: 124.
Madrid-Navarro CJ, Sanchez-Galvez R,
Martinez-Nicolas A, Marina R, Garcia
JA, Madrid JA, Rol MA. (2015). Disrup-
tion of circadian rhythms and delirium,
sleep impairment and sepsis in critically
ill patients. Potential therapeutic impli-
cations for increased light-dark contrast
and melatonin therapy in an ICU environ-
ment. Current Pharmaceutical Design;21:
3453– 3468.
Mistraletti G, Taverna M, Sabbatini G, Car-
loni E, Bolgiaghi L, Pirrone M, Cigada M,
Destrebecq ALL, Carli F, Iapichino G.
(2009). Actigraphic monitoring in critically
ill patients: preliminary results toward an
“observation-guided sedation”. Journal of
Critical Care;24: 563– 567.
Motohashi Y, Reinberg A, Levi F, Nougier J,
Benoit O, Foret J, Bourdeleau P. (1987).
Axillary temperature: a circadian marker
rhythm for shift workers. Ergonomics;30:
1235– 1247.
Ono H, Taguchi T, Kido Y, Fujino Y, Doki Y.
(2011). The usefulness of bright light
therapy for patients after oesophagec-
tomy. Intensive & Critical Care Nursing;27:
158– 166.
Paul T, Lemmer B. (2007). Disturbance of cir-
cadian rhythms in analgosedated intensive
care unit patients with and without cranio-
cerebral injury. Chronobiology International;
24: 45– 61.
Portaluppi F, Smolensky MH, Touitou Y.
(2010). Ethics and methods for biological
rhythm research on animal and human
beings. Chronobiology International;27:
1911– 1929.
Renetti R, Lissen GC, Halberg F. (2007). Pro-
cedures for numerical analysis of circa-
dian rhythms. Biological Rhythm Research;
38: 275– 325.
Ritchie HK, Stothard ER, Wright KP. (2015).
Entrainment of the human circadian clock
to the light-dark cycle and its impact on
patients in the ICU and nursing home
settings. Current Pharmaceutical Design;21:
3438– 3442.
Simons KS, Laheij RJF, van den Boogaard M,
Moviat MAM, Paling AJ, Polderman
FN, Rozendaal FW, Salet GAM, van der
Hoeven JG, Pickkers P, de Jager CPC.
(2016). Dynamic light application ther-
apy to reduce the incidence and duration
of delirium in intensive-care patients: a
randomised controlled trial. The Lancet
Respiratory Medicine;4: 194– 202.
Stern M, Broja M, Sansone R, Gröne M, Skene
SS, Liebmann J, Suschek CV, Born M,
Kelm M, Heiss C. (2018). Blue light expo-
sure decreases systolic blood pressure, arte-
rial stiffness, and improves endothelial
function in humans. European Journal of Pre-
ventive Cardiology;25: 1875– 1883.
Sunderram J, Sofou S, Kamisoglu K,
Karantza V, Androulakis IP. (2014).
Time-restricted feeding and the realign-
ment of biological rhythms: translational
opportunities and challenges. Journal of
Translational Medicine;12: 79.
TaguchiT. (2013). Bright light treatment for pre-
vention of perioperative delirium in elderly
patients. Journal of Nursing Education and
Practice;3: 10.
Taguchi T, Yano M, Kido Y. (2007). Inuence
of bright light therapy on postoperative
patients: a pilot study. Intensive & Critical
Care Nursing;23: 289– 297.
Touitou Y, Reinberg A, Touitou D. (2017). Asso-
ciation between light at night, melatonin
secretion, sleep deprivation, and the inter-
nal clock: health impacts and mechanisms
of circadian disruption. Life Sciences;173:
94– 106.
Van Dycke KCG, Pennings JLA, van Oostrom
CTM, van Kerkhof LWM, van Steeg H,
van der Horst GTJ, Rodenburg W. (2015).
Biomarkers for circadian rhythm disruption
independent of time of day. PLoS One;10:
Vinzio S, Ruellan A, Perrin AE, Schlienger
JL, Goichot B. (2003). Actigraphic assess-
ment of the circadian rest-activity rhythm
in elderly patients hospitalized in an acute
care unit. Psychiatry and Clinical Neuro-
sciences;57: 53– 58.
Weiss B, Spies C, Piazena H, Penzel T, Fietze I,
Luetz A. (2016). Exposure to light and dark-
ness and its inuence on physiological mea-
sures of intensive care unit patients-a sys-
tematic literature review. Physiological Mea-
surement;37: R73– R87.
© 2019 British Association of Critical Care Nurses
... Of the 18,577 potentially eligible citations, 44 studies met inclusion criteria (Fig. 1). Of these, 18 (41%) recruited patients only [9,10,14,15,[22][23][24][25][26][27][28][29][30][31][32][33][34][35], 17 (39%) recruited HCPs only [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52], 5 (11%) mixed participants [6,13,[53][54][55] and 4 (9%) family members only [56][57][58][59]. Most (84%) studies were published after 2012 and reported data from Europe (n = 21; 48%) or North America (n = 19; 43%) ( Table 1). ...
... Newly built or renovated ICUs/ICU rooms were evaluated in 27 (61%) studies [6,9,10,13,22,[24][25][26][27]31,33,36,37,[42][43][44][45][48][49][50][51][52][53][54][55][56]59], the remainder (n = 17; 39%) evaluated existing ICU design features [14,15,23,[28][29][30]32,34,35,[38][39][40][41]46,47,57,58]. Studies of newly built or newly renovated ICUs included the following: intervention rooms with specific design features such as circadian lighting installation; ceiling sky composition fixtures; purpose-built rooms with evidence-based (as defined by study authors) design features; and garden/outdoor spaces. ...
... Three (15%) studies measured overall patient satisfaction, reporting improved satisfaction in relation to a new ICU design [6,31,55]. The remaining three studies reported on patient experience with ICU design overall or experience of the lighting environment [25,29,30]. Six (30%) studies reported no adverse effects associated with the following ICU design features: light vs dark rooms [13,32]; high vs low visibility rooms [15]; single vs multiple room occupancy [10]; ceiling mounted photographic sky display [31]; and newly renovated room/ ICU with evidence based design (EBD) features [33]. ...
Purpose Scoping review to map outcomes and describe effects of intensive care unit (ICU) design features on patients, family, and healthcare professionals (HCPs). Materials and methods Iteratively developed search strategy executed across seven databases. We included studies (January 2007 to May 2020) exploring ICU design features using any study design. We grouped studies into 12 design features and categorized outcomes into four domains. Results Of 18,577 citations screened, 44 studies met inclusion criteria. Newly built or renovated ICUs/ICU rooms were evaluated in 27 (61%) studies; 17 (39%) evaluated existing designs/features. Most commonly evaluated design features were lighting (24, 55%), single vs multi-occupancy rooms/pods (17, 39%), and family-centered design (13, 30%). We identified 63 distinct outcomes in four domains; HCP-related (20, 45%); patient-related (20, 45%); family-related (11, 25%); and environment-related (7, 16%). Eleven (25%) studies measured patient/family-reported outcomes. In studies evaluating single occupancy rooms, three reported increased family satisfaction, two reported decreased delirium burden, while six reported negative consequences on HCP wellbeing and working. Conclusion Studies evaluating ICU design measure disparate outcomes. Few studies included patient/ family-reported outcomes; fewer measured objective environment characteristics. Single room layouts may benefit patients and family but contribute to adverse HCP-related outcomes.
... Alterations to melatonin levels are observed in critically ill patients at the intensive care unit (ICU) [8]. Plenty of factors, such as light, noise and interventions pertinent to the ICU environment, have been demonstrated to worsen variability to the 24-h rhythms of many body functions [9]. The 24-h variability of physiological parameters such as heart rate, mean arterial pressure and body temperature are affected [9][10][11]. ...
... Plenty of factors, such as light, noise and interventions pertinent to the ICU environment, have been demonstrated to worsen variability to the 24-h rhythms of many body functions [9]. The 24-h variability of physiological parameters such as heart rate, mean arterial pressure and body temperature are affected [9][10][11]. Furthermore, the critical illness per se and sepsis, which is a clinical state during the stay in the ICU, can lead to circadian dysrhythmia and melatonin variability disturbance, as many studies have demonstrated [12]. ...
Full-text available
s Aim: To examine whether the serum melatonin levels in ICU patients are affected by light exposure in the "light" and "dark" parts of the ICU. Method: We measured serum melatonin levels of 10 ICU patients having their bed positioned in the "light part" (artificial and natural light) and "dark part" (only artificial light) of the ICU at two different time points, 8:00 ("morning") and 20:00 ("evening") during a 24-96-h period. Results: Serum melatonin levels did not differ between "morning" (112 ± 15 pg/ml) and "evening" (87 ± 13 pg/ml) in ICU patients. Overall, higher melatonin levels were detected in female patients compared to male patients. Significantly higher light intensity was detected in the "light part" compared to the "dark part" of the ICU, not only in the "morning" but also in the "evening". However, by dividing patients according to their bed positioning ("light part" versus "dark part") in the ICU, no difference was detected in the serum melatonin levels. Similarly, the ratio ("morning" versus "evening") of light intensity and melatonin levels did not differ between the light and dark parts of the ICU. Conclusion: Studies reporting melatonin patterns in ICU patients are heterogeneous and contradictory, which renders this topic highly challenging. Larger studies regarding the effect of light exposure on melatonin levels in ICU patients are required to reveal the true impact and indicate potential nursing interventions.
... This observational study was conducted in a small, single-ward University ICU at a Greek general hospital in Athens, as refereed to a previous study [7]. Generally, total admissions to this ICU are low because the study site is a training hospital without a highdependency unit (HDU), with HDU patients instead assigned to the ICU, resulting in a long mean length of stay. ...
... We found that ACTG maybe useful to record and distinguish the rest-activity circadian rhythms in ICU patients. According to our preliminary data, our ICU light exposure (lux) during daytime and nighttime are within the normal range [7]. Also, M-10 and L-5 measurements in our population are higher, RA is lower and IS, is higher compared to healthy population [3,4]. ...
... El sistema de iluminación imita la luz natural según el momento del día, siguiendo el ciclo circadiano, permitiendo que los pacientes mantengan los ciclos naturales del cuerpo durante su estancia en la UCI. 19,20 De este modo, el despertar del paciente, así como su adaptación al medio es menos traumática, reduciendo la estancia hospitalaria en la UCI, ya que facilita su descanso y ayuda a disminuir la desorientación que pueden sufrir los pacientes tras permanecer varios días ingresados. ...
De los libros a los respiradores: Como convertir una Biblioteca en una Unidad de Cuidados Intensivos en tiempo récord Raquel López Sánchez, 1 ( (Raquel López Sánchez) Resumen Objetivo: Describir nuestra experiencia en la transformación de una biblioteca en una unidad de cuidados intensivos ante una situación de alta presión asistencial. Resultados principales: La nueva UCI Biblioteca es una unidad de vanguardia que combina la última tecnología, una gran funcionalidad y flexibilidad con un alto confort tanto para los pacientes como para el personal sanitario. La unidad ha sido creada en unos periodos de tiempo límite, debido a la necesidad de contar con un mayor número de camas de cuidados críticos ante la segunda ola de la pandemia. La creación de la UCI se ha basado en garantizar una mayor calidad del cuidado y facilitar el desarrollo de la labor asistencial a los profesionales. Conclusión principal: La UCI Biblioteca, cumple los criterios de humanización, flexibilidad, eficiencia, confortabilidad y confort, siendo considerada una UCI de última generación. Palabras clave: SARS-CoV-2. Infecciones por coronavirus. Pandemia. Enfermería. Unidad de Cuidados Críticos. Tecnología. From books to respirators: How to turn a Library into an Intensive Care Unit in record time Abstract Objective: To describe our experience in transforming a library into an intensive care unit in a high-pressure care situation. Results: The new intensive care unit (ICU-Library) is a vanguard unit that combines the latest technology, high functionality and flexibility with high comfort for both patients and staff. This unit has been created in a short time period because due to the need for more intensive care beds during the second wave of the pandemic. The creation of the ICU-library was based on ensuring a higher quality of care and facilitating the development of the care work of professionals. Conclusion: The ICU-Library meets the criteria of humanization, flexibility, efficiency, convenience and comfort, and is considered a cutting edge unit. I
... Further, light intensity has been shown to impact the heart rates of ICU patients. Positioning of the bed relative to windows can determine the light intensity, and higher light intensity leads to higher heart rate (Korompeli et al., 2019). Light intensity and duration were also studied relative to ICU patients' mortality. ...
Objectives This systematic review presented the current status of literature on the outcomes resulted from sensory stimuli in critical care environments as well as the environmental interventions that can improve or impede the impact of such sensory stimuli. Methods Articles found through a systematic search of PsycINFO, Web of Science, and PubMed databases, in combination with a hand search, were reviewed for eligibility by two independent coders. Reporting and quality appraisals were based on PRISMA and MMAT guidelines. Results Out of 1118 articles found, and only 30 were eligible. Final articles were comprised of issues related to noise, lighting, and temperature. Identified sensory stimuli resulted in psychological and physiological outcomes among both patients and staff. Examples include impacts on stress, delirium, sleep disturbances, poor performance and communication. The environmental factors that influence sensory stimuli included layout, room size, artificial lighting, presence of windows and acoustical interventions. Conclusion Literature on the impact of sensory stimuli on staff is scarce compared to patients. Studies on environmental interventions are inadequate and lack structure. The physical environment can impact the patient and staff outcome resulting from noise, lighting, and temperature. When applied strategically, sensory stimuli can result in positive outcomes among patients and staff.
... Objective measures of stress load possibly by examining stress factors and measuring catecholamines levels, especially at the submission time in order to provide context to cortisol levels found in the study, would have been valuable. In addition, the study would have been improved by using core BT [27,28]. In addition, the daily excretion of free cortisol (nmol/24 h) measured in urine would have been valuable. ...
Full-text available
Background: Evidence suggests that fluctuations of cortisol and vital signs can emerge during the course of mild Traumatic Brain Injury (mTBI). Objective: To investigate fluctuations of cortisol and vital signs during the acute phase of mTBI in hospitalised patients. Methods: 30 participants (19 patients with mTBI and 11 controls) were examined for saliva cortisol dynamics, heart rate (HR), systolic arterial pressure (SAP), diastolic arterial pressure (DAP), mean arterial pressure (MAP) and body temperature (BT) fluctuations for four consecutive days. Also, the participants completed the Athens Insomnia Scale and Epworth Sleepiness Scales, in order to check for sleep problems. Results: Patients showed elevated levels of cortisol relative to controls (peak at 8 am and lowest levels at 12 am), as well as for most physiological parameters. MAP was significantly higher for patients throughout the measurement period, and BT was elevated for patients relative to controls at almost all measurements of the first and second day. Mean HR tended to track at non-significantly higher levels for the mTBI group. Patients' sleepiness and insomnia values (ESS and AIS) were initially significantly higher relative to controls but the difference dissipated by day 4. Conclusion: The increase in absolute values of cortisol and vital signs measurements, indicates that in the acute phase of mTBI, a stressfulprocess is activated which may affect sleep quality as well.
... Another shortcoming of the sophisticated technological equipment is it creates sound and noise. Sound, noise and other factors, such as incorrect lighting, that are generated in the intensive care patients' surroundings has been shown to affect the patients negatively (Darbyshire et al., 2019;Delaney et al., 2017;Korompeli et al., 2019). Stimuli from the equipment could increase the levels of stress, often affecting the patients' sleep and circadian rhythm, which could then lead to ICU-delirium or other medical illnesses (Brummel & Girard, 2013;Lu et al., 2019;Madrid-Navarro et al., 2015). ...
Full-text available
This dissertation is available at: ISBN 978-91-88838-74-2 (printed) ISBN 978-91-88838-75-9 (pdf) ISSN 0280-381X, Skrifter från Högskolan i Borås, nr. 106 Electronic version Abstract Aim: The overall aim of this doctoral thesis was to examine and evaluate if and how an intensive care unit (ICU) room, which had been designed using the principles of evidence-based design (EBD), impacted the safety, wellbeing and caring for patients, their family members and staff. Methods: Paper I explored the nursing staff experiences of working in an EBD intensive care patient room through 13 interviews that were analysed by qualitative content analysis. Paper II focussed on the meaning of caring and nursing activities performed in two patient rooms-one EBD refurbished and one standard. Ten non-participant observations were conducted, which were followed by interviews. The data were analysed using a phenomenological hermeneutical approach. Paper III evaluated the relationship between a refurbished intensive care room and adverse events (AE) in critically ill patients. A total of 1,938 patients' records were included in the analysis. Descriptive statistics and binary logistic regressions were conducted. Paper IV studied visitors' (N = 99) experiences of different healthcare environmental designs of intensive care patient rooms through questionnaires. Descriptive statistics and linear regressions were conducted for the analysis. Main results: The refurbished intervention room was reported as a positive experience for the working nursing staff and the visiting family members. The nursing staff additionally indicated the intervention room strengthened their own wellbeing as well as their caring activities. Although there were no observed, objective differences regarding the caring and nursing activities due to the different environments, the differences were instead interpreted as being due to different developed nursing competencies. The visitors reported the enriched healthcare environment to have a higher everydayness and a feeling that it was a safer place compared to the control rooms. The findings revealed a low incident of AEs in both the intervention room as well as in the control rooms, lower than previous described in literature. The likelihood for adverse events were not significantly lower in the intervention room compared to the control rooms. Conclusion: This dissertation contributed to the existing knowledge on how a refurbished patient room in the ICU was experienced by nursing staff and visiting family members. The dissertation also showed the complexity of conducting interventional research in high-tech environments. The new knowledge on the importance of the healthcare environment on wellbeing, safety and caring must be considered by stakeholders and decision-makers and implemented to reduce suffering and increase health and wellbeing among patients, their families and staff.
... 23 Inappropriate lighting has been shown to cause incidents and increased heart rates, indicating the patients are under stress. 24,25 Noise is often still found to be well above the WHO recommendations, resulting in disturbed circadian rhythm and causing delirium in intensive care patients. 26,27 However, by improving the sound environment in the ICU, the frequency of delirium in critically ill patients was found to decrease significantly. ...
Full-text available
Background Healthcare environment can affect health. Adverse events (AEs) are common because rapid changes in the patients' status can suddenly arise, and have serious consequences, especially in intensive care. The relationship between the design of intensive care units (ICUs) and AEs has not been fully explored. Hence, an intensive care room was refurbished with cyclic lightning, sound absorbents and unique interior, and exterior design to promote health. Aims The aim of this study was to evaluate the differences between a regular and a refurbished intensive care room in risk for AEs among critically ill patients. Design This study retrospectively evaluated associations of AEs and compared the incidence of AEs in patients who were assigned to a multidisciplinary ICU in a refurbished two‐bed patient room with patients in the control rooms between 2011 and 2018. Methods There were 1938 patients included in this study (1382 in control rooms; 556 in the intervention room). Descriptive statistics were used to present the experienced AEs. Binary logistic regressions were conducted to estimate the relationship between the intervention/control rooms and variables concerning AEs. Statistical significance was set at P < 0.05. Results For the frequency of AEs, there were no significant differences between the intervention room and the control rooms (10.6% vs 11%, respectively, P < 0.805). No findings indicated the intervention room (the refurbished room) had a significant influence on decreasing the number of experienced AEs in critically ill patients. Conclusions The findings revealed a low incident of AEs in both the intervention room as well as in the control rooms, lower than previously described. However, our study did not find any decreases in the AEs due to the design of the rooms. Relevance to clinical practice Further research is needed to determine the relationship between the physical environment and AEs in critically ill patients.
Full-text available
A fundamental aspect of human physiology is its cyclical nature over a 24-h period, a feature conserved across most life on Earth. Organisms compartmentalise processes with respect to time in order to promote survival, in a manner that mirrors the rotation of the planet and accompanying diurnal cycles of light and darkness. The influence of circadian rhythms can no longer be overlooked in clinical settings; this review provides intensivists with an up-to-date understanding of the burgeoning field of chronobiology, and suggests ways to incorporate these concepts into daily practice to improve patient outcomes. We outline the function of molecular clocks in remote tissues, which adjust cellular and global physiological function according to the time of day, and the potential clinical advantages to keeping in time with them. We highlight the consequences of "chronopathology", when this harmony is lost, and the risk factors for this condition in critically ill patients. We introduce the concept of "chronofitness" as a new target in the treatment of critical illness: preserving the internal synchronisation of clocks in different tissues, as well as external synchronisation with the environment. We describe methods for monitoring circadian rhythms in a clinical setting, and how this technology may be used for identifying optimal time windows for interventions, or to alert the physician to a critical deterioration of circadian rhythmicity. We suggest a chronobiological approach to critical illness, involving multicomponent strategies to promote chronofitness (chronobundles), and further investment in the development of personalised, time-based treatment for critically ill patients.
Full-text available
Many physiological and cellular processes cycle with time, with the period between one peak and the next being roughly equal to 24 h. These circadian rhythms underlie ‘permissive homeostasis’, whereby anticipation of periods of increased energy demand or stress may enhance the function of individual cells, organ systems or whole organisms. Many physiological variables related to survival during critical illness have a circadian rhythm, including the sleep/wake cycle, haemodynamic and respiratory indices, immunity and coagulation, but their clinical significance remains underappreciated. Critically ill patients suffer from circadian dysrhythmia, manifesting overtly as sleep disturbance and delirium, but with widespread covert effects on cellular and organ function. Environmental and pharmacological strategies that ameliorate or prevent circadian dysrhythmia have demonstrated clinical benefit. Harnessing these important biological phenomena to match metabolic supply to demand and bolster cell defenses at the apposite time may be a future therapeutic strategy in the intensive care unit.
Full-text available
Intensive care units provide specialised care for critically ill patients around the clock. However, intensive care unit patients have disrupted circadian rhythms. Furthermore, disrupted circadian rhythms are associated with worse outcome. As light is the most powerful ‘re-setter’ of circadian rhythm, we measured light intensity on intensive care unit. Light intensity was low compared to daylight during the ‘day’; frequent bright light interruptions occurred over ‘night’. These findings are predicted to disrupt circadian rhythms and impair entrainment to external time. Bright lighting during daytime and black out masks at night might help maintain biological rhythms in critically ill patients and improve clinical outcomes.
Aims: Previous studies have shown that ultraviolet light can lead to the release of nitric oxide from the skin and decrease blood pressure. In contrast to visible light the local application of ultraviolet light bears a cancerogenic risk. Here, we investigated whether whole body exposure to visible blue light can also decrease blood pressure and increase endothelial function in healthy subjects. Methods: In a randomised crossover study, 14 healthy male subjects were exposed on 2 days to monochromatic blue light or blue light with a filter foil (control light) over 30 minutes. We measured blood pressure (primary endpoint), heart rate, forearm vascular resistance, forearm blood flow, endothelial function (flow-mediated dilation), pulse wave velocity and plasma nitric oxide species, nitrite and nitroso compounds (secondary endpoints) during and up to 2 hours after exposure. Results: Blue light exposure significantly decreased systolic blood pressure and increased heart rate as compared to control. In parallel, blue light significantly increased forearm blood flow, flow-mediated dilation, circulating nitric oxide species and nitroso compounds while it decreased forearm vascular resistance and pulse wave velocity. Conclusion: Whole body irradiation with visible blue light at real world doses improves blood pressure, endothelial function and arterial stiffness by nitric oxide released from photolabile intracutanous nitric oxide metabolites into circulating blood.
Background: Bright light treatment aims to improve circadian rhythms in patients living indoors with poor light-dark transitions by complementing insufficient natural light and highlighting the difference between their day- and night-time activities. In addition to bright light treatment, it is called “phototherapy” or “high-intensity light therapy”, and has been reported to be effective to prevent delirium and sleep disorders in the elderly. Under such circumstances, this study examined the validity of bright light treatment as a perioperative care approach for the elderly who are regarded as vulnerable to delirium due to hospitalization or therapeutic intervention. Methods: The study was conducted in the mixed surgical ward of approximately 200 beds, located in Kyoto Prefecture. Subjects were elderly male and female patients who underwent surgery for lower limbs, mainly the femur, and were randomly divided into intervention and control groups. The intervention group received bright light treatment with approximately 2,500 lx of bright light from the day after admission; on the day of surgery and at postoperative week 1, while the control group was treated with normal light during this period. The evaluation of delirium was conducted based on the results of nurses’ observation and the Japanese-Version NEECHAM Confusion Scale (NEECHAM scale). In addition to this, information regarding the patients’ activities of daily living was also collected. As physiological indices, light-exposure-dependent changes in blood serotonin levels and stress-dependent changes in blood cortisol levels were also evaluated. The period of the study was between 2008 and 2010; data were collected from November to February in each year, when the number of target patients increased. Results: As a result, data regarding 24 patients were obtained within this 2-year period. Excluding those with severe dementia, a total of 16 (intervention: 6; and control: 10) were studied. As a result, delirium occurred in the patients who underwent surgery of the lower limbs, mainly the femur, within the period between the day of surgery and postoperative day 3. The type of delirium was hyperactive in all cases, and its symptoms persisted for 3 to 4 days. Conclusion: The incidence of delirium was generally lower in the intervention than in the control group, suggesting the validity of bright light treatment.
Purpose: We sought to characterize ambient light exposure in the intensive care unit (ICU) environment to identify patterns of light exposure relevant to circadian regulation. Methods: A light monitor was affixed to subjects' bed at eye level in a modern intensive care unit and continuously recorded illuminescence for at least 24h per subject. Blood was sampled hourly and measured for plasma melatonin. Subjects underwent hourly vital sign and bedside neurologic assessments. Care protocols and the ICU environment were not modified for the study. Results: A total of 67,324 30-second epochs of light data were collected from 17 subjects. Light intensity peaked in the late morning, median 64.1 (interquartile range 19.7-138.7) lux. The 75th percentile of light intensity exceeded 100lx only between 9AM and noon, and never exceeded 150lx. There was no correlation between melatonin amplitude and daytime, nighttime or total light exposure (Spearman's correlation coefficients all <0.2 and p>0.5). Conclusions: Patients' environmental light exposure in the intensive care unit is consistently low and follows a diurnal pattern. No effect of nighttime light exposure was observed on melatonin secretion. Inadequate daytime light exposure in the ICU may contribute to abnormal circadian rhythms.
Patients in intensive care suffer from severe illnesses or injuries and from symptoms related to care and treatments. Environmental factors, such as lighting at night, can disturb patients’ circadian rhythms. The aim was to investigate whether patients displayed circadian rhythms and whether a cycled lighting intervention would impact it. In this pilot study (N = 60), a cycled lighting intervention in a two-bed patient room was conducted. An ordinary hospital room functioned as the control. Patient activity, heart rate, mean arterial pressure and body temperature were recorded. All data were collected during the patients’ final 24 h in the intensive care unit. There was a significant difference between day and night patient activity within but not between conditions. Heart rates differed between day and night significantly for patients in the ordinary room but not in the intervention room or between conditions. Body temperature was lowest at night for all patients with no significant difference between conditions. Patients in both conditions had a natural circadian rhythm; and the cycled lighting intervention showed no significant impact. As the sample size was small, a larger repeated measures study should be conducted to determine if other types of lighting or environmental factors can impact patients’ well-being.
Exposure to Artificial Light At Night (ALAN) results in a disruption of the circadian system, which is deleterious to health. In industrialized countries, 75% of the total workforce is estimated to have been involved in shift work and night work. Epidemiologic studies, mainly of nurses, have revealed an association between sustained night work and a 50–100% higher incidence of breast cancer. The potential and multifactorial mechanisms of the effects include the suppression of melatonin secretion by ALAN, sleep deprivation, and circadian disruption.
ICU patients typically exhibit pathologic wakefulness, poor quality of daytime sleep, nocturnal sleep fragmentation, and sleep patterns that feature the absence of SWS and REM. This paper offers a review of the existing literature examining circadian desynchronization in critically ill patients, highlighting contributing factors identified by scholars, and circadian abnormalities observed in these patients. It discusses potential implications for clinical practice and suggests avenues of future research. Elucidating the role of circadian rhythms in the management of critical illness can guide future chronotherapeutic approaches and optimise patient outcomes.
Sleep-wake patterns are often significantly disturbed in critically ill patients. This disturbance is closely linked to secondary brain dysfunctions in these patients. Sedation not only impairs sleep quality in ICU patients but also has detrimental effects on short- and long-term outcome. In other contexts, light therapy has been proven to be effective in maintaining and resynchronizing circadian rhythmicity in humans. The objective of this systematic review was to analyse studies that investigated the effect of exposure to light or darkness on physiological measures and clinical outcomes of adult ICU patients. Studies were systematically identified by searching electronic bibliographic databases (The Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, 2002) and MEDLINE via PubMed). The search algorithm identified a total of 156 articles, 10 of which were taken into final review. These 10 selected articles included 3 were monocentric RCTs, five prospective cohort studies, one retrospective cohort study, and one manuscript that included a partial systematic review of the literature. Included trials were published between 2007 and 2015. Five of these studies used multiple intervention approaches while four trials used a single intervention approach. Among all studies, 1,278 patients were analysed (489 prospectively). There was a high heterogeneity among the studies in terms of applied intervention and outcome measures. The most frequent methodological limitations were a lack of precise definitions regarding the illuminance and the light spectrum utilised. The analyses indicate that further studies including clearly defined interventions with objective outcome measures, as these are currently lacking, would add significant knowledge to this new field of research.