Cooling Vest May Reduce Heat Stress, Improve Thermal Comfort, and Preserve Cognitive Performance of Surgeons While Performing Surgery
Phase: NA
Conditions: Body Temperature Changes
Sponsor: The Cleveland Clinic

1 | P a g e  
 
       
 
 
 
 
Cooling Vest May Reduce Heat Stress, Improve Thermal 
Comfort, and Preserve Cognitive Performance of Surgeons 
While Performing Surgery 
 
Version 4.0  
September 03, 2020 
 
 
Daniel I. Sessler, Jill Byrne, and Colleagues 
 
 
Department of Outcomes Research 
Anesthesiology Institute 
Cleveland Clinic 
9500 Euclid Ave __ P77 
Cleveland, OH 44195  
 
 
 
 

 
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Amendments: 
Protocol date changed from April 28, 2020 Version 2.0 - to July 15, 2020 Version 3.0: 
Page 7 of 16 under METHOD section changed the age limit from 30-65 years of age to 25-65 years of age. 
 
Protocol date changed from July 15, 2020 Version 3.0 – to September 3, 2020 Version 4.0 
Page 7 of 16 under METHOD section changed the surgical helmet system from an exclusion to an inclusion as 
long as the system is consistently worn for each of the surgeon’s four cases.  
Page 9 of 16 under Secondary Outcome #1- mean core temperature.  Oral temperatures of the participants 
will be measured preoperatively and postoperatively prior to completing the C3B battery assessment.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
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Version 4.0 September 03, 2020 
 
INTRODUCTION 
Heat Stress is a serious problem affecting surgeons in operating facilities across the United States 
and throughout the world.  Surgeons are literally drenched from perspiration while wearing impervious 
surgical gowns and protective clothing which increases the incidence of health related maladies, such 
as fatigue and dehydration (Satarifard, Gaeini, & Choobineh, 2012; Nerbass et al., 2017), decreased 
thermal comfort, and alterations to cognitive performance (Berg et al., 2015), potentially increasing 
surgical errors (Zwolinska & Bogdan, 2012). Human beings respond to heat stress via a cascade of 
physiological responses (increased acute circulatory system response, central nervous system 
activation and molecular responses increase production of heat shock proteins to protect cells).  
These mechanisms are activated in an effort to adapt or normalize systemic and cellular responses of 
the body which initially improves brain function and ideally enhances cognitive performance (Logan & 
Barksdale, 2008), although repeated triggers to the stress response systems have a cumulative “wear 
and tear” impact on body functions which contribute to cognitive decline and other health related 
morbidities (Satarifard, Gaeini, & Choobineh, 2012; Logan & Barksdale, 2008).  
Decrements in cognitive performance occur when core temperature increases by about 1⁰C 
(Reinersten et al., 2008; Simmons et al., 2008). The level of cognitive decline depends on exposure 
duration, the intensity and complexity of the activity, andꟷ importantlyꟷ the degree of hyperthermia 
(Gauoa et al., 2011; Simmons et al., 2008). There have been several heat stress studies performed in 
industrial settings and in climatic heat chambers.  Processing speed and reaction time, short-term 
memory, and decision are all impaired (Gaoua et al., 2011; Sun et al., 2012; Piil et al., 2017; Mazlomi 
et al., 2017).  
Cooling the skin reduces the unpleasant sensations caused by excessive heat exposure (Simmons et 
al., 2008). Localized cooling of the torso during systemic heat exposure reduces physiological stress 
by lowering body skin and core temperatures, decreasing heart rate, reducing sweat rate, and 
improving perception of thermal comfort (Chang, Song, & Yang, 2015). Cooling vests worn under 
impervious surgical gowns serve as a heat sink and reduce unpleasant sensations and the symptoms 
of physiological stress (Smolander et al., 2004; Kenney et al., 2011; Reinersten et al., 2008).  
We propose to test the primary hypothesis that wearing a cooling vest during surgery improves 
surgeons’ perception of thermal comfort. Secondary, we will test the hypothesis that wearing a 
cooling vest during surgery reduces surgeons’ mean-body temperature and preserves their 
cognitive performance.   
 
Specific Aims 
1. Our primary aim is to evaluate surgeons’ self-rated thermal comfort with and without a cooling 
vest during prolonged and strenuous surgery.  
Primary hypothesis: Surgeons’ self-rated thermal comfort is improved by wearing a cooling vest 
during prolonged and strenuous surgery. 
2. A secondary aim is to evaluate surgeons’ mean-body temperature with and without a cooling 
vest during prolonged and strenuous surgery.   

 
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Version 4.0 September 03, 2020 
Secondary hypothesis 1: Surgeons’ mean-body temperature, estimated from core and mean-
skin temperature, is reduced by wearing a cooling vest during prolonged and strenuous surgery.   
 
 
3. Another secondary aim is to evaluate surgeons’ cognitive performance with and without a cooling 
vest just after prolonged and strenuous surgery.   
Secondary hypothesis 2: Surgeons’ cognitive performance is better preserved by wearing a 
cooling vest during prolonged and strenuous surgery compared to the same surgeons’ cognitive 
performance without wearing a cooling vest during prolonged and strenuous surgery.   
4. An additional secondary aim is to evaluate the surgeons’ perceived ergonomic workload with and 
without a cooling vest during a prolonged and strenuous surgery.  
Secondary hypothesis 3: Surgeons’ perceived ergonomic workload is less demanding by 
wearing a cooling vest during prolonged and strenuous surgery compared to the same surgeons’ 
perceived ergonomic workload without wearing a cooling vest during a prolonged and strenuous 
surgery.   
 
Background and Significance 
Heat stress is a serious problem affecting the physiological and psychological responses of surgeons 
in operating rooms (OR) across the United States and throughout the world as body heat is trapped 
under protective impervious surgical gowns increasing body temperature (Satarifard, Gaeini, & 
Choobineh, 2012), possibly altering cognitive performance (Berg et al., 2015), and potentially 
increasing surgical errors (Zwolinska & Bogdan, 2012). Physical efforts of individuals to adapt to 
higher temperatures, or acclimate, within an occupational environment is dependent on the type of 
work performed, thermal condition and insulated layers of clothing worn (Zwolinska & Bogdan, 2012).  
Cooling systems are sometimes used to reduce thermal discomfort and to improve comfort, decrease 
sweating, and increase work productivity (Lango et al., 2009). In a met-analysis by Chan, Song, and 
Yang (2015), the use of microclimate cooling systems in occupational settings attenuated increases 
in core temperature, sweat rates, and improved human performance.  Research does not exist to 
capture surgeons’ perceptions of comfort, skin and core body temperatures in real-time operating 
conditions and whether surgeons experience a degree of heat stress sufficient to impair their 
cognitive performance.  A gap in research also exists to identify whether a cooling vest intervention 
worn by surgeons while performing surgery will improve comfort and/or reduce negative physiological 
and psychological responses to heat stress (Lango et al., 2009).  
Environmental, Personal, and Situational OR Conditions Impacting 
Surgeons 
The Facility Guidelines Institute recommends the ambient temperature levels in each OR are 
monitored and maintained at 20-24⁰C (68⁰ - 75⁰F) which contributes to heat stress experienced by 
surgeons.  AORN Standard Practice Guidelines, Safe Environment of Care Protocol states: Ambient 
temperature levels in each OR are monitored and maintained at 21-24⁰C to reduce hypothermia and 
improve surgical outcomes experienced by patients (AORN, 2017). It is estimated that 20% of 
surgical patients experience unintentional hypothermia, core body temperature dropping below 36⁰C, 

 
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potentially increasing perioperative complications including delayed wound healing, surgical site 
infections, and surgical blood loss (Sessler, 2016).  
Regulated ambient operating room temperatures to protect vulnerable sedated patients from 
hypothermia may be warm for surgeons as their elevated body temperatures predispose sterile 
surgical fields to contamination from surgeons’ sweat dripping onto the field (Berg et al., 2015). 
Additionally, the level and duration of discomfort experienced by surgeons at the field are also 
impacted by close physical proximity among operating members, patient warming devices, physical 
exertion, body position, and use of lead x-ray aprons which collectively contribute to elevated body 
temperatures, excessive fluid loss, and alterations in cognitive performance (Berg et al., 2015; 
Nerbass et al., 2017).  
Surgical gowns and additional layers of personal protective clothing have a considerable impact on 
the body temperature and comfort of the surgeon (Zwolinska & Bogdan, 2012). Surgical gowns are 
medical products that comply with occupational safety regulations instituted by the Association for the 
Advancement of Medical Instrumentation (AAMI) to ensure barrier protection to prevent high-risk 
contaminations, penetration by liquids, or any microbial transmission (Reinersten et al., 2015). The 
gowns are manufactured from nonwoven material fibers, which are bonded to each other by friction 
and/or cohesion and/or adhesion (AORN, 2017). In addition to the impervious gowns, additional 
safety requirements stipulate surgical personnel wear goggles, glasses with side guards face masks, 
knee-high shoe covers, waterproof aprons, or additional sleeve layers to be worn, dependent on the 
type of surgery, and double gloving to reduce the risk of infection (AORN, 2017).   
Physiological and Psychological Responses to Heat Stress 
Human beings respond to heat stress via a cascade of acute physiological responses to initially 
enhance the body’s response to heat stress in which systemic and cellular functions attempts to 
regulate and regain control throughout the stress event (Bouchama & Knochel, 2002). The initial 
reactions include an acute circulatory system response, central nervous system activation, and 
molecular responses to increase production of heat shock proteins which work to protect cells from 
damage or cell death (Bouchama & Knochel, 2002). Following the acute response, most individuals 
acclimate to physiologic changes to maintain a balance state within body systems. Repeated daily 
exposure and prolonged contact to heat stress predispose some individuals to develop adverse 
physiological and psychological responses to heat stress (Conrad & Bimonte-Nelson, 2010; Moran et 
al., 2006; Logan & Barksdale, 2008).  
Initially, an acute circulatory system response to heat stress occurs whereby cardiovascular 
activity diverts blood flow to the body surfaces, increasing peripheral blood volume to bring about 
profuse sweating (Horowitz & Robinson, 2007) which evaporates in ambient temperatures and 
naturally cools the body (Amorium et al., 2015) unfortunately, not for surgeons as sweat is blocked 
from evaporating. At the same time the cardiovascular activity occurs, the central nervous system 
reacts to warm temperatures and moderate physical activity through activation of the hypothalamic-
pituitary-adrenal (HPA) axis (Nater, Skoluda, & Strahler, 2013). Initial activation of the HPA axis, the 
body’s stress response, or the fight-flight reaction, protects organs from permanent harm by 
increasing alertness and protecting against pathogens by boosting the immune system response 
(Ryann et al., 2016). Released from the HPA axis, glucocorticosteriods, primary stress hormones, are 
sent to bind with available glucose in the bloodstream which are routed to the brain to support 
cognitive performance and decision making functions during stressful situations (Ryann et al., 
2016).  

 
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At the molecular level, cells initially respond to heat stress by synthesizing highly conserved sets of 
polypeptides, heat shock proteins (HSPs), the stress proteins essential for survival at normal and 
elevated temperatures (Kregel, 2002). Elevated levels of HSPs measured during heat exposure 
suggest these proteins play an important role in maintaining cellular homeostasis, or a balance state, 
in response to heat stress (Horowitz et al., 2004). Cell protection is a critical function of HSPs to 
develop thermotolerance, a defense mechanism of cells to protect tissue from damage associated 
with heat stress exposure by increasing transcription (production) of HSPs, creating a temporary state 
of heat tolerance or balance (Horowitz et al., 2004).  
Following the initial rapid acute responses of the systemic and cellular processes, individuals 
acclimate, or acclimatize to heat stress, by increasing levels of extracellular fluid and blood plasma, 
activation of stress hormones, and conservation of salt by the kidneys which improve the body’s 
ability to resist dehydration (Bouchama & Knochel, 2002) and increase a balance state of adaptation 
(Horowitz & Robinson, 2007). Additionally, allostasis, an advanced flexible version of homeostasis, 
signals the body to remain stable during exposure to stressful events. This complex process 
continually monitors and adapts the variability occurring among hormones, temperature, and blood 
pressure (Logan & Barksdale, 2008).  
Chronic activation or daily exposure to heat stress threatens the body’s efforts to maintain a 
balanced state, eventually becoming fatigued and physiological and psychological responses 
deteriorate with repeated exposure to heat (Logan & Barksdale, 2008). Each time the stress response 
is activated, physiological adjustments are made, which have a cumulative “wear and tear” effect on 
body functions (Satarifard, Gaeini, & Choobineh, 2012; Logan & Barksdale, 2008). Several adverse 
physiological reactions occur when permanent triggers continually activate the release of stress 
hormones from the neuroendocrine system resulting in elevated levels of corticosteroids, which alter 
the immune system, suppress the digestive system, and burden the reproductive system (Nadar 
Skoluda, & Strahler, 2013; Logan & Barksdale, 2008). Long-term exposure to elevated corticosteroids 
increases the occurrence of anxiety, depression, heart disease, and weight gain contributing to health 
related morbidities (Satarifard, Gaeini, & Choobineh, 2012). The effects of elevated and prolonged 
exposure to glucocorticosteriods may leave the hippocampus region of the brain vulnerable to 
potential injury neurotoxicity or metabolic challenges (Conrad & Bimonte-Nelson, 2010) potentially 
resulting in dysregulation of the HPA axis and alterations in cognitive performance (McEwen, 
1998).  
Cognitive performance is a brain function allowing individuals to use acquired knowledge to work 
through mental processes and exposure to stress (Berg et al., 2015). The brain controls voluntary 
and involuntary activities including, but not limited to; attention, perception, mood, emotion, appetite, 
and memory (Kamphuis et al., 2012). Alterations in voluntary and involuntary activities resulting from 
heat stress depend on the length and source of heat exposure, the length and complexity of the duty 
to be performed and the skill level of the participant (Gaoua et al., 2011). Individuals who have 
acquired high skill levels and experience with particular repetitive tasks may be able to tolerate 
subsequent effects of heat stress for a longer duration of time (Hancock, Ross, & Szalma, 2007). 
Several heat stress studies performed in industry and simulated climatic heat chambers, measuring 
processing speed and reaction time short-term or working memory, and executive function of 
participants, reported an increased number of errors and impairment of cognitive performance 
(Gaoua et al., 2011; Sun et al., 2012; Piil et al., 2017; Mazlomi et al., 2017).  
Cooling the body is the most effective means of improving human performance (Chan, Song, & Yang, 
2015). Cognitive functions of the brain respond to cooling by improving perceptions of thermal 

 
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comfort, decreasing cardiovascular strain, and less decrements to cognitive performance are noted 
(Goaua et al., 2011; Simmons et al., 2008; Chan, Song, & Yang, 2015).  
Surgeons experience discomfort from elevated body temperatures while performing surgery, but the 
presence and/or absence and the amount of alterations to cognitive performance are not known 
(Berg et al., 2015; Lango et al., 2009; Zwolinska & Bogdan 2011) and if cooling the body preserves 
resources, reduces threats to cognitive performance, and reduces perceptions of a physically 
demanding ergonomic workload.  
Environmental conditions (ambient OR temperatures, overhead lighting, electrical equipment), 
personal factors (personal protective equipment, metabolic heat, core and skin temperatures) and 
situational factors (type and length of a surgical procedure, perceived ergonomic workload) contribute 
to the presence of occupational heat stress experienced by surgeons performing surgical procedures. 
Surgeons’ physiological and psychological responses to heat stress are measureable through a self-
reported response to thermal comfort and perceived ergonomic workload, skin and core body 
temperature sensors, and a cognitive battery assessment. The physiological and psychological 
measure of surgeons’ responses to heat stress can be influenced by wearing a cooling vest during 
the surgical procedure (Figure 1).  
 
Figure 1. Conceptual Framework.  
 
Methods 
The trial will be conducted with Cleveland Clinic IRB approval and consent from participating 
surgeons. The trial will be registered at ClinicalTrials.gov. A full statistical analysis plan will be 
developed before any data are evaluated. Reporting will be consistent with the CONSORT guidelines. 
Subject selection   
Inclusion criteria are: 1) surgeons who perform elective major orthopedic surgery such as total hip 
and knee arthroplasties scheduled for 90 to 150 minutes at the Cleveland Clinic Main Campus; 
2) Orthopedic surgeons ages of 25-65 years old, as body temperatures may be lower and less stable 

 
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in the elderly (Waalen & Buxbaum, 2011), who operate frequently enough to participate in four cross-
over cases; 3) Surgical procedures in which surgical helmet systems or airborne barrier protection 
devices are worn are included as long as the surgeon wears the system for all four cases being 
measured. 
Exclusion criteria are: 1) Surgical cases that require surgeons to sit on stools during the procedure, 
which may impact temperature and energy expenditure; 2) Surgeons who report having a recent 
illness within 24 hours prior to the surgery, symptoms producing a febrile condition; 3) Surgeons who 
worked the previous evening; and  4) Surgeons who wear lead X-ray gowns. 
Surgeon research subjects will be recruited by posting information about the study on the Orthopedic 
and Rheumatology Institute website. All human subject research protocols instituted by the Cleveland 
Clinic will be followed and documented. Participating surgeons will be advised of all known risks and 
benefits of study as well as information describing the requirements of the study and data 
management. The surgeons will be advised of the option to stop participation at any time. Written 
informed consent will be obtained from each surgeon. 
Participating surgeons will be assigned a study number and only this number will be included on 
case-report forms. A single cross-linking record will identify specific surgeons for the purpose of 
organizing cross-over cases. Otherwise, analysis will be based on study number and no individual 
data will be linked to specific surgeons. Case-report forms will be kept locked in a secure research 
office and data-acquisition iPads will be encrypted.  
We do not plan to obtain consent from patients for this comparative effectiveness trial that evaluates 
an FDA exempt device designed to improve surgeons’ comfort.   
Protocol 
We propose a randomized cross-over trial using a uniform and strongly balanced 4-period design in 
which will include four operations for each surgeon.  Surgeons will be randomized to 1 of 4 
sequences: ABBA, BAAB, AABB or BBAA.  The design is “uniform” in that each treatment appears 
the same number of times within each sequence (uniform within sequence) and if each treatment 
appears the same number of times within each period (uniform within each period). It is strongly 
balanced with respect to first-order carryover effects because each treatment precedes every other 
treatment, including itself, the same number of times. 
 
We chose this design versus a parallel group design because 1) it removed the potential for 
confounding, even with a small sample size, as comparisons are made within subject, and not 
between subjects; 2) the design is very efficient since within-subject comparisons are correlated, 
obviating the need for a larger study which would also not be practical in this setting.  Also, no 
differential carryover effect is expected in this study, removing one of the main concerns with 
crossover trials. 
Surgeons will be randomly assigned to use either the CoolSource™ cooling vest (worn between 
scrubs) and a conventional surgical gown for each of 4 surgeries. Sequence of treatments within   
surgeons will be randomized (ABBA, BAAB, AABB or BBAA), and determined using the PLAN 
procedure in SAS, such that each surgeon will wear vest and non-vest twice.  The sequencing will not 
be shared with any study personnel.  Allocation for each case will be concealed with a web-based 
system that will be accessed only shortly before surgery.  
We will target an ambient temperature of 21°C ± 1°C, and try to maintain the same temperature of 
each of the four study cases for each surgeon. The CoolSource vest holds six reusable cooling packs 

 
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located bilaterally on the shoulders, angled flank along the base of the rib cage, and along each side 
of the spine, mid-back. The vest will be donned over hospital-issued scrubs after all temperature 
sensing devices have been applied and before surgical hand scrubbing. Surgeons will wear the vest 
throughout surgery, and for a few additional minutes while postoperative assessments are made 
(details below).   
The weight of the disposable cooling vest is 1 kg which is evenly distributed over both shoulders. The 
cooling packs have an insulated cover to reduce condensation or sweating while seated inside the 
vest pocket. The flexible frozen reusable cooling packs will be inserted into each of the six pockets 
and the vest belt will be tied to hold the cooling packs securely. The disposable cooling vests will be 
discarded after each case, and the cooling packs returned to a freezer.  
Measurements 
A questionnaire detailing demographic information (age, height, weight, age, ethnicity, and education 
level) training level, specialty program, and estimated past case volume will be completed by 
participating surgeons before their first case.   
Temperature of the freezer holding the cooling packs will be assessed before randomization to 
confirm that the temperature is <0°C.  
Before every surgical case starts the time the surgeon dons the cooling vest and the time the surgeon 
dons the sterile surgical gown will be recorded.  
Primary Outcome will be self-rated thermal comfort.  Immediately after surgery, while still 
gowned, surgeons will rate their thermal comfort on a 0-10 Likert scale, with 0 representing extreme 
cold, 5 being thermal comfort, and 10 representing extreme heat. Two points on the 11-point Likert 
scale will be considered a clinically important difference.  
Secondary Outcome #1 - mean core temperature.  The first secondary outcome will be the mean 
core temperature for a case, calculated as the time-weighted average over the taken measurements. 
The surgeon’s core body temperature will be monitored by a validated wireless wearable 
iThermonitor WT701 biosensor which estimates core temperature within ±0.5⁰C (Pei et al., 2018). 
The sensor will be applied to the surgeon’s right axilla 15-20 minutes prior to the surgical hand scrub 
performed at the start of surgery and secured with an adhesive cover. A small patch of axillary hair 
will be clipped or shaved as necessary. After the temperature sensors are applied, the surgeon’s oral 
temperature will be measured by the Femometer adult digital oral thermometer which meets 
professional accuracy standards for digital thermometers (ASTM E1112-00) to support the accuracy 
of the iThermonitor core body temperature measurement. The surgeon’s oral temperature will be 
measured for a second time when the surgeon exits the surgical field prior to taking the C3B battery 
assessment.  
Secondary Outcome #2 - mean skin temperature.  The second secondary outcome will be the 
mean skin temperature for a case, calculated as the time-weighted average over the taken 
measurements.  Mean skin temperature will be estimated from skin temperature from the back of the 
upper chest, deltoid arm, thigh, and calf using the formula [MSTR = 0.3 tchest + 0.3 tarm + 0.2 tthigh + 0.2 tleg 
or 0.3(tchest + tarm) + 0.2(tthigh + 0.2 tleg)] (Ramanathan, 1964).  Skin temperature will be continuously 
measured using wireless patches, TempTraq, which meet professional accuracy standards for digital 
thermometers (ASTM E1112-00). The sensors will remain affixed with adhesive dressing on the 
surgeon’s body surface throughout surgery and approximately 10 minutes required for post-operative 
testing.  

 
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Secondary Outcome #3 will be surgeons’ cognitive performance, measured with the C3B 
battery. The self-administered C3B is a performance-based battery of cognitive tests which measure 
visual memory; episodic learning and delayed memory (five learning trials with a total score of 70) 
and processing speed; information processing speed and incidental memory (15 symbols repeated 
for 120 seconds). Also, relevant distractions or interruptions (phone call, pager, staff, equipment, and 
other) will be recorded and the frequency in which they occur during the C3B battery test. Both tests 
will be aggregated using z-scores and summing the z-scores within patient. A greater than 10% 
within-subject difference in total scores will be considered significant.  Testing will take place right 
after surgery with surgeons still gowned. The surgeons will sit with the iPad touch screen placed on a 
desk in front of them for approximately 10 minutes to complete the cognitive test. To minimize 
learning during the trial, participating surgeons will complete the cognitive assessment battery before 
the first study day. For subsequent cases, the test will be administered prior to the surgical hand 
scrub and after the end of surgery. The C3B test modules use auditory test instructions and on-
screen visual test stimuli consistent with symbols, single digits, and single letters.  
Secondary Outcome #4 will be surgeon’ perceived ergonomic workload measured with Borg 
CR10 scale of exertion and the rating-of-fatigue (ROF) scale.  
Immediately after surgery, while still gowned, surgeons will rate their perceived exertion on a 1-10 
Borg CR10 scale, with 1 representing very slight exertion, 5 being severe, and 10 representing 
maximal exertion. Perceived fatigue will be rated on a 0-10 ROF scale, with 0 representing not 
fatigued at all, 5 moderately fatigued, and 10 total fatigue & exhaustion. Two points difference on 
either scale will be considered a clinically important difference. Time the surgeon removes the sterile 
surgical gown and the cooling vest after completing the C3B will be recorded. Also, total amount of 
time the surgeon wore the sterile surgical gown / cooling vest in minutes will be calculated.  
Ambient operating room temperatures will be monitored at ≤15-minute intervals with an electronic 
thermometer positioned eight feet from the base of the OR table, outside of the surgical field on the 
circulating nurses’ workstation.  
Data Analysis  
Participants’ age, weight, height, and other continuous demographics and baseline characteristics will 
be summarized using descriptive statistics (n, mean, median, standard deviation, minimum and 
maximum), while race, surgical specialty, as well as other categorical variables will be summarized 
with frequency tabulations.   The 4 sequence groups will be compared on baseline variables 
descriptively. 
Specific Aim 1) Evaluate the difference between surgeons’ self-rated thermal comfort with and 
without a cooling vest during prolonged and strenuous surgery.  0-10. 
Perceived measure of thermal comfort for both conditions, with and without a cooling vest will be 
analyzed by descriptive statistics recommended for ordinal Likert scale items – i.e., frequencies and 
median [quartiles].   
We will use a linear mixed effects model to test the treatment effect of the cooling vest on mean 
thermal comfort.  We will adjust for treatment, sequence and period effects, and include subject as a 
random effect to account for the within-subject correlation.  We will test for differential carryover effect 
by assessing the treatment-by-period interaction.  If no interaction is detected the interaction term will 
be removed and the treatment effect assessed in a main effects model.  
Specific Aim 2) Evaluate the difference between the surgeons’ core, mean skin, and mean 
body temperatures with and without a cooling vest during a prolonged strenuous surgery.  

 
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For each temperature we will used a linear mixed effects model to test the treatment effect of the 
cooling vest on a subject’s temperature during the case.  We will adjust for treatment, sequence and 
period effects, and include subject as a random effect to account for the within-subject correlation.  
We will test for differential carryover effect by assessing the treatment-by-period interaction.  If no 
interaction is detected the interaction term will be removed and the treatment effect assessed in a 
main effects model.  
Specific Aim 3: Evaluate the difference between the surgeons’ measure of cognitive 
performance with and without a cooling vest just after a prolonged strenuous surgery. 
Cognitive performance will be measured by the C3B performance-based battery of cognitive tests at 
the end of the case.  An overall score for a subject after a particular case will be calculated by first 
rescaling (e.g., so that each item ranges from 0 to 100) and then averaging the scores across the 
battery. Treatment effect will be assessed using a linear mixed effects model as described for Aims 1 
and 2.   
The significance level will be 0.05 for the primary outcome (Aim 1) and 0.05 across the 3 secondary 
outcomes (2 temperatures, cognitive function), such that the secondary outcomes will be assessed at 
a significance criterion of 0.05/3=0.017.  SAS statistical software version 9.4, Carey, NC, will be used 
for all analyses. 
Specific Aim 4: Evaluate the difference between the surgeons’ perceived ergonomic workload 
with and without a cooling vest during a prolonged and strenuous surgery. 
Perceived ergonomic workload will be measured by duration of the surgical procedure recorded in 
minutes, surgeons’ report of the number of hours slept prior to the study day, Borgs’ visual analog 
scale for exertion (0-10), and the Rating of fatigue scale (0-10).  
Perceived ergonomic workload for both conditions, with and without a cooling vest will be analyzed by 
descriptive statistics recommended for ordinal measured items – i.e., frequencies and median 
[quartiles].   
We will use a linear mixed effects model to test the treatment effect of the cooling vest on mean 
perceived levels of exertion and fatigue.  We will adjust for treatment, sequence and period effects, 
and include subject as a random effect to account for the within-subject correlation.  We will test for 
differential carryover effect by assessing the treatment-by-period interaction.  If no interaction is 
detected the interaction term will be removed and the treatment effect assessed in a main effects 
model.  
 
Sample Size Justification.   
Sample size calculation is based on having 90% power at the 0.05 significance level to detect a 
difference of 2 or more (on a scale of 0-10) on surgeons’ self-rated thermal comfort with and without a 
cooling vest.  With an estimate SD (s) of 3 for thermal comfort in each group, and an assumed within-
subject correlation ( ) of 0.5, the estimated SD of the within-subject difference would be 
2
2
2
1
2
1 2
2
,or 2(3 )
2(0.5)(3)(3)
3
s
s
s s




.   Within these assumptions we would need a total of 26 
subjects to have 90% power to detect a difference of 2 or more on mean thermal comfort in this 
crossover design.  The detectable difference corresponds to an effect size (Cohen’s D) of 0.66, which 
is medium to large.   For the 3 secondary outcomes each using a significance criterion of 
0.05/3=0.017, we would have 90% power to detect an effect size of 0.76. 
 

 
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Our assumptions of variability and within-subject correlation for the primary aim will be reassessed in 
an internal pilot study after 13 subjects have competed the 4 cases, and the total sample reassessed 
based on the findings.  
 
To ensure that sensors, iPad, and wireless technology can be monitored during a real-time surgical 
procedure, a small trial of two or three case studies will be conducted to ensure all processes work 
properly, which will not be included in the final data analysis. Periods of poor data or lead 
disconnection will be marked for exclusion in analysis.  
 
Innovation 
The discomfort surgeons experience during long surgical procedures combined with an inability to 
evaporate sweat through impervious surgical gowns prompted the innovative design of the 
disposable CoolSource™ Cooling System. The cooling vest is worn by surgeons under the 
impervious gown to reduce heat and improve comfort while performing surgery. The positive changes 
in mood, attention, and productivity have been reported by staff and surgeons in a product trial which 
supported the need for research to investigate the impact heat stress has in which supported the 
need for research to investigate the impact heat stress has in real-time operating conditions.  
The innovative design of this study measures data by wireless sensor technology during real-time 
surgical procedures without disrupting the surgery, as previous studies utilized simulated conditions. 
Furthermore, limitations are numerous when trying to generalize findings discovered in structured 
simulated studies as there is a wider range of effecting factors in real-time investigations (Mazlomi et 
al., 2017). Information obtained from this study will support the development of prescriptive measures 
and standards to address heat stress in surgeons to alleviate perceptions of discomfort and improve 
physiological and psychological well-being.  
 
Protection of Human Subjects 
The research study is being conducted according to the purposes outlined in the research protocol 
and the primary responsibility of the informed consent is designed to protect the rights, welfare, and 
well-being of the participants. The risks and benefits of the study are reasonable to the anticipated 
benefits and the importance of generalizable knowledge that is expected to result.  
Identified Risks: 
 Risks to breach of confidentiality: The records of this research will be kept confidential and 
every effort will be made to protect participants’ confidentiality through encrypted coded data 
and will not include any information that will make it possible to identify a participant.  Any 
reports that may be published will not include any information that will make it possible to 
identify a participant.  Research records will be kept in a locked file and access will be limited 
to the researchers and hospital review board responsible for protecting human participants.  
 Participants will be advised of the entire protocol as well as the voluntary option to withdraw 
from the study at any time.  
 Shaving small skin areas (approximately 2” x 2”) for temperature sensor placement may be 
necessary for adhesive cover to adequately adhere to skin surfaces which could cause mild 
discomfort, redness, or itching as the body hair regrows.    

 
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 Potential risks to comfort, elevated body temperatures, and cognitive performance (e. g. short-
term memory and/or processing speed) in occupational heat stress studies naturally occur 
while surgeons are operating, however, the cooling vest intervention administered in the study 
may reduce these potential risks.   
 There is no evidence that OR personnel wearing the cooling vest under the impervious sterile 
surgical gown offer any risk to patients as there is no direct contact.  
Steps to minimize risks:  
 Attenuate first-time cooling-vest users’ concerns for perception of discomfort related to cooling 
packs or added weight, all participants will have the opportunity to wear the cooling-vest prior 
to any of the randomized trials.  
 All members of the research team will be appropriately trained, maintained appropriate 
credentials, licensing privileges, and institutional competencies.  
Identifying benefits:   
 The vest design was designed to cool areas of the body that do not cause discomfort over a 
period of approximately two hours, and the cooling packs do not come in direct contact with 
participant’s skin as it is worn over scrubs.   
 Heat stress studies have shown that wearing a cooling garment in stressful thermal 
environments can decreased heart rates, reduce sweat rates, and improve human 
performance.  
 
 Surgeons who routinely wear the cooling vest perspire less while operating.  This is a 
substantial advantage because when surgeons perspire, beads of contaminated sweat can fall 
into the patient’s open incision, contaminating the case and predisposing patients to infections.   
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
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