Decreasing Intraoperative Skin Damage in Prone Position Surgeries
Phase: PHASE4
Conditions: Pressure Injury
Sponsor: University of California, Los Angeles

Decreasing Intraoperative Skin Damage in Prone Position Surgeries 
NCT04884737 
March 24, 2023 
Study Protocol and Study Analysis Plan 
 
 

Study Protocol 
Recruitment 
Patients from neurological and orthopedic surgery groups were recruited for the study at 
a 281-bed academic Medical Center in the greater Los Angeles area. Per approval by the 
University of California, Los Angeles, Office for Human Research Protection Program, research 
staff identified scheduled participants for surgery in the prone position, sent them an information 
sheet about the study, and then contacted them by phone to determine their interest in the study. 
Participants were eligible for the study if they were scheduled to undergo orthopedic or 
neurological surgery in prone position, 18 years of age or older, and able to provide verbal 
informed self-consent. Exclusion criteria were less than 18 years old, inability to provide verbal 
informed consent, and scheduled for surgery only in a position other than prone position.  
Skin Assessments 
On the day of surgery, research staff obtained written HIPAA consent from participants 
and confirmed consent to participate in the study. Research staff collected visual skin assessment 
and sub-epidermal (SEM) measures for all participants at the anterior chin, upper cheeks, mid 
forehead (face), right and left upper chest above nipple line, and iliac crest, both pre-operatively 
in the Pre-Post Anesthesia Care Unit (PACU) and post-operatively in the PACU or after transfer 
to the floor unit. Once the pre-operative assessments were completed for intervention 
participants, research staff placed the multidimensionally flexible silicone foam (MFSF) 
dressings to the face (chin, cheeks, forehead), chest and iliac crest. Following surgery, research 
staff removed the MFSF dressings in the PACU or on transfer to the floor unit and then visual 
skin assessment and SEM measures were obtained. For all participants, visual skin assessments 

and SEM measures were obtained daily on the floor unit until post-operative day five or 
discharge from hospital (whichever occurred first).   
Visual Skin Assessment. Trained research staff assessed skin health through direct 
independent visual assessments. Eight anatomic locations were assessed: mid forehead, chin, and 
right and left upper cheek, upper chest above nipple line and iliac crest. Areas of visual skin 
discoloration were palpated for blanchability in persons with light skin tones and any pressure 
injuries (PrIs) were assessed for size and stage. Training for visual skin assessment emphasized 
identification of stage 1 PrIs and deep tissue injury (DTI) because these conditions may be 
difficult to detect. Skin discoloration severity was graded as slight (pink or slight redness in 
persons with light skin tones and increase in normal skin color in persons with dark skin tones), 
minimal (redness in persons with light skin tones and deepening of normal skin color in persons 
with dark skin tones), moderate (bright redness in light skin tones and purple in dark skin tones), 
or severe discoloration (dark red to purple in light skin tones and black to blue-grey in dark skin 
tones). In persons with light skin tones, blanchability based on finger palpation was defined as 
blanchable or non-blanchable; blanching was not considered for persons with dark skin tones. 
Stage 1 PrIs were defined as skin discoloration with severity of minimal or greater. PrIs more 
severe than Stage 1 were classified using the NPIAP’s 2019 classification system. For skin that 
demonstrated none of the above visual characteristics, the assessment was considered normal 
skin. The presence or absence of scar tissue, dry skin, rashes, skin tears, tatoos, and extensive or 
thick hair was also recorded.  
Subepidermal Moisture Measures. Subepidermal moisture (SEM) was measured at each 
anatomic location on clean dry skin using the Provizio ® SEM Scanner (BBI LLC, Bruin 
Biometrics, Los Angeles, California, US) dermal phase meter. Using dielectric parameters, the 

device transmits high-frequency, low-power electromagnetic waves of 32 kHz via an electrode 
that requires light skin touch.  In the skin, the induced electrical field interacts mainly with water 
molecules closest to the electrode, with depth of interaction depending on the diameter of the 
circular electrode (in this study depth was 4 mm). The portion of electromagnetic energy that is 
not absorbed by tissue water is reflected and measured by the device and displayed in three 
seconds in the measuring unit picoFarads (pF) (range, 0-7 pF). The electrical properties of free 
and bound water are nearly identical and thus the measure is reflective of total water content in 
the tissue. 
 
Definition Intraoperative Acquired PrIs. Intraoperative acquired PrI (IAPrI) was defined 
two ways for each anatomic location.  First, as erythema/skin discoloration of minimal or greater 
severity by visual skin assessment. Second, by calculating the difference between pre-operative 
and the post-operative SEM value (hereafter SEM Delta); SEM Deltas greater than or equal to 
0.6pF were considered indicative of IAPrIs.  
Medical Record Data  
Research staff extracted medical, surgical, and demographic information was extracted 
from participants’ electronic health records (EHR) using an investigator-developed abstraction 
tool. Data abstracted included demographic data (gender, age, race/ethnicity),  medical data 
(height, weight, body mass index, comorbidities such as diabetes, hypertension, peripheral 
vascular disease and, smoking status, medical diagnoses, Braden Scale for predicting Pressure 
Sores (Braden) score, use of any PrI preventive strategies such as support surface use, 
repositioning schedules), surgery type, surgery length, use of vibration machines or other 
instruments in surgery, length of time in PAR unit, anesthesia used, use of vasopressors during 
surgery, estimated blood loss, volume of fluids provided during surgery, blood pressure during 

surgery, American Society of Anesthesiologists physical status score and documentation of any 
skin damage. Using EHR data, a Scott-Triggers IAPrI risk assessment score was calculated for 
each participant. The Scott-Triggers tool examines four characteristics: age 62 years or older: 
albumin less than 3.5mg/dL or BMI less than 19 or greater than 40; American Society of 
Anesthesiologists physical status classification system (ASA) 3 or greater; and estimated surgery 
time over 3 hours. Each characteristic affirmed scores a point and scores greater than 1 indicate 
high risk for IAPrIs (37).  
Study Analysis Plan 
The two outcome measures, IAPrI incidence by visual assessment and SEM Deltas 
indicative of PrI, were compared between participants undergoing prone surgery with standard 
care (no dressings, pressure reduction positioning on the operating table) and those with standard 
care and the intervention (use of MFSF dressings placed on chest, iliac crest, and face). Using 
Fisher’s Exact test statistics, the percent of participants with IAPrI on face, chest, and iliac crest 
as defined above were compared between the two groups for initial post-operative assessment 
and postoperative days 2 and 3 assessments. There were insufficient participants to evaluate 
postoperative days 4 and 5.  
Using binary logistic regression analyses, demographic, medical and surgical factors 
were compared for prospective participants who did and did not develop skin damage or IAPrIs 
controlling for group. Factors that increase risk for IAPrIs were evaluated including: hospital 
length of stay, surgery length, body mass index (BMI), and skin tone. Cochran Mantel-Haenszel 
statistics were used to compare the groups.