Baylor University Medical Center Proceedings October 2017 - 416

weight (11). Only adult manikins were utilized for this study
since the majority of cardiac arrests occur in adults (12). Baubin
and associates studied the compression characteristics of CPR
manikins and found that the standard CPR manikin used in
this study was consistent 100% of the time in the amount
of pressure it took to perform an adequate chest compression
(11). The standard CPR manikin used in this study had a 16
cm diameter with a moderate thorax resistance similar to that
in humans (11).
Based on BMI guidelines, manikins to mimic an obese and
a morbidly obese adult were created, manufactured, and tested
by a professional in the ﬁeld of manikin design and manufacturing. The manikins were manufactured by taking molds of the
standard manikin and adding the calculated amount of a foam
substance of a consistency similar to adipose tissue to obtain
the proportional equivalent of an obese person and morbidly
obese person based on body casts of two individuals matching
the BMI criteria for obese and morbidly obese. The body casts
of the two individuals were also used to make the "skin." The
thorax framework and the sensors from a standard CPR manikin
were in the correct anatomical position in the new manikins.
The new manikins were tested for consistency in measuring
adequate chest compression by the research team.
The participants were asked to perform two cycles of chest
compressions (15 compressions per cycle) on each size manikin
at a rate of 100 per minute at a depth of at least 2 inches per current AHA guidelines, with a 5-second pause between the cycles
of chest compressions (12). Manikins were placed on hospital
beds with backboards under the manikin to replicate an inhospital scenario. The quality of compressions for each manikin
was recorded. At the time of the study, a member of the research
team recorded the number of times the electronic skill reporter
indicated an adequate compression. These data were veriﬁed by
a printout obtained from the electronic skill reporter by another
member of the research team. The quality of chest compressions
was measured as the number of successful compressions out of
30 attempts. For each participant, demographic data were also
collected, including age, ethnicity, gender, height, weight, and
upper body strength. All participants' heights and weights were
obtained on a calibrated medical scale at the time of participation in the study. Upper body strength was measured using a
handheld dynamometer using the manufacturer's protocol for
strength testing.
SAS Enterprise Guide 6.1 (SAS Institute, Cary, NC) was
used for data analysis. A P value < 0.05 was considered statistically signiﬁcant. Descriptive statistics were summarized on participants' demographics. The outcome, the number of successful
compressions out of 30 trials on each manikin, was compared
to the AHA standard (28 out of 30) using Wilcoxon rank sum
test. Comparison was performed on the outcome between the
three manikins using Wilcoxon signed rank test. The Bonferroni method was used for multiple comparison correction for
both the Wilcoxon rank sum test and the Wilcoxon signed rank
test. The relationship between the outcome and participants'
demographic variables was assessed using a generalized linear
model with Poisson as the link function.
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Table 1. Demographic and personal characteristics of the
61 participants
Variables

Result*

Age (years)

42 ± 10

Weight (lbs)

162 ± 37

Height (cm)

166 ± 8

Body mass index (kg/m2)

27 ± 6

Upper body strength (lb)

74 ± 24

Female

50 (82%)

Black

5 (8%)

Asian

10 (17%)

White

41 (68%)

Hispanic

4 (7%)

*Presented as mean ± standard deviation for continuous variables and n (%) for categorical variables.

RESULTS
Sixty-one health care professionals were recruited and agreed
to participate as "rescuers." Their characteristics (age, gender, ethnicity, height, weight, BMI, and upper body strength) were recorded (Table 1). The age range of participants was 22 to 62 years
old. Their height ranged from 150 to 188 cm. Eighty-two percent
of participants were female, which was anticipated since most
health care workers are female. Their BMI ranged from 18.38 to
43.49, and their upper body strength ranged from 40 to 140 psi.
When the number of successful compressions performed
by rescuers was compared to the AHA guidelines, performance
on the normal-sized manikin was not signiﬁcantly diﬀerent
from the AHA standard (P = 0.09), but performance on the
other two manikins was signiﬁcantly lower than the standard
(P = 0.0001) (Table 2). Pairwise comparison in the number
of successful compressions among these three manikins was
performed. The performance on the normal-sized manikin was
signiﬁcantly better than that on both obese and morbidly obese
manikins, with P = 0.0001 for each comparison. There was no
signiﬁcant diﬀerence in performance between the two obese
manikins (P = 0.10).
A multivariate regression analysis was performed on the
data from the normal manikin and rescuer characteristics.

Table 2. Comparison of successful compressions by manikin size
Successful compressions after 30 attempts
Manikin

Median

Range

P value*

Normal

0-30

0.09

Obese

0-2

0.0001†

Morbidly obese

0.0001†

*Compared to the American Heart Association guideline of 28/30 attempts, Wilcoxon
rank sum test.
†Statistically

significant after Bonferroni correction for multiple comparisons.

Baylor University Medical Center Proceedings

Volume 30, Number 4

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