Study protocol
To perform the study, we used the SimulResp versions 2015.10.11.01 (2015
version) and 2012.06.09.01 (2012 version). The two versions were
considered equivalent as the formula within the software remained
unchanged, only the design of the interface changed. All tests were
performed by OF or DB. OF ran the SimulResp 2012 version, under windows
7 (Microsoft, Albuquerque, NM), on a 2011 computer SONY VAIO (Sony,
Minato, Japan) equipped with a Intel Core i3 processor (Intel, Santa
Clara, CA) and DB ran the 2015 version, under window 8.1, on a 2016
computer ASUS X541UV (Asus, New Taipei, Taiwan) equipped with a 2.50 GHz
dual core Intel Core i7-6500U processor.
Blood
gas values: pH, arterial partial pressure in CO2(PaCO2), arterial partial pressure in O2(PaO2) and arterial oxygen saturation in
O2 (SaO2) were simulated at different
time points for several types of subjects with different
characteristics. For each combination, the following subjects’
characteristics were specified: age, weight, height, type of patient,
and ventilation mode (spontaneous (SV) or mechanical (MV) ventilation).
The characteristics were systematically entered in the same order: age,
weight, height, type of patient, gender, ventilation mode.
“Personalized” type of patient was selected when mechanical
ventilation was chosen, in order to enter the ventilation parameters:
inspired oxygen fraction (FiO2), positive end expiratory
pressure (PEEP), respiratory rate (RR) and tidal volume (Vt). By
default, the gender was set to male and switched to female as needed.
When available hemoglobin value was entered or considered as normal when
missing. Each simulation was repeated three times to address potential
input error and in case of a mismatch, a fourth simulation was performed
to verify or eventually replace the outlier.
A preliminary study was conducted to assess for several assumptions of
the SimulResp configuration: the range of age within which
SimulResp was supposed to be
accurate and its ability to remain stable even when the simulation speed
was modified, from 2 to 4000 times. Blood gas values (pH,
PaCO2, PaO2 and SaO2)
were simulated for several fictive healthy subjects with different
characteristics: gender (M, F) and age (1, 2 ,4, 6, 8, 10, 12, 14, 16,
18 years old), with a 50th percentile weight and
height at different simulation speeds (from 1 to 4000) and were
collected after a virtual patient
clinical evolution (VPCE) of 30 minutes.
First phase of the
study
The first phase intends to assess the accuracy, the robustness, the
repeatability and the reproducibility of SimulResp when simulating blood
gas values of healthy fictive subjects. The first phase of the study
consisted in assessing SimulResp’s predictions with simulated healthy
subjects. Based on the results of the preliminary study, the tests were
restricted to subjects from 8 to 18 years old (8, 10, 12, 14, 16, 18
years), with different characteristics; gender (M, F) and weight
(10th, 50th and
90th percentile). Blood gas values were collected 3
times for each patient at a VPCE of 30 minutes, 3 and 24 hours, with a
simulation speed of respectively 64, 258 and 1048. This study was
conducted for both spontaneously breathing and mechanically ventilated
subjects. For mechanically ventilated subjects, the following
ventilation parameters were set: FiO2 21%, PEEP 3
cmH2O, Vt 7.5mL/kg, normal RR for age (9)