EVALUATION OF A NEW DIGITAL TRANSCUTANEOUS TCPCO2

1
HEALTH SYSTEM
EVALUATION OF A NEW DIGITAL TRANSCUTANEOUS TCPCO2
SPO2 COMBINATION SENSOR AND ITS CORRELATION TO
ABG PaCO2 MEASUREMENTS Daniel D. Rowley, BS,
RRT-NPS, RPFT, Brian K. Walsh, BS, RRT-NPS, RPFT,
Barry Young, BS, RRT, Frank J. Caruso, BS,
RRT Pulmonary Diagnostics and Respiratory Therapy
Services University of Virginia Health System,
Charlottesville, Virginia
CONCLUSION In our patient sampling the SenTec
TCPCO2 monitor was proven to have a good
correlation with PaCO2. This can reduce the need
for ABG needle sticks in many patients and reduce
the overall cost and patient discomfort
associated with the procedure. The difference
between the CO2 measurements could be related to
the standard deviation of the two compared
devices and/or the identified pre-existing
medical condition. We find this device
especially intriguing in the clinical settings of
non-invasive positive pressure ventilation, adult
high frequency oscillatory ventilation (HFOV)
where end-tidal CO2 measurement and clinical
assessment can be difficult or impossible, and in
the Emergency Department for trending CO2 levels
in patients presenting with COPD exacerbation.
Further studies will need to be done to determine
if temperature and/or vascular disease plays a
clinically significant roll in the overall
accuracy of this TCPCO2 measuring device.
BACKGROUND Obtaining ABGs for measuring PaCO2
can be painful for patients, time consuming and
perilous for healthcare providers. In an attempt
to improve patient satisfaction while reducing
risks associated with percutaneous and invasive
ABG sampling, we evaluated the CO-OXSYS Digital
Sensor (also known as the V-Sign Digital Sensor)
made by SenTec AG (www.sentec.ch) to determine if
it would yield clinically accurate TCPCO2
measurements when compared to ABG PaCO2 samples.
The monitors single digital sensor is designed
to continuously record TCPCO2 and SPO2
measurements, but our interest was to record only
TCPCO2 measurements for the purpose of our
analysis.
METHOD 25 patients ranging between 10 months to
79 years of age were randomly and prospectively
identified as needing an ABG for clinical
indications unrelated to the TCPCO2 device
evaluation. Patient demographic and clinical
data points were obtained and recorded while the
SenTec sensor was self-calibrating. After sensor
calibration was confirmed the sensor was attached
to the tragus of each patients ear per
manufacturer guidelines. An ABG was obtained 15
minutes after sensor application and simultaneous
TCPCO2 measurements were recorded. ABG samples
were subsequently analyzed with a Rapidpoint 405
analyzer and the measured PaCO2 levels were
recorded next to the corresponding TCPCO2 values.

CONTINUING EVALUATION 45 additional TCPCO2 and
PaCO2 samples have been obtained since our
abstract underwent peer review. Our cumulative
sample size (n70) has been separated into one of
three categories based upon the level of support
each patient received at the time of sample
analysis. Preliminary data analysis of the
cumulative sample size is consistent with our
initial sample entry, but it has yet to receive
critical peer review. Once reviewed, however, we
expect to publish our overall data as we believe
that it will be of value for a variety of
clinical circumstances.
CMV (n 45) HFOV (n 9) Other (n 16)
RESULTS 20 of the patients required
vasopressors at the time of sample analysis. We
found a reliable correlation between the TCPCO2
and the PaCO2 (R2-0.61, plt0.001). Neither age
nor temperature (36.0C 38.6C) appears to
affect the accuracy of CO2 measurement. However,
we observed clinically significant (gt5 Torr)
variation in 3 patients, 2 of which required
vasopressors and were known to have peripheral
vascular disease.
Non-Ventilated Patients
Conventionally Ventilated Patients
90
70
80
60
70
50
60
40
50
30
CO2 Measurement (Torr)
40
CO2 Measurement (Torr)
20
30
10
20
0
10
1
3
5
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
7
-10
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
-20
-10
Sample
Sample
TCPCO2
PaCO2
Difference
Difference
TCPCO2
PaCO2