2006 OPEN FORUM Abstracts
EVALUATION OF A NEW PULSE CO-OXIMETER; NONINVASIVE MEASUREMENT OF CARBOXYHEMOGLOBIN IN THE OUTPATIENT PULMONARY LAB AND EMERGENCY DEPARTMENTS
Twila
Layne, BS,
RRT, RPFT, Carolyn Snyder, RRT, Don Brooks, RRT, Dr. Suresh Enjeti, MD, Pulmonary Physiology Department, Erlanger
Health System, Chattanooga, TN.
Background: In the past, pulse
oximeters have been unable to measure dyshemoglobins such as carboxyhemoglobin
(COHb). We used the Masimo Rad-57, (a
new eight-wavelength Pulse CO-oximeter, which is designed to noninvasively
measure COHb levels (SpCO) as well as traditional SpO2 values) in
clinical settings in the outpatient pulmonary lab to evaluate patient's smoking
history and in the emergency department to evaluate burn victims from fires to
find out the accuracy of the device and its clinical usefulness.
Methods: One hundred thirty six
outpatients who presented to the outpatient pulmonary lab for arterial blood
gas (ABG) draws were also monitored with the Pulse CO-oximeter for their SpCO
level at the time of the blood draw. Prior to obtaining SpCO values, the
patient's smoking history was recorded. The arterial blood sample was analyzed
using an Avox 4000 CO-oximeter and the COHb results were recorded alongside the
SpCO values from the Pulse CO-oximeter. Using a SpCO level of 6% as a positive
indication of smoking, we set out to test both the positive and negative
predictive value of the Pulse CO-oximeter in this setting. Also, in the
emergency department, twenty-one patients who presented with burns or inhalation
injuries from fires were monitored with the Pulse CO-oximeter in addition to
the standard monitors used on these patients in the emergency room. When ABG's
were drawn, the COHb values from the blood CO-oximeter were recorded alongside
the SpCO values from the Pulse CO-oximeter.
Results: In the
pulmonary lab study, there were 24 smokers, 112 non-smokers, 70 males, 66
females, with a mean age of 63.4 years. The COHb ranged from 0 to 14.1%, with a
mean (±SD) of 1.6% (±2.5%) in this population. The bias (COHb - SpCO) and
precision were -0.65% and 1.8% respectively.
Using a 6% SpCO as the threshold for prediciting smoking, 11 tested
positive for smoking, with 15 false negatives and 2 false positives. The
calculated positive predictive value of the test was 82% and the negative
predictive value was 88%. In the Emergency Room study, there were 15 males and
6 females with a mean age of 38.9 years, exposed to burns or inhalation
injuries. The COHb ranged from 0 to 31% in this population. The bias (COHb - SpCO)
and precision were -0.54% and 4.34% respectively.
Conclusion: The Pulse CO-oximeter
performed well in both the Pulmonary Lab and the Emergency Department
environments, with an extremely small bias compared to CO-oximetry measured
COHb. Based upon this preliminary data, this 6% SpCO threshold may be
acceptable to predict smoking history in patients in the pulmonary lab. When
used according to manufacturer's instruction, the Pulse CO-oximeter is quite
reliable at detecting elevated CO levels in patients presenting to either the
pulmonary lab or the emergency department.