Focus
on Respiratory Care, Winter 2001
A Review of Medica's EasyBloodGas Analyzer
by Paul Mathews, RRT, PhD, FCCP
General Description: The EasyBloodGas (EBG) analyzer is compact and lightweight. Listed as a CLIA moderate complexity level device, the analyzer is designed for use with both whole blood, syringe, or capillary samples. It requires 100 uL syringe sample or 75 uL capillary sample sizes. With a footprint of 14.5" (W) X 12.5" (H) X 7" (D) (37 cm X 32 cm x 18 cm) and weighing only 16 lbs (7.3 kg), this analyzer is very easily portable and can be used with a minimum of counter space.
The electrodes, valve, and reagent-waste modules are simple to install and use clear illustrations printed on the inside of the case. These and the waste module are self-contained and disposable. The reagent-waste module, sensor module and electrode modules are all plug-in types and are accessible without tools of any kind—a nice feature. Maintenance and troubleshooting are enhanced by an excellent diagnostic software system, coupled with a fax or telephone service call system.
Analysis Capabilities: The EasyBloodGas analyzer has direct analysis capability for whole blood pH, PCO2 and PO2. Additionally, it calculates the following eleven (11) parameters: Temperature corrected pH - (pH (T), Temperature corrected PCO2 - (PCO2 (T), Temperature corrected PO2 - PO2 (T), Total CO2 (TC O2), Bicarbonate - HCO3-, Base Excess of blood - BEb, Base Excess of extracellular fluid — BEecf, Standard Bicarbonate - SBC, O2 Saturation calculated at normal P50 - SAO2c, Alveolar—Arterial O2 Gradient—A-aDO2, and Respiratory Index-RI. The operator's manual (Section 6.6) provides a thorough and complete explanation of the derivation of all the calculated values including the relevant mathematical formulas. The preceding parts of Section 6 (1-5) describe the operating principles and theories of operation of the electrodes, including a really neat, and for once, easily understandable, explanation of the Nernst equation. Measurement ranges are pH—6.900 to 7.900; PCO2 —8.0—150.0 mm Hg; PO2—10.0—700.0 mm Hg. Analysis time is 125 sec with either automatic or on-demand calibration. The user can input patient ID number (up to 14 digits), temperature (5-45°C), hemoglobin (3.0-30.0 g/dL) and FIO2 (10-100%). Sample temperatures are maintained at 37° C. Input data is entered via a numeric keypad and output is provided by a graphic display and an onboard 27 column thermal printer. Ancillary devices include a RS-232 interface port and a barcode reader.
Operational Features: Sampling can be achieved by a sample probe method from blood samples contained in syringes or by aspiration from a capillary tube. The syringe method requires 100 uL of blood, while the capillary method requires 75 uL. Analysis time averages 125 seconds per sample with little variation. All reagents are sealed and contain liquid tonometered calibrants, which completely eliminates the need for expensive, high pressure, calibration gases (which also further reduces space need considerations).
Quality Control Features: An integral quality control program stores and maintains the results of the last 30 quality control runs at each of the three levels tested. The EasyBloodGas analyzer prints a Levey-Jennings graph of these results making trend identification very concise and simple. The analyzer stores over 60 patient data sets and compares each set to pre-selected "normal" ranges, allowing for the flagging of "out of range" data.
Test Conditions: All testing was done in the Pulmonary Function Laboratory at the University of Kansas Medical Center in Kansas City, Kansas over a period of thirty days. The EasyBloodGas machine was used at the University of Kansas pulmonary function laboratory to help evaluate the pros and cons of using the system in a testing area. All blood gas samples were arterial and were obtained from patients ordered to have blood gas analysis as part of their pulmonary diagnostic studies. Since our normal procedure is to withdraw 3-5 mL of arterial blood—leaving a surplus after analysis—no additional blood was required and institutional review board (IRB) approval of our procedures were not necessary. Order of analysis was switched at each drawing to control for any time error. Each patient's blood gas sample served as its own control and in doing so reduced or eliminated the within-subject variability error. We only subjected the measured blood gas values (pH, PaCO2, PaO2) to statistical analysis, employing the SPSS desktop as the statistical program. We performed 26-paired ABG analyses using the EasyBloodGas analyzer and our pre-existing IL 1620 analyzer.
Results: Initial, pre-statistical analysis observations revealed the maximum variability data shown in Table 2. All of this variability occurred in the first 4 tests suggesting a training effect. The remaining samples revealed much closer results with pH values within 0.015 units, PaCO2 below 1.5 mm Hg difference and PaO2 in the area of a 2 mm Hg difference. None of these differences were seen as clinically relevant. Based on the "closeness" of the data, we decided not to perform statistical tests of difference.
Table 2: Maximum deviation values for pH and blood gases
EasyBloodGas and IL 1620
Parameter
pH
PCO2 (mmHg)
PO2 (mm Hg)
EasyBloodGas: 7.433 38.0 101
IL 1620: 7.405 36.2 97
Table 3 illustrates the mean difference between the paired pH, PaCO2,
and PaO2 results from each analyzer. This indicates an excellent degree
of inter-instrument agreement on the analysis. It should be noted that
the PaO2 values include one patient with values in the high 300 mm Hg
whose sample exhibited a 19 mm Hg difference between instruments this
was not considered to be important at those partial pressure ranges. Other
than that one outlier, all other variations fell within the area of instrument
accuracy. Due to the "closeness” of the data, we decided not to perform
statistical tests of difference.
Table 3: Mean difference for pH and blood gases
EasyBloodGas and IL 1620
pH PCO2 (mm Hg)
PO2 (mm Hg) 0.010 0.64 1.3
Observations: As the
name states, the EasyBloodGas analyzer is indeed very easy to use and
setup. Although an on-site representative set up the system for us, it
was put together easily within 5-10 minutes with few parts and little
complication. The actual system is made up of only 7 separate components.
There are 4 electrodes (PO2, PCO2, pH and ref), a sensor module, valve
module and a self-contained reagent module that also doubles as a waste
container. Only a single rubber tube connecting the waste module to the
pump motor needed to be installed by the operator, something which was
done quickly and easily. The initial calibration and set-up check took
only 30 minutes. Total time then, from unpacking to "ready to analyze"
was an astounding 40 +/- 5 minutes. During the thirty-day testing period
we had the opportunity to fix a malfunctioning valve module. This gave
us the opportunity to utilize the troubleshooting algorithms in the Operator's
Manual and test the customer support hotline. As with the setup and calibration,
these proved to be efficient and effective. The Operator's Manual is compact,
concise and comprehensive; making good use of detailed illustrations and
well thought-out directions and information. Once we received the new
module, it was as easy as 1,2,3 to replace the component and get the analyzer
back up and running. The company has subsequently redesigned the valve
module. The EasyBloodGas analyzer is not only easy, but very accurate
as well. Without a doubt, one of the main positive attributes of the Medica
system is indeed its true portability. The fact that the system is not
tied down with gas cylinders and associated tubing, combined with its
light weight and small footprint, makes the system very easy to handle.
We were very impressed with what Medica has achieved in such a small package.
Assessment and Recommendations: The name
EasyBloodGas sums up the system nicely. The system and instructions are simple
to use and maintain and results are accurate. The absence of complicated parts
and instructions make the system appealing for labs and testing areas that
do not have the resources or technical experience to handle bigger systems.
Changing modules, electrodes and reagents is a quick and simple—snap-out
and snap-in process. We did feel that the Medica system took a little longer
than we're used to, to run a sample (about 125 seconds), but there is little
clinical significance to this. We also felt that the printer with the system,
although working fine, could be improved upon. It was somewhat loud and slow,
in our opinion, compounding somewhat, the time it takes to actually run and
report results. A construction issue lies in the housing for the aspirator
as well. The housing feels loose and is made of a thin plastic which made
us wonder how the housing would stand up to a high volume of samples going
through the system. Overall, however, we were pleased and impressed with the
operations, design and excellent support associated with the EasyBloodGas
analyzer manufactured by Medica. It is well-priced and especially useful,
we would say, in moderate-use lab situations or labs in areas where technical
services are difficult or expensive to obtain. In locations where portability
and space limitation or access to high quality compressed calibration gases
is difficult, the EasyBloodGas analyzer would be very high on our list of
desirable blood gas analyzers. We liked the unit overall and recommend it
for consideration when you're next in the market to purchase a portable blood
gas analyzer. The company can be reached at 800-777-5983 and/or at www.medicacorp.com
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