1. You run a control solution through a blood gas analyzer as part of daily quality control. The measured high PO2 value is 9 torr outside of the acceptable range. Prior runs were all in range. You should:

A. report results after compensating for the deviation
B. replace the PO2 electrode and recalibrate the analyzer
C. analyze another control solution for comparison
D. perform a two-point calibration and rerun the control

A single or sporadic value that falls outside the acceptable quality control range (typically ± 2 SD) is known as a random error. Whenever a random analysis error occurs, you should recalibrate the analyzer and rerun the control (using a solution). Should the repeat analysis yield the same results, the problem more likely is a more serious bias error, requiring that the analyzer be taken out of service and undergo full maintenance.
The correct answer is: perform a two-point calibration and rerun the control

2. Which of the following is true regarding calibration of exhaled nitric oxide (NO) gas analyzers?

A. inlet flows should mimic breathing (variable flow/pressure)
B. daily 2-point (zero/high %NO) calibration is required
C. room air can be used as the ‘zero’ calibrating gas
D. daily 1-point using a standardized NO% is sufficient

Exhaled nitric oxide (NO) gas analyzers should be calibrated daily using the 2-point method, i.e., measuring a ‘zero’ gas and a ‘high’ gas containing a standardized NO concentration. Since room air contains NO, it cannot be used to zero the analyzer. Instead, the zero gas is generated by removing NO from air (the ‘knockout’ method). Because analysis is very sensitive to changes in reaction chamber pressure, calibration (and sample analysis) always should be performed at a constant inlet sample flow.
The correct answer is: daily 2-point (zero/high %NO) calibration is required

3. When reviewing statistical quality control data on a blood gas analyzer, you note a single pH measurement among 30 that falls below the ± 2 SD “in control” standard for your lab. Which of the following is the most likely cause of this error?

A. statistical probability/chance
B. contaminated buffer solutions
C. incorrect analysis procedures
D. failure of the pH electrode

A single pH measurement among 30 that falls outside a lab’s ± 2 SD “in control” standard represents a random error or error of imprecision. Random errors in blood gas quality control usually are due to statistical probability (a chance occurrence), sample contamination or sample mishandling. Contaminated buffers, incorrect analysis procedures, component failure and incorrect calibrating gas concentrations are causes of systematic or bias errors.
The correct answer is: statistical probability/chance

4. You are analyzing quality control samples on a blood gas analyzer as part of a routine quality control program. Multiple but not successive PCO2 values fall above and below the two standard deviation limit. You should:

A. record the results as an acceptable
B. record the results as an acceptable after correcting for the difference in measurements
C. record the results as an acceptable if they are within +/- 2 SD of the mean
D. perform a two-point calibration and reanalyze the control sample

Frequent random errors like this indicate a lack of precision, i.e., poor repeatability of measurement. Any instrument that demonstrates poor repeatability over time is deemed “out- of-control.” In such cases, you would have to identify the problem, take appropriate corrective action and re-confirm that the analyzer is back in-control prior to the reporting results for any patient sample.
The correct answer is: perform a two-point calibration and reanalyze the control sample

5. Which of the following blood gas quality control procedures is designed to assure that the output of the analyzer is both accurate and linear across the range of measured values?

A. statistical quality control.
B. performance validation
C. control media verification
D. automated calibration

The blood gas quality control procedure designed to assure that the output of the analyzer is both accurate and linear across the range of measured values is called calibration. Blood gas analyzers regularly calibrate themselves by adjusting each electrode’s output signal when exposed to media having known values, usually precision gas mixtures and standard pH buffer solutions. Normally parameters are measured at two levels, usually a low and a high value.
The correct answer is: automated calibration

6. When calibrating a portable computerized spirometer, its volume readings consistently fall outside the ± 3% range. Which of the following is the most likely cause of this problem?

A. flow sensor misassembled or damaged
B. failure to remove bacterial filter before calibration
C. flow sensor tubing not connected to computer
D. incorrect selection of prediction equations

Likely causes for the volume readings of a portable spirometer consistently falling outside the ± 3% calibration range include the following: (1) an incorrect temperature or pressure/altitude input; (2) a loose connections or leak in system; (3) a misassembled or damaged flow sensor; or (4) a flow sensor that is obstructed with foreign matter. Neither prediction equation selection nor use of a bacterial filter during calibration should effect the volume measurement. On the other hand, if the flow sensor were not connected to computer, no volume whatsoever would be recorded.
The correct answer is: flow sensor misassembled or damaged

7. When reviewing statistical quality control data on a blood gas analyzer, you note a single PCO2 measurement among 30 that falls below the ± 2 SD “in control” standard for your lab. Which of the following is the most likely cause of this error?

A. contamination of the sample
B. incorrect calibrating gas %
C. incorrect analysis procedures
D. failure of the PCO2 electrode

A single pH measurement among 30 that falls outside a lab’s ± 2 SD “in control” standard represents a random error or error of imprecision. Random errors in blood gas quality control usually are due to statistical probability (a chance occurrence), sample contamination or sample mishandling. Contaminated buffers, incorrect analysis procedures, component failure and incorrect calibrating gas concentrations are causes of systematic or bias errors.
The correct answer is: contamination of the sample

8. Which blood gas analysis/hemoximetry quality control procedure involves plotting the results of control media analyses on a graph and comparing these plots against derived range limits?

A. machine calibration
B. statistical quality control
C. preventive maintenance
D. control media verification

Internal statistical quality control normally involves plotting the results of control media analyses on a graph and comparing these plots against statistically derived limits, usually ± 2 standard deviations. Control results that fall outside these limits indicate analytic error.
The correct answer is: statistical quality control

9. The reference procedure used to establish accuracy for blood PO2 and PCO2 measurements is:

A. hemolysis
B. manometry
C. equilibration
D. tonometry

Tonometry is the reference procedure to establish accuracy for blood PO2 and PCO2.
The correct answer is: tonometry

10. Based on a review of the following control chart data, which of the following is indicated?

A. single random error
B. negative bias error
C. multiple random errors
D. positive bias error

This Levy-Jennings control chart shows systematic error or bias. Note that the last 10 control runs reveal a downward trend in the measured values for the analyte. Over time, this particular trend is shifting the mean above the control value, causing a negative bias in measurement. Bias errors like these are serious, indicating either incorrect procedure or instrument component failure.
The correct answer is: negative bias error

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