1. RET 2414L Pulmonary Function Testing Module 6.0
Arterial Blood Gases - Sampling, Equipment, Calibration, and Quality Control
RET 2414L
Pulmonary Function Testing
Module 6.0

2. Arterial Blood Gases Equipment Arterial Blood Gas (ABG) Kit
Prepackaged and contains all necessary equipment
3 – 5 cc syringe
Pre-heparinized
22ga x 2 needle
Alcohol swap
Gauze pad
Biohazard bag
Misc. items

3. ABG Specimen Collection/Handling
Site Selection

4. ABG Specimen Collection/Handling
Site Selection
Radial Artery - 45 insertion angle
Requires modified Allen’s test for collateral circulation
Brachial Artery - 60 - 90 insertion angle
Femoral Artery - 90 insertion angle
Dorsalis Pedis Artery
Site must be adequately compressed until clotted
Approximately 5 minutes
Patients receiving anticoagulation therapy take longer

5. ABG Specimen Collection/Handling
Hazards
Hematoma
Arterial laceration
Hemorrhage
Vasovagal reaction
Sympathetic nervous system response to pain
Loss of limb

6. ABG Specimen Collection/Handling
Blood gas specimen should collected anaerobically
Expel air bubbles immediately
In Vivo Values Air Contamination pH
PCO PO

7. ABG Specimen Collection/Handling
Blood gas specimen must be adequately anticoagulated
Sodium heparin
Lithium heparin (electrolytes)
Sample volume should be 1 – 2 ml
Each laboratory has its own protocol

8. ABG Specimen Collection/Handling
Sample should be analyzed as soon as possible
If iced sample can be stored
Glass syringe – 1 hour
Plastic syringe – 15 minutes
Remember: Blood is living tissue that continues to consume O2 and produce CO2

9. ABG Specimen Collection/Handling
Specimen should be adequately identified
Patient name / ID number
Date / Time
Ordering physician
Accession number
Puncture site
Oxygen adjunct and FiO2
Ventilator settings (if applicable)

10. ABG Specimen Collection/Handling
Transport specimen to laboratory in a biohazard container
Analyze specimen on an instrument that has been recently calibrated
Temperature correct specimen in analyzer
Increase in patient temp: PO2, PCO2, pH
Decrease in patient temp: PO2, PCO2, pH

11. Arterial Blood Gases Equipment Blood Gas Analyzer Electrolyte Solution
Electronic Circuitry
Electrolyte Solution
Electrodes

12. Arterial Blood Gases Electronic circuitry Equipment
Takes electrical current changes produced in the electrodes and provides a visual display
Electrolyte Solution
Helps to promote chemical reactions and electrical current

13. pH, PCO2, PO2 Arterial Blood Gases Electrodes Equipment
Utilized to measure values of ABG
pH, PCO2, PO2
All other blood gas values are calculated

14. Arterial Blood Gases Sanz Electrode pH Electrode Equipment
Consists of two electrodes:
sampling/measuring electrode
reference electrode and electrolyte solution

15. Arterial Blood Gases Sanz Electrode (pH)
The pH electrode is a microelectrode, shown here with its plastic jacket. At the tip is a silver-silver chloride wire in a sealed-in buffer behind PH-sensitive quartz glass. The reference electrode contains a platinum wire in calomel paste that rests in a 20% KCL solution. The blood sample is introduced in such a way that it contacts the measuring electrode tip and the KCL. A voltmeter measure the potential difference across the sample, which is proportional to the pH

16. Arterial Blood Gases Severinghaus Electrode PCO2 Electrode Equipment
May also be referred to as a modified Sanz electrode

17. Arterial Blood Gases Severinghaus Electrode (PCO2)
The PCO2 electrode is a modified pH electrode. The electrode has a sealed-in buffer; an Ag-AgCl reference band is the other half-cell. The entire electrode is encased in Lucite jacket filled with bicarbonate electrolyte. The jacket is capped with a Teflon membrane that is permeable to CO2. A nylon mesh covers the pH-sensitive glass, acting as a spacer to maintain contact with the electrolyte. CO2 diffuses through the Teflon membrane, combines with electrolyte, and alter the pH. The change in pH is displayed as partial pressure of CO2.

18. Arterial Blood Gases Clark Electrode PO2 Electrode Equipment
May also be referred to as a polarographic electrode
Periodic/routing cleaning of the tip with pumice is required because polypropylene attracts protein

19. Arterial Blood Gases Clark Electrode (PO2)
The PO2 electrode contains a platinum cathode and a silver anode. The electrode is polarized by applying a slightly negative voltage of approximately 630 mV. The tip is protected by a polypropylene membrane that allows O2 molecules to diffuse but prevents contamination of the platinum wire. O2 migrates to the cathode and is reduced, picking up free electrons that have come from the anode through a phosphate-potassium chloride electrolyte. Changes in the current flowing between the anode and cathode result from the amount of O2 reduced in the electrolyte and are proportional to partial pressure of O2.

20. Arterial Blood Gases
Calibration Procedures
To assure appropriate electronic function of the electrodes, calibration procedures are performed
Performed automatically every 30 minutes by the ABG machine
Performed on the pH, PCO2, PO2 electrodes
Specific procedure for each electrode

21. Arterial Blood Gases Calibration Procedures 2-Point Calibration
A “low” concentration and a “high” concentration is used at both ends of the physiological range to be measured
Multiple-Point Calibration (3 or more points)
Verifies whether the gas analyzer is linear or not

22. Arterial Blood Gases pH Electrode Calibration Procedures
Uses two specific buffers with approximate values of:
6.840 buffer
referred to as the zero point or low point buffer
7.384 buffer
high point or slope point buffer

23. Arterial Blood Gases pH Electrode Calibration Procedures
Each buffer is injected into the sample chamber, one at a time
The values of the buffer that is injected, should be displayed on the ABG machine within a specific SD (standard deviation)

24. Arterial Blood Gases pH Electrode Calibration Procedures
Standard deviation for pH is
If value displayed is within the SD, machine is electronically calibrated
If value displayed is outside of the SD, machine needs to be adjusted to assure electronic function

25. Arterial Blood Gases Calibration Procedures PO2 & PCO2 Electrode
Uses two specific concentration of gases for each electrode with approximate concentrations of CO2 and O2
Uses two different tanks of gas to accomplish this

26. Arterial Blood Gases Calibration Procedures PO2 & PCO2 Electrode
Tank One
Low CO2 (5%) - balance
High O2 (12% or 20%)
Balance Nitrogen
Tank Two
High CO2 (10%) – slope
O2 (0%)

27. Arterial Blood Gases Calibration Procedures PO2 & PCO2 Electrode
Must convert tank concentration from % to mm Hg
(PB – PH2O) x tank concentration = mm Hg
(760 – 47) x = mm Hg

28. Arterial Blood Gases Calibration Procedures PO2 & PCO2 Electrode
The values calculated for the CO2 and O2 concentration should be displayed on the ABG analyzer within a specific SD (standard deviation)

29. Arterial Blood Gases PO2 & PCO2 Electrode Calibration Procedures
Standard deviation for PO2 and CO2 is + 0.5
If values displayed are within the SD, machine is electronically calibrated
If value displayed is outside of the SD, machine needs to be adjusted to assure electronic function

30. Arterial Blood Gases Calibration Procedures Troubleshooting
If the ABG machine will not calibrate, check:
The buffers
The mixed gases
The electrode’s membrane
The electrode itself

31. Arterial Blood Gases Quality Control
Calibration vs. Quality Control
Calibration is when the equipment is adjusted or corrected to match the control standards
Quality Control testing must be performed on a regular basis to determine the accuracy and precision of the equipment against a known standard

32. Arterial Blood Gases Quality Control Accuracy vs. Precision
Accuracy refers to the mean (average) value of several measurements
Precision refers to how consistently the same measurement will produce the same results

33. Arterial Blood Gases Quality Control Must be run every shift
Utilize a known concentration of gases and buffers in a vial of liquid
Run three levels of QC
Level 1 – Acidosis
Level 2 – Normal
Level 3 - Alkalosis

34. “KNOWN VALUE IN MUST EQUAL
Arterial Blood Gases
Quality Control
“KNOWN VALUE IN MUST EQUAL
KNOW VALUE OUT!”

35. Arterial Blood Gases Quality Control
When QC is run it must be recorded and maintained onsite; in the ABG laboratory
Must be available for review by State agencies on demand

36. Arterial Blood Gases Quality Control Plotting In control Trend
Random Error
Out of Control

37. Arterial Blood Gases Quality Control In control
All QC runs are within the acceptable +SD

38. Arterial Blood Gases Quality Control Trend
All QC runs within the acceptable +SD but trending towards one side of the SD

39. Arterial Blood Gases Quality Control Random Error
All QC runs within the acceptable +SD except for one run

40. Arterial Blood Gases Quality Control Out of control
Two or more QC runs are out of the acceptable +SD

41. Capnography
Capnography is the continuous, noninvasive monitoring of expired CO2 and analysis of the single-breath CO2 waveform

42. Capnography Capnography is performed utilizing: Infrared analyzer
CO and CO2 absorb infrared radiation

43. Capnography Capnography is performed utilizing:
Infrared analyzer
Requires accurate calibration
2 gas concentrations used
Room air
5% CO2 mixture
Inaccurate reading can occur when:
Condensation of water in sample tubing, connectors, or sample chamber
Flow changes after calibration
Saturation of a desiccant column
Long sampling lines can cause waveform damping