ABG Equipment

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Arterial Blood Gases

- Sampling,Equipment, Calibration,and Quality Control

RET 2414L

Pulmonary Function Testing

Module 6.0


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Equipment

Arterial Blood Gas (ABG) Kit

Prepackaged and contains all necessaryequipment 3 5 cc syringe

Pre-heparinized

22ga x 2 needle

Alcohol swap

Gauze pad

Biohazard bag

Misc. items


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ABG Specimen Collection/Handling

Site Selection


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Site Selection

Radial Artery - 45insertion angle Requires modified Allens test for collateral circulation

Brachial Artery - 60- 90insertion angle

Femoral Artery - 90insertion angle

Dorsalis Pedis Artery

Site must be adequately compressed untilclotted Approximately 5 minutes Patients receiving anticoagulation therapy take longer


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Hazards

Hematoma

Arterial laceration

Hemorrhage

Vasovagal reaction Sympathetic nervous system response to pain

Loss of limb


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Handling

Blood gas specimen should collected

anaerobically Expel air bubbles immediately

In Vivo Values Air Contamination

pH 7.40 7.45

PCO2 40 30

PO2 95 110


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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


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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 toconsume O2 and produce CO2


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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)


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Handling

Transport specimen to laboratory in a

biohazard container

Analyze specimen on an instrument thathas been recently calibrated

Temperature correct specimen in analyzer Increase in patient temp: PO2, PCO2, pH

Decrease in patient temp: PO2, PCO2, pH


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Equipment

Blood Gas Analyzer

Electronic Circuitry Electrolyte Solution

Electrodes


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Equipment

Electronic circuitry

Takes electrical current changes produced in theelectrodes and provides a visual display

Electrolyte Solution

Helps to promote chemical reactions andelectrical current


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Equipment

Electrodes

Utilized to measure values of ABG

pH, PCO2, PO2

All other blood gas values are calculated


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Equipment

pH Electrode

Sanz Electrode

Consists of two electrodes:

sampling/measuring electrode

reference electrode and electrolyte solution


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The pH electrode is amicroelectrode, shown here withits plastic jacket. At the tip is asilver-silver chloridewire in a

sealed-in buffer behind PH-sensitive quartz glass. Thereference electrode contains aplatinum wirein calomel pastethat rests in a 20% KCL solution.The blood sample is introduced in

such a way that it contacts themeasuring electrode tip and theKCL. A voltmeter measure thepotential difference across thesample, which is proportional tothe pH

Sanz Electrode(pH)


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Equipment

PCO2 Electrode

Severinghaus Electrode

May also be referred to as a modified Sanzelectrode


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The PCO2 electrode is a modifiedpH electrode. The electrode hasa sealed-in buffer; an Ag-AgClreference band is the other half-cell. The entire electrode is

encased in Lucite jacketfilledwith bicarbonate electrolyte. The

jacket is capped with a Teflonmembranethat is permeable toCO2. A nylon meshcovers thepH-sensitive glass, acting as aspacerto maintain contact withthe electrolyte. CO2 diffusesthrough the Teflon membrane,combines with electrolyte, andalter the pH. The change in pH isdisplayed as partial pressure ofCO2.

Severinghaus Electrode

(PCO2)


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Equipment

PO2 Electrode

Clark Electrode

May also be referred to as a polarographicelectrode

Periodic/routing cleaning of the tip with pumiceisrequired because polypropylene attracts protein


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The PO2 electrode contains aplatinum cathodeand a silveranode. The electrode is polarizedby applying a slightly negativevoltage of approximately 630 mV.The tip is protected by apolypropylene membranethatallows O2 molecules to diffuse butprevents contamination of theplatinum wire. O2 migrates to thecathode and is reduced, picking upfree electrons that have come fromthe anode through a phosphate-

potassium chloride electrolyte.Changes in the current flowingbetween the anode and cathoderesult from the amount of O2reduced in the electrolyte and areproportional to partial pressure ofO2.

Clark Electrode (PO2)


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Calibration Procedures

To assure appropriate electronic function of

the electrodes, calibration procedures areperformed

Performed automatically every 30 minutes bythe ABG machine

Performed on the pH, PCO2, PO2electrodes

Specific procedure for each electrode


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2-Point Calibration

A low concentration and a highconcentration is used at both ends of thephysiological range to be measured

Multiple-Point Calibration (3 or more points)

Verifies whether the gas analyzer is linear ornot


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pH Electrode

Uses two specific buffers with approximatevalues of:

6.840 buffer referred to as the zero point or low point buffer

7.384 buffer high point or slope point buffer


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pH Electrode

Each buffer is injected into the sample chamber,one at a time

The values of the buffer that is injected, shouldbe displayed on the ABG machine within aspecific SD (standard deviation)


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pH Electrode

Standard deviation for pH is + .005

If value displayed is within the SD, machine iselectronically calibrated

If value displayed is outside of the SD, machineneeds to be adjusted to assure electronic function


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PO2& PCO2Electrode

Uses two specific concentration of gases for eachelectrode with approximate concentrations of CO2and O2

Uses two different tanks of gas to accomplish this


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PO2 & PCO2 Electrode

Tank One Low CO2 (5%) - balance High O2 (12% or 20%) Balance Nitrogen

Tank Two High CO2 (10%) slope O2 (0%) Balance Nitrogen


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Must convert tank concentration from % tomm Hg

(PBPH2O) x tank concentration = mm Hg

(760 47) x 0.12 = 85.65 mm Hg


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PO2& PCO2Electrode

The values calculated for the CO2and O2concentration should be displayed on the ABGanalyzer within a specific SD (standard deviation)


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Standard deviation for PO2and CO2is + 0.5

If values displayed are within the SD, machine is

electronically calibrated

If value displayed is outside of the SD, machineneeds to be adjusted to assure electronic function


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Troubleshooting

If the ABG machine will not calibrate, check:

The buffers

The mixed gases

The electrodes membrane

The electrode itself


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Quality Control

Calibration vs. Quality Control

Calibration is when the equipment is adjustedor correctedto match the control standards

Quality Control testing must be performed on a

regular basis to determine the accuracyandprecisionof the equipment against a knownstandard


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Quality Control

Accuracy vs. Precision

Accuracy refers to the mean (average) value ofseveral measurements

Precision refers to how consistently the same

measurement will produce the same results


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Quality Control

Must be run every shift

Utilize a knownconcentration of gasesand buffers in a vial ofliquid

Run three levels of QC

Level 1 Acidosis

Level 2 Normal

Level 3 - Alkalosis


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Quality Control

KNOWN VALUE IN MUST EQUAL

KNOW VALUE OUT!


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Quality Control

When QC is run it must be recorded

and maintained onsite; in the ABGlaboratory

Must be available for review by State

agencies on demand


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Quality Control Plotting

In control

Trend

Random Error

Out of Control


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Quality Control

In control

All QC runs are within the acceptable +SD


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Quality Control

Trend

All QC runs within the acceptable +SD buttrending towards one side of the SD


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Quality Control

Random Error

All QC runs within the acceptable +SD exceptfor one run


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Quality Control

Out of control

Two or more QC runs are out of theacceptable +SD


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Capnography

Capnography is the continuous, noninvasivemonitoring of expired CO2 and analysis of thesingle-breath CO2 waveform


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Capnography

Capnography is performed utilizing:

Infrared analyzer

CO and CO2 absorb infrared radiation


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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 waveformdamping

ABG Equipment

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