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50 Cards in this Set
- Front
- Back
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Describe conditions when a blood gas should be drawn
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1- hypoxia - to determine therapy
2-change in therapy 3-status of cardiopulmonary system |
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List info from patient chart needed prior to obtaining an ABG
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1-physician order
2-hx and physical 3-check for anticoagulants 4-check for bleeding disorder 5-check for vascular disorder- Reynaud's disease: hardening of arteries, arterial spasms will constrict and patient's arm will turn blue 6-oxygenation- order vs actual. check level and write down. Order should be the same as what is actual or corrected. 7-vent settings: write down FIO2,rate volume, and mode. Patient must be stable for 20 min 8- Hb- females: 12-16, males: 13-17 9-Temperature |
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What is the advantages and disadvantages of the brachial artery?
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Advantages: brachial is larger
Disadvantages: nerve and vein nearby, deeper than radial and has facia tissue around it. It has limited collateral flow. |
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Where is the brachial artery located?
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located on the antecubital fossa of the forearm
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Where is the radial artery located?
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located on the lateral aspect of the forearm at the wrist.
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What are the advantages and disadvantages of the radial artery?
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disadvantages: small nerve, the site rolls
advantages: collateral circulation, artery is accessible, fat, tendon and muscle surrounds the artery so less pain, no large veins so the sample won't be venous. |
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Where is femoral artery located?
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located on the inguinal canal of the groin area. last resort.
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What are the advantages and disadvantages of the femoral artery?
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advantages; large blood supply and easy to palpate
disadvantages: large vein near, the artery is very deep, nearby abdomen can be punctured, location is embarrasing, no collateral circulation |
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Describe the components of the PO2 electrode
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- anode = silver
- cathode = platinum - ampmeter for measurement -plastic membrane - O2 moves through and gases difuse through thin membrane. -KCL solution |
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Describe the principles of operation for the PO2 electrode
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-AKA Clark Cell or Polarographic Electrode
-Same principle as the polarographic oxygen analyzer. -Electrolysis occurs by the following reaction: O2 + 2H+ 4e = H2O2 + 2e- = 20H- -The electrons flow from the cathode to the anode. The flow (current) is measured by the ammeter. There is a KCL electrolyte solution. - The more the O2, the more electrons move across the membrane to the cathode, then to the Silver anode, then measured on Ampmeter |
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Describe the components of the PH electrode
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-plastic membrane is gas specific and only allows one gas through
-PH sensitive glass membrane -Sodium bicarb and phosphate buffer inside. -is measured by voltmeter -Silver electrode |
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Describe the principles of operation for the PH electrode
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-same as PCO2 electrode
-gas diffuses through a silicon membrane allowing the following reaction to occur: CO2 + H2O = H2CO3 = H+ + HCO3- |
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Describe the components of the PCO2 electrode
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-plastic membrane is gas specific and only allows one gas through
-is measured by voltmeter -Silver electrode -KCL solution |
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What is the principle operation for the PCO2 electode (Severinghaus)
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CO2 diffuses through a silicone membrane allowing the following reaction to occur:
CO2 + H2O = H2CO3 = H+ + HCO3- so basically you are adding a hydrogen ion |
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How does formula apply in blood gas analyzers:
CO2 + H2O <->H2CO3 <-> H+ + HCO3- |
CO2 and H+ ions are directly related. As CO2 goes up, H+ ions go up and it determines how much electrons move.
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What is one difference between the Severinghaus electrode and the PO2 electrode?
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The Severinghaus does not use platinum, only silver
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Define calibration and state the purpose?
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Adjusts the electronic circuitry so that the value being measured is the same as the value being displayed.
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What is the purpose of two point calibration?
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This measures 2 points on a theoretical scale.
1- isoelectric or zero point 2- known point (higher on the scale) |
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Iso electric point defined:
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The isoelectric point (pI), sometimes abbreviated to IEP, is the pH at which a particular molecule or surface carries no net electrical charge.
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Both one point and two point calibrations are...
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...done at the same time and on a regular basis...
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online definition of two point calibration at a chemistry website.
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A two-point calibration is a more accurate calibration technique than the one-point calibration. The two-point calibration adjusts the meter at two different pH values, thus the meter has been adjusted so that its response is accurate at more than one point along the linear equation. The second calibration point is selected on the basis of the type of solution (acidic or basic) to be measured so that the linear response can be established.
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online definition of a one point calibration at a chemistry website
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Sometimes a one point calibration is only needed. Typically, a one-point calibration is made by placing the electrode in pH = 7.00 buffer and adjusting the meter to read 7.00, ZERO (offset). The Slope is kept at 100% or at the previously calibrated value. This method gives a reasonable accuracy.
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One point calibration is used for what?
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is used to adjust for a slope drift
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Describe the purpose and technique of quality control for blood gas analyzers
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The entire process of providing consistent and effective management and results. consistency.
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State the purpose of two point and one point calibration:
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One point calibration: used to adjust for a slope drift, done prior to ABG analysis to correct for drift of the calibration line.
Two point calibration: method to adjust the circuitry to correctly read out that which is being measured |
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Describe the technique of quality control for blood gas analyzers
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3 small vials used of known test samples:
one is normal one is acidotic (high CO2) one is alkalotic (low CO2) |
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what do you do if you have unacceptable blood gas results?
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Unacceptable results requires:
a. Recalibration of the blood gas machine b. Required maintenance c. Cleaning, replacement of electrodes d. Documentation e.Rerunning of quality controls |
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State the use and purpose of the Levy-Jennings Plot:
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Levy-Jennings Plot: uses a standard of how far the control results are from the expected values, acceptable values are within 2 standard deviations from normal, >2 not acceptable
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List the effects of temperature on blood gas values:
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Blood gas analyzers run at 37° C
Pt hypothermic → analyzer warms sample, gives results that are higher than inside the pt (more common) Pt hyperthermic → analyzer cools sample, gives results that are lower than inside the pt (hyperthermia is quickly treated therefore not as common) |
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State the measurement obtained from a co-oximeter and the relationship to blood gas values
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A co-oximeter measures PO2
It measures absorption at several different wavelengths to distinguish oxyhemoglobin, carboxyhemoglobin, methemoglobin, and reduced hemoglobin to determine the oxyhemoglobin saturation: the percentage of oxegenated Hb compared to the total amt of Hb. |
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State the Beer-Lambert Law
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The amount of light that gets transmitted through an object is equal to the intensity of light that enters minus the amount of light that gets absorbed by distance, Hb concentration, and a density coefficient.
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10. Describe pulsatile and non-pulsatile components of pulse oximetry:
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Pulsatile (AC component): amount of light absorbance measured with each pulsation
Non-pulsatile (DC component): amount of light that is comprised of fat, skin muscle, venous blood, non pulsatile arterial blood and other tissues. |
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List factors that may cause inaccurate POX readings:
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a. ambient light
b. low perfusion c. vascular dyes d. motion e. nail polish f. large levels of dyshemoglobins |
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what is a co-oximeter??
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A pulse CO-oximeter measures absorption at additional wavelengths to distinguish CO from O2 and determines the blood oxygen saturation more reliably.
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State the Beer Lambert law
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amount of light transmitted through an object is equal to light entered minus light that gets absorbed by distance hemoglobin concentration and density coefficient.
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two point calibration defined:
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• Two Point Calibration: This measures 2 points on theoretical scale.
1) 1st point is an isoelectric point of no electrical potential 2) 2nd is known point higher on scale. - Basically on 2 point calibrations will create straight line for calibration. |
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one point calibration defined:
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• One Point Calibration: Done prior to bld gas analysis to correct for drift of calibration line.
Bring drifting back to original base line. |
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List the hazards of arterial puncture and how to prevent/treat each one
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1-hematoma - apply pressure
2-seeping - apply pressure 3-arterial spasm - vasoconstriction, no pulse. needle out and look fo rnew site. 4-arterial shutdown-vasoconstriction. no pulse. very low BP. may need to move to brachial 5- severed artery - never move needle side to side. massive bleeding. get help. prevention by proper procedure. 6- hit or nick nerve 7- hit or nick bone 8-bruising 9-psychological - patient can hyperventilate, hide needle 10- infection - use aseptic technique |
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Describe the equipment used and set up for arterial puncture
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1- alchohol/ betadine wipes
2 - sterile gauze 3 - rubber needle stopper 4 - syringe cap 5 - container for ice 6 - ice 7 - small towel 8 - ABG slip 9 - patient label 10- dry lithium heparin syringe 1 to 1.5 inch |
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What are the sizes of syringes?
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23-25 gauge (smaller) radial
22-23 gauge (medium) brachial 18-22 gauge (large) femoral |
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How to prep equipment for ABG?
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take cap off syringe, open packets and get ready to go, open gauze, open bag of ice, have items labeled already.
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Describe technique for ABG
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Check chart
Obtain kit Introduce self and explain procedure Wash hands/ gloves Lay out equipment Perform Allen’s test Place rolled cloth under wrist or arm to hyperextend it Patient sitting up Arm face up and stabilized Clean site with betadine then alcohol Dry site with gauze Loosen cap from needle of the syringe Using the tips of your middle and index finger palpate together, visualizing the position of the radial artery. Place the tip of the needle approximately 1 cm distal to your fingertip positioning the hand and arm holding the syringe in line with the patient arm. (bevel side up) |
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Explain the purpose and technique of the Allen’s test
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Purpose: to determine the level of collateral circulation through the ulnar artery. In the event of complications with the radial artery, circulation to the hand won’t be compromised.
Technique: look for strongest pulse, raise arm, tight fist, occlude arteries, open fist, release ulnar side, check for color return. |
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Describe the technique for obtaining the arterial sample from each possible site
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Position of needle: bevel up. Do a single smooth movement, single motion in. If no flash, go a little deeper, withdraw slightly, angle over and go back in. Obtain 1 cc of blood. If you can’t do it in 3 tries, then go get help. Apply pressure to area to stop bleeding. Roll syringe to mix the heparin in sample and lock it.
Radial- 45 degree angle Brachial -90 degree angle Femoral- 90 degree angle – rotate leg outward. Feel for pulse as compressions are administrated 3 finger positions: •With one finger point towards the artery and aim needle towards that •Place both fingers horizontal to artery and aim for area in between •Place both fingers vertical to artery and aim for area in between |
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State factors that may cause inaccurate blood gas results, sampling error and how to prevent them
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Bubble air: air can cause inaccurate reading of PO2 and PCO2 values because air has oxygen. Invert syringe and tap until air bubble rises to the top and uncap and with gauze push air and bubble out and recap. Then roll and place in ice.
Venous sample: redo for arterial. It will be slower and darker when sample is drawn. There will be no flash. Most common to do this in the femoral area. |
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Describe the equipment and technique to obtain a cap blood sample
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Equipment:
1-Capillary tube – with heparin 2-lancet 3-capillary tube Caps 4-Alcohol swabs and/or Betadine swabs 5-Sterile gauze 6-Warming cloth 7-Ice and bag for ice 8-Gloves 9-Patient label Steps: •Arterialize the site by increasing blood flow: heel, toe, or finger. Wrap the warming cloth around hand and vasodilation occurs so there is more blood at the location for 5 minutes •Clean site •Lance quickly. Stick around periphery. Avoid the center because there is more nerves in the center and fatty acids can clot the sample. •Droplet appears: don’t take this one as it has cellular fluid. Remove with gauze •Gently milk the site: don’t squeeze but push upward •Big droplet appears •Apply the tube to the site and 1-2 droplets will fill the tube. Do not push tube in or twist it. •Cap the tube •Apply gauze and apply pressure |
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List types of heparin used & any adverse effect.
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Dry Lithium Heparin
Liquid Sodium Heparin Changes PCO2 without changing pH |
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purpose of rolling blood sample
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We Roll tube to mix the blood with the heparin to prevent the blood from clotting in the tube and ruin our blood sample.
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pH Measuring Electrode (Severinghaus electrode)
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•Key component of pH electrode is pH sensitive glass. H+ ion align along both sides of gas & there is believed to be electron transfer thru glass.
•Modified pH electrode that works on conversion of CO2 CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3- -CO2 & pH is same based on H+ ion sensitive glass. -The creation of free H+ ions from CO2 based on amt in bld. These H+ ions align along pH sensitive glass similar to pH electrode. •Constant electrons flow is established by Silver/Silver Chloride reference half cell. •Severinghaus needs H+ to create current •Voltmeter: measures total amt of electron that goes thru pH & CO2 |
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PO2 Measuring Electrode (Clark electrode) –
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•PO2 electrode utilizes Silver/Silver Chloride reference electrode which becomes anode. Platinum wire is cathode. O2 crossing over polypropylene mm undergoes electrolytic reduction at exposed end of cathode. Electrons released flow to anode. This flow is measured by an ampmeter & read out as PO2.
•Clark needs O2 to create current •AmpMeter: measures difference b/t electron current. |
