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Monitoring/Blood Gas

Analysis and Monitoring of Gas Exchange

QuestionAnswer
What is analysis? Discrete measurements of fluids or tissue that must be removed from the body.
What is monitoring? An ongoing process by which clinicians obtain and evaluate dynamic physiological processess in a timely manner, usually at the bedside.
What is a monitor? A device that provides the important data to the clinician in real time, usually without removal of samples from the body.
What is a pulse oximeter? An inexpensive and portable, noninvasive monitoring device that provides estimates of arterial blood oxyhemoglobin saturation levels.
Spectophotometry detects oxygen saturation
What is spectophotometry? Measurement of color in a solution by determining the amount of light absorbed in the ultraviolet, infrared, or visible spectrum, widely used in clinical chemistry to calculate the concentration of substances in a solution.
According to the principles of spectophotometry... Every substance has a unique pattern of light absorption, much like a fingerprint. A substances pattern of light absorption varies predictably with the amount present.
Plethysmography detects heart rate
What is plethysmography? use of light waves to detect changes in the volume of an organ or tissue; pulse oximeters use the principle of photoplethysmography to measure the arterial pulse.
A pulse oximeter consists of a sensor, processor, and display unit.
What are some causes that may cause a pulse oximeter to not read properly? Nail Polish Low Blood Pressure (low perfusion) Dopamine (vasoconstrictors) Hypothermia Motion artifact ethnicity
What is the #1 thing that causes a pulse ox not to work correctly? Motion artifact
Sa02 and Sp02 should be roughly equivalent
Sa02 comes from hemoximetry
sp02 comes from pulse oximetry
A pulse oximeter measures the oxygen saturation of the blood
What are the advantages of pulse oximetry? Non-invasive continuous can be used to spot check -self calibrating
Pulse oximetry is based on 2 principles? spectophotometry plethysmography
THe pulse ox consists of 2 light beams and a photodetector (Red/Infrared)
The measurement sites with the pulse ox include. Fingers/Toes Ear Lobes Bridge of Nose Forehead
The Pulse oximeter should be left on for at least how many seconds? 20 seconds
What should you always chart when using pulse oximetry? The device and 02 liter flow. Date, time, position, Fi02, placement site, compare with ABG results.
What are the pulse oximetry indications? Monitor oxygen saturations (use value as a trend) Evaluate response to theraputic or diagnostic procedure. Comply with recomendations and regulations
What are the contraindications? Monitoring after a house fire. CO should be less than 1 in a normal person.
What are hazards/complications of pulse oximetry? False Values Pressure Sores Electrical Shocks/burns
What are the limitations of pulse oximetry? Motion artifact low perfusion states dysfunctional hgbs intravascular dyes lighting skin pigmentation nail polish/coverings
A pulse oximeter is within what accuracy of the hemoximitry value? +- 3-5 %
The lower the Sa02 value the less reliable the sp02 value will be
What are the qualifiers for home oxygen? A Pa02 of less than 44 mm Hg A sp02 of 87% during activity
Capnometry The measurement of C02 in respiratory gases.
Capnometer Device that measures C02
Capnography graphic display of c02 levels
dead space portion of inhaled air that does not take place in gas exchange.
Capnography is used primarily in the OR and Critical Care Unites
Capnography is used to assess ventilation
End exhalation has the highest level of c02
Capnography mesures carbond dioxed exhaled at the airwsay
PETCO2 End Tidal C02
What are the advantages of capnography? It's non invasive Continuous Measures exhaled C02 and cuts down on ABG sticks
What is principal of capnography? Spectrophotometry (infrared absorption)
Method? Infrared absorption and a photodetector.
Sampling systems Mainstream/sidestream
Mainstream sampling systems are inserted directly in line with the ventilator circuit
Sidestream sampling systems are off to the side of the circuit
C02 absorbs infrared light
Because C02 absorbs infrared radiation, the greater the concentration of C02 in the sample the less infrared light that will arrive at the detector.
What are advantages of mainstream capnometers sensor at patient airway fast response (crisp waveform) No short lag time (real time reading) No sample flow to reduce tidal volume
What are disadvantages of mainstream capnometers? secretions and humidity can block sensor window. Sensor requires heating to prevent condesnation. Requires frequent calibration. Bulky sensor at patient airway Does not measure N2O Difficult to use with nonintubated patients.Cleaning
What are the advantages of sidestream capnometers? No bulky sensors or heaters at airway Ability to measure N20 Disposable sample line Ability to use with nonintubated patients
What are disadvantages of sidestream capnometers? Secretions block sample tubing trap required to remove water from the sample. Frequent calibration required Slow response to C02 changes Lag time between C02 changes and measurement. Sample flow may decrease tidal volume.
Sudden changes associated with Changes in High PETC02 sudden increase in Cardiac output sudden release of tourniquet. Injection of sodium bicarbonate.
What are gradual changes associated with High PETCo2? Hypoventilation Increase in C02 production.
What are sudden conditions associated with low PETC02 SUdden hyperventilation Sudden decrease in cardiac output Massive pulmonary embolism Air embolism Disconnection of the ventilator obstruction of the ET tube
What are gradual conditions associated with low PETCO2 Hyperventilation decrease in oxygen consumption decreased pulmonary perfusion
You should use capnography as a trend and corrolate with blood gas values
What are the indications of capnography? Monitor exhaled C02 (use value as a trend) Evaluate response to therapuetic or diagnostic procedure. Monitor severity of pulmonary disease. Determine tracheal intubation. Monitor ventilator circuit/artificial airway integrity.
Name more indications of capnography. Evaluate ventilator and patient interface. Monitor adequacy of blood flow. Monitor respiratory C02 when administered therapuetically.
What are the contraindications to capnography? None
What are the hazards of capnography? False values Positioning Weight Increased deadspace.
What are the limitations? Requires adequate response time. Moisture/Secretions Requires calibrations
If there is a leak you may have false values
The difference of PaC02 and PETC02 increase as dead space increases
Stae I of capnograph curve Expiratory pure deadspace
Stage II of capnograph curve mixture of deadspace/ventilatory CO2
Stage III of capnograph curve Pure C02 (end exhalation)
Stage IV of capnograph curve Inhalation of oxygen.
What are other methods of capnography? Calormetric C02 detector Mass spectometer Raman Spectroscopy.
A colormetric CO2 detector changes from purple to yellow if C02 is detected
In healthy adults PETCO2 is 1-5 mm HG less than PaC02
Transcutaneous monitoring is primarily used in neonates/small children
Transcutaneous monitoring is time intensive
Transcutaneous monitoring measures Pa02 and PaC02
The Ptc02 is measured with a clark electrode
The PtcC02 is measured with a Severinghause electrode
What are the advantages of transcutaneous monitoring? non-invasive continuous can monitor hyperoxygination
What is the principle of transcutaneous monitoring? Diffusion through skin surface Requires stabilization time.
Where are the measurement sites abdomen chest lower back
Transcutaneous monitoring provides estimates of PaC02 and Pa02 with sensor. Sensor is heated up to 42 degress celsius. this allows for diffusion.
What are the indications of transcutaneous monitoring? Monitor PaO2 and PaC02 (use value as a trend) Evaluate response to theraputic or diagnostic procedure.
What are the contraindications of transcutaneous monitoring? Poor skin integrity allergy to adhesive
If you have a leak the C02 will read 0
Transcutaneous monitoring must correlate with ABG initially
Transcutaneous monitoring doesn't reflect oxygen delivery or content
What are the hazards/complications of transcutaneous monitoring? False values tissue/skin erythema blisters burns skin tears must change site every 2-6 hours
limitations of transcutaneous monitoring include prolonged stabilization required low perfusion states skin thickness improper electrode placement improper calibration labor intensive
What are ABG indications? To monitor ABG values. To evaluate response to therapeutic or diagnostic procedures. to monitor disease progression or severity.
What are the puncture sites? Radial artery (requires modified allens test) Brachial artery Femoral artery.
The femoral artery risky, huge veins and arteries, a fibrinolytic automatically rules out femoral sticks.
Radial artery Collateral circulation superficial and easy to palpate Is the number 1 artery for sticking Not near large veins. Relatively pain free
The brachial artery is risky, nerves and large veins. No collateral circulation. Increased risk for venous samle
Modified allens test Occlude radial/ulnar artery. Make fist, release fist, release ulnar artery. Should pick up within 10-15 seconds for + allens test.
What are the contraindications for ABG? negitive modified allen's test avoid lesions or surgical shunts avoid infection of PVD Avoid femoral site on outpatients High dose anticoagulation
What are the hazards/complications? Thrombosis or air embolis Hemorrhage hamatoma arteriospasm loss of blood flow or circulation infection trauma vasovagal response pain sample contamination
There are preset and self filling syringes
Arterial blood gas supplies gloves/safety glasses 3 CC syringe/ 22-25 Guage needle anticoagulant-liquid sodium heparin crystalized lithium heparin. Needle cap/syringe plug local anesthetic (1%xylocaine/tuberculin syringe) Alcohol or betadine wipe gauze pad bandage cup of i
What do you chart on your blood gas? Date/Time, Patient Name and room number, Initials, site, Fi02, ventilator settings, temperature, 0xygen therapy device
Pre-analytical errors occur before the sample is inserted into the machine
Post-analytical errors happen while running the machine
Pre- analytical errors bubble contamination- for 21% fi02 pa02 will increase. For 100% fi02, pa02 will go down. Delay in sample- pa02 will decrease pac02 will increase. Anxiety paco2 will decrease pa02 will increase. venous sampling- lowers ph, increases pac02 and decrease p
What is one more pre-analytical error? Excessive heparin- makes the sample more acidic. You'll see visable froth
What are some post-analytical errors? incorrect callibration error in sampling
Blood gas analyzers are calibrated at 37 degrees celsius
Pa02 changes7% for each degree celsius.
PaC02 changes 4% for each degree celsius
What are indications for an arterial line? continuous ABP monitoring Repeated ABGs
Where are insertion sites? radial brachial femoral
What are the component parts of the a-line? starter sheath pressure transducer high pressure tubing and pressure bag 3 way stop cock flush tape or sutures
The high pressure tubing and pressure bag prevents blood from coming out of the body
The pressure bag should be set at 300 mm HG or 50 mmHG above systolic ABP
What are requirements for sample? gloves and safety syringes 2 syringes (waste/ABG syringe) syringe plug gauze bad cup of ice label
What are the hazards and complications same as abg #1 complication is clotting infection is a complication
The CBG is an alternative to the abg procedure
The CBG gives a rough estimate of pH and pc02. P02 is of no value of est. oxygenation.
How is the procedure done? blood is collected in a heparinized glass capillary tube and the site must be warmed before procedure.
The site prep and handling of the CBG is the same as ABG sampling
Which population uses the CBG? Infants and small children
CBGs should be avoid in critical cases infants less than 24 hours old
The sites for the CBG include the heel of foot, fingertip and ear lobe
The ABG laboratory include the operator interface measuring chamber calibrating gas tanks reagent containers waste/disposable container transmittal system
The operator interface includes controls, keypad, software, screen display
Measuring Chamber incorporates a 3 electrode system (measures 02, PC02, PH)
PH has 2 electrodes (halfcells) Reference chamber and measuring chamber
Measured values PaC02 severinghaus electrodce pH: uses 2 electrodes or half cells Pa02: Clarck (polaropgraphic) electrode (galvonic fuel cell)
What are the derived values? Sa02, HC03, BE/BD you need co-oximetry to measure true Sa02
ABG analysis process? Verify order and follow procedure document procedure analyze sample follow lab documentation procedure
Quality assurance accreddidation JCAHO, College of American Pathologists
Purpose of quality assurance to prevent innaccuracies
Components of quality assurance record keeping, performance validation, preventative maintenance, automated calibration, calibration verification, remedial action, documentation
Created by: kparkerlehman