1. Problems with the PCO2 electrode!
    • Degradation and Protein contamination of membrane slows diffusion of CO2  across membrane
    • Electrolyte depletion
    • Routine maintenance is important
  2. Problems with PO2 electrode!
    • Electrode contamination and degradation – alters diffusion of O2
    • Depletion of electrolyte
    • Tip must be “polished” periodically
  3. PCO2 electrode measures CO2 by!
    CO2 is hydrated in electrolyte and forms H ions, voltage develops proportional to CO2   
  4. PO2 Electrode measures O2 by!
    O2 is reduced; electrons flow from anode to cathode proportional to # of molecules of reduced O2  , current is measured (amperometric)
  5. What devices are used to measure Hb?
    • Oximetry
    • Co Oximetry
    • Hemoxitry
  6. What are the two forms of Hb that a pulse ox can measure? 
    O2Hb and reduced Hgb (RHb)
  7. Some factors that might cause a pulse ox to read inaccurate?
    • Vascular dyes
    • Nail polish
    • Skin pigment
    • Ambient light
  8. Drift with colibration!
    • difference between current & previous calibrations
    • Indicates electrode’s stability
  9. When and where are you more likely to get a vein instead of an artery?
    More likely in hypotensive patient & with femoral artery puncture
  10. Random errors!
    • Isolated result outside of control limit
    • Minor significance
    • Should be observed carefully, but disregarded
  11. Systemic errors!
    Recurrent measurable deviation away from the mean
  12. Trending errors
    • Progressive measurement either increasing or decreasing
    • Causes – aging electrode, protein contamination
  13. Shifting error!
    • Relatively abrupt change in measurement followed by a cluster or plateau
    • Causes – bubbles on sensor tip, temp change, contaminated calibrants
  14. Precision!
    • Extent to which repeated measurements of same “known” can be reproduced
    • Defined in terms of variability based on standard deviation (SD) of a series of measurements
    • Index of dispersion of repeated measurements
    • Indicated by pattern of “hits” at a target
  15. Accuracy!
    • Extent to which a “known” results in value approximating that “known”
    • Mean of repeated measurements approximates “known”
    • Or, how closely measured results reflect the true / actual value
    • Problems are usually characterized by systematic errors
    • Indicated by closeness to the “bull’s-eye” of a target
  16. Transcutaneous monitoring!
    Most heat skin site to 40-45 C ̊to arterialize capillary blood flow: ↑temp - ↓response time
  17. Why is Transcutaneous monitoring done?
    Continuous monitor of oxygenation and ventilation
  18. Precautions for Transcutaneous monitoring!
    • Move electrode every 2-6 hours to prevent burns especially in neonates
    • Both sensors require calibration & periodic recalibration (q 2-6 hours)
    • 5-30 minutes warm-up may be required for equilibration after sensor placement
    • Can trend oxygenation when PaO2-PtcO2 gradient is established
    • Close correlation in neonates, patients with normal cardiac output
  19. Leukocyte Larceny
    • Patients with severe leukocytosis (Leukemia) will demonstrate very fast metabolic changes (↓PaO2)
    • Samples from such patients should be drawn in glass syringe, iced, analyzed immediately
  20. Air in sample!
    • If PaO2 < 158mmHg, air bubble will cause PaO2 to increase
    • If PaO2 > 158mmHg, air bubble will cause PaO2 to decrease
  21. Mixed venous blood!
    • Mixed venous – average of all venous blood returning to the heart
    • Obtained from a catheter in the pulmonary artery
  22. How can you identify an mixed venous sample!
    • Suspected when patient’s clinical status is better than ABGs suggest
    • Crosscheck with pulse oximeter or ask another therapist to obtain a new sample
  23. Recommended amount of heparin!
    • Lithium heparin
    • 1000 U/ml
    • 0.05 mls per 1.0 ml of blood sample
  24. What is the primarily result of too much heparin?
    Excessive volume causes decrease in CO2 and ↓pH
  25. What sample is more vournable to heparin?
    PCO2 and infants
  26. What are the effects of metabolism on blood gases?
    • Decrease in pH
    • Decrease in PaO2
    • Increase in CO2
  27. Room temp blood gases should be analyzed within...
    30 minutes
  28. Iced samples blood gases should be analyzed within...
    2 hours
  29. Effects of temperature on normal blood gases!
    • ↑temp → ↑PaO2 and ↑PaCO2 
    • Both should be reported
    • Problem: Normal blood gases at various temps are unknown
  30. Which electrode is least accuracte?
  31. Proficiency Testing!
    • Measurement of unknowns (“blinded samples”) & comparing with other labs using same method (interlaboratory)
    • Provides measure of absolute accuracy of laboratory
  32. Standard devation!
    Degree of dispersion or scattering of values from the average
  33. Preanalytical errors!
    • During puncture
    • During transportation (ice slush for more uniform cooling if delay >30 minutes)
    • Wrong patient
    • Sample Handling
    • Incorrect therapy or documentation
  34. Analytical errors!
    • Failure to mix sample
    • Failure to allow time for analysis to “end-point”
  35. Postanalytical errors!
    • Transcription
    • Verbal reports
    • •Importance of “read back”
    • Posting to wrong patient
    • Failure to report “critical” values
    • Correct interpretation
    • Redraw, repeat on another analyzer if necessary!!!
  36. Standards for RC departments and Pulmonary Labs guidelines!
  37. 2013 patient safety goals!
Card Set
Test three