Card Set Information
Problems with the PCO2 electrode!
Degradation and Protein contamination of membrane slows diffusion of CO2 across membrane
Routine maintenance is important
Problems with PO2 electrode!
Electrode contamination and degradation – alters diffusion of O2
Depletion of electrolyte
Tip must be “polished” periodically
PCO2 electrode measures CO2 by!
CO2 is hydrated in electrolyte and forms H ions, voltage develops proportional to CO2
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)
What devices are used to measure Hb?
What are the two forms of Hb that a pulse ox can measure?
O2Hb and reduced Hgb (RHb)
Some factors that might cause a pulse ox to read inaccurate?
Drift with colibration!
difference between current & previous calibrations
Indicates electrode’s stability
When and where are you more likely to get a vein instead of an artery?
More likely in hypotensive patient & with femoral artery puncture
Isolated result outside of control limit
Should be observed carefully, but disregarded
Recurrent measurable deviation away from the mean
Progressive measurement either increasing or decreasing
Causes – aging electrode, protein contamination
Relatively abrupt change in measurement followed by a cluster or plateau
Causes – bubbles on sensor tip, temp change, contaminated calibrants
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
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
Most heat skin site to 40-45 C ̊to arterialize capillary blood flow: ↑temp - ↓response time
Why is Transcutaneous monitoring done?
Continuous monitor of oxygenation and ventilation
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
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
Air in sample!
If PaO2 < 158mmHg, air bubble will cause PaO2 to increase
If PaO2 > 158mmHg, air bubble will cause PaO2 to decrease
Mixed venous blood!
Mixed venous – average of all venous blood returning to the heart
Obtained from a catheter in the pulmonary artery
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
Recommended amount of heparin!
0.05 mls per 1.0 ml of blood sample
What is the primarily result of too much heparin?
Excessive volume causes decrease in CO2 and ↓pH
What sample is more vournable to heparin?
PCO2 and infants
What are the effects of metabolism on blood gases?
Decrease in pH
Decrease in PaO2
Increase in CO2
Room temp blood gases should be analyzed within...
Iced samples blood gases should be analyzed within...
Effects of temperature on normal blood gases!
↑temp → ↑PaO2 and ↑PaCO2
Both should be reported
Problem: Normal blood gases at various temps are unknown
Which electrode is least accuracte?
Measurement of unknowns (“blinded samples”) & comparing with other labs using same method (interlaboratory)
Provides measure of absolute accuracy of laboratory
Degree of dispersion or scattering of values from the average
During transportation (ice slush for more uniform cooling if delay >30 minutes)
Incorrect therapy or documentation
Failure to mix sample
Failure to allow time for analysis to “end-point”
•Importance of “read back”
Posting to wrong patient
Failure to report “critical” values
Redraw, repeat on another analyzer if necessary!!!
Standards for RC departments and Pulmonary Labs guidelines!
2013 patient safety goals!
IDENTIFY PATIENTS CORRECTLY
IMPROVE STAFF COMMUNICATION
USE MEDICINES SAFELY
IDENTIFY PATIENT SAFETY RISKS
PREVENT MISTAKES IN SURGERY