analysis of abg samples l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Analysis of ABG Samples PowerPoint Presentation
Download Presentation
Analysis of ABG Samples

Loading in 2 Seconds...

play fullscreen
1 / 18

Analysis of ABG Samples - PowerPoint PPT Presentation


  • 862 Views
  • Uploaded on

Analysis of ABG Samples. ABG Analysis, Introduction. pH, PaCO 2 , PaO 2 are measured directly by special electrodes contained in a device made for that purpose Other indirect measurements can be made or calculated from the above measurements i.e., HCO 3 - , O 2 Sat. pH.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Analysis of ABG Samples' - august


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
analysis of abg samples

Analysis of ABG Samples

SVCC Respiratory Care Programs

abg analysis introduction
ABG Analysis, Introduction
  • pH, PaCO2, PaO2 are measured directly by special electrodes contained in a device made for that purpose
  • Other indirect measurements can be made or calculated from the above measurements i.e., HCO3-, O2 Sat.

SVCC Respiratory Care Programs

slide3
pH
  • pH electrode is constructed of two half cells, which develop an electrical potential when connected together
  • Reference electrode maintains a constant potential and is bathed in KCl
  • Glass electrode (Sanz electrode) develops an electrical potential that is proportional to the amount of H+ present

SVCC Respiratory Care Programs

paco 2 electrode severinghaus
PaCO2 Electrode (Severinghaus)
  • Measures carbon dioxide tensions by allowing the CO2 gas to undergo a chemical reaction that produces hydrogen ions
  • The hydrogen ion concentration produced is directly proportional to the PCO2 in contact with the membrane of the electrode
  • Operates on the principle of electric potential between electrodes
  • CO2 + H2O H2CO3 H+ + HCO3-

SVCC Respiratory Care Programs

o 2 electrode clark
O2 Electrode (Clark)
  • Is a polarographic device that measures oxygen tensions by oxidation/reduction reactions, a chemical process that generates measurable electrical currents
  • Has platinum cathode and silver anode immersed in an electrolyte solution
  • Volume of O2 will be directly proportional to the number of electrons used in the cathode rxn. and by measuring current ∆ is a measure of O2 diffused across membrane

SVCC Respiratory Care Programs

qa in blood gas analysis
QA in Blood Gas Analysis
  • ABG lab must be able to assure accurate and reliable results
  • The above is accomplished by applying protocols in 3 areas: - pre-analytic error - calibration - quality control

SVCC Respiratory Care Programs

pre analytic error
Pre-analytic Error
  • All factors that cause variance in lab results prior to the sample arriving in the ABG lab.
  • 4 factors assoc. with signif. P. E. are: - air bubbles in sample

- time delay (iced sample with more than 60 min. or uniced with more than 10 min.)

- blood clots in sample

- small sample size where excessive anticaogulation is suspect

SVCC Respiratory Care Programs

calibration
Calibration
  • Purpose is assure consistency
  • Def.: the systemic standardization of the graduation of a quantitative measuring instrument
  • Calibrating standards for blood gas analyzers should simulate the physical properties of blood and meet manuf. specs.
  • When 2 standards are used ---> 2-point calibration, performed after 50 blood gases or at least every 8 hours

SVCC Respiratory Care Programs

calibration cont d
Calibration (cont’d)
  • A “one-point calibration” is an adjustment of the electronic response of an electrode to a single standard and is performed more freq. than a 2 pt. cal., ideally prior to each sample analysis

SVCC Respiratory Care Programs

ph calibration
pH Calibration
  • Several types of buffer solutions are acceptable for pH electrode calibration
  • Buffers are excellent standards because of their long shelf life and stability for days after being opened
  • 2-point cal. of pH electrode is done by setting the “slope” potentiometer to a low pH buffer (6.84) and setting the “balance” potentiometer with a near-normal buffer (7.384) with an accuracy of +/- 0.005

SVCC Respiratory Care Programs

paco 2 calibration
PaCO2 Calibration
  • PaCO2 electrode may be calibrated by introducing a known gas concentration
  • Gases used are 5% and 10% CO2, +/- .03% - 1-point cal. uses 5% standard to set the “balance” point - 2-point cal. uses 5% for “balance” point and 10% for “slope” point
  • PCO2 = (BP - 47 mmHg) x %CO2

SVCC Respiratory Care Programs

po 2 calibration
PO2 Calibration
  • Properly calibrated PO2 electrodes perform within the manuf. stated accuracy in PaO2 ranges below 150 mmHg but may vary 20% at 500 mmHg
  • 0% oxygen is used for the “slope” point and 12% or 20% for the “balance” point
  • PO2 = (BP - 47 mmHg) x % O2

SVCC Respiratory Care Programs

quality control
Quality Control
  • Refers to a system that documents the accuracy and reliability of the blood gas measurements and is essential to assure accuracy in the blood gas lab
  • Media available as blood gas controls include:

- aqueous buffers

- glycerin soltn.

- human/animal serum and blood - artificial blood

  • A QC system must ID problems and specify corrective action, document. of accept. oper.

SVCC Respiratory Care Programs

qc cont d
QC (cont’d)
  • Documentation of QC is usu. on Levy-Jennings Chart which shows measured results on the y axis versus time of measurement on the x axis
  • SD is used to summarize a mass of data: the difference between a number in a data set and the mean of the data set is called a deviation. A deviation shows how much a number varies from the mean

SVCC Respiratory Care Programs

qc cont d15
QC (cont’d)
  • A properly functioning electrode that repeatedly analyzes a known value will produce results within a rel. small range, e.g., a PaCO2 electrode that analyzes a 40 mmHg standard 100 times will produce results where 2/3 of the measurements are 39 - 41 mmHg and nearly all measurements fall in 38 - 42 range
  • 95% of the control measurements should fall within 2 SD

SVCC Respiratory Care Programs

qc cont d16
QC (cont’d)
  • Random errors indicates a value outside of 2 SD of the mean: a single random error has minor signif., but if number increased the machine and techniques must be evaluated
  • Systematic errors is recurrent measurable deviation from the mean
  • Causes of systematic errors:

- contaminated standard

- variations in electrode temp.

- inconsistent introduction of standard

SVCC Respiratory Care Programs

qc cont d17
QC (cont’d)
  • Causes of systematic error (cont’d) - inconsistent calibration technique - change in QC standard storage or prep. - electrode problems, e.g., protein contamin., membrane malfunction, contamin. electrolyte, or electrical problems

SVCC Respiratory Care Programs

qc levels
QC Levels
  • Level 1 simulates a patient hypoventilating
  • Level 2 simulates a patient with normal ventilatory status
  • Level 3 simulates a patient hyperventilating

SVCC Respiratory Care Programs