chapter 19

The accuracy of pulse oximetry reading is usually within ______ of invasive hemoximetry readings

+2% to 4%

How many electrodes are used to measure the three primary parameters?

3

Patients with healthy lungs achieve their steady-state in how many minutes?

5

Normal range for venous O2 saturation

60% to 80%

What should your sample size be for capillary sampling?

75 to 100 mcl or 0.075 to 0.1 mL

Most clinicians consider pulse oximeter readings unreliable at saturations less than _______

80%

which procedures provide more accurate data but carry greater risk?

Invasive Procedures

volumetric capnography is the graphic display of?

CO2 VS expired Vt that allows for the measurement of physiologic dead-space fraction & volumetric CO2 secretion

Capnometry is the measurement of

CO2 in respiratory gases

Capnography is the graphic display of

CO2 levels VS. time as they change during breathing

Access for ABG sampling from a intravascular line is provided by?

a three way stop cock

Venous blood gases (VBG) are obtained from?

central venous cath or PA cath which can access both the superior vena cava & a main branch of the PA

blood samples for most point of care analyzers should not be ____ and ran within how many minutes after being obtained?

chilled, & obtained within 1-2 minutes

End-tidal PCO2(PETCO2) is used to estimate _______ and normally averages _____________

estimate dead space ventilation normally averages 3 to 5 mmhg less than PaCO2

SaO2 measures are obtained by

hemoximetry

Infection & thrombosis are more likely with?

indwelling catheters

Why would a clinician used both invasive & noninvasive approaches together?

invasive to establish the patients baseline and then noninvasive for ongoing monitoring of the patient

Capnometers use what two different methods to sample the respiratory gases

mainstream sampling and sidestream sampling

important transmission-based and safety precautions

never recap a used needle without a safety device Never handle a used needle using both hands Never point a used needle toward any part of the body Never bend, break, or remove used needles from syringes by hand Always dispose of used syringes, needles, and other sharp items in appropriate puncture-resistant sharps containers

Blood gas monitoring: Transcutaneous blood gas monitoring provides?

noninvasive estimates of arterial PO2 & PCO2 through a skin sensor

Name the primary analytes or parameters in a blood sample that are measured with a ABG

pH CO2 PO2

Modified allen test cannot be performed on who

patients who are unconscious or uncooperative

Patients with unhealthy lungs achieve their steady-state in how many minutes?

require up to 30 minutes

The accuracy of blood gas testing depends on what?

rigorous quality control

Capillary sampling is used as an alternative to direct arterial access in?

small children & and infants

Random error

sporadic out of range data points occur errors of precision

hypoxemic patients are routinely given.......

supplemental O2

Point of care testing

takes blood gas analysis from the lab to the patients bedside

Performance validation is the process of?

testing a new instrument to confirm accurate measurements

What is the recommended site for capillary punctures for infants younger than 1 month old to avoid nerve & bone damage?

the heel

Blood gas monitors are a bed side tool that can provide measurements either continuously or at appropriate intervals without taking a blood sample. Name the two of the most common blood gas monitors?

transcutaneous blood gas monitoring and tissue O2 monitoring

regarding problems with interpreting pulse oximetry data the most important issue is to ?

treat the patient not the monitor. assess the patient & make sure their assessment actual matches the data represented.

Systemic error

trending or an abrupt shift in data points outside the statistical limit unaccuracy

In neonates what is cannulated for ABG sampling?

umbilical artery

A sample obtained from a warmed capillary site is often referred to as?

arterialized blood

In most cases, what size sample volume when collecting an ABG is considered adequate?

0.5ml to 1 ml

The actual sample volume of an ABG depends on what 3 things?

1. anticoagulant used 2. requirements of the specific analyzer 3. whether other tests will be performed on the sample.

What are the two major problems areas associated with arterial puncture?

1. difficulties getting a good sample 2. pre-analytic errors

Most pre-analytic errors when obtaining an ABG can be avoided by doing what 3 things?

1. getting all the air bubbles out (anaerobically sampling) 2.properly anticoagulant 3. and quickly analyzed

What are the most common technical errors in capillary sampling?

1. inadequate warming of capillary bed 2. squeezing of the puncture site

PROBLEM SOLIVING & TROUBLESHOOTING O2 ANALYZER: Name the common causes of analyzer malfunctions and how to troubleshoot these issues

1. low batteries (replace batteries 1st when troubleshooting) 2. sensor depletion (replace it) 3. electronic failure (taken out of service & repaired)

Other factors that can affect Pulse Oximetry accuracy includes?

1. poor peripheral circulation 2. motion artifact 3. ambient light 4.nail polish 5. dark skin pigments

Name the three indications for obtaining an ABG

1. the need to evaluate 2.need to assess the patient's response to therapy or diagnostic test 3.need to monitor the severity and progression of a documented disease process

How do you calibrate an O2 analyzer

1.expose sensor to 100% O2 2. expose other sensor to room air

Response time for O2 analyzers range from

10-30 seconds

standard deviation of what is used?

2

What is considered the Golden standard?

ABG

Name the contradictions for obtaining an ABG

Abnormal modified allen test not through an lesion or distal to surgical shunt anticoagulant therapy

When collecting a capillary sample is PO2 of any value and why?

No, PO2 is of little value in estimating arterial oxygenation. O2 saturation by pulse ox must be used

Gas exchange between the lungs and blood analyzed by measuring what?

O2 & CO2 levels in arterial blood

Name Phase 2-3 of a Normal capnogram

PCO2 levels rise sharply (2) and plateaus as alveolar gas is exhaled (3)

Name Phase 1 of a Normal capnogram

PCO2 zero at the start of expiratory breath

Name the two common types of electrochemical O2 analyzers

Polargraphic (clark) electrode & the galvanic fuel cell

To measure PO2 , blood gas analyzers use what electrode?

Polarographic

PROBLEM SOLIVING & TROUBLESHOOTING O2 ANALYZER: The best way to avoid problems is through?

Preventive maintenance. scheduled parts replaces, and routine operational testing

SPO2 measures are obtained by

Pulse oximetry reading

Which artery is the preferred site for ABG sampling and why?

Radial 1. its near suface & easy to palpate & stabilize 2. effective collateral circulation 3. not near any large veins

The most common route for indwelling catheters is?

Radial artery

To measure CO2, blood gas analyzers use what electrode?

Severinghaus

Blood gas Monitoring: The two most important factors when using a transcutaneous blood gas monitor?

age & perfusion status

Capillary sampling (if successful) provides useful estimates of ?

arterial pH & PCO2 levels