Ch. 11 - Quality Assurance in the Pulmonary Function Laboratory Flashcards

Accuracy and precision
Terms Definitions
_______ _______ is one aspect of quality assurance.
quality control
what often determines the specific procedures that are required for calibration and QC?
type of equipment used
what does the type and complexity of instrumentation for a specific test determine?
long/short term maintenance (replacing disposable items)
what are 2 other kinds of maintenance?
preventative and corrective
what are essential for a comprehensive maintenance program?
procedure manual; accurate records
a _______ is any known test signal for an instrument that can be used to determine its accuracy and precision. _________ _______ are test subjects for whom specific variables have been determined.
control; biologic controls
what is a primary means of ensuring data quality?
control procedures by which data are obtained
what are the 2 concepts that are central to quality assurance?
accuracy; precision
_______is defined as the extent to which measurements of a known quantity results in a value approximating that quantity.
accuracy
_______ is defined as the extent to which repeated measurements of the same quantity can be reproduced.
precision
the _______ observed value, rather than the _____, is often reported as the best test.
largest; mean
_________ _______is accuracy determined by measuring an unknown control and comparing the results with a large number of laboratories using similar equipment and methods.
proficiency testing
_________ is the process in which the output signal from an instrument is adjusted to match a known input.
calibration
in computerized systems, th signal produced by the spirometer is often corrected by applying a software __________ ______.
calibration factor
syringes used for calibration should be accurate to within +/-___ ml or +/-___% of the stated volume.
15; 0.5
what is an important distinction of QC with calibration?
calibration may not be needed, QC always is
a syringe of at least __-L volume should be used to generate a control signal for checking spirometers.
3
what is maximum acceptable error for spirometers?
+/- 3.5% or +/- 65 ml (whichever is larger)
volume-displacement spirometers should be checked in __-L increments across their volume range.
1
___________ ________ are also available for assessing the accuracy of commonly measured parameters such as FEV1 and FEF 25%-75%.
computerized spirometry
________ _______ are healthy subjects who are available for repeated tests.
biologic controls (lab personnel or others)
what is a disadvantage of biologic controls?
pulmonary function varies from day to day
to provide useful statistics, ___-___ sets of measurements should be recorded.
10-20
the __________ ___ _________ may be calculated by dividing the SD by the mean; __________ ___ __________ may also be calculated.
coefficient of variation; coefficient of repeatability
____-____ ______ _____ produce a biphasic volume signal. what does it do?
sine-wave rotary pumps; checks volume/flow accuracy for I and E
what devices incorporate large-volume syringes with a computer-controlled motor drive?
computer-driven syringes
_________ ___________ _______ simulates the exponential flow pattern of a forced expiratory maneuver. what is a the primary advantage?
explosive decompression devices; flow/volume signals reproduced
_____ ______ should also be performed on volume-based spirometers daily before assessing volume accuracy.
leak checks (>30 mL/min significant)
the _____ _______ from a spirometer should be <1.5 cmH2O up to flows of 14 L/sec.
back pressure
__________ ________ refers to the spirometer's ability to produce accurate volume and flow measurements across a wide range of frequencies. what is this most critical for?
frequency response; PEF and MVV maneuvers
a ________ may be used in conjunction with an adjustable compressed gas source to supply a gas at a known flow to the device.
rotameter (water-seal type does this too)
______ _______ or _________-__________ ______ of spirometry are required for diagnostic functions, validation, or when waveforms are to be measured manually.
printed records; computer-generated displays
analyzers should be calibrated to match the __________ _______ over which measurements will be made.
physiologic range
what is the most common technique for analyzer calibration and what does it involve?
two-point calibration; introducing 2 known gases
what are the two points for?
1. "zero" - low end 2. "span" - high end
the nonlinearity of each of the analyzers should be ___% or less of the full scale.
0.5
what must be included when calculating the dilution of the test gas?
volume of air in the syringe connectors (dead space)
what are 2 methods for verifying analyzer performance?
1. as dilution is analyzed, meter reading recorded, plotted against expected % 2. simulate lung volume or DLCO tests
a _____ _______ is simply an airtight container of known volume.
lung analog
a _____ ________ uses precision gas mixtures to allow repeatable DLCO measurements at different levels.
DLCO simulator (3rd method)
what is the 4th method of evaluating gas analyzers?
testing biologic controls (simplest means of checking systems that depend on accurate analysis)
how is calibration of mouth pressure transducer done?
connect it to water manometer or similar device that generates accurate pressure (+/-50 cmH2O, freq 8 hz or mroe)
what is an accurate measure of pressure in a box pressure transducer?
+/- 0.2 cmH2O
what is ideal for box calibration?
adjustable sine-wave pump connected to small syringe
how may the pneumotachometer (flow sensor) be calibrated?
apply known flow or known volume
with what is QC of plethysmographs accomplished?
isothermal lung analog, fixed resistors, biologic controls
what is measured to have a simple but effective mean of checking plethysmograph function?
VTG, RAW, both from biologic control subjects
what is another method of checking plethysmograph accuracy?
compare VTG w/ FRC determined by gas dilution (0.90; >10% - equipment malfunction)
a "____" gas is used to zero or balance each electrode. a "____" gas is used to adjust the gain of the electrode's amplifier.
low; high
the PO2 electrode is usually calibrated over a range of ______ mmHg. PCO2 range: _______; pH uses buffers with values or _____ (low) and _____ (high).
0-150; 40-80; 6.84; 7.38
the difference in calibration is termed ____ and indicates an electrode's stability.
drift
systemic errors can sometimes be masked by _________ _________. ___________ of the calibration gases or buffers is a common example.
automatic calibration; contamination
________ ______ are sufficient for ensuring proper functioning of sensors such as optodes, spectrophotometers, or fluorescence quenching devices.
electronic checks
what are the 2 methods of QC for blood gas analysis?
1. tonometry of whole blood 2. commercially preparded controls
______ is ideal for QC of gas electrodes because its viscosity and gas exchange properties are the same as those of pt samples.
blood
tonometry is the most precise control of the ____ _______.
PO2 electrode
what are the complications of tonometry?
contamination, improper temp control, inadequate gas flow
what are the 2 types of commercially prepared controls?
1. aqueous 2. fluorocarbon-based emulsions
what is one problem with aqueous controls?
poor precision of PO2
what is necessary to detect blood gas analyzer malfunction?
interpreting "control runs"
a QC value that falls within +/-__ SDs of the mean is usually considered to be "in control."
2
the normal variability that occurs when multiple measurements are performed is called _______ _____.
random error
a widely used set of rules is that proposed by ________. this approach to QC is termed the _________-____ ______.
westgard (detects errors); multiple-rule method
rules 1 and 2 detect marked changes in electrode performance, sometimes called a _____, by examining how far from the mean a single control value falls.
shift
when using the multiple-rule method, always keep a ________ _______.
Control history
how many levels of control materials are normally used to provide adequate QC for a blood gas analyzer?
3
_____________ _________ _________ consists of comparing unknown control specimens from a single source in multiple laboratories.
interlaboratory proficiency testing
what is the three primary uses of criteria of acceptability of PFT?
1. basis for decision making 2. evaluate validity 3. score/evaluate technologist
how should you examine tracings or graphics?
compare the observed tracing with the characteristics of acceptable curve/pattern
the decision to perform additional maneuvers is usually based on __________.
Repeatability
what are the key indicators for spirometry?
start-of-test and duration of effort
what are the key indicators for gas dilution lung volumes?
absence of leaks and test duration
what are key indicators for DLCOsb?
inspired vols and breath-hold times
what is an important component of quality assurance for PFT?
scoring/grading the quality of the test
what is a key component for obtaining valid data, particularly in tests that require pt instruction and encouragement?
well-trained and high motivated technologist
what also should be provided from the technologist?
feedback
what are the standard precautions that should be applied in the pulmonary function and/or blood gas lab?
1. treat ALL as contaminated 2. exercise care to prevent injuries 3. protective barriers 4. wear gloves 5. wash hands
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