Download pft training workshop - Indian Chest Society

INDIAN CHEST SOCIETY
SPIROMETRY MANUAL - 2013
By
Dr.Vijayalakshmi Thanasekaraan,
Sri Ramachandra Medical College and Research Institute
Porur, Chennai 600 116.
CONTENTS
Topics
INTRODUCTION
OVERVIEW OF PULMONARY ANATOMY AND PHYSIOLOGY
MEASUREMENT DEVICES
MEASUREMENS OBTAINED BY SPIROMETRY
INDICATIONS AND CONTRAINDICATIONS
PREDICTED NORMAL VALUES
REPRODUCIBLITY CR
TESTING TECHNIQUE
ACCEPTABILITY CRITERIA ITERIA
INTERPRETATION
QUALITY ASSURANCE
INFECTION CONTROL
CALIBRATION
SPRIOMETRY PITFALLS
PEFR
2
Why Spirometry ?
“Spirometry is the most basic and important of tests that measure pulmonary
function. It is easily performed and highly reproducible.”
David Prince, MD and James Fish MD
Journal of Respiratory Diseases, 1988.
“The performance of Spirometry serves as an essential function in the prevention,
diagnosis, observation and therapy of Chronic Obstructive Pulmonary Disease”.
Philip Herber, MD., MPH
3
INTRODUCTION
Spirometry assess the overall mechanical functions of the lung, chest wall and
respiratory muscles. Spirometry is a test in which we can measure only the functions
of the lung and not the structure of the lung as is being viewed in X-ray.
Spirometry is a non-invasive simple, effective test to measure the “lungs functions”.
Spirometer is a special device used to measure the functions of the lungs.
Hutchinson first developed the spirometer in 1846.
Spirograms are tracings or
recordings of the information obtained from the tests. The spirometric
measurements are dependent on the correct technique, accuracy of the spirometer,
performance of the correct breathing maneuver and the use of relevant predicted
normal values.
Considering the importance of respiratory diseases on public healthcare and the
economy, it is clear that spirometry deserves a lot more attention as it is a simple
and an inexpensive test.
Spirometry is important in the diagnosis and follow-up of asthma, COPD and
certain other respiratory diseases.
Staff performing the spirometry should first attend a comprehensive training course.
This is important because inadequate training will result in poor quality spirometry,
which is of little clinical value.
This Manual will help to improve the knowledge and techniques of those who are
involved in performing and interpreting spirometry in clinical practice, i.e. medical
practitioners and assisting staff.
In the main text the important facts about types of spirometers, how the test is being
actually performed and interpreted and some of the common pitfalls and problems
that are faced during performing the spirometry are covered.
4
ANATOMY AND PHYSIOLOGY OF THE RESPIRATORY SYSTEM
ANATOMY OF THE RESPIRATORY SYSTEM:
The respiratory system consists of the respiratory tract, the chest wall (with the
diaphragm and intercostal muscles), bronchial
circulation, the pulmonary
circulation and central nervous system.
The respiratory tract consist of the upper and lower respiratory tracts. The upper
respiratory tract consists of the nose, oral cavity, pharynx and the larynx. The lower
respiratory tract consists of the tracheobronchial tree, right and left lung. The
tracheobronchial tree consists of series of branching airways commonly known as
generations or orders of bronchioles. These airways progressively becomes narrower
and shorter and more numerous as they branch throughout the lungs.
After a total of about 23 divisions, the bronchioles end at alveolar ducts. Each
alveolar duct ends in clusters of alveoli (alveolar sac).
5
Major
structures and
corresponding
Generations of
the
Tracheobronchial Tree are as follows:
Structures Generations Trachea 0
Main stem bronchi
1
Lobar bronchi
2
Segmental bronchi
3
Subsegmental bronchi
4‐9
Bronchioles
10‐15
Cartilaginous airways
Conducting Zone
Non‐Cartilaginous airways
Terminal Bronchioles
16‐19
Respiratory Bronchioles
20‐23
Alveolar ducts
24‐27
Alveolar sacs
28
Site of gas exchange
Respiratory Zone
6
Blood Supply:
The lung is supplied by Bronchial arteries and Pulmonary arteries.
Bronchial artery arises from the aorta and follows the tracheobronchial tree as far as
the terminal bronchioles. Beyond the terminal bronchioles, the bronchial arteries
lose their identity and merge with the pulmonary arteries and capillaries, which are
part of the pulmonary vascular system.
Pulmonary circulation is involved in cardiac output and oxygenation of the blood.
These blood vessels in turn branch into smaller units, ending with capillaries, which
are in direct contact with each alveolus (Respiratory Unit).
Gas exchange occurs through the alveolar membrane. The air we breath contents
oxygen, carbondioxide and nitrogen. Oxygen moves from the alveoli into the blood
stream in exchange for carbon dioxide which moves out of the bloodstreams into
the alveoli. The alveoli have a surface area, for gas exchange, that is equivalent to
the size of a tennis court.
Physiology of the Respiratory System:
The main function of the respiratory tract is the exchange of gases (oxygen from the
air is exchanged with carbon dioxide in the blood).
If there is any change in the anatomy or physiology of the respiratory tract, there
will disturbance (changes) in respiratory function i.e exchange of gases. The
respiratory function is affected at three levels:
The disturbance can occur due to
1. Disturbance of ventilatory function,
2. Disturbance of pulmonary circulation or
3. Disturbance at gas exchange level.
7
Ventilation:
The word ventilation is defined as the process by which gases (air) moves between
the external environment and the alveoli.
Ventilation consists of inspiration (inhaling) and expiration (exhaling).
The
contraction of the inspiratory muscles (principle inspiratory muscle is the
diaphragm) causes the chest cavity to expand, creating a negative pressure. The
resulting flow of air into the lungs is called inspiration and it is an active process.
Expiration is a passive process resulting from the contraction of abdominal muscles
causing recoil of the of the expanded lung and chest wall.
Ventilatory function can be assessed (tested) with the help of Spirometer. This
manual deals with the measurement of ventilatory functions.
MEASUREMENT DEVICES
Spirometer and Peak flow meter
Spirometer is an instrument which measures the volume of air that is contained in
the lung and also the rate at which the gas is expelled from the lungs. Hence, the
information that can be obtained by performing the spirometry is the Volume and
Flow rate of gases. Lung volume provides information on the size of different
compartments of the lung; flow rate provide information on the rate of airflow
within the airways.
Spirometry is performed by using a spirometer, The tracings are called spirograms.
Types of spirometers:
There are 2 types of spirometers:
1. Volume spirometer
2. Flow spirometer.
8
Volume Spometers:
Volume spirometer records the forced expiratory maneuver as it is produced. The
water seal, dry rolling seal and bellows spirometers are the three most commonly
used types f volume spirometer. It holds at least 8 liters volume of air and hence is
bulky. They hold their calibration for months to years, hence there is no need to
calibrate it daily or in -between patients.
The tracing records volume in relation to time.
Flow Spirometers:
Flow spirometers measures as to how quickly air flows through a detector
and then it derives the volume by electronic means. The most common types of flow
spirometers are the pneumotachographs, hot wire anemometers, rotating vanes and
ultrasonic spirometers.
9
Flow spirometers are
usually light and are more portable than volume
spirometers.
The spirogram tracings, measure flow in relation to volume. Tracings are not
produced during actual maneuver but are reconstructed afterwards from
computerized information that has been recorded.
MEASUREMENTS :
LUNG VOLUMES & CAPACITIES:
Tidal Volume ( VT) : The volume of air that normally moves in and out of the lungs
during one quiet breath.
Inspiratory Reserve Volume (IRV): The maximum volume of air that can be inhaled
after a normal tidal volume inhalation.
10
Expiratory Reserve Volume (ERV): The maximum volume of air that can be exhaled
after a normal tidal volume exhalation.
Residual Volume (RV): The amount of air remaining in the lungs after maximal
exhalation.
Vital Capacity(VC): The maximum volume of air that can be exhaled after a
maximal inspiration (IRV+VT+ERV).
There are two major VC measurements:
•
•
Slow Vital Capacity(SVC), in which exhalation is performed slowly.
Forced Vital Capacity (FVC), in which maximal effort is made to
exhale as rapidly as possible.
Inspiratory Capacity(IC): The volume of air that can be inhaled after a normal
exhalation (VT + IRV)
Functional Residual Capacity (FRC): The volume of air remaining in the lungs after
a normal exhalation (ERV + RV)
Total Lung Capacity (TLC): The maximum amount of air that the lungs can
accommodate (IC + FRC)
Residual Volume / Total Lung Capacity Ratio (RV / TLC X 100): The percentage of
the TLC occupied by the RV)
MEASUREMENTS DIRECTLY OBTAINED BY SPIROMETRY
Spirometers measures lung volumes and airflow rates. The essential lung volumes
that can be recorded with simple spirometry are
FVC – Forced Vital Capacity
The FVC is defined as the maximum volume of air which can be exhaled as
forcefully and rapidly as possible after maximal inspiration
Peak Expiratory Flow (PEF)
It is the maximum expiratory flow that
is achieved from maximum forced
expiration from the point of maximal inspiration. (Expressed in liters/seconds.)
11
Forced Expiratory Volume in 1 second (FEV1)
Defined as the volume of air which can be forcefully expired during the first second
of expiration and is expressed in liters.
FEV1 / FVC %:
This is a calculated value. It is the Forced expiratory volume in 1 second, as a
percentage of forced vital capacity.
The ratio expresses the volume of air that the patient exhales in the first second, of
the total volume of air that he/she exhales.
FEF 25-75% (Forced Expiratory Flow) or (MMEF)(Maximum Mid Expiratory Flow)
FEF (25-75%) is Forced expiratory flow during the middle half of the FVC
The FEF25-75% is defined as the average rate of flow during the middle two quarters
of the forced expiratory effort, i.e., from 25% to 75% of the vital capacity.
INDICATIONS AND CONTRAINDICATIONS FOR SPIROMETRY
INDICATIONS (WHY SHOULD WE DO THE SPIROMETRY TEST FOR A PERSON ? )
•
To obtain the baseline lung function measurements ( To find out the normal
lung function for that individual)
•
To confirm suspected diagnosis in lung disorders
•
To evaluate or assess the level of impairment ( how much the lung functions
are affected)
•
To assess the effectiveness of therapy ( how effective is the treatment given by
the doctor)
•
To assess the progress of the disease (how is the disease, is it improving or
getting worse)
•
To screen individuals at risk of having pulmonary disease
o Smokers
o Individuals in occupations with exposures to injurious substances.
•
12
•
To assess preoperative risk.
•
To assess patients as part of a rehabilitation program.
•
Bronchial provocation test
CONTRA INDICATIONS - (WHO SHOULD NOT UNDERGO A SPIROMETRY
TEST)
Patients suffering with
•
Nausea, vomiting and vertigo
•
Hemoptysis ( coughing out blood )
•
Pneumothorax
•
Recent abdominal / thoracic surgery ( operations of abdomen or chest)
•
Recent eye surgery
•
Recent Myocardial Infarction / Unstable Angina ( Recent heart attack)
•
Thoracic aortic aneurysms ( risk of rupture of the dilated large blood vessel
(aorta) of the chest )
•
Bleeding disorder
•
Tuberculosis (TB)
•
Severe head injury
WHAT ARE THE COMPLICATIONS OF DOING SPIROMETRY ?
Will the subject or person doing the test experience any problem while doing the
test ?
Subjects might experience:
1. Light headedness (slight headache)
2. After giving bronchodilator, subjects may develop bronchospasm or
palpitation.
13
PREDICTED NORMAL VALUES
Subject’s (one who performs the test i.e spirometry ) values are usually compared
with reference values as percentage predicted values. This percentage predicated
value is obtained from healthy normal populations through various studies.
For spirometric recording the following demographic details are necessary.
- Age
-
Height
-
Sex
-
Race
-
Weight
An appropriate reference value: for predicted normal values
An appropriate reference value (Knudson, Crapo and Miller) should be chosen.
Factors that affect the normal predicted values:
Four factors must be known to determine a predicted normal value- Age, Height,
Sex and Race.
1. Age:Lung volumes decline after age 25 for males and age 20 for females. As a
person gets older, the natural elasticity of the lungs decreases and the
lung volumes and capacities are reduced .
2. Height and body size:Tall and larger people have larger lungs than short people. Body size has a
tremendous effect on Pulmonary Function Test ( PFT ) values. A short and
small people will have a smaller PFT than a man of the same age who is
much larger or taller.
3. Sex:At a given age, males have larger lungs than females. Usually the lung
volumes and capacities are larger in males than the females.
4. Race:Race affects PFT values. Therefore the doctor and technicians must use
the appropriate reference values of a race to compare a patients
measured PFT values.
14
Normal reference for FEV1 and FVC values
For adults > 18 yrs old refer:
1. Knudson et al,ARRD – 1983: 127:725-734.
2. Morris, Koski and Johnson, ARRD - 1971;103:57-67
For Children <18yrs refer:
1. Polgar and Wang, ARRD – 1979;120:625-695
2. Hus et al, Paediatric-1979;95:14-23.
These referred predicted values are for Caucasian population.
Therefore for Indian population, multiply these predicted values of FEV1 and FVC
by 0.90.
Percent of predicted normal values:Percent of predicted values are used to determine how a subject’s test value is,
compared with normal population.
The test value is “abnormal” if the percent of predicted value is less than the
expected lower limit of normal.
Formulae for calculating percentage of predicted values:Observed FVC @ BTPS
% of predicted FVC = ------------------------------- X 100
Predicted FVC
Observed FEV1 @ BTPS
% of predicted FEV1 = ------------------------------- X 100
Predicted FEV1
15
TESTING TECHNIQUE
Spirometry should be performed by qualified Technicians.
Spirometry is totally patient effort dependent
Technique of performing spirometry:To get a good result the procedure should be explained in simple known
language known to the subject. The technician should demonstrate the procedure
himself/herself. Several times and good encouragement and explanation to the
patient is needed prior to testing.
Spirometric tests require the subject to exhale as forcibly as possible after
taking a full deep breath. This effort of the subject is called Forced Expiratory Effort
(Maneuver).
Technique for performing spirometry (breathing test):Enter the subject’s name, age, sex, height, weight and race in the computer.
1. Get the confidence of the subject by talking to him/her in a pleasing manner.
a. Greet the subject by saying “hello”
b. Explain to the subject the purpose of the test !
“This is to measure the maximum amount of air that he/she can
breathe in and out of the lungs and also to measure the speed (rate of
flow) of air that goes in and out of the lungs, after taking in a deep
breath”
2. Precautions to be taken before doing a test by the subject
a. Do not smoke for one hour before test
b. Do not drink alcohol within four hours of test
c. Do not eat a large meal within two hours of test
d. Do not perform vigorous exercise within 30 minutes of test
16
e. Do not use drugs like salbutamol / terbutaline for atleast 4hrs prior to
the test
f. Do not perform if there are contraindications to conduct the test
g. To avoid caffine containing products before the test
3. Subject preparation:a. The subject has to remove any loose dentures, and also if there are
light fitting dentures.
b. Loosen tight clothing
c. Nose clips may be applied
4. Positioning:a. Position to perform the test. Upright posture to be maintained.
i. Children below 6 years - standing position.
ii. Obese adults - standing.
iii. Adults - sitting.
b. Posture.
i. Elevate the chin and extend the neck slightly
c. Proper positioning of mouth piece.
Place the mouth piece about 1 inch deep inside the mouth. Bite
the mouth piece with the teeth and make an air tight seal with the help
of the lips. The tongue should not block the opening of the mouth
piece. The mouth piece is connected to a tube which is connected to
the spirometer.
17
d.
Testing procedure
While testing a patient, record her or his details as follows
1. Check for contraindications to testing
2. Record height and weight without shoes
3. If the patient is unable to stand or has dorsal spine deformity, measure
arm span (distance between right middle finger tip to left middle fingertip
with the arms outstretched).
4. Patient should be in sitting posture well supported and upright in a chair
both feet flat down on the ground.
“As the patient breaths in normally for 3 to 4 times, ask the patient to take a deep
breath to fill the lungs as much as he/she can. When he/she reaches the total lung
capacity immediately, ask the patient to blowout continuously to a point till his/her
lungs are almost empty. Then ask the patient to take a deep breath immediately
without a gap. After the procedure remove the mouthpiece.
Ask the Patient repeat to the same procedure few more times (maximum 8 times)
till he/she get an acceptable spirogram tracing.
Then, as per the advice of the doctor, an inhaled medication will be given and the
test will be repeated after 15 minutes. This is to find out whether the patient will be
benefited (Reversibility) with the medications.
Spirogram results are used to detect possible condition that affects subject’s ability
to exhale fully as forcefully as possible. The results are compared with the predicted
values. The goal of spirometry testing session is to obtain acceptable maneuvers and
a reproducible test.
The technician should NOT discourage the patient by saying “WRONG” or why
did you do like this?
18
NORMAL FLOW -VOLUME AND VOLUME-TIME CURVE
FLOW VOLUME LOOP
The flow-Volume Curve is a graphic analysis of
the flow generated during the FVC maneuver,
plotted against volume change. It is usually
followed by the Forced inspiratory volume
maneuver, plotted similarly. Flow is usually
recorded in liters per second and the volume in
liters, BTPS
Decrease in Flow-obstruction
Decrease in Volume - restriction
INTERRPRETATION OF FLOW VOLUME LOOP
Spirometry is used for screening and as an aid in the diagnosis of certain respiratory
disorders. The presence of ventilatory abnormality can be inferred if any of FEV1,
FVC, PEF or FEV1/FVC ratio are outside the normal range.
Some diseases cause obstruction to the flow of air in the respiratory system and
certain other diseases causes restriction, wherein the lungs cannot expand.
Flow volume loops show flow rate as the lung empties- the shape of the loop
depends on the mechanical properties of the lung.
Different diagnoses provide different shaped loops:
1. Normal- on exhalation there is a rapid rise to the maximal expiratory flow
followed by a steady uniform decline until exhalation is complete.
2. Asthma- typically the curve is a smooth concave shape as airway obstruction
is relatively constant throughout expiration.
19
3. COPD- typically the curve is angled or ‘kinked’ as COPD lungs collapse with
forced expiration.
4. Restrictive diseases- the curve is typically a normal height but with a very
steep gradient as the lung volume is diminished.
Examination of the shape of the flow-volume curve can help to distinguish different
disease states. Inspiratory curve and up to the peak of the expiratory limb is effort
dependent, whereas the slope of the expiratory limb is effort independent.
Spirometry results can be categorized as:
Normal
Restrictive ventilatory defects
Obstructive ventilatory defects
In obstructive patterns:
Flows are reduced.
Eg.Bronchial Asthma
In Restrictive patterns:
Volume is reduced. Eg.Kyphoscoliosis
Mixed patterns:
Both Flow and volume are reduced.
20
1. First look at FEV1 and FVC ratio. If ratio is normal look at FVC. If FVC is
normal look at FEF25-75%. If FEF 25-75% is normal then the spirometry is
Normal.
2. Look at FEV1 and FVC ratio. If the ratio is less look at FVC. If FVC is normal
then look at FEV1. If FEV1 is more than 95% of predicted then probably the
spirometry is Normal.
3. Look at FEV1 and FVC ratio. If ratio is normal look at FVC. If FVC is normal
look at FEF25-75%. If FEF25-75% is less than the predicted then spirometry
may be Normal or it may indicate Early Small airways obstruction.
4. Look at FEV1 and FVC ratio. If the ratio is less look at FVC. If FVC is normal
then look at FEV1. If FEV1 is less than 95% predicted then there is AIRWAY
OBSTRUCTION.
5. Look at FEV1 and FVC ratio. If the ratio is normal, then look at FVC. if FVC
is lower than the predicted value it is RESTRICTIVE.
6. Look at FEV1 and FVC ratio. If the ratio is less, look at FVC. If FVC is
decreased then it indicates MIXED OBSTRUCTIVE and RESTRICTIVE.
CLASSIFICAITON OF VENTILATORY ABNORMALITIES BY
SPIROMETRY
Values
FEVI
Obstruction
↓
FVC
↓
Or Normal
↓
FEV1/FVC
Restriction
↓
Or Normal
↓
Mixed
↓
Normal
Normal
↓
Normal
Normal or
↑
↓
Normal
21
CAUSES OF OBSTRUCTIVE PATTERNS:
1. Bronchial asthma.
2. Chronic obstructive pulmonary disease (includes chronic bronchitis and
emphysema)
OBSTRUCTIVE PATTERN - FLOW VOLUME AND VOLUME TIME CURVE
Severity of airway obstruction
Mild
Moderate
Moderately severe
Severe
Very severe
FEV1 (% of Pred)
≥ 70
≥ 60 and < 70
≥ 50 and < 60
≥ 34 and < 50
<34
22
COMMON CAUSES OF RESTRICTIVE PATTERNS:
1.
2.
3.
4.
5.
6.
7.
8.
Interstitial lung disease.
Idiopathic pulmonary fibrosis
Sarcoidosis/beryllium disease
Thoracic cage deformities such as kyphoscoliosis
Congestive heart failure
Neuromuscular disease
Obesity.
Poor effort.
RESTRICTIVE PATTERN - FLOW VOLUME AND VOLUME TIME CURVE
SEVERITY OF CHEST RESTRICTION
Mild
Moderate
Moderately severe
Severe
Very severe
VC (% of Pred)
≥ 70 but < LLN
≥ 60 and < 70
≥ 50 and < 60
≥ 34 and < 50
<34
23
MIXED PATTERN - FLOW VOLUME AND VOLUME TIME CURVE
UPPER AIRWAY OBSTRUCTION: ( upto larynx, trachea)
Fixed obstruction
24
REVERSIBILITY
Significant reversibility of airway obstruction - a change of 12% and >200ml in the
FEV1 following bronchodilator
Post BD - Pre BD
Calculating reversibility (%)= ________________ x 100 = % of change
Post BD
(BD –Bronchodilator)
25
QUALITY ASSURANCE IN PFT LAB
Spirometry is among the most useful and accurate measurement of lung function.
When not performed correctly, the values obtained can be misleading.
A good quality assurance (QA) program is essential to assure that spirometry results
are beneficial.
A)Components of a good Spirometry Quality Assurance program:
a) Procedure manual
b) Accurate spirometry equipment
c) Daily spirometry checks
d) Monthly spirometry quality reports
e) Equipment maintenance records
f) Technician training and review
g) Maneuver quality checks.
1. Daily spirometer accuracy checks:
Daily check for leaks and volume accuracy of the spirometer are needed. Lab
should keep accurate records of all equipment testing done for a leak
detection, calibration and maintenance.
2. A supervisor should review and grade the quality of all spirometry tests
(calibration check records). Monthly or quarterly reports or test session
quality (by technician ) are essential part of a spirometry QA program. At
least 95% of all tests should have acceptable quality. Supervision or
retraining of a technician is indicated when the over all spirometry test
quality falls below a 90% success rate.
3.
Equipment maintenance records:
For each Spirometer, maintain a quality log which records calibration checks,
maintenance, upgrade and repairs including date and time, name of the
technician, procedures performed and remedial steps taken.
26
4.
Technician training and review - well trained and competent technician is the
most important factor in good quality spirometry results.
5.
Maneuver quality checks:
Technician must coach each subject in performing acceptable maneuver and
recognize the patterns of poorly performed maneuver. He must know which
is the acceptable and reproducible maneuver.
B. Calibration checks and other equipment quality control measures
Spirometers are calibrated to record the true volume of air exhaled into them. If
their accuracy is not checked, errors will go undetected. Calibration checks must be
carried out with all types of spirometer as a daily routine and a log should be kept.
Additional calibration checks are needed if the ambient temperature changes during
the day or the equipment is moved.
A calibration syringe injects a known volume of air through the spirometer. The
spirometer should record within 3% of this known volume.
1. 1+/- 30ml for a 1-litre syringe
2. 1 +/- 90ml for a 3-litre syringe
The calibration of some spirometers can be updated if it is outside these limits.
Others must be returned to the manufacturer for recalibrating. The spirometer
should also be verified using a biological control usually a member of staff without
lung disease. The lung function values of the control are determined by daily
spirometry, at the same time of day over a two-week period and calculation of
The mean value for each spirometry parameter
The normal range ( +/-5% of the mean)
27
TERMINOLOGIES:
For purposes of spirometric testing, acceptable is defined as free from error.
Reproducible is defined as being without excessive variability when performed
several times.
At least three technically acceptable efforts should be obtained, ideally with less
than 0.15L variability for FEV1 and FVC between the highest and second highest
results.
Check Linearity of spirometer weekly:
This new procedure requires that a 3 liter syringe be used to deliver 3 constant flows
at a low flow rate, 3 at mid range flow rate , and 3 at higher flow rate. All flows must
result in 3 L readings with an accuracy of +3.5%.
Daily checks for volume accuracy of the spirometer are needed. Flow spirometer
should be checked for volume accuracy at 3 different flows every day before use.
Quality control for spirometry and flow volume measurements
This is a check done to test the technique and the equipment.
This should be done on a standard subject. A standard subject is one who is readily
available in the department, who is stable and has reasonably normal lung function.
The standard subject should be capable of generating a peak flow of at least
550L/min in order to test the instrument’s linearity
at high flows. The standard
subjects should be tested every 3 months and the FEV1 and FVC recorded. Prior to
performing this periodically on the standard subject, the normal range for the
subject should be determined. At least 10 acceptable tests over a period of several
days should be done. After doing the test, mean and standard deviation for FEV1
and FVC should be determined.
28
Quality control means checking the accuracy and/or precision of the device after
calibration.
If a known quantity of air measured by the spirometer approximates the known
value then the instrument is accurate. If the same parameter is measured repeatedly
and the consequent values are similar then the instrument is precise.
Acceptability Criteria 2005 (ATS – ERS)
Acceptable tests must meet the following 8 criteria:
1.
2.
3.
4.
5.
6.
7.
8.
Good start ( no back extrapolation error)
No cough during the first second
No early termination
No valsalva maneuver
No leak
No obstruction of mouthpiece
No extra breaths
Achieves a one second plateau after a 6 second or greater blow
Recommended EOT Criteria:
Slow Vital Capacity (SVC)-VC measurement is recommended prior to FVC
measurement-this is a new recommendation (ATS/ERS 2005.)
(Six second FVC) - A test duration (FET-Forced Expiratory Test)) of six seconds now
defines a good end of test-this means that the subject has tried to exhale for six
seconds. (ATS/ERS 2005 guidelines).
Problematic Examples compared with well- performed maneuvers
29
In case of repeating up to 8 trials but still if it does not meet ATS criteria, then report
the value as NOT meeting ATS criteria.
The repeatability criteria are used to determine when more than 2 acceptable FVC
maneuvers are need. DO NOT use these criteria to exclude the results from reports.
A repeatability criterion is a minimum requirement only.
30
Minimum 3 acceptable &
Reproducible trials (Flow
Volume)
Minimum 3 acceptable &
Reproducible trials (volume–time)
Reproducibility Criteria:
•
Obtain 3 acceptable tests, ie. Each test should meet the stated acceptability
criteria.
•
The two largest values for FVC should agree to within 0.15L
•
The two largest values for FEV1 should agree to within 0.15L.
31
Repeatability formula for FEV or FEV1.
(Highest value – 2nd highest value ) = Should NOT be more than 150ml.
32
This This acceptability and reproducibility effort obtained by spirometry is used for
interpreting the results.
EQUIPMENT MAINTENANCE (OR) REPAIR
Spirometer should have a routine maintenance schedule. Records should be kept
indicating the dates and description of maintenance.
RECORDS
Record should be kept for
1) Calibration
• Results
• Name of the person performing the calibrations
2)
Quality control
Results from standard subjects
3)
4)
Equipment manual
Patient results
• Date and time of procedure
• Name of the person performing the procedure
TECHNICIAN’S ROLE IN QUALITY CONTROL:
Quality control is important for any laboratory for standardization. The
technician’s performance should be continuously monitored for quality control.
Technician’s performance should be obtained from the feed back forms.
INFECTION CONTROL
Infection transmission via spirometry equipment is rare (Miller et al, 2005), but
sensible precautions must be taken to protect patients and staff. Patients with active
respiratory infection should not be tested unless it is essential for sound medical
reasons.
Disposble mouthpieces, nose clips and filters should be used, and one-way
mouthpieces reduce the risk of cross-infection via accidental inhalation through the
spirometer. Handwashing before and after using spirometry equipment and
33
between patients is one of the most effective methods of preventing infection.
Disposable gloves should be worn when handling mouthpieces.
It is essential that equipment is disinfected and sterilized regularly according to the
manufaturer’s instructions and local infection control policy. Keep a log book of
cleaning procedures and the date, time and details of patients tested on the
equipment. This will enable risk assessment and the tracing of patients should a
patient with active infection be inadvertently tested. Immuncompromided patients
must be tested on newly disinfected equipment.
I.
REFER TO YOUR USER MANUAL for manufacturer’s recommendations
regarding cleaning and calibration procedure appropriate to your instrument
II.
MOUTHPIECES
1) Preferably disposable
2) Preferably have a one way valve or a filter to prevent cross infection
III.
TURBINES /PNEUMOTACHS/ TRANSDUCERS
Extra should be available so that they can be cleaned and dried in- between
patients.
CLEANING
Cleaning for spirometers with transducers/ turbine / pneumotachs.
IV.
PROCEDURE;•
Disconnect and remove the transducer /turbine/ pneumotach holder from
the spirometer.
•
Immerse the transducer in the cleaning solution for 10 minutes
•
Rinse in cold running water
•
Wash transducer / pneumotach / turbine in detergent and rinse again in
running water.
•
Place transducer/ pneumotach /turbine in a towel and dry (DO NOT WIPE
DRY )
34
CHECK USER MANUAL FOR CLEANING ADVICE specific for your
Spirometer. Alcohol and chlorine solutions should be avoided.
FREQUENCY OF CLEANING
Clean the spirometer at least once monthly.
EQUIPMENT QUALITY CONTROL
A log of calibration check with date and time to be documented.
Documentation of repairs or any other alterations made If there is any change
in software or hardware.
SAFETY PROCEDURES:
1. Equipment precaution:
The major equipment precaution for the spirometry test are
prevention of electrical shock during the procedure to the patient /
staff.
2.
Infection control measures in spirometry lab: ( see previous page also)
A. Equipment.
1. The use of Pneumotachograph or other electric sensor can be easily
cleaned and sterilized.
2. Infection is prevented by rigorously cleaning and de- contaminating
periodically (weekly or monthly) or using disposable, low resistance
micro aerosol filter inserted between the subject and the spirometer to
prevent contamination.
3. Mouth pieces: Disposable.
4. Nose clips should be sterilized.
35
B. Personal protection.
1. Prevention of infection to Technician exposed to contaminated
spirometer surfaces through proper hand washing or use of barrier
devices (eg: latex gloves).
2. Avoid cross contamination, Reusable mouthpieces, breathing tubes,
valves, nose clips should be sterilized or disinfected regularly.
C. In settings where tuberculosis or other disease spread by droplet are
likely to be encountered, proper attention to environmental engineering
controls, such as ventilation, air filtration or ultraviolet decontamination
of air should be used to prevent disease transmission.
36
SPIROMETRY PITFALLS
Pitfalls of spirometry can be due to
•
•
•
•
Equipment
Technician
Patient
Physician
Equipment
•
•
•
Maintenance
Calibration
Environmental Engineering Control
Pitfalls of the technique and equipment related spirometry errors.
• Spirometry
- Quality
To be monitored
- Testing Technique
- Problems with equipment
Interpretation errors
•
•
•
•
•
•
•
•
Biological and environmental factors
Age,sex,standing height or race
Weight and BSA in children
Altitude
Place of testing
Smoking and other Environmental exposures
Normal Diurnal Variation
Abnormality of the test “Lower limit of the Normal”
Technical and methodological errors
•
Technician
- Well motivated, Enthusiastic, competent and should have Patience
• Equipment
- Different Technician & Different instruments
• Patient
- Effort and co-operation is very important
- Elderly and sick need to be motivated
37
Conclusion:
Spriometry must be performed correctly on well-maintained equipment and the
results should be accurately interpreted. Training is essential. Staff responsible for
spirometry testing must ensure they are competent for the task.
38
BRONCHIAL PROVOCATION TEST
Methacholine challenge
Histamine challenge
Cold
Do spirometry before and after challenge and find out whether there is a decrease in
the FEV1/FVC values of more than 20% from baseline. This helps in the diagnosis
of Bronchial Asthma.
SPIROMETERIC TESTS IN CHILDREN
Can be performed above the age of 6 years
Technician needs a lot of Patience
Clear and simple instructions to be given
Forced expiratory flow in children should be only for 3 seconds and NOT for 6
seconds as in adults.
39
PEAK EXPIRATORY FLOW RATE (PEFR)
This is a simple method of measuring airway obstruction and it will detect moderate
or severe diseases.
PEFR is the rate of measurement of the maximum flow of air that can be forcefully
expelled from the lungs after full inspiration. It is achieved in <10 milli seconds of a
forced expiration and it represents airflow from central conducting airways.
It is an effort dependent index of ventilatory function.
PEFR is measured with a hand held device called Peak flow meter.
There are 2 types of Peak Flow Meters
1. Original Wright’s Peak Flow meter.
2. Mini Wright’s peak flow meter.
In late 1950s, Martin Wright designed and produced the first meter to measure the
peak expiratory flow.
40
Mini Wright’s peak flow meter is available in various shapes and sizes.
The readings are from Zero to 800 L/mt
Normal values are related to the patients height is as follows:
Height (cm)
PEFR(L/min)*
120
215
130
260
140
300
150
350
160
400
170
450
180
500
*mean; SD = ±100
Ref: Monash University
An easy to remember approximation is:
PEFR(L/min)=[Height(cm)-80]X5
Significance of measuring PEFR:
1. Helpful in distinguishing restrictive from obstructive lung diseases.
2. To determine the diagnosis of bronchial asthma in asymptomatic
patients.
3. To point out as to what has triggered the Asthma attack, such as
Exercise Induced Asthma.
4. To assess the effectiveness of asthma medication and treatment plan.
41
5. To stop or add medication as per the advice of the Doctor.
6. Peak flow measurements can alert patients and doctor and It helps the
patient to seek emergency medical care
Contraindications for PEFR:
1. Hemoptysis
2. Acute Myocardial Infarction.
3. Aneurysm
4. Recent surgery in eye, heart, etc.
Normal Values:
¾ It depends on the age, sex and height of the individual.
¾ These values are greater in tall people, adults and males.
¾ PEFR is higher when patients are well and lower when the airways
(conducting tubes) are narrowed or obstructed as in Bronchial Asthma.
¾ PEFR readings are variable for same age group hence there is NO predicted
Comparable values. Hence the subject’s best effort becomes the BEST PEFR
reading (predicted value) for that person/ individual.
¾ A single PEFR reading is NOT helpful.
PROCEDURE FOR PERFORMING PEAK FLOW:
¾ PEFR should be taught by qualified technicians or technologist to the
patients.
¾ The technician should introduce himself or herself to the patient saying “
hello” I am so and so……….
¾ Tell the subject why the test is being conducted and taught.
¾ Tell that it has to be repeated 3 times to get the best results.
¾ Ensure that the subject is able to understand the technique and willing to
carry out the instruction as this is effort dependent.
42
EQUIPMENT REQUIRED:
Mini Wright Peak flow meter
Disposable mouthpieces.
Position of the subject - standing/ sitting up erect
Age –
Children above 6 years of age, teenagers and adults
STEPS:
¾ Wrights peak flow meter should be held horizontally by the subject in a
standing/sitting up erect position.
¾ The sliding pointer should be at zero level. The subject’s fingers should NOT
BE on the scale.
¾ The subject has to take a deep breath in and keep the mouth piece and lightly
bite and tightly seal with the lips.
¾ Then the subject has to blow out as hard and fast as he/she can.
¾ Then enter the reading where in pointer stops.
¾ Then reset the pointer to zero and repeat for another 2 times and select the
best of three readings.
¾ Then, if the Doctor wants bronchodilator reversibility testing to be done
he/she will order for PEFR to be repeated after giving medication by
inhalation. Then the subject will be given medication and PEFR repeated after
15 minutes in the above mentioned steps. This will help the Doctor to assess
the effect of medication.
¾ PEFR are often classified into three zones of measurements according to
American Lung Association.
43
¾ Green- Yellow- Red. The colour system is based on the colours of the traffic
lights.
ZONE
Green
Yellow
Red
READING
80-100% of the usual/
Normal.
Peak
flow
reading are CLEAR
Description
A PEFR reading in the green
zone indicated that the
asthma is under good
Control
50- 80% of the normal Caution is indicated. It may
peak flow.
mean that the respiratory
airways are narrowing and
additional medications may
be required.
Less than 50% of the It indicates medical
usual/ normal PEFR.
emergency. Severe airway
narrowing may be occurring.
Action to be taken
immediately.
As a general rule, the subject’s best effort (recorded during the remission days for
2-3 weeks) are noted and considered as personal best.
If Peak Flow values are 80% or more of the personal best it is normal.
If it is 50-80%
If< 50% of the best
Moderate obstruction
Severe obstruction
INFECTION CONTROL:
1. Hand washing of the technician before and after the insertion of the mouth
piece into the peak flow meter.
2. Disposable mouth pieces.
44
A FEW QUESTIONS ON PEFR:
¾ WHAT IS PEAK FLOW METER?
¾ WHAT IS A PEAK EXPIRATORY FLOW RATE (PEFR)?
¾ PEFR TECHNIQUE TO GET GOOD VALUES
¾ WHAT IS NEEDED TO GET A GOOD RESULT OF PEFR?
¾ WHAT ARE THE DEMOGRAPHIC FEATURES NECESSARY TO DO PEFR?
¾ DOES THE USE OF PEAK EXPIRATORY FLOW METER HAVE ANY SIDE
EFFECTS?
¾ IS IT DIFFICULT TO DO PEFR?
¾ WHERE ALL CAN YOU PERFORM PEFR?
¾ AT WHAT TIME OF THE DAY SHOULD PEFR BE DONE?
¾ CAN A PATIENT SUBJECT TO DO PEFR BY HIMSELF OR HERSELF?
¾ HOW MANY TIMES SHOULD ONE PERFORM PEFR?
¾ WHAT IS THE ADVANTAGE OF PEFR OVER SPIROMETRY?
¾ IS IT COMPARABLE WITH PREDICTED VALUE LIKE SPIROMETER?
¾ WHAT DOES PEFR RESULT TELL YOU?
45
SUMMARY
In order to obtain a good spirometric test result
1.
2.
3.
4.
5.
Explain the procedure to the subject
Demonstration the maneouver yourself
See how the subject inhales maximally
While performing the procedure, technician should actively coach
If the performance is poor, point it our politely to the patient
Technique for performing spirometry
1. Establish a good relationship with subjects
2. Collect the subjects demographic data and environmental data.
3. Explain briefly why the test is being performed
Reasons you might have to delay or postpone the test7
1.
2.
3.
4.
5.
Smoking
Heavy meal
Recent use of bronchodilator
Recent respiratory infection
Medical and surgical contraindication
References:
1. Niosh spirometry training guide January 23, 1997
2. Pulmonary function testing for clinicians by Virendra Singh. Indian asthma
care society. First edition 1999.
3. Spirometry. The measurement and interpretation of ventilator function in
clinical practice by Associate Professor David P. Johns.
4. Spirometry function procedure manual, National Health and Nutritional
examinational survey – III.
5. Monash University.
46
Acknowledgements:
The General Body members of Indian Chest Society (ICS).
The faculty, staff, technician and technologists of the department of Pulmonology,
Sri Ramachandra Medical College and Research Institute, Porur, Chennai 600 116.
47