4. Measurements of lung function provide an
assessment of the severity, reversibility,and
variability of airflow limitation, and help
confirm the diagnosis of asthma in patients
older than 5 years.
Lung Function Measurements
5. Lung Function Measurements
• Changes in lung function over time
(Spontaneously or in response to therapy)
- Spirometry (FEV1, FVC, and their ratio)
- Peak expiratory flow rate
(PEFR or “peak flow”)
• Airway hyperresponsiveness to stimuli
- Methacholine challenge test
- Exercise challenge test
8. Breathing Tests
Spirometry Testing:
lung volumes in/out,
lung flow of air in/out
Peak Flow Monitoring:
lung flow of air in/out
9. What is a Peak Flow Meter?
A peak flow meter is a device, which records
the peak or maximal flow during a forced
expiratory manoeuvre (PEFR = Peak
Expiratory Flow Rate).
In other words, a peak flow meter measures
how fast air can be expelled from the lungs.
10. The peak expiratory flow (PEF), also called
peak expiratory flow rate (PEFR) is a person's
maximum speed of expiration, as measured
with a peak flow meter, a small, hand-held
device used to monitor a person's ability
to breathe out air
What is a Peak Flow Meter?
13. Peak Flow Meters
A portable device that can help measure air
flow in and out of the lungs
May not be useful for children under the age
of 5
Can be a good indicator of air flow in and
out of the lungs in those over age 5
14. Peak Expiratory Flow Rate
(PEFR)
Normal Values:
Normal values vary based on a person's age,
sex, and height.
Peak flow measurements are most useful
when a person compares the number on a
given day to his or her "personal best."
15. Peak Expiratory Flow Rate
(PEFR)
Normal Values:
Normal values are related to the patient's
height as follows:
An easy to remember approximation is:
PEFR (L/min) = [Height (cm) - 80] x 5
16.
17. The average range for an adult for peak flow
lies between PFR 450 (EU) and PFR 600 (EU)
Because the peak flow depends on age,
gender, race and height, the measured result
is compared to that predicted for a person’s
age, gender, and height, using special charts
and the measurement is compared with what
would be expected.
18. Measurements must be compared against a
recognised chart of normal values, but
perhaps more importantly as a comparison
against the individual's normal range.
19. Peak Flow measurement
Minimum of 3
acceptable blows
Standing position is
preferred
Nose clip not
necessary
No cough
Blow duration 1 to 2
seconds
20. Your "personal best" peak flow rate is the
highest peak flow rate you can reach over a two-
to three-week period when you feel good and
have no asthma symptoms.
This flow rate serves as a benchmark in your
daily self-management plan.
Because everyone's asthma is different, your
personal best will be unique to you.
Determining your personal best
21. To determine your personal best, Typically,
you'll take readings twice a day for two
weeks when you're not having symptoms.
The highest consistent reading during the
trial period is your "personal best" peak flow
rate.
Determining your personal best
22. To take a peak flow reading: put the marker to
zero, take a deep breath, seal your lips around
the mouthpiece, then blow as hard and as fast
as you can into the device, Note the reading.
Repeat three times. The 'best of the three' is the
reading to record on the chart
22
23. When recording a peak flow result, the three
readings should be within 20 litres per
minute of each other; if not the peak flow
rate recording should be repeated up to five
times.
23
24. Hannah uses her peak flow meter every morning and evening.
This helps her see how well she is breathing.
25. Peak Flow Diary
First #________ Second #________ Third #________
200
250
300
350
400
450
500 1
3
5
7
9
11
13
15
17
19
Day
PeakFlow
26. When peak flow is being monitored regularly,
the results may be recorded on a peak flow
chart.
It is important to use the same peak flow
meter every time.
Peak flow values are best if they are checked
at the same time each day, preferably once in
the morning and again at night.
27. The results are effort-dependent and physician
participation/encouragement may be necessary
to obtain usefully accurate readings
The best of three readings should be determined
Always try and obtain a baseline peak flow
reading prior to any treatment, because
patients/physicians tend to clinically under-
estimate the degree of airway obstruction
28.
29.
30.
31. a two-week diary of peak flow readings done by
a child who has quite bad asthma
31
32. PEFR
Lowest in the morning
Highest at night
Careful instruction is required
Effort dependent
33. To find your personal best peak flow
number, take peak flow readings:
1. Twice a day for two to three weeks when
asthma is in good control
2. At the same time in the morning and in the
early evening
3. You should always use the same peak flow
meter, and disregard any readings that
are very different from the rest
34. Your personal best PEF is important because it
is the number to which all of your other peak
flow readings will be compared.
Daily measurements are compared to personal
best PEF
Your asthma action plan, developed along with
your asthma doctor, is based on this number.
35. Once you have determined your personal
best PEF, work with your asthma care
provider to determine at what point you
should start taking quick-relief drugs to
relieve an asthma attack or seek emergency
medical attention. These are called your
asthma peak flow zones.
All of this information should be recorded in
your personal asthma action plan.
36. The color coded zones on a peak flow meter are
similar to the signals on a traffic light
representing safety, caution and danger, which
is an indication of whether an individual’s
asthma is under control.
37. PEFR Zones
Red: Below 50% of Personal Best
Yellow: 50% to 80% of Personal Best
Green: 80% to 100% of Personal Best
38. Treatment plan based on PEF
and/or on symptoms
Red Zone (severe deterioration)
Take supplementary medications
Go to emergency if no response
Yellow Zone (deterioration)
Take supplementary medications
Green Zone (control of asthma)
Take regularly prescribed treatment
39. Green Zone
PEFR (Peak Expiratory Flow Rate) 80% to 100%
of personal best.
You should be relatively symptom free and can
maintain your current medical regimen.
If you are on chronic medications and peak
flow is constantly in the green zone with
minimal variation, your physician may consider
gradually decreasing your daily medication.
40. Yellow Zone
PEFR 50-80% of personal best. "CAUTION" -
asthma is worsening. Acute exacerbation may
be present
A temporary increase in asthma medication is
indicated. If you are on chronic medications,
maintenance therapy will probably need to be
increased. Contact your physician to fine-tune
your therapy
41. Red Zone
PEFR below 50% of personal best.
"DANGER" - asthma control is failing.
Use your inhaled bronchodilator. If peak
flows do not return to the yellow zone,
contact your physician immediately, as you
must employ aggressive therapy under
medical direction.
45. PEFR Zones
Green: 80%-100% of personal best
– Routine treatment can be continued; consider
reducing medications
Yellow: 50%-80% of personal best
– Acute exacerbation may be present
– Temporary increase in medication may be needed
– Maintenance therapy may need increases
Red: Less than 50% of personal best
– Bronchodilators should be taken immediately; begin
oral steroids; clinician should be notified if PEF fails
to return to yellow or green within 2 – 4 hours
46. As a tool, individual PEFR readings must be
viewed as a trend and in collaboration with
other data rather than a single measurement.
It is important to know that your peak flow
meter only measures the amount of airflow
out of the large airways of the lungs.
47. Changes in airflow caused by the small
airways (which also occur with asthma) will
not be detected by a peak flow meter.
Therefore, it is important for you to also be
aware of your symptoms and early warning
signs to best manage your asthma.
48. Asthma Action Plan
a) is a guide for physicians to act based on changes in
the patient’s severity of asthma
b) is a written self-management guide for patients to
make adjustments to their asthma treatment
c) is a set of written instructions based on age groups of
the asthma patients
d) is developed by the patient based on his own
response to treatment
e) should be memorized by patients so that they can act
quickly without the need to refer to written
instructions.
48
49. Written asthma action plans
Mini peak flow meters are inexpensive and have an
important role in educating patients about their
asthma.
Using home recordings, the doctor or nurse and
patient can work together to develop plans with
criteria that indicate the need for a change in
treatment, a visit to the doctor, or emergency
admission to hospital.
49
50. Written asthma action plans
This management plan should be written down for the
patient and should be reviewed periodically.
The peak flow can help the patient to interpret the
severity of symptoms and need for help.
It should be based on the patient’s best known peak
flow value
Abort exacerbations by timely stepping up of
reliever and preventive medication50
52. Modern PEF meters are relatively inexpensive,
portable, plastic, and ideal for patients to use in
home settings for day-to-day objective
measurement of airflow limitation.
53. The severity of asthma is reflected not only
in the level of baseline airflow limitation, but
also in its variability, particularly across 24
hours .
Ideally PEF should be measured first thing in
the morning when values are usually close
to their lowest and last thing at night when
values are usually at their highest.
54. Normal Asthma
Circadian Changes in PEFR
Morning peak flow
Evening peak flow
PEFR(%Predicted)
100%
50%
100%
50%
PEFR recorded twice-daily over 2 weeks
55. Daily Variability of PEFR
PEFR at night – PEFR at morning
-----------------------------------------------x 100%
½ (PEFR at night + PEFR at morning)
56. One method of describing diurnal PEF
variability is as the amplitude (the difference
between the prebronchodilator morning
value and the postbronchodilator value from
the evening before), expressed as a
percentage of the mean daily PEF value
58. Another method is the minimum morning
prebronchodilator PEF over 1 week, expressed
as a percent of the recent best (Min%Max) .
This latter method has been suggested to be the
best PEF index of airway lability because it
requires only a once daily reading, it correlates
better than any other index with airway
hyperresponsiveness, and the calculation is
simple.
60. Measurements are lowest in the AM, and
highest in the evening
The magnitude of peak flow variability is
generally proportional to the severity of the
disease
Daily Variability of PEFR
61. A diurnal variation in PEF of more than 20
percent is considered to be diagnostic of
asthma, the magnitude of the variability
being broadly proportional to disease
severity
In mild intermittent asthma or in severe
intractable disease, variability in PEF may
not be present or may be lost.
62. In more severe asthma, diurnal variation and
reversibility may not be a feature until after a
trial of glucocorticosteroids.
Even then, the more severe forms of the
disorder may take many weeks of treatment
before reversibility becomes apparent.
64. Monitoring of asthma treatment
Zone
PEF
(% of best)
Daily variability
of PEF
Green > 80% < 20%
Yellow 50-80% 20-30%
Red <50% >30%
65. Classification of Severity
CLASSIFY SEVERITY
Clinical Features Before Treatment
Symptoms Nocturnal
Symptoms
FEV1 or PEF
STEP 4
Severe
Persistent
STEP 3
Moderate
Persistent
STEP 2
Mild
Persistent
STEP 1
Intermittent
Continuous
Limited physical
activity
Daily
Attacks affect activity
> 1 time a week
but < 1 time a day
< 1 time a week
Asymptomatic
and normal PEF
between attacks
Frequent
> 1 time week
> 2 times a month
2 times a month
60% predicted
Variability > 30%
60 - 80% predicted
Variability > 30%
80% predicted
Variability 20 - 30%
80% predicted
Variability < 20%
● The presence of one feature of severity is sufficient to place patient in that category.
● Patients at any level of severity –even intermittent asthma –can have severe attacks.
67. Measuring PEFR in a patient with asthma is
analogous to measuring blood pressure with a
sphygmomanometer or blood glucose to guide
insulin dosage.
The PEFR is used by the physician to assess the
severity of asthma as a basis for adding medication,
monitoring response to chronic therapy, and
detecting deterioration in lung function before
symptoms develop.
67
68. The physician may consider more
aggressive therapy if the patient’s highest
PEFR value is less than 80 percent of
predicted value and/or daily variability is
more than 20 percent.
68
69. It is recommended that clinicians consider peak
expiratory flow rate monitoring for patients over
5 years of age with moderate or severe asthma.
Regular home monitoring may detect decreased
lung function and signs of an impending asthma
episode before it becomes more severe.
69
71. Peak expiratory flow (PEF) measurements can
be an important aid in both diagnosis and
monitoring of asthma.
PEF measurements are ideally compared to the
patient’s own previous best measurements
using his/her own peak flow meter.
Why do we do peak flows?
72. Why do we do peak flows?
For diagnostic purposes
Comparison to normal/predicted values
Reversibility testing – bronchodilator and
corticosteroid
Peak flow diaries – diurnal variation and serial
peak flows
Exercise challenge tests
To monitor control of asthma
– Prn monitoring
73. Peak expiratory flow measurement is
recommended for:
1) Diagnosis:
– Diurnal variability of peak expiratory flow rate
greater than 20% for at least three days in a week
for two weeks is typical of asthma.
– Or improvement in peak expiratory flow:
10 minutes after high-dose bronchodilator through
a spacer.
After a six-week course of inhaled steroids.
After 14 days of 30 mg prednisolone.
74. GINA 2011
Although spirometry is the preferred method
of documenting airflow limitation, an
improvement of 60 L/min (or ≥ 20% of the pre-
bronchodilator PEF) after inhalation of a
bronchodilator, or
Diurnal variation in PEF of more than 20%
(with twice-daily readings, more than 10%),
suggests a diagnosis of asthma.
75. PEF measurement may be of use not only in
establishing a diagnosis of asthma and
assessing its severity but also in uncovering
an occupational cause for asthma.
When used in this way, PEF should be
measured more frequently than twice daily
and special attention paid to changes
occurring inside and outside the workplace.
76. 2. Assessment of the response to treatment.
3. Monitoring:
– The use of peak flow recording in monitoring
asthma must be part of an individual
management plan for the patient.
– Regular home monitoring of PEF is sometimes
useful because it can help patients detect early
signs of asthma deterioration , particularly in
patients with poor perception of symptoms..
77. – Quality of life indicators may be as good as
peak flow for predicting exacerbations:
Have you had any asthma symptoms during the
day
Any difficulty sleeping because of symptoms
Has the asthma interfered with usual activities,
eg work, school
78. Although long-term PEF monitoring for most patients
with persistent asthma can be valuable and may be an
ideal, this is not always be possible for reasons of
cost, cooperation, and availability of peak flow meters.
Long-term monitoring is particularly recommended for
those patients with severe asthma, for those with poor
perception of severity, and for those who have ever
been hospitalized.
79. Not a stand-alone tool
Peak flow monitoring should not be used as a
substitute or stand-alone tool for monitoring
asthma severity.
It should be used in conjunction with symptom
assessment, which is the first and simplest
means of monitoring.
Peak flow monitoring is an objective tool to
confirm subjective ‘perceptions’ of an
individual’s asthma.
80. Limits on usefulness
Because PEFR is dependent on the level of
client effort and because it may be more
sensitive to large airway than small airway
narrowing, its usefulness may be limited in
some populations, e.g. young children or
individuals who are not highly motivated to
give their best effort. Always do a ‘best of
three’ reading.
Spirometry measuring FEV1 is more
sensitive to minor narrowing of the airways.
81. Limits on usefulness
Note: PEFR Values may vary up to 20%
above and below any given value and still be
‘normal’.
The level of symptoms is an important
factor to take into account when determining
asthma severity.
82. Due to the wide range of ‘normal' values and
high degree of variability, peak flow is not the
recommended test to identify asthma, however,
it can be useful in some circumstances.
When regular peak flow monitoring is
recommended, it is usually done in addition to
reviewing asthma symptoms and frequency of
reliever medication use.
Limits on usefulness
83. PEFR - Pros and Cons
Advantages
– With in 1 to 2 minutes,
– Inexpensive (meter costs less than Rs.1000)
– Simple, useful for frequent follow up use
Disadvantages
– Very much effort dependent
– Insensitive to small changes
– Small airways cannot be assessed
– Large inter & intra subject variation;↓accurate
85. Interpretation of peak flow
Normal peak flow
Normal airways!
Well controlled or stable asthma
Mild COPD and asymptomatic smokers
Early restrictive lung disease (Can sometimes
be raised)
86. Interpretation of peak flow
Reduced peak flow
Upper airway obstruction e.g. Bronchial Ca,
goitre.
Obstructive airways disease e.g.asthma, COPD
Advanced restrictive lung disease e.g.UIP, FA
Chest wall abnormalities e.g. scoliosis,
neuromuscular disease
87. PEFR! What is it?
Maximum flow rate
during a forced
expiration.
Indicator of airflow
obstruction , Primarily
measures large airway
function
Peak flow is an effort
dependant test
PEFR are different for
everyone. They are
based on age, sex and
height
Useful in diagnosis and
monitoring of asthma
and diurnal variation
Not as useful in COPD
89. Peak expiratory flow rate measurements are not
as accurate as the spirometry measurements
Spirometry is the preferred method of measuring
airflow limitation and its reversibility to establish
a diagnosis of asthma.
90. Particular encouragement to record peak flow
should be given to:
1. Poor perceivers, in whom symptoms do not reflect
changes in objective measured obstruction
2. Patients with a history of sudden exacerbations
3. Patients with poor asthma control
4. Times of adjustment in therapy, either up or down
5. Situations where a link to a precipitating factor is
suspected
6. Periodic recordings in stable asthma to establish
usual levels and confirm reliability of symptoms
90
91. Use of diary cards
Although acute attacks of asthma occasionally have a
sudden catastrophic onset, they are more usually
preceded by a gradual deterioration in control, which
may not be noticed until it is quite advanced.
A few patients, probably around 15-20%, will be
unaware of moderate changes in their airflow
obstruction even when these occur acutely; these
patients are at particular risk of an acute exacerbation
without warning.
91
92. These patients, They should be encouraged to
take regular peak flow recordings and enter
them on a diary card to permit them to see
trends in peak flow measurements and react to
exacerbations at an early stage before there is
any change in their symptoms.
92
93. Written asthma action plans
Mini peak flow meters are inexpensive and have an
important role in educating patients about their
asthma.
Using home recordings, the doctor or nurse and
patient can work together to develop plans with
criteria that indicate the need for a change in
treatment, a visit to the doctor, or emergency
admission to hospital.
93
94. Question 1
Complete the following:
A variation of serial peak flow readings over
a two week period are considered diagnostic
in . . .
a) . . . asthma.
b) . . . COPD.
c) . . . pneumonia.
d) . . . tuberculosis
94
95. Correct answer:
a) . . . asthma.
Feedback:
Variation of more than 20% of the best peak
flow with a minimum change of at least 60
litres/minute for three days in a week over a
two week period is considered diagnostic of
asthma.
95
96. Question 2
For patients with asthma, how many times a
day should a peak flow reading be taken?
a) Daily.
b) Twice a day.
c) Three times a week.
d) Once a week.
96
97. Correct answer:
b) Twice a day.
Feedback:
The British Thoracic Society recommends
twice daily readings for patients with
asthma, morning and evening
97
98. Question 3
Peak flow meters record:
a) the lowest rate of air expelled from the
lungs through an open mouth.
b) forced expiratory volume.
c) forced vital capacity.
d) the highest rate of air expelled from the
lungs through an open mouth.
98
99. Correct answer:
d) the highest rate of air expelled from the
lungs through an open mouth.
Feedback:
Peak flow meters record the highest rate at
which air can be expelled from the lungs
through an open mouth
99
100. Question 4
When recording peak flow results, within
how many litres/minute should the three
readings be?
a) 10 litres per minute of each other.
b) 20 litres per minute of each other.
c) 100 litres per minute of each other.
d) 30 litres per minute of each other.
10
0
101. Correct answer:
b) 20 litres per minute of each other.
Feedback:
When recording a peak flow result, the three
readings should be within 20 litres per
minute of each other; if not the peak flow
rate recording should be repeated up to five
times.
10
1
102. Quiz Practice
Which is true regarding Peak Expiratory Flow
(PEF)?
I. Primarily measures large airway function
II. Is a recognized means of monitoring asthma
III. Serial measurements of PEF are used a guide to
treat asthma
IV. When less than 50% of personal best, it is an
indication that immediate treatment is required
a. I only
b. II and III
c. II, III, and IV
d. I, II, III, and IV
