Patients
with asthma frequently have poor
recognition of their symptoms and poor
perception of severity. Monitoring of coughing, wheezing, and
breathing patterns may be inaccurate or
incomplete in the assessment of the
severity of asthma. In ancient days, the
diagnosis and monitoring of severity of
various diseases was based on medical
history and examination. However, it
involved a lot of judgement error. Now,
we have handy tools which measure
severity of diseases accurately. A
thermometer, for example, measures
temperature and a glucometer, diabetes.
Breathing tests are now available to
measure severity of diseases with airway
obstruction, such as asthma. Breathing tests are done to
measure lung functions by spirometers or
peak flow meters. These tests provide
direct assessment of airflow limitation,
variability, and reversibility. These
measurements contribute to the diagnosis
and monitoring of the disease.
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Spirometer Test
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Spirometers measure amount and
rate of air a patient
can expel from lungs in single
breath i.e. vital
capacity,
forced vital capacity, and timed
measurements such as the forced
volume of air that can be
expired in 1 second (FEV1),
which is the best single measure
of lung function for assessing
airflow limitation
or asthma
severity.
Spirometers provide a
description of how well lungs
are functioning by measuring the degree of
impairment
of lung functions.
However, spirometers may be
cumbersome and expensive, and
thus used primarily in
clinic
and hospital settings for
diagnosis and long-term
monitoring of asthma. Adults and children over 5-6
years of age can easily perform
this test.
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Spirometers determine
the amount of air the lungs can hold and
the speed at which the air can be exhaled out of
the airway or bronchial tubes. Although
many asthmatic have normal lung volume,
their obstructed bronchial tubes prevent
air from being exhaled at a normal rate
of speed, and their rate or airflow is
abnormal. |
If the first set of
breathing tests show abnormal results,
the patient will be asked bronchodilater
drugs and repeat the test. Testing
the amount of air you can exhale in one second is the
most important test in asthma. If the second test show
more than 15-20 percent improvement in the one second
vital capacity, the diagnosis of asthma is almost
certain.
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Why
spiormetry is important ?
Pulmonary tuberculosis, pneumonia,
bronchiectasis, pneumoconiosis,
chronic obstructive pulmonary
disease (COPD) and bronchial asthma
are the common respiratory disease
prevalent in India. Asthma and
COPD are the most common cause of
death in rural India. Patient
suffering from infective
respiratory disease such as
tuberculosis and pneumonia are
cured after adequate anti
microbial therapy, but a sizeable
number of patients continue to
suffer from from fibrotic sequelae
of these disease. Apart from
these, there is going to be large
group potential respiratory
patient in future. They are the
person exposed to smoke, pollution
and various type of occupational
dust.
Clinical
examination and skiagram of chest
are poor indicators in diagnosis
and monitoring these disease. In
the disease of lungs and heart, a
skiagram of chest are poor
indicators in diagnosis and
monitoring of these disease. In
the disease of lungs and heart, a
skiagram of chest provides
information about anatomical
abnormalities, but not the
functional ones. To detect
abnormal heart beat,
electrocardiogram(ECG) is needed
and skiagram by itself is not
helpful. Similarly, to evaluate
lung functions, it is spirometry
that is important, not the skigram
of chest. In other words, "spirometry
is like the ECG of lungs".
How
can PFT improve care of
asthma patients?
A patient of asymptomatic
hypertension will continue therapy
only when explained the importance
of normal blood pressure
measurement. Similarly, a patient
of asthma and COPD should be
explained the importance of normal
pulmonary testing (PFT) before
stopping the treatment. Thus using
peakflow or spirometer in guiding therapy of asthma, COPD and other
non infectious diseases can
improve care of these patients and
reduce the mortality and
morbidity, there by displacing
COPD from the position of the top killer
disease.
Why
should every doctor know about
spirometry?
More than half of the population
of India suffer from respiratory
disease or are the potential
patient of these disease.
There\fore any doctor involved in
care of asthma, COPD or pulmonary
fibrosis should understand the
basics of pulmonary function
testing. Spirometer is
helpful in evaluating the level of
functional impairment, determining
reversibility of such defect and
distinguishing the pattern of such
impairment.
Why
has spirometry not been in common
practice?
Spirometry is an effort dependent
test which requires a great deal
of effort and persuasion of part
of both the patient and
technician. In absence of proper
training and effort, inadequately
done spirometry may give a
diagnosis of restrictive or
obstructive disease even in
healthy subject. Wrongly done
spirometry has undetermined the
importance of this valuable test.
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Peak
Flow Meter Test
Peak
flow meters record peak
expiratory flow rate (PEFR),
the fastest rate at which air can
move through the airways during a
forced expiration starting with
fully inflated lungs. The PEFR
correlates well with FEV1. Peak
flow meters are small, portable,
convenient and inexpensive devices which can be
used with just little bit
training. They They can be used
not only in hospital and clinic
settings but also in home and
office settings to help diagnose
asthma, assess its severity, and e valuate response to therapy. Peak
flow meters can further serve as
early warning systems because a
change in measurement from a
patient's norm can signal trouble
hours or even days before symptoms
are felt, early enough to take
action to prevent an attack. Healthy persons have good PEFR but
it gets reduced in presence of
asthma and reduction is
proportional to the severity of
asthma. Take a
test to know whether you are
using your peak flow meter
accurately or not?
PEFR
is used for diagnosis by first
comparing a patient's PEFR with
his normal or personal best PEFR
or with a predicted PEFR value.
The predicted values are provided
with all peak flow meters and are
adjusted for height, race, sex,
and age.
What
is Normal PEFR? And how it helps
in asthma diagnosis?
Peak
flow values depend on a number of
factors including your age, sex,
height and ethnic origin. Your
peak flow increases until you are
about 40 years old then decreases
after that time. There are
two kinds of 'normal' reading you
might come across; these are
outlined below.
Predicted
Peak Flow
Peak flow readings
have been taken on people who do
not have asthma, of different age,
sex and height and the same ethnic
origin. The readings obtained are
commonly used as a reference point
and are called predicted peak
flows. Your predicted peak flow is
based on the peak flow of someone
who is the same age, height, sex
and ethnic origin, but who does
not have asthma. The problem with
comparing readings to these
values, is that you can fall quite
a long way above or below your
predicted peak flow (which is an
average) and still be normal! This
is why it is much better to
compare your readings to your
personal best peak flow.
Personal
Best Peak Flow
There are wide variations in PEFR
of normal persons depending upon
age, sex, height and
socio-economic factors. Therefore,
an exact cut off point of PEFR
similar to body temperature is not
possible. Most useful index is to
measure "personal best"
PEFR. It is taken by recording
PEFR 3-4 times a day for several
asymptomatic days (when symptoms
of asthma are minimal) . The
highest reading in this record is
termed as the "personal best
PEFR" and considered normal
for that particular person.
A
PEFR lower than personal
best/predicted may indicate either
airway narrowing and airflow
limitation or a loss of lung
volume (which suggests a lung
disease other than asthma). A
diagnosis of asthma is also
indicated when:
- Reversibility
test is positive.
- PEFR variability is more
than 20%.
- There
is 15% or greater decrease in
PEFR after running or other
exercise.
What
is a Reversibility
test?
This is another application of a
peak flow meter. Magnitude of
increase in peak flow after
administration of bronchodilator
medicine is recorded. It is
expressed in percentage. More than
20% increase after bronchodilator
is diagnostic of bronchial asthma.
PEFR
variability throughout the day?
PEFR varies slightly at different
times of a day. The lowest PEFR is
recorded in the early morning and
the highest in the afternoon. The
difference of the highest and the
lowest PEFR expressed as a percent
of the lowest PEFR is termed as
diurnal PEFR variability. More
than 20% variability is diagnostic
of bronchial asthma. A high PEFR
variability is indicative of
increased severity of asthma.
Daily
PEFR monitoring for 2-3 weeks is
useful for establishing a
diagnosis (it helps identify
patterns of variability) as well
as for identifying environmental
triggers and guiding decisions for
therapy. The patient should record
PEFR readings at home for a short
period and report the results. The
peak flow readings provide
objective measurements of
variability and response to
therapy. If during a 2-3 week
period, the patient cannot achieve
80% of personal best/predicted
PEFR (even after taking a
bronchodilator), it may be
necessary to give a course of
corticosteroid tablets to achieve
a personal best PEFR for the
patient.
How
PEFR measurement is useful ?
PEFR measurement is useful in
following situations:
- When
diagnosis is not certain
If asthma is suspected, then
the disease can be confirmed by
recording PEFR regularly two
times a day. If PEFR variability
is more than 20 percent, asthma is
confirmed.
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asthma
diagnosis by peak flow meter
Example:
Ramesh, nine year old talented
boy, who was known by this
frequent admission to the local
hospital for his pneumonia. As a
matter of fact, whenever Ramesh
had a bad throat, he developed
cough, fever and breathing
difficulty, the doctor
always found him suffering with
pneumonia and got him admitted to
the hospital. After getting
treatment of glucose drip and
antibiotics, he used to recover
from mysterious disease diagnosed
as pneumonia. Lately,
on his last admission, a
pediatrician diagnosed him with
Bronchiolitis, which was still a
sinister disease.
Curiosity:
- Why doctors always found Ramesh
suffered with pneumonia?
- How the problem was solved?
The helpless
father took his son to an asthma
expert where Ramesh was correctly
diagnosed for asthma, by a simple
test peak flow meter.
Expert
comments:
Peak
flow meters is very helpful in
confirming suspectable asthma. If
Ramesh was again tested by
previous procedure his asthma
could
never have been confirmed.
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- How
to decide when
to reduce or stop drugs
Usually drugs of asthma are to be
taken for long duration but if you
feel alright and want to stop
medicines then measure your PEFR.
If it is within 10% of your
personal best and diurnal PEFR
variability less than 15% then
treatment can be reduced. First,
morning dose of the drugs is
reduced or stopped and if PEFR
stays normal then reduce or stop
the night dose.
- How
to assess severity of asthma
Severity of asthma can be measured
by two parameters of peak flow:
Reduction in PEFR and increase in
diurnal PEFR variability.
- How
to identify triggering factor of
your asthma
Daily record of peak flow taken in
morning and night gives an
accurate assessment of severity of
asthma. Lowered values of morning
peak flow on any day suggest
exposure to a trigger factor on
the previous day. The patient
should list the suspected trigger
factors during preceding 12 hours,
on the day of lower peak flow and
write in the chart. Such a list of
suspected factors prepared on days
of lower peak flow days are
screened periodically to search
common trigger factors. Repeated
appearance of a factor in the
chart confirms it as a trigger
factor of asthma.
Usually multiple factors are
responsible for aggravation of
asthma and a PEFR chart prepared
for few months would identify most
of them. By this method both
allergic and non-allergic trigger
factors can be identified. Allergy
skin testing identify only
allergic trigger factors.
- Problem
of under or over-sensing
Sometimes
an asthma patient does not
perceive symptoms of asthma and
stop medicines. But PEFR shows a
severe reduction, indicating a
severe disease. In such cases
medicine must be continued to
protect airways from permanent
damage in form of irreversible
airway disease. In absence of
symptoms such a patient becomes
victim of under-treatment which
may lead to fatality. Problem of
other extreme is oversensing
asthma problem. Some people are
more sensitive and even slightest
asthma symptoms are sensed as
grave emergency. Such patients
have to visit emergency department
repeatedly. These patients are
likely to be victim of
over-treatment. Both these
problems can be solved by making a
regular record of PEFR and making
therapeutic adjustments
accordingly.
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OVER-SENSING
MILD ASTHMA
Example:
A very renowned retired professor
of a university has got asthma
disease. The gentleman was very
methodical and particular about
mannerism. He had asthma at the
age of 59. Initially it bothered
him a little and slight cough and
chest tightness were the only
symptoms he was having. Then an
article was published in a
magazine that asthma mortality is
raising world over. It rose 146
percent in the last decade. Many
of the patients died of asthma
were having chest tightness and
were poor perceiver of asthma
severity. It made him conscious.
Now every time he had chest
tightness it increased his anxiety
further on. On many occasions he
rushed to emergency department and
got immediate relief. But
recurrence was a rule. His whole
routine was disturbed. It added
the stress further.
Curiosity:
- What has made life of retired
professor stressful?
- How
the problem was solved ?
He
then consulted an asthma specialist
who advised him to measure his
asthma by a peak flow meter and
measure peak expiratory flow rate
(PEFR) regularly specially at the
time of chest tightness episode.
His personal best PEFR reading was
9L/sec and it never fell below
7L/s at the time of chest
tightness episodes. It assured him
that his lung power was reasonably
good and symptoms of mild asthma
were over-sensed. Now he is back
to his routine work. Whenever he
gets an episodes of chest
tightness he simply records the
peak flow reading and get
reassurance.
Expert
Comments:
It is a case having psychological
complicated asthma. The patient's
problem was over-sensing the
asthma mortality. When he started
measuring his asthma by a peak
flow meter he realised that he had
only mild asthma not life
threatening fatal asthma.
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Related
links
Understand
Warning Signals (Asthma Symptoms)
Peak
Flow Diary
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