What are pulmonary function tests (PFTs), spirometry, and peak expiratory flow (PEF) measurements?

Pulmonary function tests (PFTs)—as the name implies—
are tests designed to measure and assess lung function.
PFTs were originally research tools, available
only in specialized academic hospital centers. They
are now widely available and are frequently performed
because of their usefulness in the diagnosis and treatment
of asthma. Keep in mind as you read this answer that the
lung function abnormalities seen in active asthma on PFT
testing are, by definition, reversible.

The term PFTs is used to collectively describe several
different specific tests of lung function. Spirometry is the
single most useful of the PFTs when it comes to asthma
diagnosis and treatment. Spirometry, in turn, includes
two important subtests. The first is called the peak expiratory
flow, abbreviated PEF. The second is the FEV1,
the forced expiratory volume in 1 second. Measurements
of PEF and FEV1 are thus parts, or subtests, of the
spirometry portion of the PFTs. The availability of inexpensive,
highly portable, and easy-to-use peak-flow monitors
makes it possible for every person with asthma
(even children) to measure his or her peak flow at home
on a daily basis in order to monitor asthma activity.
FEV1 measurements, on the other hand, require the use
of a spirometer, which is more costly, requires special
maintenance, and is not presently advised for home use.
Self-monitoring of PEF allows a person with asthma
insight into his or her condition and permits an assessment
of asthma control. Both PEF and FEV1 play a
pivotal role in the National Asthma Education and
Prevention Program’s (NAEPP’s) asthma diagnosis,
classification, and treatment guidelines.
To perform spirometry and PEF, the patient is first
asked to take a deep breath of room air. Then, that
biggest single breath is forcefully and rapidly exhaled
into a mouthpiece connected to the spirometer or peak
flow meter. The maneuver is repeated several times during
testing to ensure accurate and reproducible values.
The spirometer measures the exhaled lung volume, as
well as the flow of air through the mouthpiece for the
time that exhalation takes place.

The spirometry measurements
are recorded by the spirometer and are printed
out and graphed for review and future reference.
Each individual patient measurement is compared to
a predicted value. The predicted values for pulmonary
function tests are based on three variables: age, height,
and gender.Predicted values are different for a 21-year-old,
6-foot-tall man than for a 5-foot-tall, 64-year-old
woman. It follows that the PEF value (and the FEV1) that
would be considered within normal limits for a short,
older female with asthma would be abnormally low if
obtained by a tall, adolescent male with asthma, even
though they both had asthma.
Because asthma is characterized as a disease of lung emptying,
exhalation time is abnormally prolonged in symptomatic
asthma. Anyone with active asthma who attempts
to blow out all the candles on a birthday cake with one
single mighty blow of air knows about impaired lung emptying
firsthand! Depending on the degree of asthma and
other factors, such as how much airway narrowing, or
bronchospasm, is present, full exhalation during spirometry
might last as long as 14 seconds rather than the normal
5 to 6 seconds.The FEV1 and PEF values reflect the
efficiency and status of lung emptying, and thus provide
information about how a person with asthma’s lung
function is affected by his or her condition.
The FEV1 measures the amount (volume) of air that is
exhaled in the first second of forceful exhalation during
spirometry as you breathe out as hard and as fast as you
can after you have taken in a deep breath.When asthma
is poorly controlled, it takes longer than predicted for
the lungs to fully empty. Since the total exhalation time
is prolonged in symptomatic or inadequately controlled
asthma, it follows that the amount (volume) of air exhaled
during the first second of that exhalation is lower than
predicted. The FEV1 decreases in symptomatic or poorly
controlled asthma. With treatment, the lungs empty
more efficiently, and the FEV1 value returns to a normal
range. When asthma is suspected, spirometry is performed
before and after inhalation of a short-acting
bronchodilator medication to look for the normalization
of the FEV1—a phenomenon called reversibility. The
most up-to-date guidelines from the third EPR (Expert
Panel Report) of the National Heart, Lung, and Blood
Institute define a 12% or greater increase in a person’s
baseline FEV1 on spirometry after use of a bronchodilator
as a significant response.
When active or exacerbated asthma prolongs exhalation,
flow of air through narrowed air passages becomes
reduced. Spirometry in active asthma also reveals reduced
flow rates. The peak flow is the single greatest value of
flow measurement that occurs as the lungs start to empty.
Peak flows reflect the flow of air through the larger, so called
conducting airways in asthma. Peak flow generally
tracks asthma activity. Monitoring peak flow at home
allows for comparison of a person’s predicted PEF, with
his or her actual personal best measurements obtained
when the asthma is well controlled.
Home-based PEF monitoring can then help
identify even a mild exacerbation and guide medication
adjustment up or down, depending on how the PEF
value fluctuates from the personal best. Self-administered
PEF measurements over time are a component of asthma
action plans .

A peak-flow meter is an easy-to-use device designed to
help you assess the degree of your asthma control. Persons
who have moderate or severe persistent asthma,
persons with a history of severe exacerbations, and persons
who have difficulty perceiving when their asthma
worsens are most likely to benefit from self peak-flow
monitoring. Monitoring long-term, daily peak-flow
measurements detects early changes in asthma control
that require an adjustment in treatment and helps
gauge the responses to those treatment changes.
Asthma self-monitoring should be neither a bother
nor a nuisance. On the contrary, daily home peak-flow
monitoring has been shown to improve asthma control,
reduce exacerbations, and decrease absences from
school and work. Using a peak-flow monitor may also
increase your confidence as it helps you learn how to
optimize asthma control and achieve greater mastery
over your asthma. Most children can accurately measure
their peak flow under adult guidance starting at about
6 years of age. Peak-flow monitoring also allows for
objective decisions about modifying your asthma regimen
based on information contained in the written
asthma action plan your physician has provided.
If your physician gives you a prescription for home peakflow
monitoring, you will be asked to determine your
personal best value based on measurements obtained
when you feel well and are symptom-free. An asthma
action plan provides instructions on what asthma medication
to take as the peak-flow value falls into one of
three zones labeled green, yellow, or red. The green
zone includes peak-flow measurements in the range of
80–100% of your personal best. Yellow corresponds to
peak-flow measurements in the range of 60–80% of the
personal best value. The red zone includes all peak flow
values below 60% of your best. Peak-flow measurements
in the red zone indicate that your asthma is poorly controlled,
and that you will need to either contact your
physician, proceed to the emergency room, or both.

What diagnostic testing is used to diagnose asthma?

The most helpful diagnostic tests for suspected asthma
are pulmonary function tests, often referred to as PFTs
 and the single most important
PFT, both for asthma diagnosis and for follow-up, is
spirometry.Other useful medical tests include blood tests
and X-ray studies. Additional, more specialized studies
may be obtained depending on the clinical picture.

 An example of a specialized study is skin-prick testing for
suspected allergy. Blood tests are valuable in getting an
overall picture of a person’s health, as well as in excluding
other diagnoses. Assessment of immune function and
allergies, for example, can be performed in part via blood
testing. X-ray studies include conventional chest X-rays,
as well as three-dimensional chest CT (computerized
tomography) scans. Chest X-rays and CT scans provide
information about the anatomy or structure of the lungs
and larger breathing passages. In quiescent, controlled
asthma, the chest X-ray should be entirely normal. The
same is true of the chest CT scan. During an exacerbation,
however, the lungs’ appearance on an X-ray may
suggest what radiologists call hyperinflation, and the CT
might reveal air-trapping. Both findings reflect the uneven
lung filling and emptying when breathing occurs through
inflamed, constricted air tubes.
Magnetic resonance imaging, scanning, and positron
emission tomography scanning, while useful in other
types of lung diseases, are not required in diagnosing
asthma. The same is true of nuclear medicine scans,
such as ventilation-perfusion scans and gallium scans.

How is the diagnosis of asthma established?

The diagnosis of asthma is often straightforward, but
can also be time consuming and elusive. Asthma can
manifest differently in different individuals because of
its waxing and waning nature, as well as its variability.
A physician evaluating a patient with a typical, or textbook,
presentation will likely be able to diagnose asthma
correctly at the first visit. A patient with variant or
atypical symptoms may require repeat visits or specialized
diagnostic testing to confirm the suspected diagnosis
of asthma. More severe forms of asthma are usually
easier to pinpoint and diagnose accurately. Consider
some examples in each category. A previously healthy,
nonsmoking young adult who reports an episodic history
of intermittent wheezing, cough, chest discomfort,
and breathlessness with exposure to cold winter air is
describing a history typical of asthma. The college student
who sees the doctor because of a nagging cough and
who is concerned about chronic or recurrent bronchitis
and colds, might actually be asthmatic. Similarly, the
teenager who gets “really winded” playing racquetball,
and then gets used to coughing for a few hours after
each match, could certainly have asthma as well.

Asthma can be confidently diagnosed when specific
symptoms, physical examination findings, and specialized
lung test results are present. The first step in the evaluation
of suspected asthma is a complete detailed medical
history, during which the doctor and the patient meet face
to face for an in-depth conversation and exchange of
information. The patient will describe what symptoms he
or she is experiencing, and the physician will ask a series
of directed questions regarding lung health, followed by
more general health inquiries. In this fashion, the physician
will obtain information not only about the patient’s
specific pulmonary symptoms, but also about the presence
or absence of allergies, and other medical or surgical
conditions. Other important background information
derives from review of the patient’s medication history,
along with his or her travel, occupational, and social history.
Some questions may at first sound intrusive, but
should nonetheless be answered truthfully.When I ask a
patient if there is wall-to-wall carpeting in the bedroom,
or who does the vacuuming, for example, I am far from
interested in discussing domestic decorating or cleaning
arrangements. Rather, I am gathering facts to help me
decide whether an allergic response to the home environment
is a possibility. Similarly, when I ask, “Is anyone else
at home coughing, too?” or “Is anyone at home a smoker?”
I am searching for clues to help me hone in on the
correct diagnosis. All conversations between my patients
and me are entirely confidential; truthfulness between us
is an important part of the successful doctor–patient
relationship. Just as I would never think of telling a patient
an untruth, so, too, do I count on my patients to provide
me with an accurate description or history.
After history taking comes the physical exam. Most lung
specialists will perform a directed physical, with special
emphasis on the upper respiratory tract (nose, throat,
sinuses), lungs, and the skin. One can expect measurement
of vital signs, including blood pressure, respiratory
rate, pulse, and if necessary, temperature. Inspection, percussion,
and auscultation are techniques that examine the
lungs. Inspection refers to a visual look. The specialist will
check whether both lungs move in and out with each
breath, for example. Percussion involves gently tapping
on the chest, listening for clues as to whether or not the
lungs are full of air. If the lungs are full of air, the tapping
will sound resonant. If the lungs are not entirely filled
with air, then the tapping will give rise to a dull sound.
Auscultation requires a stethoscope.
The examiner will ask the patient to inhale
and exhale deeply and regularly during auscultation. The
presence or absence of wheezing is especially significant.
After the history and the physical exam are completed,
the doctor will begin to generate a list of diagnostic possibilities,
called the differential diagnosis.
The doctor’s clinical impression rates the
possible diagnoses in order of likelihood. It may sometimes
be obvious to the physician that asthma is present.
A pulmonary function test called spirometry (obtained
before and after inhalation of a bronchodilator medicine)
is indicated in order to confirm the suspected asthma
diagnosis. If spirometry is not confirmatory and if asthma
remains high on the list of possible explanations for
a patient’s symptoms, then additional diagnostic testing
is often obtained . The additional testing is helpful in excluding
alternative diagnoses and in determining
if asthma is the correct diagnosis in spite of the
spirometry results.

What are the similarities and differences between asthma and COPD?

COPD and asthma are lung ailments. Asthma and
COPD can both give rise to similar symptoms, and are
sometimes treated with the same medicines. Both conditions
can lead to variable breathlessness, wheezy breathing,
coughing, and mucus production. Some medicines
prescribed for the treatment of asthma, such as inhaled β2
agonists, corticosteroid inhalers, and theophylline, for
example, are also used in COPD treatment. Asthma and
the conditions caused by COPD may also demonstrate a
similar pattern of abnormality on the pulmonary function
test called spirometry. That similar pattern of abnormality
is called obstructive dysfunction.
To a pulmonologist involved in direct patient care,
COPD and asthma are completely different. The single
most common cause of COPD is cigarette smoking.
COPD is a disease of mid- to late-adulthood. It is the
fourth leading cause of death in the United States, and
it is a significant cause of lifestyle limitation reflecting
its chronic and progressive nature. COPD affects different
sites in the lung than does asthma, involving both
the lung tissue and the airways. COPD’s obstructive
dysfunction on spirometry is “fixed” or “irreversible”.
 Asthma has a genetic basis
and is often seen in persons who also carry a diagnosis of
allergy. It affects all ages and is frequently diagnosed
in children. The diagnosis of asthma is compatible with
a long and full life and the prognosis is excellent. Asthma
targets the lung airways. By definition, the obstructive
dysfunction demonstrated on pulmonary function tests
in asthma is reversible such that lung function has the
potential to fully normalize.

Is COPD related to asthma?

Asthma is a specific lung disease that is different from
emphysema and chronic obstructive bronchitis.COPD is
often used as a kind of shorthand to describe emphysema,
chronic obstructive bronchitis, or a combination of both.
 COPD always refers to diseases that are not asthma.
 The COPD group of lung diseases is not related to asthma,
although emphysema
and chronic obstructive bronchitis exhibit similarities to
asthma, reviewed in the next answer. Confusion seems to
arise under several circumstances. In the first case,
COPD can co-exist with asthma, typically in an older
adult with a history of cigarette smoking, and both conditions
are present together. Secondly, some medical
practitioners in a blatant misuse of language use the word
asthma to refer to the breathlessness characteristic of the
COPD group of lung diseases. They tell their patients
with pure emphysema or chronic obstructive bronchitis
that they have “a touch of asthma” rather than explaining
that the symptom of shortness of breath is a fundamental
manifestation of the COPD. Finally,COPD and asthma

What is COPD?

COPD is an acronym for the term chronic obstructive
pulmonary disease. Chronic obstructive pulmonary disease
is a descriptive term rather than a single disease,
although it usually is used to refer to emphysema or to
chronic obstructive bronchitis.

Technically, COPD refers in a general way to several
different lung conditions that demonstrate an abnormality
on spirometry, a type of pulmonary function test.
The abnormality that characterizes COPD is
called obstructive dysfunction. Several different lung
conditions typically exhibit the obstructive dysfunction
pattern of abnormality on pulmonary function testing.
They include emphysema, chronic obstructive bronchitis,
exacerbated asthma, and bronchiectasis. The two
first diseases, in particular, share several features. Both
emphysema and chronic obstructive bronchitis are
associated with cigarette smoking. Both exhibit obstructive
dysfunction on spirometry that does not completely
reverse with medication, and thus demonstrate a “fixed”
or “irreversible” type of obstructive dysfunction. Both
cause respiratory symptoms such as breathlessness or
cough. Interestingly, emphysema and chronic obstructive
bronchitis frequently co-exist, usually in a current or
former cigarette smoker.
Partly because emphysema and chronic obstructive
bronchitis appear at first glance to be so similar, physicians
have taken to using the term COPD to refer
specifically to either emphysema or chronic obstructive
bronchitis, or even to a combination of both. The use
of COPD as a kind of shorthand for the smoking associated
lung diseases, whether emphysema or chronic
obstructive bronchitis, has taken hold among medical
professionals as well as the general public, despite disapproval
from some linguistic purists.

Why do I usually cough after jogging or running or after participating in sports?

The presence of a persistent cough is always abnormal.
There are many reasons why cough may develop. Each
one of us has experienced a cough at some point in our
lives, when ill with a respiratory infection or a head
cold, for example. Most coughs due to the common cold
are short lived and tend to resolve within a month’s time.
When a cough lasts longer than 3–6 weeks or assumes
a particular repetitive pattern, take note. Lung specialists
define a chronic cough as a cough that has been
present for more than 8 weeks. The majority of individuals
with chronic cough who are not cigarette smokers
have one of three causes for their cough: asthma, stomach
reflux (GERD), or postnasal drip syndrome (recently
renamed UACS for upper airway cough syndrome).
Cough that regularly occurs with or following aerobic
exercise strongly suggests the presence of asthma unless
proven otherwise.
Exercise is considered a symptom trigger in all persons
with asthma. Exercise does not cause asthma but acts as
a stimulus to bronchoconstriction in asthma and leads
to increased airway inflammation. In young children in
particular, cough with exertion should never be
ignored; it may be the tip-off to the diagnosis of asthma
since cough is the most frequent symptom of asthma in
children.
Answering the question of why you might be coughing
after running or jogging would require an evaluation
that should begin with a medical history (including any
medication you are taking), discussion of cigarette smoking
if applicable, reviewing the chronology of the symptom,
and a physical examination with close attention to
the sinuses, throat, heart, and lungs. Additional testing
might include a chest X-ray (depending on your
individual medical history) and pulmonary function
testing.