can be acute or chronic. The most common cause of an acute
cough is an acute respiratory infection. A chronic cough
is defined as a cough persisting for more than 3 weeks.
Nerves called cough receptors are located near the surface
of the upper and lower airways. Various agents, including
noxious gases and fumes, foreign bodies, viruses and bacteria,
acid and other irritants, stimulate cough receptors to send
signals to the brain. The brain then sends signals back
to the lungs and respiratory muscles. In response, there
is first a deep inhalation and then a forced exhalation.
A closed glottis initially stops the forced exhalation.
Closure of the glottis causes pressure to increase in the
lungs. When the glottis opens, air rushes out of the lungs
under high pressure and with high velocity. The increase
in airflow and pressure dislodges particles and expels them
from the airways.
produced in the body, such as substance P and bradykinin,
can also stimulate the cough reflex. Structures close to
the airways--the pericardium, esophagus, diaphragm, and
stomach also have cough receptors. The bronchial tubes in
the smaller branches and the alveoli do not have cough receptors.
A chronic cough can lead to a significant reduction in one's
sense of well-being and quality of life. Complications such
as insomnia, hoarseness, headache, dizziness, exacerbations
of asthma, urinary incontinence, rupture of nasal, anal
and subconjuctival veins, disruption of surgical wounds
and rib fractures may result. More importantly, a chronic
cough may be a signal that a significant health problem
diagnostic workups for the cause of a cough differentiate
between a chronic cough in nonsmokers with a normal chest
x-ray (CXR) and a chronic cough in smokers with or without
an abnormal CXR. The most common causes for chronic cough
in a nonsmoker with a normal CXR are postnasal drip syndrome,
asthma and gastroeso-phageal reflux disease (GERD). Medications
called ACE inhibitors are another major cause of chronic
cough. Common causes for chronic cough in smokers are bronchitis
and lung cancer. Even though a chronic cough in a nonsmoker
usually does not indicate problems as serious as these,
it should be evaluated by a physician to exclude rare but
common causes include: congestive heart failure, disorders
of the upper airways, disorders of the pericardium, bronchogenic
carcinoma, interstitial lung disease, chronic pulmonary
infection (e.g., tuberculosis), cystic fibrosis, interstitial
lung disease and psychogenic disorders.
Postnasal drip syndrome is suggested by frequent nasal discharge,
sensation of drainage in the back of the throat, and frequent
throat clearing. The syndrome is noted on physical examination
by the rough appearance, termed cobblestoning, of the back
of the throat. Sinus x-rays or sinus CT (computed tomography)
scan may show evidence of sinusitis. Causes of postnasal
drip include sinusitis, allergic rhinitis and vasomotor
rhinitis. Postnasal drip syndrome is the most common
cause of chronic cough.
cough due to postnasal drip is generally treated with decongestants
and antihistamines, with or without nasal steroid sprays.
Treatment may also include a vasoconstrictor such as oxymetalazone,
which should not be used for more than 5 days. Chronic cough
due to postnasal drip may take a few weeks to a couple of
months to resolve. Underlying sinusitis is treated with
Asthma that is asymptomatic except for cough is called cough-variant
asthma. This condition is difficult to diagnose because
the physical examination and pulmonary function test results
can be normal. Asthma may be caused by cold air, fumes,
fragrances or exercise. Coughing that starts after the initiation
of a beta-blocker also suggests asthma. Beta-blockers are
medications commonly used to treat high blood pressure,
heart disease, migraines, palpitations and other conditions.
Beta-blockers are also used in eye drops for glaucoma and
other eye problems. Beta-blocker eye drops can precipitate
asthma symptoms, including cough.
Reflux Disease (GERD)
GERD is the third most common cause of chronic cough. The
diagnosis may be obtained from the medical history alone.
Patients often present with classic symptoms of frequent
heartburn or sour taste in the mouth. If these symptoms
are present, therapy directed at GERD is initiated to resolve
the cough. Forty percent of patients with GERD do not present
with the classic symptoms. These patients may complain only
of cough. In this case, a 24-hour esophageal pH probea small
plastic catheter inserted through the nose and placed into
the esophagus, above the stomach may be performed to measure
the pH (acid concentration) in the esophagus. If the pH
in the esophagus falls below a certain level, acid is refluxing
from the stomach.
therapy directed at reflux can be given as a diagnostic
test. If the cough resolves with GERD therapy, the cough
is attributed to GERD. This is reconfirmed if the cough
returns with discontinuance of therapy.
treatment for GERD includes elevation of the head of the
bed; not eating or drinking 2 to 3 hours before bedtime;
and avoiding certain foods, such as fatty foods, chocolate,
alcohol, orange juice and caffeine. Medications directed
at reducing acid production in the stomach, such as proton
pump inhibitors, are used as well.
ACE inhibitors can be excluded as the cause of chronic cough
by discontinuing their use. The cough typically resolves
in 1 to 4 days but can take up to 4 weeks. Therefore, eliminating
the drug for a couple of days is not sufficient to exclude
an ACE inhibitor as the cause. Further confirmation is made
by the return of cough on resumption of the medication.
classes of medication need to be used if the cough is due
to an ACE inhibitor.
Bronchiectasis (chronic dilation of the bronchi or bronchioles
resulting from inflammatory disease or obstruction) can
be diagnosed by high resolution CT scan that shows the dilated
airways. Once this diagnosis is established, the cause should
be determined and, if possible, therapy initiated.
The diagnosis of chronic bronchitis is obtained from a history
of smoking and the production of sputum with the cough most
days of the week, for 3 months, in 2 successive years. Chest
x-rays are obtained to exclude other pathology. In a smoker,
any change in a chronic cough and any new cough warrant
cessation can completely resolve the cough associated with
chronic bronchitis. Bronchodilators can help the cough as
Lung cancer is the cause of a chronic cough in less than
5% of patients with a normal CXR. It is suspected as a cause
of chronic cough most often when there is an abnormal CXR
and a history of smoking. Abnormal CXR dictates that a biopsy
be performed to obtain a sample of the abnormal tissue for
analysis. When the CXR is normal and lung cancer is suspected,
a CT scan of the chest may be obtained. Bronchoscopy is
often the next diagnostic test in patients with normal radiographic
When a foreign body is suspected as the cause of chronic
cough, fiberoptic bronchoscopy is usually performed.
Nonspecific therapy for cough may be employed to relieve
symptoms until the therapy directed at the cause becomes
effective. The most commonly used cough suppressant is dextromethorphan.
Dextromethorphan is chemically related to morphine but has
no narcotic effect. Adverse effects, occurring in fewer
than 1% of people, include drowsiness, dizziness, nausea,
constipation and abdominal discomfort. Dextromethorphan
is contraindicated in a person taking a monoamine oxidase
inhibitor (MAOI). Overdose can occur and can lead to
coma and respiratory depression. Codeine is another effective
cough suppressant and may cause side effects similar to
dextromethorphan, but with increased frequency. Dependency
with prolonged use can occur with codeine.