- long-term or repeated exposure to chemicals
such as cleaning solutions, paints, industrial
chemicals used in manufacturing, pesticides
and herbicides, and aerosols - presence of ALLERGIC RHINITIS, atopic DERMATITIS,
or chronic SINUSITIS
Viral infections, physical exertion such as with
exercise, cold air, sulfite preservatives (common in
some foods), some medications, and GASTROE-
SOPHAGEAL REFLUX DISORDER(GERD) also may trigger
asthma attacks. Researchers do not know why
some people develop hypersensitivity reactions to
certain substances while other people, even
though their immune systems similarly create
antibodies, experience normal reactions. Though
researchers believe there are likely genetic factors
that underlie allergies, they have yet to isolate
them.
See also ALLERGIC ASTHMA; ANTIBODY; ATOPY;
BREATH SOUNDS; HYPERSENSITIVITY REACTION; LIVING
WITH CHRONIC PULMONARY CONDITIONS; MULTIPLE CHEM-
ICAL SENSITIVITY SYNDROME.
atelectasis The collapse of a segment or lobe of
the lung, or an entire lung. Atelectasis is fairly
common and most often spontaneously corrects
itself for full recovery. The collapse may result
from obstruction, structural damage to lung tissue,
fibrosis that destroys bronchial segments, PNEU-
MOTHORAX, PLEURAL EFFUSION, and other causes. A
form of chronic atelectasis, right middle lobe syn-
drome, results from chronic INFLAMMATIONof the
LY M P Hnodes near the area, which are beneath the
right lung’s middle lobe. A common cause of
atelectasis is taking shallow breaths, which is com-
mon in people coming out of ANESTHESIAbut still
sedated after surgery or who have abdominal or
chest wall pain.
Symptoms and Diagnostic Path
Symptoms of atelectasis vary with the rate of
onset and the extent of lung area involved. Rapid
collapse may cause sharp PAINand sudden DYSPNEA
and may also cause severe COUGH. Chronic atelec-
tasis or atelectasis that develops gradually may
produce few symptoms, though many people
develop a persistent, nonproductive cough.
The diagnostic path begins with careful AUSCUL-
TATIONfor BREATH SOUNDS. Typically the collapsed
segment causes displacement within the thoracic
cavity of the affected lung, and often the unaf-
fected lung as well as the HEART. Breath sounds
may be normal though heard in abnormal loca-
tions. The doctor may also hear wheezes or rales,
abnormal breath sounds that suggest blocked air-
ways. Chest X-RAYclearly shows the displacement
and the extent of the collapse. In the simplest
case, coughing and deep breathing may resolve
the atelectasis. In other cases, the doctor may
desire additional diagnostic imaging such as COM-
PUTED TOMOGRAPHY(CT) SCANto precisely identify
the site of the atelectasis as well as the possible
cause (such as a tumor or an obstruction). BRON-
CHOSCOPYmay allow the pulmonologist to directly
visualize the collapsed area and remove an
obstruction such as a foreign object or mucus
plug, if that is the cause of the collapse. Bron-
choscopy also permits BRONCHOALVEOLAR LAVAGEor
biopsy, if indicated.Treatment Options and Outlook
Often, segmental atelectasis requires no treatment
beyond watchful waiting or encouraging deep
breathing. The lung will correct itself. Infection
requires treatment with ANTIBIOTIC MEDICATIONS;
inflammation may require treatment with CORTI-
COSTEROID MEDICATIONS. Other medications that
sometimes relieve discomfort and help the lung
restore itself include bronchodilators, which relax
and open the airways. CHEST PERCUSSION AND POS-
TURAL DRAINAGE help keep the lungs free from
accumulated secretions, and the doctor may rec-
ommend the person lie on his or her unaffected
side to allow gravity to help restore the collapsed
segment. Rarely, the doctor may consider surgery
for chronic atelectasis that fails to respond to med-
ical treatment. Most people recover from atelecta-
sis without complications.Risk Factors and Preventive Measures
Risk factors for atelectasis include obstructive pul-
monary conditions such as CHRONIC OBSTRUCTIVE
PULMONARY DISEASE(COPD), CYSTIC FIBROSIS, chronic
BRONCHITIS, and BRONCHIECTASIS. Recent surgery
with general anesthesia is a common cause of
atelectasis. Though avoiding these circumstances190 The Pulmonary System