causes (central apnea), mechanical causes
(obstructive apnea), or a combination of both.
Central apnea is more common in premature
infants, whose nervous systems are not fully
developed, and the very elderly, whose nervous
systems may be failing. Central apnea is also more
common in people who have underlying neuro-
logic disorders or who have heart failure. Obstruc-
tive apnea may occur in children who have
greatly enlarged tonsils or adenoids and in individ-
uals who have OBESITY. Some people have irregular
breathing patterns that are, for them, normal. A
doctor should evaluate irregularities in breathing
to determine whether the circumstances merit
medical intervention.
Most people who have apnea are unaware of
apneic episodes, though others who observe them
may become alarmed (especially parents or care-
givers who notice apnea in young children).
Recurrent apnea that occurs during sleep, called
OBSTRUCTIVE SLEEP APNEA, is a serious health condi-
tion that disrupts the sleeping patterns and results
in sleep deprivation though most people are not
aware of this because they do not have conscious
recollection of the apneic episodes. Researchers
believe that severe and persistent obstructive sleep
apnea contributes to cardiovascular conditions
such as HEART FAILURE.
The diagnostic path includes careful analysis of
apnea patterns, taking into consideration the per-
son’s age, the onset of the apnea, and adverse
effects that may result (including effects resulting
from sleep deprivation). The pulmonologist may
conduct pulmonary function tests, BLOODtests to
measure levels of erythrocytes (red blood cells)
and HEMOGLOBINin the blood, and X-rays or other
diagnostic imaging procedures to look for obstruc-
tive causes. A comprehensive NEUROLOGIC EXAMINA-
TION, including ELECTROENCEPHALOGRAM(EEG), may
reveal the cause of central apnea.
Treatment targets the underlying cause of the
apnea. For some people, surgery to remedy the
cause of an obstruction may provide long-term
relief (such as TONSILLECTOMYand ADENOIDECTOMYin
children who have enlarged tonsils and adenoids).
Central apnea that results from damage to the
brainstem or other underlying neurologic disorder
can be difficult to treat. Oxygen therapy alone
may help with some central apneas.
See also ASPHYXIA; CHEYNE-STOKES RESPIRATION;
DYSPNEA; SUDDEN INFANT DEATH SYNDROME (SIDS);
TACHYPNEA.asbestosis Damage to the LUNGSresulting from
inhalation of asbestos fibers. During the first half
of the 20th century asbestos, a natural substance
mined from underground, became common in
insulating materials because of its natural heat
resistance. In the 1950s researchers linked chronic
asbestos inhalation with PULMONARY FIBROSISand a
rare form of LUNG CANCER, mesothelioma, found
almost exclusively in people with asbestos expo-
sure. In the 1970s the United States implemented
strict regulations that prohibited the use of
asbestos in many of its formerly common applica-
tions. For people who had occupational exposure
to asbestos before these restrictions, however,
asbestosis is a significant risk. Millions of Ameri-
cans live with asbestosis and hundreds die each
year from it or from lung cancer associated with
asbestos exposure.
Asbestos fibers embed in the tissues of the
lungs, causing INFLAMMATIONand granulation that
eventually leads to fibrosis (SCARtissue formation).
Some forms of asbestos are more hazardous than
others. Typically lung damage from asbestos takes
20 years or longer after exposure to manifest. The
likelihood of developing health consequences
from asbestos exposure correlates directly to the
amount of asbestos and the duration of the expo-
sure. Cigarette smokers face increased risk, partic-
ularly of lung cancer, as the asbestos and the
carcinogenic chemicals in cigarette smoke potenti-
ate each other (intensify each other’s actions in
the lungs).Symptoms and Diagnostic Path
Many people do not show symptoms of asbestosis
until the damage is fairly advanced. Because of
this, health experts recommend people with
known asbestos exposure receive annual exami-
nations to monitor the health of their lungs.
When symptoms manifest they typically include- DYSPNEA (difficulty BREATHING) with physical
exertion - dry (nonproductive) COUGH
- chest discomfort, tightness, or PAIN
184 The Pulmonary System