BREATHING STOPPAGE
BREATHING
In an adult, inhalation and exhalation occur between 13 and 17 times a minute at
rest and up to 80 times a minute during vigorous exertion. A normal, resting
inhalation takes in about 400 ml of air; a deep breath, up to 4 litres.
A i r i n h a l e d
,
R i b c a g e
r i s e s a s
i n t e r c o s t a l
m u s c l e s
c o n t r a c t —
A ir e x h a l e d
R i b c a g e
f a l l s a s
i n t e r c o s t a l
m u s c l e s
r e la x
D ia p h r a g m
c o n t r a c t s
Inhalation
Air is drawn into the lungs as the intercostal
muscles (between the ribs) contract, causing the
ribcage to rise, and the diaphragm
contracts and flattens.
D ia p h r a g m
r e l a x e s
Exhalation
Air is expelled from the lungs as the intercostal
muscles relax, causing the ribcage to fall, and
the diaphragm relaxes and resumes its
domed shape.
dioxide.
Breathing is controlled by the
respiratory centre in the
brainstem.
On
inhalation, the diaphragm contracts and
flattens. The intercostal muscles (between
the ribs) contract and pull the ribcage
up and out. The resulting increase in
volume in the chest cavity causes the
lungs to expand, and the reduced pres-
sure
draws
air
into
the
lungs.
On
exhalation, the chest muscles and dia-
phragm relax, causing the ribcage to
sink and the lungs to contract, squeez-
ing air out.
In normal, quiet breathing, less than
a tenth of the air in the lungs passes out
to be replaced by the same amount of
fresh air (the tidal volume). This new
air mixes with the stale air (the residual
volume) already held in the lungs. The
normal breathing rate for an adult at
rest is 13 to 17 breaths per minute. (See
also
respiration
.)
breathing difficulty
Laboured or distressed breathing that
includes a change in the rate and depth
of breathing or a feeling of breathless-
ness. Some degree of breathlessness is
normal after exercise, particularly in
unfit or overweight people. Breathless-
ness at rest is always abnormal and is
usually due to disorders that affect the
airways (see
asthma
), lungs (see
pul-
monary disease, chronic obstructive),
or
cardiovascular system (see
heart failure
).
Severe anxiety can result in breathless-
ness, even when the lungs are normal
(see
hyperventilation
). Damage to the
breathing centre in the brainstem due
to a
stroke
or
head injury
can affect
breathing. This may also happen as a
side effect of certain drugs.
Ventilator
assistance is sometimes needed.
At high altitudes, the lungs have to
work harder in order to provide the
body with sufficient oxygen (see
moun-
tain sickness
). Breathlessness may occur
in severe anaemia because abnormal or
low levels of the oxygen-carrying pig-
ment
haemoglobin
means that the lungs
need to work harder to supply the body
with oxygen. Breathing difficulty that
intensifies on exertion may be caused
by reduced circulation of blood through
the lungs. This may be due to
heart fail-
ure
(reduced pumping efficiency of the
heart),
pulmonary embolism
(blockage of
blood vessels in the lungs by clots), or
pulmonary hypertension
(increased pres-
sure in the arteries in the lungs).
Breathing difficulty due to air-flow
obstruction may be caused by chronic
bronchitis,
asthma, an allergic reaction,
or
lung cancer.
Breathing difficulty may
also be due to inefficient transfer of
oxygen from the lungs into the blood-
stream. Temporary damage to the lung
tissue may be due to
pneumonia
,
pneu-
mothorax
(collapsed lung),
pulmonary
oedema
(fluid in the lung), or
pleural
effusion
(fluid around the lung). Per-
manent lung damage may be due to
emphysema,
a condition in which the
small air sacs in the lungs are destroyed.
Chest pain (for example, due to a
broken rib) that is made worse by chest
or lung movement can make normal
breathing difficult and painful, as can
pleurisy
(inflammation of the membrane
that lines the lungs and chest cavity).
Pleurisy is associated with pain in the
lower chest and often in the shoulder
tip on the affected side.
Abnormalities of the skeletal struc-
ture of the thorax (chest), such as severe
scoliosis
or
kyphosis,
may cause difficulty
in breathing by impairing the normal
movements of the ribcage.
breathing exercises
Techniques for learning to control the
rate and depth of breathing. They aim to
teach people to inhale through the nose,
while expanding the chest, and then to
exhale fully through the mouth, while
contracting the abdominal muscles. The
exercises are used after chest surgery
and for people with chronic obstructive
pulmonary disease (see
pulmonary dis-
ease, chronic obstructive),
who often tend
to have difficulty breathing effectively.
Breathing exercises can also help people
with
anxiety disorders
and may also help
to relieve the symptoms of
asthma.
In
yoga
, deep, rhythmic breathing is
used to achieve a state of relaxation.
During
childbirth,
breathing exercises can
relax the mother and may also help to
control the contractions of the uterus
and reduce pain. (See also
physiotherapy.)
breathing stoppage
The cessation of
breathing
(see
apnoea).
Breathing may be stopped by an
airway
obstruction,
by damage to the brainstem
B
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