breathing difficultyLaboured or dis-
tressed breathing that includes a change
in the rate and depth of breathing or a
feeling of breathlessness. Some degree
of breathlessness is normal after exer-
cise, particularly in unfit or overweight
people. Breathlessness at rest is always
abnormal and is usually due to disorders
that affect the airways (see asthma),
lungs (see pulmonary disease,chronic
obstructive), or cardiovascular system (see
heart failure). Severe anxiety can result in
breathlessness, even when the lungs are
normal (see hyperventilation). Damage
to the breathing centre in the brainstem
due to a strokeor head injurycan affect
breathing. This may alsohappen 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 failure, pulmonary embolism, or
pulmonary hypertension. Breathing dif-
ficulty due to air-flow obstruction may
be caused by chronic bronchitis, asth-
ma, an allergic reaction, or lung cancer.
Breathing difficulty may also be due to
inefficient transfer of oxygen from the
lungs into the bloodstream. Temporary
damage to lung tissue may be due to
pneumonia, pneumothorax, pulmonary
oedema, or pleural effusion. Permanent
lung damage may be due to emphysema.
Chest pain (for example, due to a bro-
ken rib) that is made worse by chest or
lung movement can make normal
breathing difficult and painful, as can
pleurisy, which is associated with pain
in the lower chest and often in the
shoulder tip of the affected side.
Abnormalities of the skeletal structure
of the thorax (chest), such as severe
scoliosisor kyphosis, may cause difficulty
in breathing by impairing normal move-
ments of the ribcage.
breathing exercisesTechniques 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 contract-
ing the abdominal muscles. They are
used after chest surgery and for people
with chronic obstructive pulmonary dis-
ease (see pulmonary disease,chronic
obstructive). Breathing exercises can
also help people with anxiety disorders
and may help to relieve symptoms in
some people with asthma.
In yoga, deep rhythmic breathing is
used to achieve a state of relaxation.
During childbirth, breathing exercises
relax the mother and also help to con-
trol contractions and reduce pain. (See
also physiotherapy.)
breathlessnessA feeling of laboured
breathing. Breathlessness is a normal
response to exercise or exertion but
may also be caused by some underlying
disorders (see breathing difficulty).
breech deliveryA birth in which the
fetus presents buttocks first. Many
fetuses lie in a breech position before
week 32 of pregnancy, but most of them
turn by week 36. The 3 per cent that do
not turn are in 1 of 3 types of breech
presentation. A complete breech is one
in which the fetus is curled up. In a
frank breech, the legs are extended and
the feet are close to the face. In a
footling breech, 1 or both feet are posi-
tioned over the cervix. Sometimes, a
mother with a fetus in a breech presen-
tation is offered a procedure to turn the
fetus around after week 36 of pregnancy.
Often, one twin fetus is a breech. In
some breech deliveries, a Caesarean
sectionmay be recommended.
bridge, dentalFalse teeth that are
attached to natural teeth on either side
of a gap left by a missing tooth or teeth.
(See also denture.)
Bright’s diseaseAnother name for
glomerulonephritis.
brittle bonesBones with an increased
tendency to fracture. They are a feature
of osteoporosisand may occur in people
who are taking corticosteroid drugs, are
immobile, or have certain hormonal
disorders. In osteomalacia, the bonesBREATHING DIFFICULTY BRITTLE BONES
B