Transcript DYSPNEA An unpleasant sensation of difficulty in breathing

DYSPNEA
An unpleasant sensation of difficulty in
breathing
 Awareness that a small amount of exercise
leads to a disproportionately large increase
in ventilation is a common type of dyspnea,
usually described as breathlessness or
shortness of breath on exertion.

Other sensations related to breathing include
 awareness of increased muscular effort
required to expand the chest during
inspiration;
 increased effort required to expel air from
the lungs;
 sensations of fatigue from the respiratory
muscles;
 awareness of delay in air leaving the lungs
during expiration.
sensation that an inspiration is urgently
needed before expiration is completed,;
 various sensations most often described as
"tightness in the chest."
 awareness of collapse or hyperinflation of
lung units; obstruction of airways; and
distortion or displacement of lung,
mediastinum, diaphragm, or chest wall.

Clinical types of dyspnea
Pulmonary
 Cardiac
 Circulatory
 Chemical
 Central
 Psychogenic

Pulmonary dyspnea
Due to pulmonary function defects with a
result of hypoxemia and/or hypercapnia.
There are three types:
1.Inspirational dyspnea: difficult in inspiration
and characterized by three depression sign
 Indicates narrow or obstruction of larynx,
trachea or upper bronchi.
2.Expiratory dyspnea: (obstructive dyspnea)
with increased ventilatory effort induces
dyspnea even at rest, and breathing is
labored and retarded.
 presents in obstructive emphysema or
asthma

Mixed dyspnea: difficult in both inspiration
and expiration, due to severe pulmonary
diseases or chest deformities, such as
severe pulmonary tuberculosis, atelectasis(肺
不张), lung infarction, pneumoconiosis,
interstitial lung disease, pleural
effusion,pneumothorax, and so on.
Cardiac dyspnea
Left ventricular failure
 In early stages of left heart failure, cardiac
output fails to keep pace with increased
metabolic need during exercise.
 Respiratory drive therefore is increased
largely because of tissue and cerebral
acidosis, and the patient hyperventilates .
Shortness of breath is often accompanied
by lassitude or a feeling of smothering or
sternal oppression.
 Various reflex factors, including stretch
receptors in the lungs, may also contribute
to hyperventilation .


In later stages of heart failure, the lungs are
congested and edematous, the ventilatory
capacity of the stiff lungs is reduced, and
ventilatory effort is increased
Orthopnea is the respiratory discomfort that
occurs while the patient is supine, impelling
him to sit up.
 It is precipitated by an increase in venous
return of blood to a failing left ventricle that
cannot handle this increased preload.

Another reason is the increased effort of
breathing in the supine position.
 Sometimes orthopnea occurs in other
cardiovascular disorders (eg, pericardial
effusion)

paroxysmal nocturnal dyspnea (PND), the
patient awakens gasping and must sit or
stand to get his breath, which may be
dramatic and terrifying.
 PND may occur in mitral stenosis, aortic
insufficiency, hypertension, or other
conditions affecting the left ventricle

Except the same factors that cause
orthopnea, PND is also caused by the
following mechanisms:
 Increased excitability of vagus, and causes
vasoconstriction of coronary artery and
myocardial ischemia.
 Construction of smaller bronchi causes
decreasing of ventilation.

Cardiac asthma is a state of acute
respiratory insufficiency with bronchospasm,
wheezing, and hyperventilation. It may be
indistinguishable from other types of asthma,
but the cause is left ventricular failure
Circulatory dyspnea
Air hunger (acute dyspnea occurring in
terminal stages of exsanguinating (使无
血)hemorrhage) is a grave sign calling for
immediate transfusion.
 Dyspnea also occurs with chronic anemia,
coming on only during exertion, unless the
anemia is extreme.

Chemical dyspnea
Diabetic acidosis (blood pH 7.2 to 6.95)
induces a distinctive pattern of slow, deep
respirations (Kussmaul breathing). However,
because the breathing capacity is well
preserved, the patient rarely complains of
dyspnea.
 In contrast, the uremic patient may complain
of dyspnea because of severe panting
brought about by a combination of acidosis,
heart failure, pulmonary edema, and anemia.

Central dyspnea



Cerebral lesions (eg, hemorrhage) and head injury
are often associated with intense hyperventilation
that is sometimes noisy and stertorous(打鼾).
irregular periods of apnea alternate with periods in
which 4 or 5 breaths of similar depth are taken
(Biot's respiration).
Decreased Paco2 causes reflex CNS
vasoconstriction with reduced cerebral perfusion
leading to a beneficial secondary decrease in
intracranial pressure.
Psychogenic dyspnea
Hysterical types of overbreathing are
common.
 In one type, continuous hyperventilation
leads to acute alkalosis from "blowing off"
CO2 ; positive Trousseau and Chvostek
signs may result from lowered serum
calcium ion levels.

Another type is characterized by deep,
sighing respirations with the patient
breathing at maximal depth until respiration
is "satisfactory," when the hyperventilatory
impulse subsides. This is frequently
repeated.