Bronchial Asthma
Definition: Paroxysmal attacks of cough,, dyspnea, and wheezes are caused
by generalized obstruction of the airways due to Bronchial Hyper-reactivity to
variety of stimuli they are associated with a high degree of reversibility of the
obstruction either spontaneously or after treatment.
Characteristic feature in asthmatics is the bronchial hyper-reactivity,
condition resulting in increased bronchial responses (i.e. that is bronchial
obstruction) following the stimulus that does not cause such a Response in normal
individuals. The degree of .bronchial hyper-reactivity Varies from patient to
patient and the severity of the disease depends on.
The degree of hyper-reactivity.
The following stimuli trigger the bronchial hyper-reactivity in asthmatics
and this result in bronchial obstruction.
- Allergens as house dust, pollens, dangers and certain food in atopic
patients (in patients with atopic diseases)
- Exposure to strong odours and irritant fumes such as sulfur dioxide,
tobacco smoke, cooking odours, air pollutants in cities..etc.
- Viral infections as respiratory syncytial virus, adenovirus and rhinovirus.
- Rapid changes in the environmental temperature or barometric pressure.
- Muscular exercise.
- Emotional disturbances.
Etiology:
Many factors contribute to the etiology of bronchial asthma. These factors
are present in varying proportions in different individuals:
1. Neurogenic mechanism:
Cholinergic receptors in the bronchial, mucosa are easily stimulated by
various stimuli (e.g. cold air, smoke, irritant odours) and evoke an exaggerated
response (bronchoconstrilion) by a vagal reflex.
2. Brochemical mechanism:
In patients with bronchial asthma, beta adrenergic receptors beta adrenergic
are reduced number or function (beta adrenergic receptors blockade).
The hyperactive cholinergic receptors and defective beta adrenergic
receptors speak of an autonomic imbalance in patients with bronchial asthma
(Intrinsic asthma).
, 3. Immunologic mechanisms (Allergic, Atopic, or Extrinsic Asthma)
Atopic patients exposed to certain allergens e.g. molds, house dust produce
specific becomes attached to the mast cells present IgE which in the bronchial
mucosa. On reexposure to the same antigen _________ an antigen antibody
reaction occurs on the surface of mast cells leading to liberation of chemical
mediators (histamine and leukotrienes e.g. slow, reacting substance of
anaphylaxis). These mediators have direct action on the bronchial wall and profuse
bronchoconstriction, edema of the mucosa and increased mucous secretion. In
addition they stimulate the cholinergic receptors leading to bronchoconstriction.
Pathophysiology:
Airway obstruction in bronchial asthma is produced by:
a) Spasm of the smooth muscle,
b) Edema of the mucosa,
c) Congestion and infiltration of the bronchial walls by inflammatory cells as
eosinophils, neutrophils.
d) Intraluminal exudation of mucus, shed ded epithelial cells and
inflammatory cells. It is evident that bronchial asthma is an inflammatory
reaction of the bronchial tree.
The obstruction of the airways produces increased airway resistance to the
air flow with premature closure of the bronchi in expiration. These will lead to the
following impairments (disorders).
1. Air trapping and hyperinflation of the lung alveoli.
2. Disturbed gaseous exchange mush may in: Hypoxia, Hypercapnea, and
low pH.
3. Cardiovascular changes in the form of pulmonary hypertension, right
ventricular strain and decreased left ventricular filling may occur.
Clinical Manifestations :
1. One of the clinical manifestation of asthma is may have its onset at any
age ; 50% of patients usually start to suffer before 2 year and 80 — 90% /have
their attacks before 4-5 years
2. Another clerical manifestation of paroxysms of cough is, dyspnea and
wheezes that vary in severity between different patients. The paroxysms may occur
at a certain time of the year (e.g. in winter or spring) or may occur at any time (i.e.
not seasonal).
Definition: Paroxysmal attacks of cough,, dyspnea, and wheezes are caused
by generalized obstruction of the airways due to Bronchial Hyper-reactivity to
variety of stimuli they are associated with a high degree of reversibility of the
obstruction either spontaneously or after treatment.
Characteristic feature in asthmatics is the bronchial hyper-reactivity,
condition resulting in increased bronchial responses (i.e. that is bronchial
obstruction) following the stimulus that does not cause such a Response in normal
individuals. The degree of .bronchial hyper-reactivity Varies from patient to
patient and the severity of the disease depends on.
The degree of hyper-reactivity.
The following stimuli trigger the bronchial hyper-reactivity in asthmatics
and this result in bronchial obstruction.
- Allergens as house dust, pollens, dangers and certain food in atopic
patients (in patients with atopic diseases)
- Exposure to strong odours and irritant fumes such as sulfur dioxide,
tobacco smoke, cooking odours, air pollutants in cities..etc.
- Viral infections as respiratory syncytial virus, adenovirus and rhinovirus.
- Rapid changes in the environmental temperature or barometric pressure.
- Muscular exercise.
- Emotional disturbances.
Etiology:
Many factors contribute to the etiology of bronchial asthma. These factors
are present in varying proportions in different individuals:
1. Neurogenic mechanism:
Cholinergic receptors in the bronchial, mucosa are easily stimulated by
various stimuli (e.g. cold air, smoke, irritant odours) and evoke an exaggerated
response (bronchoconstrilion) by a vagal reflex.
2. Brochemical mechanism:
In patients with bronchial asthma, beta adrenergic receptors beta adrenergic
are reduced number or function (beta adrenergic receptors blockade).
The hyperactive cholinergic receptors and defective beta adrenergic
receptors speak of an autonomic imbalance in patients with bronchial asthma
(Intrinsic asthma).
, 3. Immunologic mechanisms (Allergic, Atopic, or Extrinsic Asthma)
Atopic patients exposed to certain allergens e.g. molds, house dust produce
specific becomes attached to the mast cells present IgE which in the bronchial
mucosa. On reexposure to the same antigen _________ an antigen antibody
reaction occurs on the surface of mast cells leading to liberation of chemical
mediators (histamine and leukotrienes e.g. slow, reacting substance of
anaphylaxis). These mediators have direct action on the bronchial wall and profuse
bronchoconstriction, edema of the mucosa and increased mucous secretion. In
addition they stimulate the cholinergic receptors leading to bronchoconstriction.
Pathophysiology:
Airway obstruction in bronchial asthma is produced by:
a) Spasm of the smooth muscle,
b) Edema of the mucosa,
c) Congestion and infiltration of the bronchial walls by inflammatory cells as
eosinophils, neutrophils.
d) Intraluminal exudation of mucus, shed ded epithelial cells and
inflammatory cells. It is evident that bronchial asthma is an inflammatory
reaction of the bronchial tree.
The obstruction of the airways produces increased airway resistance to the
air flow with premature closure of the bronchi in expiration. These will lead to the
following impairments (disorders).
1. Air trapping and hyperinflation of the lung alveoli.
2. Disturbed gaseous exchange mush may in: Hypoxia, Hypercapnea, and
low pH.
3. Cardiovascular changes in the form of pulmonary hypertension, right
ventricular strain and decreased left ventricular filling may occur.
Clinical Manifestations :
1. One of the clinical manifestation of asthma is may have its onset at any
age ; 50% of patients usually start to suffer before 2 year and 80 — 90% /have
their attacks before 4-5 years
2. Another clerical manifestation of paroxysms of cough is, dyspnea and
wheezes that vary in severity between different patients. The paroxysms may occur
at a certain time of the year (e.g. in winter or spring) or may occur at any time (i.e.
not seasonal).
