BRONCHIAL
ASTHMA
Asthma is defined as a chronic
inflammatory disease of airways that is characterized by increased
responsiveness of the tracheobronchial tree to a multiplicity of stimuli, in
which many cells and cellular elements play a role. This inflammation causes
recurrent episodes of wheezing, breathlessness, chest tightness and coughing,
particularly at night or in the early morning. These episodes are usually
associated with widespread but variable airflow obstruction that is often
reversible either spontaneously or with treatment.
Some of the
principal cells identified in airway inflammation include mast cells,
eosinophils, epithelial cells, macrophages, and activated T lymphocytes. The
mechanism of inflammation in asthma may be acute, subacute, or chronic, and the
presence of airway edema and mucus secretion also contributes to airflow
obstruction and bronchial reactivity. Varying degrees of mononuclear cell and
eosinophil infiltration, mucus hypersecretion, desquamation of the epithelium,
smooth muscle hyperplasia, and airway remodeling are present.
ETIOLOGY
Genetic
factors are of major importance in determining a predisposition to the
development of asthma.
The stimuli
that incite acute episodes of asthma can be grouped into seven major categories:
·
allergenic,
·
pharmacologic,
·
environmental,
·
occupational,
·
infectious,
·
exercise-related, and
·
emotional
PATHOGENESIS
Allergic asthma is dependent on an IgE response controlled by T and B
lymphocytes and activated by the interaction of antigen with mast cell–bound
IgE molecules. After taking up an immunogen, these cells migrate to the local
lymph nodes where they present the material to T cell receptors. This leads to
the differentiation of the cell to a TH2 subset and also causes B
lymphocytes to switch their antibody production from IgG and IgM to IgE. Once
synthesized and released by B cells, IgE circulates in the blood until it
attaches to high-affinity receptors on mast cells and low-affinity receptors on
basophils. Immune mechanisms appear to be causally related to the development
of asthma in 25 to 35% of all cases. The pathophysiologic hallmark of asthma is
a reduction in airway diameter brought about by contraction of smooth muscle,
vascular congestion, edema of the bronchial wall, and thick, tenacious
secretions. All these can cause to airway remodeling, which is associated with
structural changes due to long-standing inflammation and may profoundly affect
the extent of reversibility of airway obstruction. BA begins to look like COPD.
IgE-dependent activation of mast
cells leads to release from them big amount of products of arachidonic acid metabolism. These bioactive substances are
not all the time in cells like histamine
or serotonin, and appear during cells activation and then secreted in extracellular fluid. Free arachidonic acid is used in
two metabolic ways: with the help of cyclooxygenase it changes into prostoglandings , and with the
help of lipooxygenase into the
leukotrienes. Formation of different
forms of prostoglandings depends on kind of cells where all these processes
happen. One of forms of prostoglandings PgD2 producing a bronchoobstructive action much more strong
then histamine does.
The typical aspirin-sensitive asthma is most studied. Aspirin inhibits prostaglandin G/H synthase 1 (cyclooxygenase type 1).
CLINICAL FEATURES
A
basic clinical sign of bronchial asthma is an attack of shotness of breath
because of convertible bronchial obstruction of bronchial tubes due to contraction of smooth muscle, edema of mucous membrane of
bronchial tubes and hypersecretion of mucus. The net
result is an increase in airway resistance, a decrease in forced expiratory
volumes and flow rates, hyperinflation of the lungs and thorax, increased work
of breathing, alterations in respiratory muscle function, changes in elastic
recoil, abnormal distribution of both ventilation and pulmonary blood flow.
During chest examination we can find:
- End-expiratory wheezing or a prolonged
expiratory phase is found most commonly, although inspiratory wheezing
can be heard.
- Diminished breath sounds and chest
hyperinflation may be observed during acute exacerbations.
- The presence of
inspiratory wheezing or stridor may prompt an evaluation for an upper
airway obstruction such as vocal cord dysfunction.
Displays of symptoms increase at
night or in an early morning. Symptoms can increase at the physical loadings,
viral infections, influence of allergens, smoking, change of external
temperature condition, strong emotions, action of chemical aerosols, reception
of some medications. Sinusitis, rhinitis, nasal
polyposis are preceded aspirin-sensitive asthma. Combination
of clinical picture of shortness of breath with unbearableness of aspirin and nasal polyposis is named by aspirin or asthmatic triad.
DIAGNOSTICS
Diagnosis is
based on the presence of special symptoms which characterized by day's and
seasonal variability. Thick, stringy mucus, which
often takes the form of casts of the distal airways (Curschmann's spirals),
when examined microscopically, often shows eosinophils and Charcot-Leyden
crystals. The total white blood cell count
may be slightly increased during an
acute attack, and eosinophilia is common.
Pulmonary function tests reveal
abnormalities typical of obstractive dysfunction, and partial reversibility
(improvement FVC or FEV1 of at least 12% or improvement
in FEF 25-75 of at least 25%) is
often demonstrated after an inhaled bronchodilator
is administered.
An allergist
inspection includes:
-
collection of
allergist anamnesis (presence at patient of eczema, seasonal or
whole-year allergic rhinits, food or medicinal allergy, and also BA and atopic
diseases of his family members). U should
ask about respiratory diseases, age of sick in the moment of beginning disease,
seasonality, improvement of the state of house or at work, concomitant
diseases).
-
Total serum immunoglobulin E
levels greater than 100 IU are frequently
observed in patients experiencing allergic reactions, but this finding is not
specific for asthma and may be observed in patients with other conditions (eg,
allergic bronchopulmonary aspergillosis, Churg-Strauss syndrome).
-
Allergy skin testing is a useful adjunct in individuals with atopy. The allergens that most
commonly cause asthma are aeroallergens such as house dust mites, animal
danders, pollens, and mold spores. Two methods are available to test for
allergic sensitivity to specific allergens in the environment: allergy skin
tests and blood radioallergosorbent tests (RAST). Allergy immunotherapy may be
beneficial in controlling allergic rhinitis and asthma symptoms for some
patients.
-
Methacholine- or
histamine-challenge testing
-
Bronchoprovocation testing with either methacholine or histamine
is useful when spirometry findings are normal or near normal, especially
in patients with intermittent or exercise-induced symptoms.
Bronchoprovocation testing helps determine if hyperreactive airways are
present, and a negative test result usually excludes the diagnosis of
asthma.
Differential diagnosis
The differentiation of asthma from other diseases associated with
dyspnea and wheezing is usually not difficult, particularly if the patient is
seen during an acute episode. A personal or family history of allergic diseases
such as eczema, rhinitis, or urticaria is valuable contributory evidence.
Recurrent episodes of bronchospasm can occur with carcinoid tumors , recurrent
pulmonary emboli , and chronic bronchitis. In chronic bronchitis there are no true symptom-free periods, and one
can usually obtain a history of chronic cough and sputum production as a
background on which acute attacks of wheezing are superimposed.
Eosinophilic pneumonias are often associated with asthmatic symptoms, as are various chemical
pneumonias and exposures to insecticides and cholinergic drugs. Bronchospasm is
occasionally a manifestation of systemic vasculitis with pulmonary involvement.
Differential
diagnostics of COPD and BA
|
Sign
|
COPD
|
BA
|
|
Allergy
|
Not characteristic
|
characteristic
|
|
Cough
|
Periodic or permanent
|
paroxysmal
|
|
Shortness of breath
|
Permanent
|
Attacks of expiration shortness of
breath
|
|
Daily allowance changes of FEV1
|
Less than, than 10% from normal
|
More than 12% from normal
|
|
Bronchial obstruction
|
Making progress decline of function
of lungs
|
There is not a making progress
decline of function of lungs, convertibility is characteristic
|
|
Eosinophilia of blood and sputum
|
Not characteristic
|
Characteristic
|
CLINICAL
CLASSIFICATION
Intermittent asthma:
1. Intermittent symptoms occurring
less than once a week
2. Brief exacerbations
3. Nocturnal symptoms occurring
less than twice a month/
4. Asymptomatic with normal lung
function between exacerbations.
5. FEV1 or PEF rate greater than
80%, with less than 20% variability
Mild persistent
1.Symptoms occurring more than once
a week but less than once a day 2.Exacerbations affect activity and sleep
3. Nocturnal symptoms occurring
more than twice a month
4. FEV1 or PEF rate
greater than 80% predicted, with variability of 20-30%
Moderate
persistent
1. Daily
symptoms
2. Exacerbations
affect activity and sleep
3. Nocturnal
symptoms occurring more than once a week
4. FEV1
or PEF rate 60-80% of predicted, with variability greater than 30%
Severe persistent
1.Continuous
symptoms
2.Frequent
exacerbations
3.Frequent
nocturnal asthma symptoms
4.Physical
activities limited by asthma symptoms
5.FEV1
or PEF rate less than 60%, with variability greater than 30%
TREATMENT
The goals for successful management of asthma include the following:
- Achieve and maintain control of symptoms.
- Prevent asthma exacerbations.
- Maintain pulmonary
function as close to normal levels as possible
There are the
followings levels of control: complete, partial, uncontrolled
Complete
control
|
Description
|
Control
flow
|
|
Daily symptoms
|
not
|
|
Limitation of activity
|
not
|
|
Nightly symptoms
|
not
|
|
Using of в2-agonists for a
removal
attacks of shortness of breath
|
not
|
|
FVD
|
normal
indexes
|
|
acute condition
|
not
|
Drug therapy of BA:
– the different ways of introduction of drugs
are used:
- inhalation
-
peroral
-
parenterally.
Preparations
for treatment BA used protractedly for maintenance of BA control.
Most
preferable way – inhalation. For rapid relief of symptoms short-acting beta-agonists are used . Sometimes more expressed positive
answer is observed from short-acting cholinergic
antagonist.
|
Drugs
|
Dose (mcg)
|
Duration of action
|
|
short-acting
beta-agonists:
salbutamol (Ventolinum),
Fenoterol (Berotek).
|
100
100
|
4-6
4-6
|
|
short-acting cholinergic antagonist:
Ipratropiya bromide (Ipravent)
|
20, 40
|
6-8
|
|
Combined
drugs
(short-acting beta-agonists +
short-acting cholinergic antagonist:
Fenoterol + Ipratropiya bromide (berodual)
salbutamol + Ipratropiya bromide ()
|
|
|
Inhaled
Glucocorticoids
These
drugs are indicated in patients with persistent symptoms. These drugs share the
ability to control inflammation, facilitate the long-term prevention of
symptoms, reduce the need for oral glucocorticoids, minimize acute occurrences,
and prevent hospitalisations.
|
Drugs
|
Dose on inhalation
|
|
Beklometazon (Beklofort, Beklazon)
|
200-500 mcg
|
|
Budesonid (Budekort)
|
200-400 mcg
|
|
Flutikazon (Fliksotid)
|
100-250 mcg
|
|
Mometazon (Asmaneks)
|
200-400 mcg
|
The most high
type of safety and low system biotavailability
is marked at Flutikazon and Mometazon.
Cromolyn
sodium and nedocromil sodium-their major therapeutic effect is to inhibit the
degranulation of mast cells, thereby preventing the release of the chemical
mediators of anaphylaxis.
Long-acting inhaled β2-agonists should not be used for symptom relief or for exacerbations. Use only with
inhaled glucocorticoids.
Long-acting
inhaled β2-agonists
Drugs |
Dose (mcg)
|
Duration of
action
|
|
Long-acting
inhaled β2-agonists
Salmeterol (Serevent)
Formoterol (Zafiron)
|
25,
50
4,
12
|
12
12
|
|
Long-acting
cholinergic antagonist
Tiotropiya bromide (Spiriva)
|
18
|
24
|
Combination
beta-agonist/corticosteroid
Inhaled combination medication used frequently in the treatment of
asthma consists of a long-acting beta-agonist and inhaled corticosteroid .
SERETID (salmeterol +fluticasone) has dosages 50/25, 125/25, 250/25.
Simbikort
(Budesonid + Formoterol) – 200/
4
There are different deliverable
devices – evohaler, дискус,
твист-халер, турбухалер, easy breathing. It is
better to appoint the high doses of inhalation steroids
through
spacer (demonstration). Modern deliverable device is NEBULAYZER (nebula means fog).
With their help it is possible to inhale long and
short acting beta-agonists, inhaled glucocorticoids.
Glucocorticoids are the most potent and most effective
anti-inflammatory medications available. Systemic steroids are most beneficial
in acute illness, when severe airway obstruction is not resolving, and in
chronic disease, when there has been failure of a previously optimal regimen
with frequent recurrences of symptoms of increasing severity. A preference
gives to prednisolone (5 mg=1 tab.) or to
Methylprednisolone (4 mg = 1 tab.)
METHYLXANTHINES
Theophylline
and its various salts are medium-potency bronchodilators with questionable
anti-inflammatory propertie.
For
maintenance therapy, long-acting theophylline compounds are available and are
usually given once or twice daily. Single-dose administration in the evening
reduces nocturnal symptoms and helps keep the patient complaint-free during the
day. They are now considered second-line therapy, and as such they are rarely
used in acute situations and infrequently in chronic ones.
For basic -
the long-term control of asthma inhaled
glucocorticoids, inhaled glucocorticoids with long-acting beta-agonists,
long-acting cholinergic antagonist, systemic steroids, long-acting
theophylline, combined short-acting beta-agonists are used.
step approach in treatment of
bronchial asthma
|
Intermittent
asthma
|
Mild
persistent
|
Moderate
persistent
|
Severe
persistent
|
|
A
controller medication is not needed.
The
reliever medication is a short-acting beta-agonist as needed for symptoms
|
The
controller medication is an inhaled corticosteroid (200-500 mcg), cromolyn
(adult: 2-4 puffs tid/qid; child: 1-2 puffs tid/qid), nedocromil, or a
leukotriene antagonist. If needed, increase the dose of corticosteroid and
add a long-acting beta-agonist or sustained-release theophylline, especially
for nocturnal symptoms.
The
reliever medication is a short-acting beta-agonist as needed for symptoms
|
The
controller medication is an inhaled corticosteroid (800-2000 mcg) and a
long-acting bronchodilator (either beta-agonist or sustained-release
theophylline) A combination medication of salmeteorol/fluticasone (Advair) is
a preferred choice to improve compliance. Other agents may include
leukotriene modifying agents or omalizumab.
The
reliever medication is a short-acting beta-agonist as needed for symptoms
|
The
controller medication is an inhaled corticosteroid (800-2000 mcg), a
long-acting bronchodilator (beta-agonist and/or theophylline), and long-term
oral corticosteroid therapy.
The
reliever medication is a short-acting beta-agonist as needed for symptoms.
|
Mucolytic agents are used in
symptomatic therapy (group of bromhexine, ambroxole (lasolvan).
Information on the clinical course of asthma suggests
a good prognosis, particularly for those whose disease is mild and develops in
childhood. Prophylaxis
Primary – individual and social conditions,
directed on avoidance of disease- healthy way of life, improvement of house
conditions, effective treatment of rhinosinusitis, chronic infection.
Second – full and in time treatment of exacerbations,
selection of adequate base therapy, treatment of concomitant diseases.
