The Respiratory System
asthma is characterised by paroxysms (episodes) of breathlessness, chest
tightness and wheezing, resulting from narrowing of the airways by a
combination of muscle spasm, mucosal swelling and viscid bronchial secretions.
These changes are thought to be manifestations of a complex inflammatory
reaction within the bronchial wall involving mast cells, eosinophils and other
airflow obstruction, which characteristically fluctuates markedly, causes
mismatch of alveolar ventilation and perfusion and increase the work of
breathing. A narrowed bronchus can no longer be effectively cleared of mucus
by the act of coughing and many of the smaller bronchi become obstructed by
Bronchial asthma occurs at all ages and it has been
estimated that 5% of adults and 7% to 10% of children suffer from it. Because
asthma is a heterogeneous disease triggered by a variety of inciting agents,
there is no universally accepted simple classification. Nevertheless, it is
customary to classify asthma into two major categories based on the presence
or absence of an underlying immune allergic disorder: early onset (also
called extrinsic or atopic asthma) and late onset (also called
intrinsic or non-atopic asthma).
is the most common type of asthma. Atopy
is a hereditary tendency to be hypersensitive to certain allergens and to
readily produce large quantities of IgE antibodies. It is common for asthma to
have its onset in childhood and generally it occurs in atopic individuals who
readily form IgE antibodies to commonly encountered allergens. Fortunately,
complete remissions are common among children.
allergic disorders such as hay fever and atopic eczema are often present, and
a family history of these disorders and of “early onset?asthma is common.
It is unusual for a single allergen to be the sole cause of asthma. The
allergens responsible for asthma in atopic individuals generally enter the
bronchi with the inspired air and are derived from organic material such as
pollen, mite-containing house dust, cockroaches, feathers, animal dander and
exposures to these agents will have stimulated the formation of IgE and an anaphylactic antigen-antibody reaction (Type I hypersensitivity)
in the bronchi may follow further exposure to specific allergen. This causes
the release, from the cells in the bronchial wall, of pharmacologically active
substances (e.g., histamine, leukotriens, prostaglandins) which provoke mucus
secretion, bronchial constriction and an inflammatory reaction of allergic
type in the bronchial wall characterised by increased vascular permeability,
oedema formation and accumulation of inflammatory cells (mainly eosinophils).
Persistent inflammation of bronchi leads to damage to the bronchial
epithelium, which is thought to be responsible for bronchial
hyper-responsiveness and bronchospasm. Much less frequently similar effects
may be produced by ingested allergens derived from certain foods such as fish,
eggs, milk, yeasts and wheat, nuts, peas, which presumably reach the bronchi
via the blood stream.
Asthma can occur
at any age in non-atopic individuals and because the majority of these
patients are adults this type of asthma if often called late onset asthma. It
would appear that external allergens play no part in the production of this
form of the disease to which the term ?i style="mso-bidi-font-style:normal">intrinsic
asthma?is sometimes applied. Triggering mechanisms are non-immune and
include: exposure to cold air, strong scents, dust and tobacco smoke;
respiratory viral infections, strenuous exertion, emotional stress. These
factors can also precipitate episodes of extrinsic asthma. Possible underlying
mechanism in non-atopic asthma is an imbalance between the sympathetic and
parasympathetic system but the actual details of this are unknown.
Clinical features: < BACK TO TOP >
1. Episodic asthma:
pattern is usually consistent with atopic asthma, when there are episodes of
wheezing and dyspnoea with sudden onset.
there are no respiratory symptoms between episodes.
patient may have initially unproductive cough, but toward the end of the
episode some thick, tenacious and clear mucus may be brought up.
can be triggered by known factors (exposure to allergens and non-specific
stimuli) or may be spontaneous.
may be mild or severe and may last for hours or days, stopping spontaneously
or, usually, on therapy.
severe cases there is very marked dyspnoea, cyanosis, sweating (signs of
respiratory failure), and this condition must be treated as an emergency (so
called status asthmaticus).
2. Chronic asthma:
often found in non-atopic individuals.
main complaints are chest tightness, wheeze, breathlessness especially marked
cough and wheeze during the night can also occur.
are chronic unless controlled by appropriate therapy.
Episodes of more severe asthma can occur with cough and productive mucoid sputum.
Diagnosis: < BACK TO TOP >
history often provides very important clues.
Physical signs in the chest. During an attack the chest is held near the
position of full inspiration and the percussion note may be hyper-resonant,
reflecting the hyperinflation of the lungs. Expiration phase is prolonged and
high pitched expiratory wheezing may be heard. There are usually no abnormal
physical signs between attacks except in patients with chronic asthma who are
seldom without some expiratory wheezing.
Radiological examination. In an acute attack of asthma the lungs may appear
hyperinflated. Between episodes the chest X-ray is usually normal.
Pulmonary function tests. Due to hyperinflation TLC and RV are both
increased. Measurement of the FEV1,
VC and PEF (all of them are diminished) provide a fairly reliable indication
of the degree of airflow obstruction and can also be used to determine whether
and to what extent it can be relieved by inhaled bronchodilator drugs, or to
confirm that the obstruction is provoked by exercise or occupational exposure
Arterial blood gas analysis. Measurements of arterial blood-gas pressures (PO2 and PCO2)
are important in the management of patients with severe acute asthma (status
asthmaticus). Expected findings are reduced partial pressure of oxygen and
sometimes increased partial pressure of carbon dioxide. Blood pH can be
reduced (respiratory acidosis).
Skin hypersensitivity tests. A prick is made in the skin with a fine needle
through a drop of an aqueous extract of the substance to be tested. A positive
reaction is indicated by the development of oedema and redness, which begin to
appear within a few minutes. It is seldom possible with these tests to
identify one particular allergen as the cause of asthma in an individual
patient (usually several allergens give a positive result) and their chief
value is to distinguish atopic from non-atopic subjects.
Specific IgE antibodies to inhalants may be detected by radioallergosorbent
test (RAST). If this testing is not available or inconclusive, measuring total
serum IgE may help establish the patient’s atopic constitution (however this
is not specific for asthma).
Eosinophilia (increased count of eosinophils) is a common finding and in many asthmatics it correlates with severity of asthma. Eosinophilia may also be found in other allergic conditions as well as in parasitic infestations (e.g., intestinal worms).
Management < BACK TO TOP >
Avoidance of allergens can be effective only if one allergen is the cause
of the asthma. The vast majority of asthmatic patients are hypersensitive to a
wide range of allergens and attempts to avoid them are all impracticable. Some
measures such as having polished floors instead of carpets and regular washing
of curtains and blinds, frequent cleaning/wet dusting/vacuuming and using dust
mite protectors on pillows and mattresses are always helpful.
Hyposensitisation is the only specific measure for the prevention of damaging
antigen-antibody reaction. It involves the subcutaneous injection of initially
very small, but gradually increasing doses of extracts of allergens, believed
to be responsible for the patient’s asthma as demonstrated on the skin
hypersensitivity test. Due to the possible risk of producing an acute
anaphylactic reaction, this method has been largely abandoned in many
drugs in asthma
[Intal] and nedocromil [Tilade]
administered by inhalation can prevent mediator release from mast cells,
therefore must be given regularly (they are not effective during an attack);
they appear to be more effective in children than adults for unknown reasons
can be administered by inhalation (beclomethasone [Becotide], budesonide [Pulmicort],
fluticasone [Flixotide]) or orally (prednisolone [Delta-Cortef, Panafcortelone]
and methylprednisolone [Medrol]) in prevention of attacks; or even
intravenously (hydrocortisone [Hysone, Nordicort]) in status asthmaticus
antagonists (montelukast [Singulair], zafirlukast [Accolate]) are the
latest drugs that block inflammatory mediators leukotrienes which have an
important role in bronchospasm, mucus secretion and chronic inflammation.
These drugs are administered prophylactically in form of one tablet a day for
long-term control and prevention of symptoms.
b2-adrenoreceptor agonists such as salbutamol [Ventolin], salmeterol [Serevent]
or eformoterol [Foradile, Oxis] are given by inhalation, adrenaline is used in
children usually by intramuscular or subcutaneous injection
xanthine drugs such as theophylline [Aminophylline] which is usually used
intravenously in asthmatic attack
antagonists (ipratropium [Atrovent]) are given by inhalation, but they are
less effective than b2-agonists;
however they can be given together
Oxygen in case of severe acute asthma, which is a medical emergency
Prognosis < BACK TO TOP >
Nutrition < BACK TO TOP >
Nutrition that alleviate or prevent asthma :-
Herbs < BACK TO TOP >
Herbs that alleviate or prevent asthma :-
Dr Zoran Pletikosa)
3 5 June 20096December 2005
10 December 2004 Human Rights DayInternational Day of Disabled Persons
World Environment Day
speaker Mr NgThian Watt the Principal Trainer from
Napoleon Hill Associates MalaysiaDetails