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<
 The Respiratory SystemEmphysema Clinical features, Diagnosis, Management, Prognosis, The
word emphysema means inflation
in the sense of unnatural distension with air. Pulmonary emphysema is characterised by permanent enlargement of the
alveoli accompanied by destruction of
their walls. There are several conditions in which enlargement of air
spaces is not accompanied by destruction; this is more correctly called
overinflation. For example, the distension of air spaces in the opposite lung
after unilateral pneumonectomy (surgical removal of one lung, e.g. in lung
cancer) is compensatory overinflation rather than emphysema. One
rare form of pulmonary emphysema (less than 1% of all cases) is found in young
adults associated with genetically determined a1-antitrypsin
deficiency
(autosomal recessive trait), and it is important as a prototype of
pathogenetic mechanisms that may play a part in people without this
deficiency. a1-antitrypsin (normally produced by the liver and
present in serum, tissue fluids, and macrophages) is a component of the
complex protease inhibitor system which inhibits the activity of protease
enzymes that may be secreted by neutrophils and macrophages during
inflammation. Particles from air (e.g., smoke or dust) that reach the alveolar
spaces are normally phagocytosed by alveolar macrophages (there are no cilia
nor production of mucus in the alveoli), but if they are overwhelmed they may
rupture releasing lysosomal proteolytic enzymes and chemotactic mediators that
attract inflammatory cells. During this inflammatory process a1-antitrypsin deficiency increases the likelihood of
developing emphysema because damaging proteolysis in lung tissue is not
sufficiently inhibited. In
most patients the disease is caused by cigarette
smoking and usually associated with chronic bronchitis. Inhalation of
cigarette smoke activates macrophages and airway epithelial cells in the
respiratory tract to release several neutrophil chemotactic factors.
Neutrophils and macrophages then release proteolytic enzymes such as elastase,
proteinase 3 and so called matrix metalloproteinases (collagenase and
gelatinase). The end result of these processes is destruction
of alveolar walls by “digestion?which presumably can not be
sufficiently blocked by protease inhibitors such as a1-antitrypsin,
secretory leukoprotease inhibitor (secreted from respiratory epithelial cells)
and tissue inhibitors of matrix metalloproteinases. However, emphysema may
develop in people who never smoked, and most people who have smoked never
develop overt emphysema, suggesting that some individual predisposition
(probably genetic) may play a part. There is accumulating evidence that
oxidative stress by reactive oxygen species from cigarette smoke or
inflammatory cells has an important role in COPD. Histologically, there is stretching, thinning and destruction of alveolar walls. With advanced disease, adjacent alveoli become confluent, creating large air spaces. With the loss of elastic tissue in the alveolar septa, there is reduced radial traction on the small airways which normally keeps them open (small airways have no cartilage reinforcements). As a result, they tend to collapse during expiration, which is an important cause of chronic airflow obstruction in severe emphysema. In addition to alveolar loss, the number of alveolar capillaries is diminished, which contributes to pulmonary hypertension by reducing the capacity of pulmonary vascular bed (“pulmonary pipeline?. Clinical features: < BACK TO TOP >
Progressive
and disabling exertional breathlessness (dyspnoea) is the most important
complaint.
Cough
and cyanosis are not prominent in pure emphysema in contrast to chronic
bronchitis.
There is
visible laboured breathing with indrawing of suprasternal and supraclavicular
areas, as well as of the intercostal spaces during inspiration.
An
increase in the antero-posterior diameter of the chest relative to the lateral
diameter may be noted due to increased amount of air in the lungs (‘barrel
chest?.
Prolonged
expiration and characteristic “pursed-lip?breathing (the patient exhales
against partially closed lips, as if ready to whistle) in attempt to prevent
air trapping may be observed.
Weight
loss is common and may be so severe to suggest a hidden malignant tumour. It is
due to increased metabolism (cause unknown) and is largely explained by a loss
of skeletal muscle and wasting of limb muscles.
Well
developed clinical pattern is often referred to as the “pink
and puffing?/i> type because patients are not cyanosed (but they are not
pink either) and are struggling to squeeze the air out of the lungs with each
expiratory effort. Complications:
Pulmonary bullae are inflated thin-wall spaces (balloons) created by rupture of alveolar
walls, usually situated just under the pleura. A subpleural bulla may rupture
and cause spontaneous pneumothorax (discussed later). Respiratory failure with hypoxaemia and cyanosis, and right heart failure due to pulmonary hypertension are generally late complications. Diagnosis: < BACK TO TOP >
Radiological
examination (X-ray) often finds bullae (these are diagnostic) and/or unusually
translucent lung fields, with a low flat diaphragm (a sign of hyperinflation);
however it may be normal in early stages.
Computed
tomography (CT) can detect emphysema with certainty and today is the most
commonly used technique; it is much more sensitive than X-ray. Pulmonary function tests are consistent with airflow obstruction (VC, FEV1 and PEF reduced), but TLC and RV are increased reflecting trapped air; gas transfer factor (a measurement of gas exchange) usually significantly reduced due to reduction in size of the gas exchange membrane. Management < BACK TO TOP >
There
is no specific remedy for generalised emphysema and the patient should avoid
inhaled irritants.
Bronchodilators
offer some benefit even though they do not significantly improve spirometric
findings.
Treatment
of any associated bacterial infections is very important.
Physiotherapy
and breathing exercises could help (pursed-lip breathing), occasionally oxygen
is administered.
In case
of giant bullae which are compressing normal tissue, surgical resection could
be considered.
For
young patients especially with a1-antitrypsin
deficiency heart and lung transplantation is an option.
Several
inhibitors of proteinases are now in clinical development; alternatively
supplementation of endogenous antiproteases is an alternative option. Recently in many centres lung reduction surgery is offered to seriously ill patients with emphysema. It has been proposed that surgical removal of permanently damaged lung areas allows other still functioning lung regions to expand and increase ventilation. Prognosis < BACK TO TOP >
(source :
Dr Zoran Pletikosa) |
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