CHRONIC RESPIRATORY INFECTIONS
There is no clear dividing line between an acute and a chronic respiratory infection but generally
speaking chronic infection goes on for longer than a few weeks and requires hospital
investigation and prolonged treatment. The principle infections in this category are empyema,
lung abscess, bronchiectasis and tuberculosis.
Empyema Thoracis
This is pus within the chest cavity and is usually a complication of pneumonia although cases
can occur from trauma to the chest cavity (surgery including endoscopy and non surgical
trauma) and occasionally from metastatic infection, e.g. right sided endocarditis in intravenous
drug abusers. Many patients with an empyema have risk factors. Most common are those
leading to aspiration, diabetes, alcohol abuse and abnormalities of immunity. Occasionally an
empyema will develop distal to an obstructing lesion, usually lung cancer.
Diagnosis
Patients usually present with the symptoms of their pneumonia ie cough, sputum, dyspnoea,
chest wall pain fever and sweats and loss of appetite; occasionally they can present insidiously
with weight loss, cachexia anaemia and little else. An empyema is usually suspected on the
basis of a chest x-ray but occasionally with a posterior empyema the radiological signs may not
be obvious. A fluid collection in the chest cavity can be confirmed by ultrasound or CT scanning
and a diagnosis is made by aspiration of the fluid. When the fluid has been removed you
should smell it. If it smells like rotten eggs then you have an anaerobic empyema. If the fluid
removed looks like pus then you have an empyema, if it is serous fluid or only mildly turbid the
pH of the fluid should be measured. A pH of < 7.25 suggests the development of a complicated
para-pneumonic effusion and the need for its drainage. As with all pleural fluid, the sample
should be sent for microbiology, including tuberculosis, for cytology and for biochemistry
measurements of protein, glucose and LDH.
Bacteriology
The commonest organisms are strep milleri, anaerobic organisms, strep pneumoniae, and
staphylococci.
Treatment
a. Antibiotics
Amoxicillin in the first instance unless anaerobic when Metronidazole should be used in
addition. Antibiotic treatment should be reviewed when positive cultures are obtained. In a
patient known to be MRSA positive, antibiotics active against the cultured MRSA should be
considered.
b. Drainage of Pus
Initially, this is usually done with a large bore chest drain. This should not be performed by an
amateur. The patient should be referred urgently to the thoracic surgeons if sepsis cannot be
controlled with antibiotics and tube drainage (unusual). Surgical management of an empyema
is usually performed after the empyema has matured when the surgeon will not only clear the
pus from the hemithorax but will removed the leathery rind which develops over the lung and
can cause significant restriction.
Underlying Disease
Always think about underlying disease in patients presenting with empyema or lung abscess
and whether it has been diagnosed and treated effectively.
Lung Abscess
The definition of a lung abscess is an infection leading to necrosis of the lung with or without
cavity formation. Abscesses can be single or multiple. Underlying causes are similar to that for
empyema with the major cause being recurrent aspiration. As with empyema, bloodstream
spread should be considered especially if multiple; in a young fit person, necrobacillosis should
be considered (read about it).
Diagnosis
Presenting symptoms typical of pneumonia. The diagnosis is usually made on the basis of a
chest x-ray when a cavitating lesion is seen. Note that the differential diagnosis of a cavitating
lesion on a chest x-ray is wide. Occasionally, the diagnosis is made on the basis of a CT scan
where necrosis can be seen before cavitation occurs.
Bacteriology
The commonest organisms are strep milleri, anaerobic organisms strep pneumoniae,
staphylococci. It is important to obtain good respiratory samples for culture since antibiotic
treatment is likely to be prolonged and it is important to get it right.
Treatment
Treatment is with antibiotics, drainage; the physiotherapists can be very helpful in organising for
drainage of abscess through positioning of the patient. Occasionally if the patient is extremely
toxic it may be necessary to perform transthoracic tube drainage of an abscess. Surgery is
rarely required.
Bronchiectasis
Bronchiectasis literally means ectatic or enlarged bronchi therefore the diagnosis is always
made by imaging the bronchi; however bronchiectasis is also commonly understood to mean
chronic bronchial sepsis, in other words, the patient will cough up purulent sputum on a daily
basis. It is important to remember that not everybody who coughs up purulent sputum on a
daily basis will have demonstrable bronchiectasis on their high resolution CT scan (the
investigation of choice for demonstrating bronchiectasis).
Clinical pointers to suggest
bronchiectasis are recurrent haemoptysis and pleurisy and features of underlying diseases
which cause bronchiectasis, such as sinusitis.
Causes of Bronchiectasis
a. Structural
Damage from infection such as tuberculosis, whooping cough, severe pneumonia, allergic
bronchopulmonary aspergillosis, recurrent aspiration, congenital problems such as
sequestration or poor collagen function (as in tracheobronchomegaly).
b. Mucociliary Clearance Abnormalities
Primary ciliary dyskinesia, cystic fibrosis, Young’s syndrome.
c. Immune Deficiency
Largely hypogammaglobulinaemia either primary or secondary.
d. Associated with other diseases, mainly connective tissue diseases such as rheumatoid
arthritis, ulcerative colitis.
Management
A specific treatment for the underlying abnormality is unusual but patients with
hypogammaglobulinaemia commonly have immunoglobulin infusions regularly and there are
some treatments for cystic fibrosis which are aimed at the underlying defect.
General management of bronchiectasis revolves around management of infection and
treatment of airways obstruction.
Treatment of Infection
The vicious cycle hypothesis is that damage to the bronchi leads to infection because of
inadequate clearance; infection leads to inflammation and further damage to the bronchi and so
on; thus bronchiectasis is a progressive disease.
Sputum culture is an essential part of management of bronchiectasis in order to guide
appropriate antibiotic therapy. In mild bronchiectasis the most common organisms are the
pneumococcus, haemophilus influenzae and moraxella catarrhalis.
As bronchiectasis
progresses and particularly in women, pseudomonas aeruginosa starts to be a problem.
Occasionally, staphylococcus aureus is seen in sputum but if this is cultured regularly then the
possibility of cystic fibrosis and allergic bronchopulmonary aspergillosis should be investigated.
Acute exacerbations are treated with courses of oral or intravenous (particularly with
pseudomonas) antibiotics.
Long term suppressive treatment with antibiotics. In mild bronchiectasis, rotating courses of
simple oral antibiotics such as aminopenicillins, tetracyclines, macrolides and trimethoprim can
be given. This is often used in the winter period, there is no good evidence for this
management but there are a number of patients who seem to benefit from it.
In more severe bronchiectasis, particularly if infected with gram negatives such as
pseudomonas, nebulised Colistin or Tobramycin can be used on a regular basis to suppress
infection and inflammation.
In some patients with bronchiectasis and some with chronic bronchial sepsis without
bronchiectasis, the prescription of low dose macrolide leads to marked symptomatic
improvement. It is thought that the effect of the macrolide is immuno-modulatory rather than
antibiotic.
Other Management
The majority of patients with bronchiectasis will benefit from inhaled and/or oral bronchodilators.
Evidence for the use of inhaled steroid is poor but nevertheless, it is frequently used.
Respiratory physiotherapists are valued for their ability to teach patients clearance techniques.
Some patients find nebulised hypertonic saline helpful in this respect and others find mucolytics
such as N-Acetylcysteine useful.
Nebulised DNase is only of proven value in cystic fibrosis bronchiectasis.
All patients with bronchiectasis should be immunised against pneumococcus and have annual
influenza vaccination.