A brief look at Pneumonia

Pulmonary infections occur when normal lung or systemic defence mechanisms are impaired. Primary defences of the respiratory tract include; the mucocilary escalator, flushing action of saliva, cough reflex (impaired in stroke, brain tumours, laryngeal cancer etc.), filtering by nasal cavity (nasal hair), phagocytosis by alveolar macrophages and normal flora.

When presented with a pulmonary infection, cough is often a common symptom. A number of diagnoses can be derived from the symptom of cough, and are summarised in the figure below.
Goutam.Saha via rhmis.kerala.gov.in

In response to last Friday's case 'An unwelcomed pulmonary Tourist' the clinical presentation and associated history would favour the diagnosis of Pneumonia.

Described as the  "captain of the men of death" by Sir Willian Osler, Pneumonia  at the simplest level is a inflammatory condition of the lung.

Cause
Pneumonia can be caused by a variety of viruses, bacteria, and sometimes fungi. Pneumococcal pneumonia is caused by bacteria called Streptococcus pneumoniae. S. pneumoniae is also called pneumococcus.

Symptoms
 
Mikael Häggström via Wikipedia

Diagnosis
A diagnosis of pneumonia can based upon;
  • Symptoms
  • Physical exam
  • Lab tests (e.g. Sputum Cultures)
  • Chest x-ray
A study by Heckerling et al (1990), formulated a rule to predict the probability of an infiltrate with the respiratory tract. The five signs they used in their rule are as follows;
  • Fever > 37.8 °C (100.0 °F)
  • Pulse > 100 beats/min
  • Rales/crackles
  • Decreased breath sounds
  • Absence of asthma
Treatment
Treatment is often based on the type of Pneumonia, but antibiotics are typically prescribed.



References
  • Heckerling PS, Tape TG, Wigton RS, et al. (1990). "Clinical prediction rule for pulmonary infiltrates". Ann. Intern. Med. 113 (9): 664–70. PMID 2221647.
  • Robin's Pathologic Basis of Disease
  • Ganong's Review of Medical Physiology, 23e
  • Pneumonia in Dorland's Medical Dictionary

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