Emergency Medicine Pneumonia

Pneumonia is inflammation within the lung caused by infection with micro-organisms. Clinically the diagnosis is made either by physical signs or radiological evidence of consolidation within the lungs. The terms pneumonitis and alveolitis also imply inflammation but in practice are reserved for conditions associated with chemical and physical injury to the lungs. Physical signs to localize abnormalities in the chest are not very reliable and in practice without good chest Xrays it is difficult to distinguish pneumonia from other chest infections, particularly in patients with pre-existing lung disease. Pneumonia occurs throughout the world but there is little comparative data between countries (Bulla & Hitze, 1978). The major bacterial cause ofpneumonia remains Streptococcuspneumoniae (MacFarlane et al., 1982; British Thoracic Society, 1985) but its incidence has been declining in the past 30 to 40 years. This has been attributed both to the introduction of penicillin and sulphonamides and improving social conditions (Crofton & Douglas, 1981). The largest decrease in incidence has been in the infant population and the rise seen in the elderly indicates that pneumonia is a common terminal event at the end of life. The total number ofdeaths in patients under 50 years in the UK is still 3 to 5 times that due to asthma (Charlton et al., 1983). In all ages males have a higher mortality than females. Pneumonia is more common in the winter months and also in areas where there is atmospheric pollution. There is little community based information about the epidemiology of pneumonia using radiological techniques to confirm the presence of pneumonia and most studies relate to hospital admissions. In Bristol (White et al., 1981) 210 consecutive patients admitted to hospital with a primary diagnosis of pneumonia between 1974 and 1980 were studied; pneumonia due to Mycoplasma pneumoniae was the most common (14% of patients) compared with pneumococcal pneumonia (11.5% patients) and influenza A pneumonia. In this study however, no pathogen was detected in about half of the patients. The high incidence of mycoplasma pneumonia probably occurred because of a minor epidemic in Bristol at the time. In a similar study of 127 patients in Nottingham (MacFarlane et al., 1982) aetiological diagnosis was obtained in 124 patients. In this study pneumococcal pneumonia accounted for 76% of cases and Legionnaires' disease was the next most common diagnosis, 15% of cases. Recently the British Thoracic Society survey ofpneumonia has confirmed that St. pneumoniae and M. pneumoniae are the most common agents (British Thoracic Society, 1985). Epidemics of viral infection such as respiratory syncytial virus are associated with increase in the incidence of pneumonia. Communities where individuals live in close contact, such as the long-house dwellers of Papua New Guinea and gold-miners in South Africa are particularly prone to epidemics of pneumonia (Oseasohn et al., 1978).