[Truncated abstract] This thesis describes the epidemiology and outcome of acute asthma managed by ambulance paramedics, in the metropolitan area of Perth, Western Australia, for the period of 1990 to 2001. The primary aim of this thesis was to determine demographic, socio-economic and clinical trends for ambulance transported patients with asthma, their outcomes and how they have changed over time. The Perth metropolitan area, located in the south-western corner of Western Australia (WA), accounts for 72% of the state’s population, which was approximately 1.3 million people at Census 2001. This thesis was structured around the analysis of twelve years of St John Ambulance (WA) data. Ambulance data was linked using probabilistic matching techniques to the Western Australian Data Linkage System, custodian of links to thirty five years of morbidity and mortality data of the state’s population . . . Unique geography, a monopolistic ambulance service and access to extensive linked data provided ideal conditions for this population-based epidemiological study of patients with asthma who were transported by ambulance. Observed trends in age and gender characteristics of patients, ambulance codes and temporal variables appear to be consistent over time. Monitoring trends in the use of ventilation procedures recorded in hospital data provided useful indicators for describing the epidemiology of severe, lifethreatening asthma in the prehospital setting. Findings from this study were found to be consistent with published literature.

[Truncated abstract] Background Emergency department (ED) presentations of respiratory infections are not well described. Baseline ED data are needed to monitor trends, and to help evaluate the impact of health interventions, and assess changes in clinical practice for these conditions. Aims: To describe the epidemiology of respiratory infections diagnosed in Western Australian hospital EDs from 2000 to 2003; to determine the extent and usefulness of bacterial cultures ordered in hospital, and to describe and evaluate the antibiotic prescribing pattern in the ED setting. Methods: The cohort consisted of patients diagnosed with a respiratory infection at the ED of Perth's major metropolitan teaching hospitals from 1 July 2000 to 30 June 2003. The analysis was based on a linked data set containing patient data from the Emergency Department Information System, the Hospital Morbidity Data Set, the death registry, and the Ultra Laboratory Information System. Further, a sample of patient medical records from 1 adult hospital was examined to assess antibiotic prescribing practice. Results: Overall, there were 37,455 presentations (28,885 patients) given an ED diagnosis of a respiratory infection. Of these, 14,884 (39.7%, 95% CI: 39.2 to 40.2) were admitted and 715 (1.9%, 95% CI: 1.8 to 2.0) died in hospital. The infections included; 48.1% acute upper respiratory infections (URI), 18.5% pneumonia, 23.5% other acute lower respiratory infections (LRI), 7.4% chronic obstructive pulmonary disease with lower respiratory infection (COPD+), 1.3% influenza or viral pneumonia and 1.2% other URI. Children accounted for 80.7% of acute URI diagnoses, COPD+ mainly affected the elderly, just over 40% of pneumonia diagnoses were in patients 65 years or older and 30.7% in patients younger than 15 years. ... The most common pathogen isolated from blood was Streptococcus pneumoniae and 10.4% (95% CI: 4.8 to 16.0) had reduced susceptibility to penicillin. For those diagnosed with pneumonia, Strep. pneumoniae accounted for over 90% of pathogens isolated from the blood of young children and isolation of Enterobacteriaceae from blood increased with age. Around 30% of patients had positive sputum cultures and from these Haemophilus influenzae, Strep. pneumoniae and Pseudomonas aeruginosa were the most common organisms grown. Of those diagnosed with pneumonia, acute LRI or COPD+, 34.7% (95% CI: 26.1 to 43.3) of S. aureus isolated from sputum and 16.4% (95% CI: 7.1 to 25.7) from blood were methicillin resistant. Of 366 adult patient medical records reviewed, 56.8% (95% CI: 51.7 to 61.9) noted that an antibiotic was prescribed in the ED and amoxycillin was the most frequently prescribed. For those with pneumonia, concordance between prescribing guidelines and practice was low. Conclusions The administrative data sets used in the present study are useful for monitoring outcomes for respiratory infections diagnosed in the ED. Pneumonia continues to place a burden on the hospital system. Routine blood and sputum cultures have limited value. However, an appropriately designed surveillance program is needed to monitor potential Abstract v respiratory pathogens and assist in monitoring the appropriateness of current empiric antimicrobial therapy.