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Among those subjects admitted with AECOPD and concomitant pneumonia, a total of 118 patients (91 males) with 150 episodes were identified. Haemophilus influenzae was the commonest organism found in sputum (26.0%), followed by Pseudomonas aeruginosa (5.5%), Streptococcus pneumoniae (3.4%), and Moraxella catarrhalis (3.4%). In contrast to most studies from other countries reporting Streptococcus pneumoniae as the most likely bacterial pathogen, Haemophilus influenzae was the commonest bacterium isolated in sputum in this cohort of patients with AECOPD and concomitant pneumonia.Chronic obstructive pulmonary disease (COPD) is a disease state characterized by airflow limitation that is not fully reversible.Exhaled breath condensate (EBC) analysis is a novel tool which has been developed in recent years and the technique is believed to reflect the lower airway lining fluid. My previous work has demonstrated the repeatability of certain inflammatory markers in the EBC of stable asthma and COPD patients.Hypothesis 1: Bacterial pathogens are the major cause of AECOPD with and without concomitant pneumonia in patients requiring hospitalization. In the one-year retrospective bacteriology study, there were 329 patients with 418 episodes of AECOPD without concomitant pneumonia. These result noted that H. influenzae was the commonest bacterium isolated in sputum in patients with AECOPD without concomitant pneumonia. In areas endemic of tuberculosis, it is advisable to use fluoroquinolones for AECOPD with caution in view of the positive sputum culture of mycobacterium tuberculosis in some patients.Hypothesis 2: Viral pathogens are an important cause of AECOPD in patients hospitalized with AECOPD. For the prospective infectious aetiology study, there were 643 episodes of AECOPD among 373 patients (307 males). Severe airflow obstruction (stable state spirometry) was associated with a higher chance of positive sputum culture (28.2% for FEV1 ≥30% vs. 40.4% for FEV1 <30% predicted normal, p=0.006). In this study, Haemophilus influenzae and influenza A were the commonest aetiological agents in patients hospitalized with AECOPD. More severe airflow obstruction was associated with a higher chance of positive sputum culture.Hypothesis 3: The rates of hospital admissions due to AECOPD are associated with indices of air pollution in Hong Kong. Concerning the effect of air pollutants on AECOPD, significant associations were found between hospital admissions for COPD with all 5 air pollutants. Adverse effects of ambient concentrations of air pollutants on hospitalization rates for COPD are evident, especially during the winter season in Hong Kong.Hypothesis 4: During the course of AECOPD, it is possible to assess inflammation in the airway by measuring biomarkers non-invasively using the method of EBC collection. To explore the course of inflammation in the airway during AECOPD, 26 patients (22 male) with AECOPD (mean percentage predicted FEV1, 44.8 +/- 14.3), 11 stable COPD and 14 age and sex-matched healthy controls were studied. Repeatability measurements of TNFalpha and LTB4 in 6 stable COPD patients were satisfactory. EBC TNFalpha level was low in patients receiving systemic steroid and antibiotic therapy for AECOPD whereas EBC TNFalpha level was also lower in stable patients receiving ICS post AECOPD than those who were not. These findings suggest a potential role for serial EBC TNFalpha for non-invasive monitoring of disease activity.Summary. The above studies have shown that bacterial pathogens are the major cause of AECOPD with and without concomitant pneumonia in patients requiring hospitalization and the commonest bacterium found in the sputum of the patients was Haemophilus influenzae. Viral pathogens are also an important cause of AECOPD in patients hospitalized with AECOPD in Hong Kong and the commonest virus identified in the NPA of the patients was influenza A. Concerning the effect of air pollutants on AECOPD, significant associations were found between hospital admissions for AECOPD with the air pollutants of SO2, NO3, O3, PM10 and PM2.5. Finally, TNFalpha could be measured in the EBC of patients during the course of AECOPD and its level was low in patients receiving systemic steroid and antibiotic therapy for AECOPD. The results suggest that it is possible to assess inflammation in the airway by measuring biomarkers non-invasively using the method of EBC collection. (Abstract shortened by UMI.)Ko, Wai-san Fanny.Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 0926.Thesis (M.D.)--Chinese University of Hong Kong, 2007.Includes bibliographical references (leaves 207-250).Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.School code: 1307