Until recently, the bronchial circulation has been relatively ignored in the research and clinical arenas, perhaps because of its small volume and seeming dispensability relative to the pulmonary circulation. Although the bronchial circulation only receives around 1% of the cardiac output in health, it serves functions that are critical to maintaining airway and lung function. The bronchial circulation also plays an important role in many lung and airway diseases; through its ability to increase in size, the bronchial circulation is able to provide lung parenchymal perfusion when the pulmonary circulation is compromised, and more recently the role of the bronchial circulation in the pathogenesis of inflammatory airway disease has been explored. Due to the anatomic variability and small volume of the bronchial circulation, much of the research to date has necessitated the use of animal models and invasive procedures. More recently, non-invasive techniques for measuring bronchial blood flow in the mucosal microvascular network have been developed and offer a new avenue for the study of this circulation in humans. In conjunction with molecular research, measurement of airway blood flow (Q(aw)) may help elucidate the role of the bronchial circulation in inflammatory airway disease and become a useful tool for monitoring therapy.
BackgroundEmpyema is a serious complication of pneumonia frequently caused by Streptococcus pneumoniae (SP). We assessed the impact of the 13-valent pneumococcal conjugate vaccine (13vPCV) on childhood pneumonia and empyema after inclusion in the Australian National Immunisation Program.MethodsFor bacterial pneumonia and empyema hospitalisations, we ascertained incidence rates (IRs) using the National Hospital Morbidity Database International Statistical Classification of Disease discharge codes and relevant population denominators, and calculated incidence rate ratios (IRR) comparing the 13vPCV period (June 2012–May 2017) with the 7vPCV period (June 2007–May 2011). Blood and pleural fluid (PF) cultures and PF PCR of 401 children with empyema from 11 Australian hospitals during the 13vPCV period were compared with our previous study in the 7vPCV period.FindingsAcross 7vPCV and 13vPCV periods, IRs per million children (95% CIs) were 1605 (1588 to 1621) and 1272 (1259 to 1285) for bacterial pneumonia, and 14.23 (12.67 to 15.79) and 17.89 (16.37 to 19.42) for empyema hospitalisations. IRRs were 0.79 (0.78 to 0.80) for bacterial pneumonia and 1.25 (1.09 to 1.44) for empyema. Of 161 empyema cases with SP serotypes, 147 (91.3%) were vaccine types. ST3 accounted for 76.4% of identified serotypes in the 13vPCV period, more than double than the 7vPCV period (p<0.001); ST19A decreased from 36.4% to 12.4%. No cases of ST1 empyema were identified in the 13vPCV period versus 14.5% in the 7vPCV period.Interpretation13vPCV resulted in a significant reduction in all-cause hospitalisations for bacterial pneumonia but empyema hospitalisations significantly increased, with emergence of pneumococcal ST3 as the dominant serotype in empyema.Trial registration numberAustralian and New Zealand Clinical Trial Registry ACTRN 12614000354684.
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