Respirology : official journal of the Asian Pacific Society of Respirology
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Oxygen is used in many clinical scenarios, however the variable performance of nasal cannulae makes determining the precise fraction of inspired oxygen (FiO2 ) difficult. We developed a novel method for measurement of the tracheal FiO2 using a catheter placed via bronchoscopy. We investigate the effects of oxygen delivery, respiratory rate, mouth position and estimated minute ventilation (VE ) on the FiO2 delivered by nasal cannulae. ⋯ Continuous measurement of the FiO2 using a transtracheal catheter provides detailed insight into inspiratory changes of the FiO2 delivered by nasal cannulae. Our study confirms that respiratory rate, VE and mouth position significantly influence the inspired oxygen concentration. These parameters should be accounted for when prescribing oxygen.
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This article provides a review of techniques for the analysis of survival data arising from respiratory health studies. Popular techniques such as the Kaplan-Meier survival plot and the Cox proportional hazards model are presented and illustrated using data from a lung cancer study. Advanced issues are also discussed, including parametric proportional hazards models, accelerated failure time models, time-varying explanatory variables, simultaneous analysis of multiple types of outcome events and the restricted mean survival time, a novel measure of the effect of treatment.
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Exercise-induced bronchoconstriction (EIB) is the temporary narrowing of the airways caused by physical exercise. Its exact pathophysiology is unclear; however, acute changes in airways pH may play a role. Exhaled breath condensate (EBC) pH was suggested as a surrogate indicator for airway acid-base status, but its value is also affected by volatile molecules and respiratory droplet dilution. The aim of the study was to assess changes in EBC pH during EIB. ⋯ The development of EIB was related to acute changes of EBC pH, which suggest the role of airway pH decrease in the pathophysiology of EIB. Exercise-induced changes in exhaled biomarkers suggest methodological precautions to avoid physical exercise before performing exhaled breath tests.
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Editorial Comment
Rheumatoid arthritis interstitial lung disease: time to take notice.
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In respiratory health research, interest often lies in estimating the effect of an exposure on a health outcome. If randomization of the exposure of interest is not possible, estimating its effect is typically complicated by confounding bias. This can often be dealt with by controlling for the variables causing the confounding, if measured, in the statistical analysis. ⋯ After creating a causal diagram for the research question, an intuitive and easy-to-use set of rules can be applied, based on a foundation of rigorous mathematics, to decide which measured variables must be controlled for in the statistical analysis in order to remove confounding, to the extent that is possible using the available data. This approach is illustrated by constructing a causal diagram for the research question: 'Does personal smoking affect the risk of subsequent asthma?'. Using data taken from the Tasmanian Longitudinal Health Study, the statistical analysis suggested by the causal diagram approach was performed.