Respir Res

BackgroundDuring 2007\ue2\u20ac\u201c2010, the National Health and Nutrition Examination Survey (NHANES) conducted a spirometry component which obtained pre-bronchodilator pulmonary lung function data on a nationally representative sample of US adults aged 6\ue2\u20ac\u201c79 years and post-bronchodilator pulmonary lung function data for the subset of adults with airflow limitation. The goals of this study were to 1) compute prevalence estimates of chronic obstructive pulmonary disease (COPD) using pre-bronchodilator and post-bronchodilator spirometry measurements and fixed ratio and lower limit of normal (LLN) diagnostic criteria and 2) examine the potential impact of nonresponse on the estimates.MethodsThis analysis was limited to those aged 40\ue2\u20ac\u201c79 years who were eligible for NHANES pre-bronchodilator spirometry (n=7,104). Examinees with likely airflow limitation were further eligible for post-bronchodilator testing (n=1,110). Persons were classified as having COPD based on FEV1/FVC < 70% (fixed ratio) or FEV1/FVC < lower limit of normal (LLN) based on person\ue2\u20ac\u2122s age, sex, height, and race/ethnicity. Those without spirometry but self-reporting both daytime supplemental oxygen therapy plus emphysema and/or current chronic bronchitis were also classified as having COPD. The final analytic samples for pre-bronchodilator and post-bronchodilator analyses were 77.1% (n=5,477) and 50.8% (n=564) of those eligible, respectively. To account for non-response, NHANES examination weights were adjusted to the eligible pre-bronchodilator and post-bronchodilator subpopulations.ResultsIn 2007\ue2\u20ac\u201c2010, using the fixed ratio criterion and pre-bronchodilator test results, COPD prevalence was 20.9% (SE 1.1) among US adults aged 40\ue2\u20ac\u201c79 years. Applying the same criterion to post-bronchodilator test results, prevalence was 14.0% (SE 1.0). Using the LLN criterion and pre-bronchodilator test results, the COPD prevalence was 15.4% (SE 0.8), while applying the same criterion to post-bronchodilator test results, prevalence was 10.2% (SE 0.8).ConclusionsThe overall COPD prevalence among US adults aged 40\ue2\u20ac\u201c79 years varied from 10.2% to 20.9% based on whether pre- or post-bronchodilator values were used and which diagnostic criterion (fixed ratio or LLN) was applied. The overall prevalence decreased by approximately 33% when airflow limitation was based on post-bronchodilator as compared to pre-bronchodilator spirometry, regardless of which diagnostic criterion was used

Computing coalitions in Multiagent Systems: A contextual reasoning approach

In multiagent systems, agents often have to rely on other agents to reach their goals, for example when they lack a needed resource or do not have the capability to perform a required action. Agents there- fore need to cooperate. Some of the questions then raised, such as, which agent to cooperate with, are addressed in the field of coalition formation. In this paper we go further and first, address the question of how to com- pute the solution space for the formation of coalitions using a contextual reasoning approach. We model agents as contexts in Multi-Context Sys- tems (MCS) and dependence relations among agents as bridge rules. We then systematically compute all potential coalitions using algorithms for MCS equilibria. Finally, given a set of functional and non-functional requirements, we propose ways to select the best solutions. We illustrate our approach with an example from robotics