A mathematical model for breath gas analysis of volatile organic compounds with special emphasis on acetone

Recommended standardized procedures for determining exhaled lower respiratory nitric oxide and nasal nitric oxide have been developed by task forces of the European Respiratory Society and the American Thoracic Society. These recommendations have paved the way for the measurement of nitric oxide to become a diagnostic tool for specific clinical applications. It would be desirable to develop similar guidelines for the sampling of other trace gases in exhaled breath, especially volatile organic compounds (VOCs) which reflect ongoing metabolism. The concentrations of water-soluble, blood-borne substances in exhaled breath are influenced by: (i) breathing patterns affecting gas exchange in the conducting airways; (ii) the concentrations in the tracheo-bronchial lining fluid; (iii) the alveolar and systemic concentrations of the compound. The classical Farhi equation takes only the alveolar concentrations into account. Real-time measurements of acetone in end-tidal breath under an ergometer challenge show characteristics which cannot be explained within the Farhi setting. Here we develop a compartment model that reliably captures these profiles and is capable of relating breath to the systemic concentrations of acetone. By comparison with experimental data it is inferred that the major part of variability in breath acetone concentrations (e.g., in response to moderate exercise or altered breathing patterns) can be attributed to airway gas exchange, with minimal changes of the underlying blood and tissue concentrations. Moreover, it is deduced that measured end-tidal breath concentrations of acetone determined during resting conditions and free breathing will be rather poor indicators for endogenous levels. Particularly, the current formulation includes the classical Farhi and the Scheid series inhomogeneity model as special limiting cases.Comment: 38 page

Cigarette smoking accelerates progression of alcoholic pancreatitis.

Background: Smoking is a recognised risk factor for pancreatic cancer and has been associated with chronic pancreatitis and also with type II diabetes. Aims: The aim of this study was to investigate the effect of tobacco on the age of diagnosis of pancreatitis and progression of disease, as measured by the appearance of calcification and diabetes.Patients: We used data from a retrospective cohort of 934 patients with chronic alcoholic pancreatitis where information on smoking was available, who were diagnosed and followed in clinical centres in five countries.Methods: We compared age at diagnosis of pancreatitis in smokers versus non-smokers, and used the Cox proportional hazards model to evaluate the effects of tobacco on the development of calcification and diabetes, after adjustment for age, sex, centre, and alcohol consumption.Results: The diagnosis of pancreatitis was made, on average, 4.7 years earlier in smokers than in nonsmokers (p=0.001). Tobacco smoking increased significantly the risk of pancreatic calcifications ( hazard ratio (HR) 4.9 (95% confidence interval (CI) 2.3-10.5) for smokers v non-smokers) and to a lesser extent the risk of diabetes (HR 2.3 (95% CI 1.2-4.2)) during the course of pancreatitis.Conclusions: In this study, tobacco smoking was associated with earlier diagnosis of chronic alcoholic pancreatitis and with the appearance of calcifications and diabetes, independent of alcohol consumption

Web-based interventions to promote physical activity by older adults: promising perspectives for a public health challenge

Regular physical activity is associated with a wide range of health benefits. As population age, promotion of physical activity should specifically target older adults, an expanding group involving potential higher health care costs in the near future. Innovative interventions focusing on physical activity behaviors of senior adults exposed promising results, most recently through the use of the Internet. If seniors and Internet are generally considered as two opposite concepts, arguments in favour of bringing them together in a public health perspective have been identified by the recent literature. Older adults are the fastest growing group of Internet users and are more prone than younger to use it for health-related subjects. Web-based interventions are effective in many health promotion sectors, including physical activity. This is particularly true when interventions target the environmental determinants of each senior citizen and are specifically designed for this population. Those early research findings must clearly be extended, particularly regarding to the long term effects of Webbased physical activity interventions. Solutions that will reduce the high dropout rate recorded in the existing literature must also be considered as a priority in order to ensure the development of this forward-looking field of research