Longitudinal validity of spirometers--a challenge in longitudinal studies.

Pulmonary function testing (PFT) in longitudinal studies involves the repeated use of spirometers over long time periods. We assess the comparability of PFT results taken under biologic field conditions using thirteen certified devices of various technology and age. Comparability of measurements across devices and over time is relevant both in clinical and epidemiological research. Forced Vital Capacity (FVC), Forced Expiratory Volume in the first second (FEV1) and Forced Expiratory Flow 50% (FEF50) were compared before and after the data collection of the Swiss Study on Air Pollution and Lung Diseases in Adults (SAPALDIA) and the European Community Respiratory Health Survey (ECRHS) cohort studies. Three test series were conducted with 46, 50 and 56 volunteers using various combinations of spirometers to compare the eight flow-sensing spirometers (Sensormedics 2200) used in the SAPALDIA cross-sectional and follow-up, two new flow-sensing instruments (Sensormedics Vmax) and three volume displacement spirometers (two Biomedin/Baires and one Sensormedics 2400). The initial comparison (1999/2000) of eight Sensormedics 2200 and the follow-up comparison (2003) of the same devices revealed a maximal variation of up to 2.6% for FVC, 2.4% for FEV1 and 2.8% for FEF50 across devices with no indication of systematic differences between spirometers. Results were also reproducible between Biomedin, Sensormedics 2200 and 2400. The new generation of Sensormedics (Vmax) gave systematically lower results. The study demonstrates the need to conduct spirometer comparison tests with humans. For follow-up studies we strongly recommend the use of the same spirometers

Acute respiratory health effects of urban air pollutants in adults with different patterns of underlying respiratory disease

OBJECTIVE: Whether underlying chronic respiratory diseases are susceptible factors for symptomatic episodes, which lead to primary-level care, in association with air pollutant exposures is unknown. We evaluated and compared association lag structures between daily ambient levels of nitrogen dioxide (NO2) and total suspended particulates (TSP) and respiratory symptom-related doctor visits in adults with different patterns of underlying chronic respiratory disease.METHODS: In a time-stratified case-crossover analysis nested within a diary panel study, 459 Swiss adult participants with asthma, chronic bronchitis, chronic obstructive pulmonary disease (COPD) and healthy participants recorded occurrence of respiratory-symptom related doctor visits (n = 1,048) in one to six four-week intervals over two years. For each disease subgroup, odds ratios (ORs) for doctor visit were estimated as a function of NO2 or TSP concentrations (per 10 micrograms per cubic meter [µg/m3]) lagged between 0-13 days in a polynomial distributed lag model.RESULTS: Higher ORs for NO2 in participants with COPD (OR: 1.17, 95%CI: 1.02-1.35) and asthma (OR: 1.15, 95%CI: 1.02-1.30) occurred at exposure lags of two and five days, respectively. Doctor visits increased by 9.1% (95%CI: 3.2-15.4%) and 4.2% (95%CI: 1.2-7.2%) over the first week following a 10 µg/m3 increase in NO2 concentration in the COPD and chronic bronchitis subgroups, respectively. The percent increase in the COPD subgroup was significantly greater (p >0.05) when compared with the healthy subgroup. Observed findings were similar for TSP.CONCLUSIONS: Respiratory problems leading to a doctor visit, associated with an increase in exposure to NO2 and TSP, may have a faster dynamic in individuals with COPD

Communication of political interest groups in Switzerland: Adressees, channels and instruments

We present a broad overview on the Swiss interest group population and the results of a quantitative online survey on the communication repertoire of 985 interest groups. We then discuss sample construction and the different addressees of interest group communication, the perceived relevance of mass media channels, and which instruments and measures are used to communicate with external and internal environments. We identify four different logics – influence, support, reputation and reciprocity – that influence the communication activities of political intermediaries such as interest groups