[Effect of a filter system on measurement data and bacterial contamination in lung function studies]

80 measurements of the airway resistance of 20 patients did not yield any significant differences with or without using a bacterial filter (Pall PF 30) (p = 0.1213). Likewise, lung function tests conducted in 61 further patients did not reveal any relevant changes caused by introducing the filter, in respect of the lung function parameters VKin, FEV1, PEF, FEF25, FEF50, FEF75 and TLCO. In these studies the flow receptors were examined for contamination by bacteria. The introduction of the bacterial filter reduced the total count of identified germs from 108, 615 to 307, i.e. by 99.7 per cent, the greatest contamination being found in those parts that were close to the patient (57.6% with filter, 97.1% without filter). Germs of the resident flora of the mouth and pharynx were identified, and occasionally also potential infectious agents such as staphylococcus aureus and streptococcus pneumoniae. The use of a filter system results in a marked decrease in the exposition to germs in lung function tests, without exercising any adverse effect on the measurement data (cross-contamination risk: 0.00078%). This is also achieved--albeit to a lesser extent--by changing those parts of the flow receptor that are close to the patient (cross-contamination risk: 0.0841%). Hence, the use of a filter system appears particularly meaningful in patients with considerable immunodeficiency (advanced stages of HIV infection).