Sources of variance in the measurement of intrapulmonary killing of bacteria

Sources of variability are described for a method used for the quantitative measurement of pulmonary resistance to inhaled bacteria in individual animals. Factors contributing significantly to variability include aerosol exposure chamber design, bacterial species used for aerosol challenge, location of animals in the chamber, and individual intrapulmonary bacterial killing rates. Laboratory error accounted for a small portion of the variance. The data demonstrate that with appropriate modifications in protocol, statistical design and analysis experiments can be performed with increased accuracy, thereby reducing the number of animals needed for each experiment.