Improved Methodology for Threshold Detection Studies in Asthmatic Children

This paper reports the differences between two methodologies for threshold detection of added resistive loads in children and adolescents. The first-generation apparatus utilized a series of laminar flow screens to present various total resistances, while in the second generation the apparatus utilized a servo-controlled cone that occluded an aperture to varying degrees. Protocol modifications in the second generation methodology included forced choice, attentional enhancements, and larger increments of added resistance. Two studies conducted 2 years apart provided data on the first and second generations of methodology. All participants in Study 1 ( N = 33) and Study 2 ( N = 33) were children with asthma. Subjects were matched for both age and asthma severity. Results showed the methodologic improvements in the second generation to be significant. Tracking and random thresholds were achieved by 85% and 82% of the subjects in Study 2 compared to 76% and 42% in Study 1, respectively. The correlation between the mean tracking and random thresholds was .40 in Study 2 compared to a statistically insignificant result in Study 1, indicating improved reliability. Raw thresholds were correlated with intrinsic resistance in both studies ( r = .29-.88), supporting the use of Weber's Law in resistive loading studies of children. Results using the second generation methodologic improvements demonstrate that children as young as age 7 can complete resistance loading protocols. Standard methodology will enhance the comparability between studies.