Thresholds of resistive load detection in children with asthma

Threshold detection of added resistive loads was studied in asthmatic children and compared to data previously obtained in a group of healthy children. The relationships between possible psychological predictors of perceptual ability, the perceptual threshold, and functional morbidity variables were also investigated. Our subjects were 103 children (mean age, 10.9 years) with asthma who completed two laboratory protocols in which they were asked to distinguish breaths with varying degrees of added resistance from unloaded breaths. Using two different computer-driven protocols, resistances were presented as percentages of each child's intrinsic respiratory system resistance (R(rs)). Cognitive ability was assessed through subtests of the Wechsler Intelligence Scale for Children, 3rd edition (WISC-III), and functional morbidity was quantified through a combination of school absences, emergency medical visits, and days hospitalized. Detection thresholds for both protocols were highly correlated with intrinsic resistance (r = 0.49 and 0.66; P < 0.001). Weber fraction thresholds were significantly lower for asthmatic children than healthy controls. Thresholds were not significantly related to either intelligence or pulmonary functional abnormalities due to asthma. Methodologic limitations require cautious interpretation of the results, but we conclude that psychophysical approaches may be useful in the study of symptom perception in pediatric asthma.