Inspiratory resistive load detection in children with life-threatening asthma.
The detection of inspiratory resistive (R) loads was studied in nonasthmatic children (NA), asthmatic children (A), and children with a history of life-threatening asthma (LTA). It was hypothesized that the LTA children would have a reduced ability to detect added mechanical loads as measured by the Weber fraction, which assesses the resistive load detection threshold (DeltaR(50)/R(0)). Subjects were separated from the investigator, were seated in a soundproofed room, and breathed through a nonrebreathing valve with the inspiratory port connected to the loading manifold. The subject's inspiratory baseline resistance (R(aw)) was measured by the interrupter method. Ten magnitudes of R loads and no-load were presented randomly 10 times each for a single inspiration. The loads were presented in three trials. Subjects pressed a button if they detected the presence of a load. The DeltaR(50) was determined from the % detection-DeltaR curve. R(0) was the sum of the subject's R(aw) and the minimal resistance of the apparatus. The DeltaR(50)/R(0) for children with life- threatening asthma was significantly greater than for asthmatic and nonasthmatic children. The increased DeltaR(50)/R(0) suggests that children with LTA are at risk of life-threatening asthma attacks, in part because it requires a greater change in resistance above their baseline resistance before they sense an increased mechanical load such as presented to them by bronchoconstriction during an asthmatic attack.
Davenport
P W
PW
Department of Physiological Sciences, Health Science Center, University of Florida, Gainesville, Florida 32610, USA. davenportp@mail.vetmed.ufl.edu
Kifle
Y
Y
D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000403:Airway Resistance; D001249:Asthma / Q000503:physiopathology* / Q000523:psychology; D002648:Child; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008297:Male; D008451:Maximal Voluntary Ventilation; D011446:Prospective Studies; D014797:Vital Capacity / Q000502:physiology