Dalhousie dyspnea scales: Pictorial scales to measure dyspnea during induced bronchoconstriction

The aim of this study was to validate our Dalhousie Dyspnea Scales in children referred for histamine bronchoprovocation challenge. Seventy-four children rated their dyspnea after each FEV₁ measurement following inhalation of doubling histamine concentrations from 0.125 to 8.0 mg/ml by the standard tidal breathing method. Serial FEV₁ and dyspnea rating using the Dalhousie Dyspnea Scales were recorded and Kendall's tau was computed for dyspnea rating versus fall in FEV₁. Subjects were split into those with positive (ΔFEV₁ ≥ 20% with PC₂₀ ≤ 8 mg/ml) or negative histamine challenge test. During histamine inhalation, dyspnea ratings on each of the subscales rose as FEV₁ fell across subjects, whether or not they were histamine-responsive (main effect), and then fell dramatically following relief of induced obstruction by bronchodilator. The Dalhousie Dyspnea Scales are useful and accurate tools to measure dyspnea due to bronchoconstriction in children.