Background: This study compared the plethysmographic lung volumes of children with sighing dyspnea with healthy children and tested the hypothesis that sighing children suffer from hyperinflation or gas trapping as a cause of dyspnea.
Methods: From January 2006 to December 2006, pediatric patients with sighing dyspnea presenting to the pulmonary clinic of a tertiary children's hospital who had no apparent cardiopulmonary diseases were prospectively enrolled; normal healthy children were invited to participate for comparison. Baseline pre-bronchodilator spirometry and post-inhaled bronchodilator spirometry were measured for the determination of bronchodilator response. Plethysmographic lung volumes were determined solely for total lung capacity, residual volume (RV) and functional residual capacity (FRC) without the use of inhaled bronchodilator according to standard procedure.
Results: Eighteen sighing children (10 boys) and 10 healthy subjects (six boys) were included in the present study. They had a median age of 13 years (range, 8-15 years) and 13 years (range, 8-17 years), respectively. The mean baseline forced vital capacity (FVC) of subjects with dyspnea was 79.4 +/- 16.7% of predicted, while that of the normal control children was 88.4 +/- 6.7%, which was not statistically significantly different. Forced expiratory volume in 1 s (FEV(1)), FEV(1)/FVC % of predicted were within normal limits and indicated no bronchodilator response. RV and RV/total lung capacity (TLC) were elevated in children with sighing dyspnea that were not measured by spirometry, but TLC and FRC measured on plethysmography (FRC(pleth)) were not increased.
Conclusions: RV and RV/TLC were higher in children with sighing dyspnea that were not measured by spirometry, but TLC and FRC(pleth) were not increased. The causal link between dysfunctional breathing patterns and changes in static lung volumes was not able to be determined in the present study. The possibility of heterogeneity of patients with sighing dyspnea obscures the significance of lung volume discrepancy in this population; further subdivision of children with sighing dyspnea in a larger cohort of patients is required.