title: High-pitched breath sounds indicate airflow limitation in asymptomatic asthmatic children.
abstract: OBJECTIVE
  Asthmatic children may have airway dysfunction even when asymptomatic, indicating that their long-term treatment is less than optimal. Although airway dysfunction can be identified on lung function testing, performing these tests can be difficult in infants. We studied whether breath sounds reflect subtle airway dysfunction in asthmatic children.
  
  
  METHODS
  The highest frequency of inspiratory breaths sounds (HFI) and the highest frequency of expiratory breath sounds (HFE) were measured in 131 asthmatic children while asymptomatic and with no wheezes for more than 2 weeks. No child was being treated with inhaled corticosteroids (ICS). Breath sounds were recorded and analysed by sound spectrography and compared with spirometric parameters. After initial evaluation, cases with more than step 2 (mild persistent) asthma were treated using inhaled fluticasone (100-200 microg/day) for 1 month, and then breath sound analysis and pulmonary function testing were repeated.
  
  
  RESULTS
  On initial evaluation, HFI correlated with the percentage of predicted FEF(50) (%FEF(50)), (r = -0.45, P < 0.001), the percentage of predicted FEF(75) (%FEF(75)) (r = -0.456, P < 0.001), and FEV(1) as a percentage of FVC (FEV(1)/FVC (%)) (r = -0.32, P < 0.001). HFI did not correlate with the percentage of predicted PEF (%PEF). The 69 children with lower than normal %FEF(50) were then treated with ICS. The %FEF(50) and %FEF(75) improved after ICS treatment, and increases in %FEF(50) (P < 0.005) correlated with decreases in HFI (P < 0.001).
  
  
  CONCLUSIONS
  Higher HFI in asymptomatic asthmatic children may indicate small airway obstruction. Additional ICS treatment may improve the pulmonary function indices representing small airway function with simultaneous HFI decreases in such patients.
authors.affiliation: Department of Paediatrics, Minami Wakayama Medical Center, Wakayama, Japan. habukawc@mwn.hosp.go.jp
authors.forename: Chizu
authors.initials: C
authors.lastname: Habukawa
authors.forename: Yukio
authors.initials: Y
authors.lastname: Nagasaka
authors.forename: Katsumi
authors.initials: K
authors.lastname: Murakami
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Takemura
mesh_terms: D000293:Adolescent; D000730:Androstadienes / Q000627:therapeutic use; D001249:Asthma / Q000175:diagnosis* / Q000188:drug therapy / Q000503:physiopathology*; D001993:Bronchodilator Agents / Q000627:therapeutic use; D002648:Child; D005260:Female; D000068298:Fluticasone; D006801:Humans; D008297:Male; D011237:Predictive Value of Tests; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000502:physiology*; D012135:Respiratory Sounds / Q000503:physiopathology*; D012720:Severity of Illness Index; D013018:Sound Spectrography; D013147:Spirometry; D055815:Young Adult
chemical_list: D000730:Androstadienes; D001993:Bronchodilator Agents; D000068298:Fluticasone