A novel sidestream ultrasonic flow sensor for multiple breath washout in children

Objective: Inert gas multiple breath washout (MBW) for measuring Lung Clearance Index using mass spectrometry and 4% sulfur hexafluoride (SF6) as the tracer gas has been shown to be sensitive for detecting early Cystic Fibrosis (CF) lung disease. However, mass spectrometry requires bulky equipment and is expensive to buy and maintain. A novel sidestream ultrasonic device may overcome this problem. The aims of this study were to assess the feasibility and clinical validity of measuring lung volume (functional residual capacity, FRC) and the LCI using the sidestream ultrasonic flow sensor in children and adolescents with CIF in relation to spirometry and plain chest radiographs. Patients and Methods: MBW using the sidestrearn ultrasonic device and conventional spirometry were performed in 26 patients with CIF and 22 healthy controls. Results: In the controls (4.7-17.7 years) LCI was similar to that reported using mass spectrometry (mean (SD) 6.7 (0.5)). LCI was elevated in 77% of the CF children (6.8-18.9 years), whereas spirometry was abnormal in only 38.5%, 61.5%, and 26.9% for FEV1, MEF25, and FEV1/FVC, respectively This was more marked in children < 10 years. LCI correlated with the Crispin-Norman score, whereas FEV1 did not. Conclusions: Sidestream ultrasonic MBW is a valid and simple alternative to mass spectrometry for assessing ventilation homogeneity in children.