False normal Lung Clearance Index in infants with cystic fibrosis due to software algorithms

• Published in: Pediatric pulmonology 2015-10, Vol.50 (10), p.970-977
• Main Authors: Anagnostopoulou, Pinelopi, Yammine, Sophie, Schmidt, Anne, Korten, Insa, Kieninger, Elisabeth, Mack, Ines, Trachsel, Daniel, Hafen, Gaudenz, Moeller, Alexander, Casaulta, Carmen, Latzin, Philipp
• Format: Article
• Language: English
• Subjects: Algorithms; Case-Control Studies; cystic fibrosis; Cystic Fibrosis - physiopathology; Female; Humans; Infant; infant pulmonary function; Male; multiple breath washout; Reference Values; Respiratory Function Tests - instrumentation; Respiratory Function Tests - methods; Software; ultrasonic flowmeter
• ISSN: 8755-6863; 1099-0496
• DOI: 10.1002/ppul.23256

Summary Background Lung clearance index (LCI), a marker of ventilation inhomogeneity, is elevated early in children with cystic fibrosis (CF). However, in infants with CF, LCI values are found to be normal, although structural lung abnormalities are often detectable. We hypothesized that this discrepancy is due to inadequate algorithms of the available software package. Aim Our aim was to challenge the validity of these software algorithms. Methods We compared multiple breath washout (MBW) results of current software algorithms (automatic modus) to refined algorithms (manual modus) in 17 asymptomatic infants with CF, and 24 matched healthy term‐born infants. The main difference between these two analysis methods lies in the calculation of the molar mass differences that the system uses to define the completion of the measurement. Results In infants with CF the refined manual modus revealed clearly elevated LCI above 9 in 8 out of 35 measurements (23%), all showing LCI values below 8.3 using the automatic modus (paired t‐test comparing the means, P