Respiratory Physiology & Neurobiology 181 (2012) 74–78 Contents lists available at SciVerse ScienceDirect Respiratory Physiology & Neurobiology j o ur nal homep age : www.elsevier.com/locate/resphysiol Evaluation of the trachea and intrathoracic airways by the acoustic reflection method in children with cystic fibrosis Nicolas Leboulanger a,b,c,e , Bruno Louis c,d,h , Harriet Corvol a,e,f , Adriana Ramirez a,e,f , Rédouane Fodil c,d,h , Frédéric Lofaso g , Brigitte Fauroux a,e,f,∗ a UPMC University Paris 06, France b Otolaryngology-Head and Neck Surgery Department, AP-HP, Armand-Trousseau Children’s Hospital, 26 Avenue du Dr Arnold Netter, 75012 Paris, France c INSERM, Unité U955, 94010 Créteil, France d Université Paris-Est, Faculté de Médecine, Créteil, France e INSERM UMR S-938, 75012 Paris, France f Pulmonology Department, AP-HP, Armand-Trousseau Children’s Hospital, 26 Avenue du Dr Arnold Netter, 75012 Paris, France g Physiology Laboratory, AP-HP, Raymond Poincaré Hospital, 104, boulevard Raymond-Poincaré, 92380 Garches, France h CNRS, ERL 7240, 94010 Créteil, France a r t i c l e i n f o Article history: Accepted 28 January 2012 Keywords: Cystic fibrosis Trachea Airways Acoustic reflection Airway resistance a b s t r a c t Tracheomalacia has been observed in older patients with cystic fibrosis (CF). The acoustic reflection method (ARM) allows a noninvasive calculation of the longitudinal cross-sectional area of the trachea (MTAv) and the airway resistance (Raw). ARM measurements were performed in 20 CF children and 20 controls during spontaneous breathing (SB), forced inspiration (FI), and forced expiration (FE). The mean MTAv value was comparable in the CF patients and the control subjects during SB, FI, and FE. The Raw was also comparable during SB and FI. However, the Raw during FE was higher in the CF patients than in the control subjects (7.9 ± 2.3 vs 5.0 ± 1.5 cmH 2 O l -1 s -1 , respectively, p < 0.001). In the patients with CF, only the Raw during FE correlated with the predicted forced expiratory volume in 1 s (R 2 = 0.37, p = 0.04). The tracheal cross-sectional area measured by the ARM is normal in children with CF but the increase in Raw during FE suggests an increase in intrathoracic airway distensibility. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Most of the morbidity and mortality in cystic fibrosis (CF) is due to the involvement of the airways and the lungs with progressive airflow obstruction, due to mucus plugging, bacterial infection, and inflammation within the bronchial walls. This persistent infection and exaggerated inflammation within the small and large airways leads to progressive destruction of the airway walls, bronchiecta- sis with bronchial and tracheal enlargement. Classical radiographs and dynamic computed tomography have indeed revealed tracheal enlargement and a high incidence of tracheomalacia in patients with CF (Griscom et al., 1987; McDermott et al., 2009). The tracheal Abbreviations: ARM, acoustic reflection method; CF, cystic fibrosis; FE, forced expiration; FI, forced inspiration; FOT, forced oscillations technique; FRC, functional residual capacity; MTAv, mean tracheal area value; Raw, airway resistance; SB, spontaneous breathing. ∗ Corresponding author at: Pediatric Pulmonology Department, 26 avenue du Dr Arnold Netter, 75012 Paris, France. Tel.: +33 144736174; fax: +33 144736718. E-mail address: brigitte.fauroux@trs.aphp.fr (B. Fauroux). size of 39 young adults with CF has also been evaluated by the acoustic reflection method (ARM), which is a non-invasive technique based on the analysis of the reflection of a single tran- sient planar wave, allowing the calculation of the longitudinal cross-sectional area profile of the examined cavity (Brooks, 1990). Whereas the tracheal size near functional residual capacity (FRC) of patients with CF did not differ from that of age-matched control subjects, the trachea of patients with CF expanded more than did the trachea of control subjects when higher volumes were attained, suggesting increased airway distensibility (Brooks, 1990). Recent animal studies suggest that the CFTR protein dysfunction may also play a role in this increase in airway diameter. Indeed, structural and functional tracheal cartilage abnormalities have been observed in two CF mouse models (Bonvin et al., 2008; Meyerholz et al., 2010), raising the question of the role of CFTR protein dysfunction in the pathogenesis of CF airway disease. As the ARM is a noninvasive, rapid and simple method to assess the cross sectional area of the large airways, we used this technique to assess the characteristics of the trachea in a group of young chil- dren with CF. The ARM has been first reported in humans in 1980 by Fredberg et al. (1980). Since then, ARM has been used to explore 1569-9048/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.resp.2012.01.015