New aspects of airway mechanics in preterm infants

¹ Dept of Paediatrics and Adolescent Medicine, University Hospital of Freiburg, Mathildenstr. 1, 79106 Freiburg, Germany; Portex Respiratory Unit, Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK; and Neonatal Unit, Homerton University Hospital, Homerton Row, London E9 6SR, UK
² Portex Respiratory Unit, Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK
³ Dept of Child Health, University of Leicester, P.O. Box 65, Leicester LE2 7LX, UK
⁴ Paediatric Respiratory Medicine, Dept of Paediatrics, University Hospital of Bern, Inselspital, 3010 Bern, Switzerland

^* To whom correspondence should be addressed. E-mail: henschen{at}kikli.ukl.uni-freiburg.de.

	Abstract

High frequency respiratory impedance data measured non invasively by the high speed interrupter technique (HIT), particularly the first anti-resonance (f_ar,1), is related to airway wall mechanics. The aim of this study was to evaluate the feasibility and repeatability of HIT in unsedated preterm infants, and to compare values of f_ar,1 from 18 preterm (postconceptional age 32-37 weeks, weight 1730-2910 g) and 18 term infants (42-47 weeks, 3920-5340 g). Among the preterm infants, there was good short term repeatability of f_ar,1 within a single sleep epoch (mean (SD) CV: 8 (1.7)%, but 95% limits of agreement for repeated measures of f_ar,1 after 3-8 hours were relatively wide (-41 Hz; 37 Hz). f_ar,1 was significantly lower in preterm infants (199 versus 257 Hz, p0.001), indicating that wave propagation characteristics in preterm airways are different from those of term infants. We suggest that this is consistent with developmental differences in airway wall structure and compliance, including the influence of the surrounding tissue. Since flow limitation is determined by wave propagation velocity () and airway cross-sectional area, we hypothesize that the physical ability of the airways to carry large flows is fundamentally different in preterm than in term infants.