Jens Bräunlich1, Friederike Goldner2, Hubert Wirtz3. 1. Department of Respiratory Medicine, University of Leipzig, Liebigstraße 20, 04103 Leipzig, Germany. Electronic address: highflow@web.de. 2. Department of Respiratory Medicine, University of Leipzig, Liebigstraße 20, 04103 Leipzig, Germany. 3. Department of Respiratory Medicine, University of Leipzig, Liebigstraße 20, 04103 Leipzig, Germany. Electronic address: hubert.wirtz@uniklinik-leipzig.de.
Abstract
INTRODUCTION: Nasal highflow (NHF) has a growing evidence in treatment of hypoxemic respiratory failure. There are preliminary data available about use in acute and chronic type-II-respiratory failure. Unfortunately underlying mechanisms of NHF are not well understood. Increase in airway pressure seems too small to explain the observed reduction in hypercapnia. Most interesting effects are wash-out of upper airways and reduction of functional dead space. There are no data available about a wash-out of lower airways. METHODS: We established a sheep lung model to evaluate CO2-wash-out in lower airways. Therefore we placed measuring and insufflation catheter in maximal expanded lung. The lung was not ventilated in order to minimize influence of CO2 rebreathing and increase in airway pressure. Airway pressure and CO2 values were measured in lower airways and in tracheal space. RESULTS: CO2 was decreased by NHF in lower airways and in tracheal space. Changes in CO2 were flow dependent. There was also an increase in airway pressure in these settings. CONCLUSIONS: NHF is able to decrease CO2 in lower airways in a flow-dependent manner. This effect is independent of an increase in airway pressure and CO2-rebreathing. So wash-out is an important reason for efficiency of NHF in decreasing hypercapnia.
INTRODUCTION: Nasal highflow (NHF) has a growing evidence in treatment of hypoxemic respiratory failure. There are preliminary data available about use in acute and chronic type-II-respiratory failure. Unfortunately underlying mechanisms of NHF are not well understood. Increase in airway pressure seems too small to explain the observed reduction in hypercapnia. Most interesting effects are wash-out of upper airways and reduction of functional dead space. There are no data available about a wash-out of lower airways. METHODS: We established a sheep lung model to evaluate CO2-wash-out in lower airways. Therefore we placed measuring and insufflation catheter in maximal expanded lung. The lung was not ventilated in order to minimize influence of CO2 rebreathing and increase in airway pressure. Airway pressure and CO2 values were measured in lower airways and in tracheal space. RESULTS:CO2 was decreased by NHF in lower airways and in tracheal space. Changes in CO2 were flow dependent. There was also an increase in airway pressure in these settings. CONCLUSIONS: NHF is able to decrease CO2 in lower airways in a flow-dependent manner. This effect is independent of an increase in airway pressure and CO2-rebreathing. So wash-out is an important reason for efficiency of NHF in decreasing hypercapnia.
Authors: M Pfeifer; S Ewig; T Voshaar; W Randerath; T Bauer; J Geiseler; D Dellweg; M Westhoff; W Windisch; B Schönhofer; S Kluge; P M Lepper Journal: Pneumologie Date: 2020-04-22
Authors: Jens Bräunlich; Dominic Dellweg; Andreas Bastian; Stephan Budweiser; Winfried Randerath; Dora Triché; Martin Bachmann; Christian Kähler; Abdel Hakim Bayarassou; Irmhild Mäder; Jens Geiseler; Norbert Köhler; David Petroff; Hubert Wirtz Journal: Int J Chron Obstruct Pulmon Dis Date: 2019-07-05