Christoph Schäfer1,2, Stefan Schumann1, Hans Fuchs3, Daniel Klotz3. 1. Department of Anesthesiology and Critical Care, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany. 2. Department of Cardiology and Cardiovascular Medicine, University Hospital of Tübingen, Tübingen, Germany. 3. Division of Neonatology, Center for Pediatrics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
Abstract
OBJECTIVES: The carbon dioxide (CO2 ) diffusion coefficient (DCO 2 ) reflects CO 2 removal during high-frequency oscillatory ventilation (HFOV). We hypothesized that despite leak flow during noninvasive HFOV (nHFOV) DCO 2 continues to indicate ventilation efficacy. METHODS: A neonatal airway model including CO2 production and an adjustable oropharyngeal leak was connected to a ventilator via bi-nasal prongs. Pressures and gas flows were measured at prongs, trachea, and leak. Oscillatory tidal volumes below (V T trachea ) and above the leak (V T prong ) were calculated from tracheal and leak flows. DCO 2 was calculated using V T trachea (DCO 2 trachea ) and V T prong (DCO 2 prong ) and compared with CO 2 partial pressure (pCO 2 ). Effects of leak flow (0, 5, or 10 L/min) on DCO 2 were assessed at fixed pressure amplitudes or predefined oscillatory volumes under steady-state pCO 2 conditions in the modeled lung. RESULTS: DCO2 trachea correlated strongly with pCO 2 , independent of the leak flow level (P < 0.0001). DCO 2 prong correlated with pCO 2 without and with moderate leak (P < 0.0001) but not with maximum leak (P = 0.1432). V T trachea correlated with the quotient of tracheal pressure amplitude and frequency irrespective of the leak (P < 0.0001). Based on the pressure amplitude at prong level (A prong ) V T trachea continued to follow a linear model of which the slopes decreased with increasing leak flow. V T prong correlated with the quotient of A prong and frequency, irrespective of the leak (P < 0.0001). CONCLUSIONS: DCO2 obtained at the airway opening at prong level reflects ventilation efficacy during nHFOV even in the presence of moderate oropharyngeal leak.
OBJECTIVES: The carbon dioxide (CO2 ) diffusion coefficient (DCO 2 ) reflects CO 2 removal during high-frequency oscillatory ventilation (HFOV). We hypothesized that despite leak flow during noninvasive HFOV (nHFOV) DCO 2 continues to indicate ventilation efficacy. METHODS: A neonatal airway model including CO2 production and an adjustable oropharyngeal leak was connected to a ventilator via bi-nasal prongs. Pressures and gas flows were measured at prongs, trachea, and leak. Oscillatory tidal volumes below (V T trachea ) and above the leak (V T prong ) were calculated from tracheal and leak flows. DCO 2 was calculated using V T trachea (DCO 2 trachea ) and V T prong (DCO 2 prong ) and compared with CO 2 partial pressure (pCO 2 ). Effects of leak flow (0, 5, or 10 L/min) on DCO 2 were assessed at fixed pressure amplitudes or predefined oscillatory volumes under steady-state pCO 2 conditions in the modeled lung. RESULTS:DCO2 trachea correlated strongly with pCO 2 , independent of the leak flow level (P < 0.0001). DCO 2 prong correlated with pCO 2 without and with moderate leak (P < 0.0001) but not with maximum leak (P = 0.1432). V T trachea correlated with the quotient of tracheal pressure amplitude and frequency irrespective of the leak (P < 0.0001). Based on the pressure amplitude at prong level (A prong ) V T trachea continued to follow a linear model of which the slopes decreased with increasing leak flow. V T prong correlated with the quotient of A prong and frequency, irrespective of the leak (P < 0.0001). CONCLUSIONS:DCO2 obtained at the airway opening at prong level reflects ventilation efficacy during nHFOV even in the presence of moderate oropharyngeal leak.
Authors: Benjamin W Ackermann; Daniel Klotz; Roland Hentschel; Ulrich H Thome; Anton H van Kaam Journal: Pediatr Res Date: 2022-02-08 Impact factor: 3.756