Premium
Carbon dioxide diffusion coefficient in noninvasive high‐frequency oscillatory ventilation
Author(s) -
Schäfer Christoph,
Schumann Stefan,
Fuchs Hans,
Klotz Daniel
Publication year - 2019
Publication title -
pediatric pulmonology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.866
H-Index - 106
eISSN - 1099-0496
pISSN - 8755-6863
DOI - 10.1002/ppul.24333
Subject(s) - leak , medicine , anesthesia , ventilation (architecture) , physics , thermodynamics
Objectives The carbon dioxide (CO 2 ) 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 CO 2 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 DCO 2 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 DCO 2 obtained at the airway opening at prong level reflects ventilation efficacy during nHFOV even in the presence of moderate oropharyngeal leak.