An Experimental and Numerical Investigation of CO2 Distribution in the Upper Airways During Nasal High Flow Therapy

S. C. Van Hove; J. Storey; C. Adams; K. Dey; P. H. Geoghegan; N. Kabaliuk; S. D. Oldfield; C. J.T. Spence; Mark C. Jermy; V. Suresh; J. E. Cater

doi:10.1007/s10439-016-1604-8

An Experimental and Numerical Investigation of CO₂ Distribution in the Upper Airways During Nasal High Flow Therapy

S. C. Van Hove
, J. Storey
, C. Adams
, K. Dey
, P. H. Geoghegan
, N. Kabaliuk
, S. D. Oldfield
, C. J.T. Spence
, Mark C. Jermy
, V. Suresh
, J. E. Cater^*

^*Corresponding author for this work

University of Auckland
University of Canterbury
Fisher and Paykel Healthcare Limited

Research output: Contribution to journal › Article › peer-review

28 Citations (Scopus)

Abstract

Nasal high flow (NHF) therapy is used to treat a variety of respiratory disorders to improve patient oxygenation. A CO₂Â washout mechanism is believed to be responsible for the observed increase in oxygenation. In this study, experimentally validated Computational Fluid Dynamics simulations of the CO₂ concentration within the upper airway during unassisted and NHF assisted breathing were undertaken with the aim of exploring the existence of this washout mechanism. An anatomically accurate nasal cavity model was generated from a CT scan and breathing was reproduced using a Fourier decomposition of a physiologically measured breath waveform. Time dependent CO₂Â profiles were obtained at the entrance of the trachea in the experimental model, and were used as simulation boundary conditions. Flow recirculation features were observed in the anterior portion of the nasal cavity upon application of the therapy. This causes the CO₂Â rich gas to vent from the nostrils reducing the CO₂Â concentration in the dead space and lowering the inspired CO₂ volume. Increasing therapy flow rate increases the penetration depth within the nasal cavity of the low CO₂Â concentration gas. A 65% decrease in inspired CO₂Â was observed for therapy flow rates ranging from 0 to 60Â LÂ min⁻¹ supporting the washout mechanism theory.

Original language	English
Pages (from-to)	3007-3019
Number of pages	13
Journal	Annals of Biomedical Engineering
Volume	44
Issue number	10
Early online date	8 Apr 2016
DOIs	https://doi.org/10.1007/s10439-016-1604-8
Publication status	Published - 1 Oct 2016

Keywords

Breathing therapy
CO washout
Computational fluid dynamics
Nasal cavity
Non-invasive ventilation

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10.1007/s10439-016-1604-8

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Van Hove, S. C., Storey, J., Adams, C., Dey, K., Geoghegan, P. H., Kabaliuk, N., Oldfield, S. D., Spence, C. J. T., Jermy, M. C., Suresh, V., & Cater, J. E. (2016). An Experimental and Numerical Investigation of CO₂ Distribution in the Upper Airways During Nasal High Flow Therapy. Annals of Biomedical Engineering, 44(10), 3007-3019. https://doi.org/10.1007/s10439-016-1604-8

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abstract = "Nasal high flow (NHF) therapy is used to treat a variety of respiratory disorders to improve patient oxygenation. A CO2{\^A} washout mechanism is believed to be responsible for the observed increase in oxygenation. In this study, experimentally validated Computational Fluid Dynamics simulations of the CO2 concentration within the upper airway during unassisted and NHF assisted breathing were undertaken with the aim of exploring the existence of this washout mechanism. An anatomically accurate nasal cavity model was generated from a CT scan and breathing was reproduced using a Fourier decomposition of a physiologically measured breath waveform. Time dependent CO2{\^A} profiles were obtained at the entrance of the trachea in the experimental model, and were used as simulation boundary conditions. Flow recirculation features were observed in the anterior portion of the nasal cavity upon application of the therapy. This causes the CO2{\^A} rich gas to vent from the nostrils reducing the CO2{\^A} concentration in the dead space and lowering the inspired CO2 volume. Increasing therapy flow rate increases the penetration depth within the nasal cavity of the low CO2{\^A} concentration gas. A 65\% decrease in inspired CO2{\^A} was observed for therapy flow rates ranging from 0 to 60{\^A} L{\^A} min−1 supporting the washout mechanism theory.",

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AB - Nasal high flow (NHF) therapy is used to treat a variety of respiratory disorders to improve patient oxygenation. A CO2Â washout mechanism is believed to be responsible for the observed increase in oxygenation. In this study, experimentally validated Computational Fluid Dynamics simulations of the CO2 concentration within the upper airway during unassisted and NHF assisted breathing were undertaken with the aim of exploring the existence of this washout mechanism. An anatomically accurate nasal cavity model was generated from a CT scan and breathing was reproduced using a Fourier decomposition of a physiologically measured breath waveform. Time dependent CO2Â profiles were obtained at the entrance of the trachea in the experimental model, and were used as simulation boundary conditions. Flow recirculation features were observed in the anterior portion of the nasal cavity upon application of the therapy. This causes the CO2Â rich gas to vent from the nostrils reducing the CO2Â concentration in the dead space and lowering the inspired CO2 volume. Increasing therapy flow rate increases the penetration depth within the nasal cavity of the low CO2Â concentration gas. A 65% decrease in inspired CO2Â was observed for therapy flow rates ranging from 0 to 60Â LÂ min−1 supporting the washout mechanism theory.

KW - Breathing therapy

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KW - Computational fluid dynamics

KW - Nasal cavity

KW - Non-invasive ventilation

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An Experimental and Numerical Investigation of CO₂ Distribution in the Upper Airways During Nasal High Flow Therapy

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Keywords

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Fabrication of rigid and flexible refractive-index-matched flow phantoms for flow visualisation and optical flow measurements

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