Optimizing Tracheal Oxygen Tension and Diffusion Ratio When Choosing High-Flow Oxygen Therapy or CPAP for the Treatment of Hypoxemic Respiratory Failure: Insights from Ex Vivo Physiologic Modelling
2.1. Physiologic Model
2.1.1. Fick’s Law
- is the transport rate of O2;
- is a diffusion coefficient;
- is the alveolar surface area;
- is the difference in tension between the alveolar oxygen and the partial pressure of oxygen in the venous blood of the pulmonary artery (A—a gradient);
- is the membrane thickness.
- The increase in relative to room air from inhaling pressurized, oxygen-enriched air;
- An increase or recruitment in alveolar surface area from positive applied pressure (continuous positive airway pressure (CPAP) or positive end expiratory pressure (PEEP)).
- is the alveolar surface area before CPAP is applied;
- is the functional residual lung capacity, and it is assumed that most respiration will occur at this lung volume;
- is the pressure applied;
- is the static lung compliance considered to be constant for non-atelectatic or non-distended lungs. Only the lung compliance is considered and assumed be approximately 40 mL/cm H2O . The chest wall compliance is not considered when computing the relative increase in alveolar surface area.
2.1.2. Alveolar Gas Equation
- is the volume fraction of oxygen in the inhaled gas;
- is the atmospheric pressure;
- is any applied pressure support, PEEP, or CPAP from respiratory equipment;
- is the water vapor pressure in the gas within the alveolus;
- is the arterial partial pressure of ;
- is the respiratory quotient (typically 0.8).
2.2. Treatment Effectiveness Model Expressed as a Diffusion Ratio
- occurs when enriched is presented to hypoxemic with PEEP;
- occurs when room air is presented to hypoxemic without PEEP.
2.2.1. Note Regarding the Clinical Meaning of
2.2.2. Patient Model
2.3. Modeling the HFNT Device
- Providing supplemental oxygen to increase and thus increase ;
- Applying high flow directly to the airway through the nares to provide a small amount of PEEP  to expand the gas exchange surface.
- The cannula flow rate;
- The fraction of inhaled oxygen, , in the cannula .
2.3.1. Device vs. Tracheal
2.3.2. Estimating Tracheal for HFNT
2.3.3. Heatmap Color Convention for Figures in this Article
3.1. Tracheal Estimation during HFNT
3.2. Effectiveness of HFNT Treatment vs. No Treatment (Diffusion Ratio)
3.3. HFNT Setting Recommendations
3.4. Analysis of HFNT without a Blender
3.4.1. Tracheal Model for HFNT without a Blender
3.4.2. Guidelines for Setting HFNT with Bleed-In Oxygen
3.5. Comparison of HFNT to CPAP with Oxygen
4.1. Significance of the Findings
4.2. Critique of the Method
Conflicts of Interest
- Powers, K.A.; Phamoon, A.S.; Powers, K.A.; Dhamoon, A.S. Physiology, Pulmonary Ventilation and Perfusion. Available online: https://www.ncbi.nlm.nih.gov/books/NBK539907/ (accessed on 28 January 2022).
- Yan, Y.; Xie, Y.; Chen, X.; Sun, Y.; Du, Z.; Wang, Y.; Li, X. Mechanical power is associated with weaning outcome in critically ill mechanically ventilated patients. Sci. Rep. 2022, 12, 19634. [Google Scholar] [CrossRef] [PubMed]
- Stocks, J.; Quanjer, P.H. Reference values for residual volume, functional residual capacity, and total lung capacity. ATS Workshop on Lung Volume Measurements. Official Statement of The European Respiratory Society. Eur. Respir. J. 1995, 8, 492–506. [Google Scholar] [CrossRef] [PubMed]
- Colbatch, H.J.; Ng, C.K. Estimating Alveolar Surface Area During Life. Respir. Physiol. 1992, 88, 163–170. [Google Scholar] [CrossRef] [PubMed]
- Cohen, J.; Small, C. Hypsographic demography: The distribution of human population by altitude. Proc. Natl. Acad. Sci. USA 1988, 95, 14009–14014. [Google Scholar] [CrossRef] [PubMed]
- Wexler, A.; Greenspan, L. Vapor Pressure Equation for Water in the Range 0 to 100 °C. J. Res. Natl. Bur. Stand. A Phys. Chem. 1971, 75A, 213–230. [Google Scholar] [CrossRef] [PubMed]
- Jolliet, P.; Bulpa, P.; Chevrolet, J.-C. Effects of the prone position on gas exchange and hemodynamics in severe acute respiratory distress syndrome. Crit. Care Med. 1998, 26, 1977–1985. [Google Scholar] [CrossRef] [PubMed]
- Otis, A.B.; Mckerrow, C.B.; Bartlett, R.A.; Mead, J.; McIlroy, M.B.; Selverstone, N.J.; Radford, E.P. Mechanical factors in distribution of pulmonary ventilation. J. Appl. Physiol. 1956, 8, 427–443. [Google Scholar] [CrossRef] [PubMed]
- Moller, W.; Celik, G.; Feng, S.; Bartenstein, P.; Meyer, G.; Eickelberg, O.; Schmid, O.; Tatkov, S. Nasal high flow clears anatomical dead space in upper airway models. J. Appl. Physiol. 2015, 118, 1525–1532. [Google Scholar] [CrossRef]
- Cortegiani, A.; Accurso, G.; Mercadante, S.; Giarratano, A.; Gregoretti, C. High flow nasal therapy in perioperative medicine: From operating room to general ward. BMC Anesthesiol. 2018, 18, 166. [Google Scholar] [CrossRef]
- Parke, R.; McGuiness, S. Pressures Delivered by Nasal High Flow Oxygen during All Phases of the Respiratory Cycle. Respir. Care 2013, 58, 1621–1624. [Google Scholar] [CrossRef] [PubMed]
- Wexler, H.R.; Aberman, A.; Scott, A.A.; Cooper, J.D. Measurement of intratracheal oxygen concentrations during face mask administration of oxygen: A modification for improved control. Can. Anaesth. Soc. J. 1975, 22, 417–431. [Google Scholar] [CrossRef] [PubMed]
- O’Reilly Nugent, A.; Kelly, P.T.; Stanton, J.; Swanney, M.P.; Graham, B.; Beckert, L. Measurement of oxygen concentration delivered via nasal cannulae by tracheal sampling. Respirology 2014, 19, 538–543. [Google Scholar] [CrossRef] [PubMed]
- Duprez, F.; de Terwangne, C.; Bellemans, V.; Poncin, W.; Reychler, G.; Sorgente, A.; Cuvelier, G.; Mashayekhi, S.; Wittebole, X. High-flow nasal cannula therapy, factors affecting effective inspired oxygen fraction: An experimental adult bench model. J. Clin. Monit. Comput. 2022, 36, 1441–1448. [Google Scholar] [CrossRef] [PubMed]
- Li, J.; Scott, J.B.; Fink, J.B.; Reed, B.; Roca, O.; Dhand, R. Optimizing high-flow nasal cannula flow settings in adult hypoxemic patients based on peak inspiratory flow during tidal breathing. Ann. Intensive Care 2021, 11, 164. [Google Scholar] [CrossRef] [PubMed]
- Basile, M.C.; Mauri, T.; Spinelli, E.; Dalla Corte, F.; Montanari, G.; Marongiu, I.; Spadaro, S.; Galazzi, A.; Grasselli, G.; Pesenti, A. Nasal high flow higher than 60 L/min in patients with acute hypoxemic respiratory failure: A physiological study. Crit. Care 2020, 24, 654. [Google Scholar] [CrossRef] [PubMed]
- Suriyakul, A.; Saiphoklang, N.; Barjaktarevic, I.; Cooper, C.B. Correlation between Hand Grip Strength and Peak Inspiratory Flow Rate in Patients with Stable Chronic Obstructive Pulmonary Disease. Diagnostics 2022, 12, 3050. [Google Scholar] [CrossRef] [PubMed]
- Polkey, M.I.; Kyroussis, D.; Hamnegård, C.-H.; Mills, G.H.; Green, M.; Moxham, J. Diaphragm strength in Chronic Obstructive Pulmonary Disease. Am. J. Respir. Crit. Care Med. 1996, 154, 1310–1317. [Google Scholar] [CrossRef] [PubMed]
|Parameter||Correlation to Oxygen Diffusion||Impact||Treatment Method|
application can increase by a factor of 5
|Small impact to in most inhabitable areas, but low atmospheric pressure can lead to altitude sickness||hyperbaric chamber or moving the patient to sea level|
|Small impact to as applied pressures are insignificant in relation to atmospheric pressure; however, the applied pressure also aids diffusion by increasing surface area.||CPAP, PEEP, or MV|
|, but is necessary especially with HFNT to prevent injury and dehydration.||Active or Passive heated humidification, natural humidification through mucosal membranes or HME|
|Inspiratory Pressure Support or Expiratory Pressure therapy to aid obstructive disease|
|Does not vary far from typical values of 0.8||Dietary changes|
|Functional Residual Capacity||FRC||3 L|||
|Alveolar SA untreated||118 m2|||
|Atmospheric Pressure||99 kPa 1|||
|Alveolar Water Vapor Pressure||47.08 mm Hg|||
|Arterial CO2 Pressure||46 mm Hg|||
|Venous O2 Pressure in the Pulmonary Artery during Hypoxemia||32 mm Hg|||
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.
© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
Truschel, B.; Polkey, M.I. Optimizing Tracheal Oxygen Tension and Diffusion Ratio When Choosing High-Flow Oxygen Therapy or CPAP for the Treatment of Hypoxemic Respiratory Failure: Insights from Ex Vivo Physiologic Modelling. J. Clin. Med. 2023, 12, 2878. https://doi.org/10.3390/jcm12082878
Truschel B, Polkey MI. Optimizing Tracheal Oxygen Tension and Diffusion Ratio When Choosing High-Flow Oxygen Therapy or CPAP for the Treatment of Hypoxemic Respiratory Failure: Insights from Ex Vivo Physiologic Modelling. Journal of Clinical Medicine. 2023; 12(8):2878. https://doi.org/10.3390/jcm12082878Chicago/Turabian Style
Truschel, Bill, and Michael I. Polkey. 2023. "Optimizing Tracheal Oxygen Tension and Diffusion Ratio When Choosing High-Flow Oxygen Therapy or CPAP for the Treatment of Hypoxemic Respiratory Failure: Insights from Ex Vivo Physiologic Modelling" Journal of Clinical Medicine 12, no. 8: 2878. https://doi.org/10.3390/jcm12082878