Quantifying and Correlating the Positive Airway Pressure and Upper Airway Gas Clearance During High Flow Nasal Cannula Therapy in Adults

• Author / Creator

  Moore, Charles P

• High flow nasal cannula (HFNC) therapy is a form of respiratory support, where high flowrates of heated and humidified gas are supplied to a patient via nasal cannula. This thesis consists of two experimental studies designed to characterize the positive pressure and upper airway washout effects of HFNC therapy. We characterized these effects by supplying HFNC to five plastic adult airway replicas, extending from the nares to trachea. The first set of experiments measured airway washout in a non breathing model, comparing 3 cannula and HFNC flowrates of 30-90 L/min. Pressure was measured by connecting the airways to a lung simulator and delivering HFNC therapy, with flowrates of 0-60 L/min. Post-hoc analysis revealed clearance times decreasing with increasing flowrate and decreasing cannula size. A predictive correlation for positive end expiratory pressure (PEEP) was developed using a minor losses model of confined flow. The second set of experiments involved simulating breathing with CO2 production in the lungs during HFNC administration. Flowrates ranged from 0-60 L/min of either air, pure oxygen or heliox gas. Washout of CO2 in the airways was heavily dependent upon HFNC flowrate, and weakly dependent upon gas and airway geometry. Washout effect was found to be independent of breathing minute volume. A second correlation for PEEP was constructed based on minor losses, and accounting for differing gas density.

• Subjects / Keywords

  • airway replica
  • high flow nasal cannula
  • respiratory support
  • deadspace washout
  • gas mixing
  • High flow therapy
  • minor losses
  • upper airway
  • pressure

• Graduation date

  Spring 2019

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-akkc-c947

• License

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