Evaluation of a humidified nasal high-flow oxygen system, using oxygraphy, capnography and measurement of upper airway pressures

• Published in: Anaesthesia and intensive care Vol. 39; no. 6; pp. 1103 - 1110
• Main Authors: RITCHIE, J. E, WILLIAMS, A. B, GERARD, C, HOCKEY, H
• Format: Journal Article
• Language: English
• Published: Edgecliff Anaesthesia Society of Anaesthetists 01.11.2011; Sage Publications Ltd. (UK); Sage Publications Ltd
• Subjects: Air Pressure; Airway Management - instrumentation; Algorithms; Anesthesia; Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy; Biological and medical sciences; Capnography; Catheters; Continuous Positive Airway Pressure; Exercise - physiology; Female; Health aspects; Heart Rate - physiology; Humans; Male; Maximal Expiratory Flow Rate; Measurement; Medical sciences; Nasal Cavity - physiology; Oximetry; Oxygen - blood; Oxygen equipment (Medical care); Oxygen Inhalation Therapy - instrumentation; Pharynx - physiology; Positive-Pressure Respiration; Respiratory Rate - physiology; Young Adult; New Zealand; Oxygen; CPAP; Positive pressure; Capnography; PEEP; Anesthesia; Humidification; Pressure measurement; oxygen inhalation therapy; nasal high flow; Inhalation
• ISSN: 0310-057X; 1448-0271
• DOI: 10.1177/0310057x1103900620

In this study, we evaluated the performance of a humidified nasal high-flow system (Optiflow, Fisher and Paykel Healthcare) by measuring delivered FiO, and airway pressures. Oxygraphy, capnography and measurement of airway pressures were performed through a hypopharyngeal catheter in healthy volunteers receiving Optiflow humidified nasal high flow therapy at rest and with exercise. The study was conducted in a non-clinical experimental setting. Ten healthy volunteers completed the study after giving informed written consent. Participants received a delivered oxygen fraction of 0.60 with gas flow rates of 10, 20, 30, 40 and 50 l/minute in random order FiO2, F(E)O2, F(E)CO2 and airway pressures were measured. Calculation of FiO2 from F(E)O2 and F(E)CO2 was later performed. Calculated FiO2 approached 0.60 as gas flow rates increased above 30 l/minute during nose breathing at rest. High peak inspiratory flow rates with exercise were associated with increased air entrainment. Hypopharyngeal pressure increased with increasing delivered gas flow rate. At 50 l/minute the system delivered a mean airway pressure of up to 7.1 cm H20. We believe that the high gas flow rates delivered by this system enable an accurate inspired oxygen fraction to be delivered. The positive mean airway pressure created by the high flow increases the efficacy of this system and may serve as a bridge to formal positive pressure systems.