Evaluation of a Humidified Nasal High-Flow Oxygen System, Using Oxygraphy, Capnography and Measurement of Upper Airway Pressures

Abstract

In this study, we evaluated the performance of a humidified nasal high-flow system (Optiflow™, Fisher and Paykel Healthcare) by measuring delivered FiO2 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, FEO2, FECO2 and airway pressures were measured. Calculation of FiO2 from FEO2 and FECO2 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 cmH2O. 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.

High-Flow Nasal Cannula Therapy in Do-Not-Intubate Patients With Hypoxemic Respiratory Distress

“…Mean age was 73 years (range 27-96 years). Diagnoses, allowing multiple conditions, included pulmonary fibrosis (15), pneumonia (15), COPD (12), cancer (7), hematologic malignancy (7), congestive heart failure (3), pulmonary embolism (2), sepsis (2), alveolar hemorrhage (1), and myocardial infarction (1). Baseline arterial blood gases showed a mean P aO 2 of 66.5 mm Hg (range 39 -121 mm Hg), a mean P aCO 2 of 42.3 mm Hg (range 26 -65 mm Hg), and a mean pH of 7.42 (range 7.30 -7.51).…”

“…5,6,[13][14][15] Humidification may benefit mucociliary clearance, mobilization of respiratory secretions, and patient comfort. 16,17 HFNC may be as effective as and better tolerated than face mask techniques.…”

Modeling the pharyngeal pressure during adult nasal high flow therapy

“…NHF has been reported to reduce respiratory rate (Rittayamai et al, 2014;Roca et al, 2010;Sztrymf et al, 2011), increase tidal volume (Corley et al, 2011;Mundel et al, 2013) and reduce minute ventilation (Braunlich et al, 2013). In practice, meeting or exceeding peak inspiratory volumes ensures accuracy of delivered oxygen concentrations when there is no requirement to entrain air to meet demand (Ritchie et al, 2011).…”

Heated, humidified, high-flow nasal oxygen usage in the adult Emergency Department

“…4,17-19 Furthermore higher oxygen flow rates achievable with HHHFNO therapy are better able to match the patient's inspiratory demands or exceed their peak inspiratory flow rates resulting in decreased variability in the fraction of inspired oxygen and therefore more consistent oxygenation. 2,16,20 Administration of oxygen through a nasal cannula also contributes to better oxygenation by washing out the nasopharyngeal anatomical dead-space allowing for the nasal cavity, pharynx and mouth to become reservoirs of oxygen. 2,4,16 Finally, the humidification of inspired gas increases mucocilliary clearance and assists with the removal of excessive secretions thus allowing for more effective gas exchange.…”