2002 OPEN FORUM Abstracts
HIGH FLOW NASAL VS HIGH FLOW MASK OXYGEN DELIVERY: TRACHEAL GAS CONCENTRATIONS THROUGH A HEAD EXTENSION AIRWAY MODEL.
Brian Tiep, MD, Mary Barnett, RN. Pulmonary Care Continuum, Western University Health Sciences, Pomona CA.
Background: The Non-rebreather mask has been the standard for delivering high flow oxygen. Unfortunately, difficulty in maintaining a facial seal often leads to a lower than expected FIO2. Some patients find the mask uncomfortable and are unable to eat or communicate while wearing it. Nasal oxygen is not typically regarded to be a high flow option, because of lack of efficacy, mucosal drying and discomfort. Recently, a high flow, warmed and humidified, nasal O2 delivery system (Vapotherm) was introduced that comfortably delivers nasal O2 up to 40 L/m. The present study was designed to measure FIO2 attainable by mask and nasal cannula and to trace the delivery flow through the upper airways.
Methods: We constructed an upper airway model to trace flow of ultrasonic fog and measure gas exchange at the model?s trachea. A mouthpiece ?T? junction at the trachea allowed the subject to breathe into the model using the model?s upper airway architecture and dynamics. We measured O2, CO2 and respiratory flow in a normal subject breathing in a consistent and controlled flow pattern at a rate of 20 breaths/min with the model wearing the mask (M) vs nasal (N) cannula. O2 was delivered at 10, 15, 20, and 30 L/m through each device.
Results: Peak FIO2 as measured at the beginning of inspiration via nasal cannula and mask: 10 L/m: N=62% M=48%; 15 L/m: N=82% M=65%; 20 L/m: N=90% M=71%; 30 L/m: N=95% M=93%. End-exhalation FEO2 via nasal cannula and mask: 10 L/m: N=38% M=37%; 15 L/m: N=52% M=52%; 20 L/m: N=54% M=50%; 30 L/m: N=72% M=71%. Ultrasonic flow studies recorded on digital video demonstrated that mask O2 remains outside the nose and mouth until the subject inhales; whereas nasal O2 is stored in the upper airways during exhalation for additional delivery upon inhalation.
Conclusions: High flow nasal cannula delivery is more efficacious than the non-rebreather mask at equivalent flows, due to O2 storage in the upper airways during exhalation poised for delivery upon the next inhalation in addition to the continuous supply flow. High flow nasal O2 can be an effective option for patients with high flow requirements. Clinical studies are recommended to evaluate the impact of high flow, warmed and humidified O2 following extubation, during sleep, and in the management of exacerbations.