in an adult model simulating high-flow nasal cannula therapy

BACKGROUND: High-flow nasal cannula therapy (HFNC) is widely used for patients with acute respiratory failure. HFNC has a number of physiological effects. Although [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] is considered to be constant, because HFNC is an open system, [MATHEMATICAL EXPRESSI...

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Bibliographic Details
Published in:Respiratory care 2017-02, Vol.62 (2), p.193
Main Authors: Chikata, Yusuke, Onodera, Mutsuo, Nishimura, Masaji, Oto, Jun
Format: Article
Language:English
Subjects:
Adult respiratory distress syndrome
Analysis
Care and treatment
Health aspects
Oxygen equipment (Medical care)
Online Access:Get full text
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Summary:BACKGROUND: High-flow nasal cannula therapy (HFNC) is widely used for patients with acute respiratory failure. HFNC has a number of physiological effects. Although [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] is considered to be constant, because HFNC is an open system, [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] varies according to inspiratory flow, tidal volume ([V.sub.T]), and HFNC gas flow. We investigated the influence of HFNC gas flow and other respiratory parameters on [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] during HFNC. METHODS: We evaluated an HFNC system and, for comparison, a conventional oxygen therapy system. The HFNC apparatus was composed of an air/oxygen blender, a heated humidifier, an inspiratory limb, and small, medium, and large nasal prongs. HFNC gas flow was set at 20, 40, and 60 L/min, and [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] was set at 0.3, 0.5, and 0.7. We measured [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] for 1-min intervals using an oxygen analyzer and extracted data for the final 3 breaths of each interval. Spontaneous breathing was simulated using a mechanical ventilator connected to the muscle compartment of a model lung. The lung compartment passively moved with the muscle compartment, thus inspiring ambient air via a ventilator limb. With a decelerating flow waveform, simulated [V.sub.T] was set at 300, 500, and 700 mL, breathing frequency at 10 and 20 breaths/min, and inspiratory time at 1.0 s. RESULTS: With HFNC gas flow of 20 and 40 L/min, at all set [MATHEMATICAL EXPRESSION NOT RREPRODUCIBLE IN ASCII] values inspiratory oxygen concentration varied with [V.sub.T] (P < .001). As the set value for [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] increased, the difference between set [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] and measured [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] increased. Neither breathing frequency nor prong size influenced [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]. CONCLUSIONS: During HFNC with simulated spontaneous breathing, when HFNC gas flow was 60 L/min, measured [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] was similar to set [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] at 0.3 and 0.5, whereas at 0.7, as [V.sub.T] increased, measured [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] decreased slightly. However, at 20 or 40 L/min, changes in [V.sub.T] related with deviation from set [MATHEMATICAL EXPRE
ISSN:0020-1324