|Year : 2017 | Volume
| Issue : 1 | Page : 43-46
High-flow oxygen therapy in hypoxemic respiratory failure: Review
Department of Respiratory Therapy Sciences, Inaya Medical College, Riyadh, Saudi Arabia
|Date of Web Publication||23-Jun-2017|
Department of Respiratory Therapy Sciences, Inaya Medical College, Riyadh
Source of Support: None, Conflict of Interest: None
High-flow oxygen therapy is a novel technology in the treatment of hypoxemic respiratory failure (HRF). The effect in neonatal and pediatric population is well known, but its efficiency in the adult patient group is not well proven. This review tried to discuss various aspects of high-flow nasal cannula (HFNC) in terms of its components, effects, and the evidence available. High-flow nasal cannula is being used as the first choice of intervention in patients with acute HRF, especially in patients who does not have critical hypercapnia. Clinicians should be very selective while choosing the adult patients for HFNC.
Keywords: Hypoxemic respiratory failure, nasal oxygen, oxygen therapy
|How to cite this article:|
Johnson S. High-flow oxygen therapy in hypoxemic respiratory failure: Review. Saudi Crit Care J 2017;1:43-6
| Introduction|| |
Hypoxemic respiratory failure (HRF) is common and frequent in patients admitted to intensive care unit and this may lead to organ dysfunction which can be severe in most cases., HRF can be because of various causes, which should be diagnosed concurrently while treating the patients symptomatically., Conventionally, HRF is treated with noninvasive or invasive mechanical ventilation which improves oxygenation, unloads the work of respiratory muscles, enhances better gas exchange, and provides adequate time to treat the underlying etiology which causes hypoxemia. Conventional strategies to treat hypoxemia has beneficial effects and some adverse effects such as increased incidence of infection, cardiovascular compromise, and increased mortality.,
| Method of Delivery|| |
High-flow nasal cannula (HFNC) is a method of ventilation wherein the combination of air and oxygen at high flow is delivered through a humidified circuit. This flow usually exceeds the patient's spontaneous breathing demand. Two systems that are currently used for HFNC are the Optiflow ™ Nasal Interfaces (Fisher and Paykel Healthcare, New Zealand) and the Vapotherm ™ system (Vapotherm Inspiration Healthcare, United Kingdom).,, HFNC provides heated and humidified gases and delivers continuous positive airway pressure; however, the precise level is not known.
[Figure 1]a shows the apparatus for the delivery of HFNC.
At the time, when supplemental oxygen is necessary, Optiflow ™ can deliver flows up to 60 L/min to meet peak inspiratory demand, thus reducing O2 dilution by room air. As shown in [Figure 1]b the maximum oxygen flow from a face mask is limited to nearly 10 L/min which is not appropriate to meet the patient's peak inspiratory demand. To resolve the variance, room air is entrained and diluting the oxygen that is provided. On the other hand, Optiflow is capable to meet this patient's peak inspiratory demand of 30 L/min confirming a precise provision of inspiratory fraction of oxygen (FiO2) to the patient.
HFNC device consist of an air/oxygen blender, an active heated humidifier, a single heated circuit, and a nasal cannula [Figure 2] and [Figure 3]. At the air/oxygen blender, the FiO2 is set from 0.21 to 1.0 in a flow of up to 60 L/min. In this device, the inspired gas is heated and humidified using active humidifier and is provided through the circuit which is connected to the patient through a nasal cannula [Figure 2].
HFNC decreases oxygen dilution, decreases respiratory dead space, and creates certain positive airway pressure, due to the expiratory resistance produced by the constant high flow delivered. The heated humidification eases secretion clearance and reduction of the development of bronchial hyperresponse.
A study was done by Möller et al. to test if nasal high flow (NHF) can clear dead space in two different models of the upper nasal airways. The models include (1) simple tube model comprising an outlet to simulate the nasal valve area, joined to a cylindrical tube to simulate the nasal cavity (2) a complex anatomically illustrative upper airway model, made from segmented computed tomography scan images of a healthy volunteer. Once the models were filled with tracer gases, NHF was supplied at different flow rates such as 15, 30, and 45 L/min. The tracer-gas clearance was determined using dynamic infrared CO2 spectroscopy and radioactive gamma camera imaging. The finding was similar for flow-dependent tracer-gas clearance in the models. Anatomically-based model showed complete tracer-gas removal from the nasal cavities within 1.0 s. The level of clearance in the nasal cavities increased by 1.8 mL/s for every 1.0 L/min increase in the rate of NHF. The main finding of this study was the fast-occurring clearance of nasal cavities by NHF therapy, which is capable of decreasing rebreathing from the dead space.
This review summarizes few articles in [Table 1] which are done in the field of HFNC in postextubation, preoxygenation, immunocompromised patients, and hematological malignancies.
| Discussion|| |
HFNC therapy has been shown to decrease ventilatory requirements by flushing out the dead space of the upper airway and enhances oxygenation by achieving patient demand with high oxygen concentrations and generating a low-level end-expiratory pressure. Gas delivered at body temperature and humidity is important for patient comfort and tolerance of therapy. Parke et al. did a study in a group of normal individuals in which they reported high-flow nasal oxygen at 100 L/min resulting in a rise in pharyngeal airway pressure of 1 cm H2O/10 L/min of flow. Respiratory rate decreased as the flow increased and electrical impedance tomography confirmed a small increase in end-expiratory lung volume. As this study was done in healthy individuals, it cannot be extrapolated to patients with lung pathology; however, the development of the device might be useful to replace or to be considered as an alternative to noninvasive ventilation (NIV) with facemask.
| Conclusion|| |
High-flow nasal cannula is being used as the first choice of intervention in patients with acute HRF, especially in patients who does not have critical hypercapnia, hemodynamical instability, and other reasons such as decreased level of consciousness which necessitates the use of NIV or invasive mechanical ventilation. Clinicians should be very selective while choosing the adult patients for HFNC. There is a need for large randomized studies comparing NIV and oxygen therapy modalities with HFNC to actually confirm the indications and contraindications of its use.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]