Most of the available data from this technique has been published in the neonatal field where it is increasingly used. As an alternative to conventional oxygen delivery for hypoxemic patients, HFNC oxygen therapy has been receiving more and more attention. The difference between patient inspiratory flow and delivered flow is large, and as a result, F IO 2 is both inconstant and often lower than expected. Meanwhile, the inspiratory flow of patients with respiratory failure varies widely in a range from 30 to more than 100 L/min. Using conventional devices, oxygen flow is limited to no more than 15 L/min. Insufficient heating and humidification leads to poor tolerance to oxygen therapy. Bubble humidifiers are commonly used for humidifying air delivered to spontaneously breathing patients, but when absolute humidity is low, patients still complain of discomfort. Usually, oxygen is not humidified at low flow, and complaints, especially dry nose, dry throat, and nasal pain, are common. Several drawbacks are associated with these devices, which may limit efficacy and tolerance of oxygen delivery. Oxygen is generally provided via face masks and nasal cannula. The patient breathes the adequately heated and humidified medical gas through nasal cannulas with a large diameter.Īdministration of supplemental oxygen has been the first-line therapy for hypoxemic patients. The gas is heated and humidified through an active heated humidifier and delivered via a single-limb heated inspiratory circuit. An air/oxygen blender, allowing from 0.21 to 1.0 F IO 2, generates up to 60 L/min flow. Principle setup of high-flow nasal cannula oxygen therapy. Even so, it helps COPD patients mainly by decreasing anatomical dead space and secondarily by improving alveolar ventilation. Since neither inspiratory push nor expiratory pull is effective in such an open circuit, HFNC cannot actively enhance V T. While interfaces for NIV increase anatomical dead space, those for HFNC actually decrease dead space. Another major difference between NIV and HFNC is the interface. The gas is heated and humidified with the active humidifier and delivered through the heated circuit (Figure 1). At the air/oxygen blender, the inspiratory fraction of oxygen (F IO 2) is set from 0.21 to 1.0 in a flow of up to 60 L/min. The apparatus comprises an air/oxygen blender, an active heated humidifier, a single heated circuit, and a nasal cannula. High-flow nasal cannula (HFNC) oxygen delivery has been gaining attention as an alternative means of respiratory support for critically ill patients. Because of poor mask tolerance, however, NIV is sometimes inapplicable. For patients with acute exacerbation of chronic obstructive lung disease (COPD), noninvasive ventilation (NIV) has become the preferred primary modality for respiratory support because it enhances inspiratory tidal volume (V T) and maintains adequate alveolar ventilation. Currently, to ensure adequate alveolar ventilation, minute ventilation is manipulated during invasive or noninvasive ventilatory support. In this, ensuring adequate alveolar ventilation is essential for expelling carbon dioxide produced in the human body. The purpose of respiratory support is to maintain adequate ventilation and oxygenation. Despite these issues, HFNC oxygen therapy is an innovative and effective modality for the early treatment of adults with respiratory failure with diverse underlying diseases. Some important issues remain to be resolved, such as its indication, timing of starting and stopping HFNC, and escalating treatment. Many published reports suggest that HFNC decreases breathing frequency and work of breathing and reduces needs of escalation of respiratory support in patients with diverse underlying diseases. Evidence with critically ill adults are poor however, physicians apply it to a variety of patients with diverse underlying diseases: hypoxemic respiratory failure, acute exacerbation of chronic obstructive pulmonary disease, post-extubation, pre-intubation oxygenation, sleep apnea, acute heart failure, patients with do-not-intubate order, and so on. Most of the available data has been published in the neonatal field. While there have been no big randomized clinical trials, it has been gaining attention as an innovative respiratory support for critically ill patients. It delivers adequately heated and humidified medical gas at up to 60 L/min of flow and is considered to have a number of physiological effects: reduction of anatomical dead space, PEEP effect, constant fraction of inspired oxygen, and good humidification. High-flow nasal cannula (HFNC) oxygen therapy comprises an air/oxygen blender, an active humidifier, a single heated circuit, and a nasal cannula.
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