High-flow nasal cannula system: not just another nasal cannu
The present article appears in JAMA Surgery.

What Is the Innovation?
Interest has been on the increase in non-invasive respiratory support modalities to harness the advantages of positive pressure ventilation while avoiding the complications associated with invasive modalities.

High-flow nasal cannula (HFNC) offers an alternative to other oxygenation therapies, including standard non-invasive positive pressure ventilation (NIPPV), and has been studied in diverse clinical settings.

The HFNC system includes a flow meter, an air-oxygen blender, a humidifier, a heated circuit, and large bore nasal prongs that interact directly with the patient. Multiple HFNC devices are commercially available and allow the clinician to set an oxygen (O2) flow rate of up to 60 L/min and a fraction of inspired oxygen (FIO2) reaching 100%.

What Are the Key Advantages Over Existing Approaches?
• Patients in acute respiratory failure may gain an advantage from support using inspiratory flow rates in excess of the 1 to 15 L/min provided by nasal cannula devices and face masks.

• Concomitant spontaneous breathing entrains atmospheric gas and dilutes delivered FIO2.
Standard nasal cannula O2 delivery at higher flow rates desiccates mucosal surfaces and may create bleeding and pain.

• Non-invasive positive pressure ventilation therapy, such as biphasic positive airway pressure, is delivered via a tight-fitting nasal or nasal oral mask that increases anatomical dead space, may induce claustrophobia, creates discomfort leading to intolerance, and increases pressure ulceration risk.

• The high flow rate used with HFNC reduces competitive spontaneous and negative pressure-flow dilution of the delivered FIO2 and concomitantly pressurizes the oropharynx and hypopharynx (2-5 cm H2O pressure).

• With each spontaneous breath, the augmented pressure reduces the work of breathing, increases inspired gas volume, and decreases ventilation-perfusion mismatching by recruiting atelectatic alveoli and improving oxygenation.

• The heated and humidified gas improves patient tolerance and maintains mucociliary blanket and elevator functions that are essential for secretion clearance.

Read more here: https://jamanetwork.com/journals/jamasurgery/article-abstract/2687238
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