An overview has been given of clinical conditions that may require additional respiratory support in the form of non-invasive ventilation (NIV) (Chapters 17 and 18) comprising of CPAP and BiPAP. NIV supports breathing using a variety of snug-fitting face masks (Figure 20.1), enabling pressure to be maintained both in the circuit and the respiratory system. HFNC (Figure 20.2) is now being used for adults with acute hypoxaemic respiratory failure (Type 1), but as yet has not been incorporated into clinical guidelines. These approaches to respiratory support benefit from the principle of applying positive pressure during expiration thereby increasing oxygenation, but differ in the extent of ventilation support delivered. NIV is now being used frequently in acute care and requires an appropriate environment with appropriately trained staff.¹ Guidance for NIV for patients with acute hypercapnic failure has been published by the British Thoracic Society and Intensive Care Society.²

Conventional high flow oxygen therapy comprises a flow of around 15 L/min, via a non-rebreathe face mask. A HFNC can generate up to 60 L/min of heated, humidified gas through the nasal cannula. The high flow of gas creates a positive resistance to expiration in the nasopharynx, which whilst small, helps keep alveoli open and improves gaseous exchange.³ A HFNC is often found more comfortable than the tight-fitting mask of CPAP.

Continuous positive airway pressure can be delivered through a number of devices, using a nasal or nasa/oral or full face mask for patients with acute respiratory failure, Type 1.