The interface: crucial for successful noninvasive ventilation.

Noninvasive ventilation (NIV) is a real advance in the management of both chronic and acute respiratory failure. It is the absence of an endotracheal or tracheostomy tube which defines NIV. The development of various interfaces have made the delivery of effective ventilation to patients without intubation possible and a good interface is crucial to success. These can be factory manufactured or customised. Driven largely by the explosion in the diagnosis and treatment of obstructive sleep apnoea there are now a wide variety of different factory-made masks of different designs, shapes, sizes and materials. It is usually possible to find something that suits most individuals and there is seldom a need for an individually made interface. Broadly speaking there are four different types: full face masks (enclose mouth and nose), nasal masks, nasal pillows or plugs (insert directly into the nostrils), and mouthpieces. A review of published studies showed that in acute NIV facial masks predominate (63%), followed by nasal masks (31%) and nasal pillows (6%). In contrast for chronic NIV nasal masks (73%) are the most commonly used followed by nasal pillows (11%), facial masks (6%) and mouthpieces (5%) [1]. More recently the use of a "helmet" has been described in hypoxaemic acute respiratory failure (ARF) with patients receiving continuous ventilation for many days [2]. Nasal masks have less static dead space, are not as claustrophobic and allow expectoration and communication more easily than full face masks. The improvement in arterial blood gas tensions appears to be slower in some studies using nasal masks compared to face masks [3]. A full face mask is usually chosen when there is significant mouth breathing, which is very common in patients with an acute exacerbation of chronic obstructive pulmonary disease (COPD), and at least during the initial phase results in better quality of ventilation, in terms of improved minute ventilation and blood gases [4, 5]. Sometimes, in the post acute situation patients can be encouraged to continue NIV, to maximise the improvement in blood gases, by switching from a full face mask to a less claustrophobic nasal mask. Semi-customised masks consist of a prefabricated frame in which a quick drying filler is injected and afterwards moulded to the patient9s face. Moulded masks which use small nasal openings, may have increased resistance, which could decrease ventilation [1]. Minimising leak is the first major challenge in both acute and chronic NIV. Leak results from a …