As critical care consumes increasing amounts of health care budgets globally there is an increasing demand for interventions that are clinically effective in the sense that they reduce patient length of stay, reduce complications and are less demanding of medical and nursing resources:

• However, the evidence base for critical care interventions is very narrow and it is often very difficult to find any intervention that meets the above criteria.

• Non-invasive ventilation (NIV) comes close if applied to patients with the appropriate indications [1].

• Like all interventions, if used indiscriminately these benefits are lost and it is the purpose of this chapter to give the reader some insight into how best to apply this technology to achieve the best outcomes.

Definition

NIV is the application of bi-level airway pressure support using a nasal or full face mask as the patient interface:

• The lower level of support will be referred to as expiratory positive airway pressure (EPAP) and the upper level as inspiratory positive airway pressure (IPAP).

• If the IPAP is set on zero then the patient will be receiving what is conventionally known as constant positive airway pressure or CPAP as it is better known.

• NIV and CPAP as terms are often used interchangeably but they should be regarded as two quite separate forms of airway support.