Objectives

The objectives of this chapter are to understand:

• the mechanisms of action of non-invasive ventilation

• the clinical applications for non-invasive ventilation in the acute setting

• the role of continuous positive airway pressure (CPAP) versus bi-level positive airway pressure (BiPAP)

• the limitations and complications of non-invasive ventilation (NIV)

• the practical application of NIV.

Introduction

NIV is the provision of ventilatory support through the patient's upper airway using a mask or similar device. Non-invasive application of CPAP does not, strictly speaking, constitute ventilatory support but in this chapter it is included under the generic term NIV. Use of NIV may avoid the need for intubation and invasive ventilation; it is also used to supplement medical therapy. There is good evidence supporting its use in patients with chronic obstructive pulmonary disease (COPD) with moderate dyspnoea and hypercapnia, and in acute cardiogenic pulmonary oedema. Non-invasive ventilation may be used in patients who are not suitable for intubation, and considered for patients with hypoxaemic respiratory failure such as asthma or community acquired pneumonia.

Modes of non-invasive ventilation

There are several different terms describing the modes of non-invasive ventilation – this terminology is confusing. Based on the level of respiratory support, the modes include:

• CMV, which requires no patient effort

• assisted spontaneous breathing or pressure support, which increases ventilation support but relies on the patient's spontaneous respiratory effort

• CPAP, during which a constant positive pressure is applied throughout the respiratory cycle.

Combinations of these modes are available. A combination of pressure support and CPAP is known as bi-level pressure support or BiPAP.