How non-invasive ventilation works

NIV provides a two level form of respiratory support, supplying inspiratory and expiratory positive airways pressure.

Non-invasive ventilation can be used in hospital wards and in high dependency and intensive care units

Inspiratory positive airways pressure, which is usually titrated up to 15-20 cm H₂O, helps offload tiring respiratory muscles and reduce the work of breathing, improves alveolar ventilation and oxygenation, and increases elimination of CO₂.

Expiratory positive airways pressure, usually at 4-6 cm H₂O, helps “splint open” the airway and flushes CO₂ from the mask. It also reduces the work of breathing by overcoming intrinsic positive end expiratory pressure, thereby reducing atelectasis and increasing the end tidal volume.

Oxygen is introduced either through a port in the facemask or through a more proximal channel in the ventilator system. It is not usually necessary to deliver humidified oxygen, but humidifiers can be added to the circuit.

When to use non-invasive ventilation in COPD

NIV is particularly successful in patients with hypercapnic respiratory failure (especially in those with an arterial blood pH of 7.25-7.35). It can also be used as a therapeutic trial before proceeding to mechanical ventilation …