Non‑invasive ventilation (NIV)
Non‑invasive ventilation (NIV) delivers positive‑pressure ventilation via an external interface (mask or helmet) without endotracheal intubation. It provides ventilatory support and/or airway splinting between simple oxygen therapy and invasive mechanical ventilation.
In acute care its principal, evidence‑based role is treating acute hypercapnic ventilatory failure (most commonly COPD exacerbations); it is also used for cardiogenic pulmonary oedema, selected cases of hypoxaemic respiratory failure and acute decompensation of obesity hypoventilation or overlap syndromes.
Safe delivery requires correct patient selection, trained staff, monitoring and clear escalation and ceiling‑of‑care decisions (see NICE NG115; QS10).
Always document indication, planned goals, and the escalation/ceiling‑of‑care decision (including whether invasive ventilation is an option) before starting NIV.
Physiology and terminology
- CPAP (continuous positive airway pressure): single continuous pressure throughout the respiratory cycle. CPAP mainly increases mean airway pressure, improves oxygenation and splints the airway.
- Bilevel NIV / BiPAP: two set pressures - IPAP (inspiratory) and EPAP (expiratory). The pressure difference (IPAP - EPAP) provides pressure support to augment tidal volume and reduce work of breathing.
- HFNO (high‑flow nasal oxygen) is a distinct therapy (heated, humidified high‑flow oxygen). HFNO provides some PEEP and dead‑space washout but does not supply pressure support in the same way as bilevel NIV (see NICE NG191).
Indications - when to consider NIV
- Acute hypercapnic (type II) respiratory failure not improving after...