If supplemental oxygen therapy or non-invasive ventilation do not help, the next step would be to intubate and commence mechanical ventilation. The decision to intubate is made primarily on clinical grounds, but broad guidelines may be as below: Indications for Intubation and Ventilation

Breathlessness, tachypnoea with respiratory rate more than 30/mt

Use of accessory muscles

Tachycardia

Hypoxia - PO₂ less than 60 mm of Hg while on maximal oxygen therapy

Hypercarbia

Respiratory muscle weakness - Polyneuropathy, myasthenia, etc.

Agitation, restlessness due to difficulty in breathing/ hypoxia

Inability to maintain airway, cough and clear secretions

Altered sensorium