Non-invasive ventilation: pressure through a mask
Non-invasive ventilation (NIV) delivers pressurised air through a tightly sealed face mask — no tube down the throat. It comes in two flavours. CPAP holds one steady pressure throughout the breath; it splints open flooded airways and is the go-to for cardiogenic pulmonary edema. BiPAP gives a *higher* pressure on the way in and a *lower* one on the way out — the inspiratory boost does part of the breathing work, which is exactly what a tiring patient with type 2 respiratory failure needs.
NIV shines in two situations above all: a COPD flare with rising CO2 and a falling pH, and acute heart-failure fluid on the lungs. It can lift a great deal of work of breathing off exhausted muscles and, used early, spares many patients from a breathing tube altogether. But it demands a co-operative, awake patient who can protect their own airway — it is not for someone who is unconscious, vomiting, or about to arrest.
Making the leap: intubation
When the mask is not enough, we secure the airway with endotracheal intubation — a breathing tube passed through the mouth, between the vocal cords, into the trachea. A balloon cuff seals it so the ventilator's pressure goes into the lungs and nothing is breathed in from the stomach. This is the gateway to full mechanical ventilation, and it lets the team control oxygen, pressure, and every breath completely.
We reach for the tube when there is failing NIV, a patient too drowsy to protect the airway, exhaustion of the breathing muscles, profound hypoxemia or hypercapnia not responding to lesser measures, or the need to fully rest a lung in severe ARDS. Intubation is not a defeat; it is taking over the work of breathing so the body can heal.
How the ventilator actually breathes
A ventilator is a precise pump. You decide a handful of things and the machine does the rest. The four settings to understand first are the tidal volume (how big each breath), the rate (how many breaths a minute), the FiO2 (how much oxygen), and the PEEP (the pressure left in the lungs at the end of each breath to keep sacs open). Together these set both the oxygenation and the CO2 clearance.
- Oxygenation is driven by FiO2 and PEEP — turn these up when the oxygen is low.
- CO2 clearance is driven by minute ventilation = tidal volume x rate — turn these up when the CO2 is high.
- Choose a mode: volume control guarantees the breath size; pressure control guarantees the pressure; support modes let the patient trigger their own breaths with a boost.
- Watch the pressures (especially the plateau pressure) to be sure you are not over-stretching the lung.