The tracheostomy tube in Fig 1 has a cuff. This seals off the upper airway. If the tube is correctly positioned within the trachea, gas can only move into and out of the lungs via the tracheostomy tube.

This means that:

• The airway is 'protected' from aspiration (like when we insert a cuffed endotracheal tube)
• Positive pressure ventilation can be effectively applied via the tracheostomy tube
• If the tube becomes blocked, the patient has no other way of getting oxygen to the lungs (as the upper airway is sealed off)

Fig 2 is a video detailing a successful cuff deflation trial in a ventilated patient.