A positive pressure ventilator delivers gas to the patient through a  set of flexible tubes, called a patient circuit. Depending on the ventilator  design, this circuit can have one or two main tubes.  

The circuit connects the ventilator to an endotracheal  tube, tracheostomy tube for invasive ventilation or a noninvasive  mask/prong.

For invasive ventilation, an endotracheal tube is  inserted through the patient's mouth or nose, or a tracheostomy tube is inserted  through an opening made by incision in the neck.

In noninvasive ventilation, the patient circuit connects  to a mask covering the mouth and/or nose or nasal prongs.

The tube used for invasive ventilation may have a  balloon cuff to provide a seal. The noninvasive mask has a seal around the mouth  and nose to prevent the loss of gas/air, ensuring the patient receives  appropriate ventilation.

Mechanical ventilation may be used at night, during  limited daytime hours, or around the clock, depending on the patient's  needs.

Some patients require mechanical ventilation for a short  period, such as during recovery from traumatic injury. Others require  ventilation long-term, and over time the needs could increase or decrease,  depending on the patient's medical status.