Positive pressure ventilation with a bag-valve mask (BVM) device is a fundamental skill at the BLS level. Delivering effective BVM ventilations can be difficult, and requires considerable practice to be done correctly. Bag-valve mask ventilations, while a critical and proven intervention for respiratory failure, are limited in their ability to provide consistent and accurate tidal volume and do not provide the protections of an advanced airway device.

Positive pressure ventilations with an advanced airway in place can provide a more efficient and protected means of ventilation over a bag-mask device. However, variables in pressure, tidal volume, rate, and oxygen concentration all present potential complications for patients undergoing positive pressure ventilation in the pre-hospital setting. The use of a mechanical ventilator allows for control of ventilation rate, volume, pressure, and oxygen concentration, as well as continuous monitoring of carbon dioxide and oxygen levels.