Positive pressure is a pressure within a system that is greater than the environment that surrounds that system. Consequently, if there is any leak from the positively pressured system it will egress into the surrounding environment.

Modes of mechanical ventilation are one of the most important aspects of the usage of mechanical ventilation. The mode refers to the method of inspiratory support. In general, mode selection is based on clinician familiarity and institutional preferences, since there is a paucity of evidence indicating that the mode affects clinical outcome. The most frequently used forms of volume-limited mechanical ventilation are intermittent mandatory ventilation (IMV) and continuous mandatory ventilation (CMV). There have been substantial changes in the nomenclature of mechanical ventilation over the years, but more recently it has become standardized by many respirology/pulmonology groups. Writing a mode is most proper in all capital letters with a dash between the cycle and the strategy (i.e. PC-IMV, or VC-MMV etc.)