Table 1.

Chatburns’ maxims for understanding ventilator operation

A breath is one cycle of positive flow (inspiration) and negative flow (expiration) defined in terms of the flow versus time curve

A breath is assisted if the ventilator provides some or all of the work of breathing

A ventilator assists breathing using either pressure control or volume control based on the equation of motion for the respiratory system

Breaths are classified according to the criteria that trigger (start) and cycle (stop) inspiration

Trigger and cycle events can be either patient initiated or ventilator initiated

Breaths are classified as spontaneous or mandatory based on both the trigger and cycle events

Ventilators deliver three basic breath sequences: CMV, IMV and CSV

Ventilators deliver five basic ventilatory patterns: VC-CMV, VC-IMV, PC-CMV, PC-IMV and PC-CSV

Within each ventilatory pattern, there are several types that can be distinguished by their targeting schemes (set-point, dual, biovariable, servo, adaptive, optimal and intelligent)

A mode of ventilation is classified according to its control variable, breath sequence and targeting schemes

CMV: continuous mandatory ventilation; IMV: intermittent mandatory ventilation; CSV: continuous spontaneous ventilation; VC: volume control; PC: pressure control. Reproduced and modified from [31] with permission from the publisher.