Mechanical Ventilation- Trigger, Limit and Cycle
So how can you work out what are the phase variables in the ventilator cycle? Go back to this page to understand the cycle variables again if you are not sure.
Trigger Variable
Does the inspiration start because a preset pressure is detected? -YES- Inspiration is pressure triggered
NO
Does the inspiration start because a preset flow is detected?- YES- Inspiration is flow triggered
NO
Does the inspiration start because a preset volume is detected?- YES- Inspiration is flow triggered
NO
Inspiration starts because a preset time interval has elapsed?- YES- Inspiration is time triggered
Limit Variable
Does peak pressure reach preset value before inspiration ends?- YES- Inspiration is pressure limited
NO
Does peak volume reach preset value before inspiration ends?- YES- Inspiration is volume limited
NO
Does peak flow reach preset value before inspiration ends?- YES- Inspiration is flow limited
Cycle Variable
Does inspiratory flow end because a preset pressure is attained?- YES- Inspiration is pressure cycled.
NO
Does inspiratory flow end because a preset pressure is attained?- YES- Inspiration is volume cycled.
NO
Does inspiratory flow end because a preset flow is attained?- YES- Inspiration is flow cycled.
NO
Inspiration ends because a preset time interval has elapsed.- YES- Inspiration is time cycled.
Chatburn RL. Classification of Mechanical Ventilators. Respir Care 1992
Mechanical Ventilation
- Peak and Plateau Pressure
- AC versus SIMV mode
- Positive End Expiratory Pressure (PEEP)
- Increase the rate or tidal volume?
- Phases of a breath- I:E ratio and cycle time
- Intubation
- Ventilation screen- what do those numbers mean?
- Pressure Support
- Modes of ventilation I
- Modes of ventilation II
- Physiologic effects
- Physiologic goals
- How do I describe how my patients ventilation?
- Trigger, Limit and Cycle
- Pressure support ventilation graphs
- ARDS and Proning
- 6 ways to be better with Bag-Valve-Mask
- Terminology
- Phase Variables
- Airway Pressure Release Ventilation (APRV)
- Pressure Volume Loop
- Lung compliance in volume controlled ventilation
- Pressure/Volume/Flow graphs
- A-a gradient
- Goals and Indications
- Anatomy of the Endotracheal Tube
- Lung Compliance
- Ventilation/Perfusion V/Q matching
- Ventilator Induced Lung Injury (VILI)
- Ventilator Associated Pneumonia (VAP)
- Phase variables...again...
- Capnography
Guidelines for the management of tracheal intubation in critically ill adults
Having read the guidelines I made these infographics. They are FREE. Just let me know your email address and they will be sent to you.



