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Patient-ventilator dyssynchrony: the patterns

A patient fighting the ventilator is giving you information. Sedating them removes the signal and leaves the cause.

William Owens, MD, Attending Intensivist Physician · Updated 2026-10-05

Rule out the emergency first

Any new dyssynchrony is a reason to check the tube, listen to the chest and look at the saturation before touching a setting or a syringe. Displacement, obstruction, pneumothorax, equipment failure and stacked breaths all present as a patient suddenly fighting, and all of them get worse if the response is more sedation.

The patterns

Pattern	What you see	Usual cause
Ineffective triggering	A visible effort, or a small dip in airway pressure, with no breath delivered	Auto-PEEP, most often. Also weakness, or a trigger set too insensitive
Double triggering	Two breaths back to back with almost no gap	The set tidal volume or inspiratory time is less than the patient wants
Flow starvation	A scooped, concave inspiratory pressure trace	Set flow below demand, or too slow a rise time
Auto-cycling	Breaths delivered with no patient effort at all	A circuit leak, water in the tubing, or cardiac oscillations being read as effort
Premature cycling	The patient keeps pulling after the ventilator has stopped	Pressure support cycling off too early
Delayed cycling	A sharp pressure spike at end-inspiration as the patient exhales against the machine	Pressure support cycling off too late, common in obstruction and with a cuff leak
Reverse triggering	The diaphragm contracts in response to a delivered breath	Deep sedation

Ineffective triggering deserves special attention

It is the most common form and the most misread. With air trapped in the chest, the patient has to drop airway pressure by the whole of the auto-PEEP before the ventilator registers any effort at all. Every one of those efforts is work that produces no breath.

The fix is to get rid of the trapping: slow the rate, lengthen expiration, treat the obstruction. Making the trigger more sensitive treats the symptom and risks auto-cycling instead.

Double triggering and lung injury

Two breaths stacked with no exhalation between them deliver twice the set tidal volume into a lung that was set up for protective ventilation. The delivered volume is the one that injures, not the set one.

It is most common in awake patients on 6 mL/kg whose own drive is demanding more. Lengthening inspiratory time often fixes it. Where it does not, the choice is a careful increase in volume or deeper sedation, and the trade is worth making deliberately rather than by default.

What to do before reaching for sedation

• Check tube position, breath sounds and saturation.
• Look at the flow trace: does expiratory flow reach zero before the next breath?
• Look at the pressure trace: is the inspiratory limb scooped?
• Perform an inspiratory pause and read the plateau; perform an expiratory pause and read total PEEP.
• Treat pain, fever, delirium and a full bladder, all of which raise respiratory drive and none of which are a ventilator problem.

Sedation is a legitimate tool once the cause is understood. Used as the first response, it removes the one sign that was telling you what was wrong.