Mastering the Vent: Cycle Dyssynchronies

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Matt Siuba
Zentensivist. ARDS, Mechanical Ventilation, RV, & Shock Enthusiast.

The Pre-brief

Understanding patient-ventilator interactions is made easier by breaking it down into the following parts:

  • Trigger, the beginning of inspiration
  • Inspiratory phase interactions (like “flow starvation”)
  • Cycle, the end of inspiration
  • Expiratory phase interactions

This gives a much more systematic framework for understanding vent waveforms, more like reading different segments of an EKG. Today, I’ll cover the most common cycle dyssynchronies in the following infographic:

The Debrief

  • Cycle refers to the end of inspiration (beginning of expiration). 
  • When we name vent dyssynchrony issues as “early” or “late”, the patient is the reference. E.g. if the vent is late to cycle relative to the patient, it is late cycling.
  • Early cycling requires clinical judgement to decide how best to ameliorate it
  • Delayed cycling is generally easier to fix, especially in conventional pressure control where you just need to shorten the inspiratory time to match the patient’s neural inspiratory time. 
  • However, understanding flow cycling for patients in pressure support is key to making proper adjustments. More on that topic here.

Further Reading


  1. Mireles-Cabodevila E, Siuba MT, Chatburn RL, A Taxonomy for Patient-Ventilator Interactions and a Method to Read Ventilator Waveforms Respiratory Care September 2021, respcare.09316; DOI:


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