Ventilator Dyssynchrony (Patient-Ventilator Asynchrony Overview)

What is Ventilator Dyssynchrony? (Patient-Ventilator Asynchrony)

by | Updated: Jan 28, 2023

Ventilator dyssynchrony is a term that describes a mismatch of the timing and gas delivery between a patient and the mechanical ventilator. Patient-ventilator asynchrony is a similar term used to describe this interaction.

This study guide provides an overview of this topic and has practice questions designed to help you learn this information.

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What is Ventilator Dyssynchrony?

Ventilator dyssynchrony is characterized by inappropriate timing of a delivered breath between a patient and the mechanical ventilator.

This increases work of breathing and makes it more difficult for the patient to breathe comfortably on the ventilator. In this case, the patient is unable to communicate, which makes it challenging for Respiratory Therapists and medical professionals.

Patient-ventilator dyssynchrony can occur in both assisted and controlled mechanically ventilated breaths.

Adverse Effects

Patient-ventilator dyssynchrony can result in several adverse effects, including the following:

  • Patient discomfort
  • Increased work of breathing (WOB)
  • Respiratory distress
  • Increased anxiety
  • Overdistension
  • Ventilator-induced lung injury (VILI)
  • Prolonged sedation
  • Prolonged duration of mechanical ventilation
  • Increased time in the ICU

Each adverse effect caused by patient-ventilator dyssynchrony is associated with an increased mortality rate.


Some examples of the common causes of ventilator dyssynchrony include the following:

  • Ineffective triggering
  • Incorrect ventilator mode
  • Incorrect ventilator settings
  • Inappropriate triggering
  • Flow dyssynchrony
  • Exhalation dyssynchrony
  • Auto-PEEP
  • Artificial airway problems
  • Drug-induced problems
  • Certain lung diseases

Dyssynchrony can occur due to many other causes as well. These are just a few of the most common examples.


The management of ventilator dyssynchrony depends on the specific cause. Since inappropriate ventilator settings are typically involved, making proper adjustments appears to be the best treatment method.

For example, the practitioner may need to adjust the flow, sensitivity, or inspiratory time. A different ventilator mode may be considered as well.

In general, the less control the ventilator has on the patient’s respiratory pattern, the less likely they will experience dyssynchrony.

Volume-controlled ventilation typically results in more cases of dyssynchrony because it controls volume, flow, and time. Pressure support ventilation (PSV), on the other hand, typically results in the least amount of cases.

Proportional Assist Ventilation (PAV) and Neurally Adjusted Ventilatory Assist (NAVA) are two ventilator modes that are effective in avoiding dyssynchrony. That is because they allow the patient to select the ventilatory pattern that is delivered.

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Ventilator Dyssynchrony Practice Questions:

1. Why is a patient-ventilator interaction not a problem during controlled ventilation?
Because the patient is not interacting with the ventilator. It is, however, a major issue during patient-triggered ventilation

2. What has poor patient-ventilator interaction been associated with?
It has been associated with an increased length of time on the ventilator, increased time in the ICU, the need for a tracheotomy, and increased mortality.

3. Issues with the artificial airway can cause what?
It can cause marked changes in the patient-ventilator interaction.

4. The development of a pneumothorax is a major cause of what?
It is a major cause of a markedly deteriorating patient-ventilator interaction.

5. Why is it unlikely that a mechanical ventilator malfunction is the cause of poor patient-ventilator interaction?
Because, with today’s mechanical ventilators, the technology is so advanced that this should never happen

6. The less control exerted by the mechanical ventilator on the patient’s ventilatory pattern, the less likely it is that the patient will develop what?
Patient-ventilator asynchrony

7. What are the general types of ventilator asynchrony?
Flow asynchrony, trigger asynchrony, cycle asynchrony, and mode asynchrony

8. Ventilator asynchrony can be caused by what?
It can be caused by an inappropriately set sensitivity, PEEP, flow, tidal volume, and inspiratory time.

9. Flow asynchrony is a result of what?
The flow provided by the ventilator being inadequate to match the patient’s inspiratory demand

10. Trigger asynchrony can manifest as what?
Missed triggering, delayed triggering, auto-triggering, double triggering, and reverse triggering

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11. Missed triggering and delayed triggering are normally a result of what?

12. Auto-triggering is normally a result of what?
It can result from circuit leaks or fluid moving back and forth in the ventilator circuit. It can also be caused by hyperdynamic contractions of the myocardium.

13. Flow asynchrony is a result of what?
It is a result of the ventilator providing less flow than the patient’s respiratory center requires.

14. When does mode asynchrony occur?
It occurs when the selected mode of ventilation does not match the patient’s ventilatory demands.

15. Why can volume ventilation be expected to cause the most asynchrony?
Because it controls volume, flow, and time.

16. Which mode of ventilation should result in the least asynchrony?
Pressure Support

17. Why do PAV and NAVA cause the least asynchrony?
Because they do not force a ventilatory pattern but follow the ventilatory pattern selected by the patient.

18. What causes trigger delay?
Auto-PEEP, poor sensitivity setting, and ventilatory malfunction.

19. How can a trigger delay be modified?
It can be modified by minimizing auto-PEEP, applying PEEP, decreasing minute volume, or setting an appropriate sensitivity.

20. What causes auto-triggering?
Circuit leaks, water in the circuit, inappropriately set sensitivity, and hyperdynamic cardiac contractions.

21. How can auto-triggering be modified?
New ventilator circuit, removal of water from the circuit, and appropriate sensitivity setting.

22. What are the four causes of poor patient-related interaction with a ventilator?
Abnormal respiratory drive, secretions in the airway, bronchospasm, and abdominal distension.

23. What are some adverse effects of a poor patient-ventilator interaction?
Unstable hemodynamics, ventilatory patterns, and gas exchange values.

24. What is the primary reason for poor patient-ventilator interaction?
A sudden change in clinical status.

25. What are the first four steps in the management of sudden respiratory distress in a ventilated patient?
(1) Remove the patient from ventilator, (2) Manually ventilate the patient with 100% oxygen, (3) Perform a rapid physical assessment, and (4) Check to be sure for a patent airway.

26. In what mode of ventilation is asynchrony most likely?
Volume-controlled Assist/Control

27. In volume-controlled ventilation, what three things can the ventilator control?
Volume, flow, and time.

28. In pressure-controlled ventilation, what two things can the ventilator control?
Pressure and time.

29. What mode of ventilation is flow asynchrony most likely?
Volume-controlled ventilation

30. How much flow does a patient with a strong ventilatory demand require?
60 L/min

31. What inspiratory time is usually appropriate to generate flow?
0.6 to 0.9 seconds

32. How can you improve flow asynchrony in pressure-controlled ventilation?
Adjust the rise time (0.4 seconds).

33. What is the primary contributor to trigger asynchrony?

34. What are some techniques for minimizing the effects of Auto-PEEP?
Decrease the inspiratory time, bronchodilation, secretion management, and increase the artificial airway size.

35. What are the potential causes for a trigger delay?
Auto-PEEP, ventilator malfunction, and an inappropriate sensitivity setting.

36. What time length should the trigger delay attempt to stay under?
It should stay under 100 milliseconds.

37. What mode of ventilation is double triggering most common in?
Volume-controlled Assist/Control

38. What are the potential causes of double triggering?
The inspiratory time is too short, or the tidal volume is too low.

39. What are some potential causes of auto-triggering?
The presence of condensation or a leak in the tube.

40. In what mode of ventilation is cycle asynchrony more common?
Pressure-controlled ventilation

41. What mode of ventilation can be the most problematic because the respiratory center of the brain cannot distinguish between mechanical and spontaneous breaths?

42. How long can it take for a patient to recover from ventilator fatigue?
24 hours

43. How quick can ventilator atrophy occur?
48 hours

44. When more variables are controlled by a ventilator, what can occur?
There is a greater outcome for asynchrony.

45. When does flow asynchrony occur?
It is most common in volume-controlled ventilation but can occur in any mode.

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46. What happens to the patient if the rise time is too slow?
The patient’s work of breathing will increase.

47. How can you prevent flow asynchrony in volume-controlled ventilation?
Increase the peak flow and decrease the inspiratory time, or change to a decelerating flow waveform

48. How can you prevent flow asynchrony in pressure-controlled ventilation?
Adjust the rise time

49. What is the biggest factor in trigger asynchrony?
The presence of auto-PEEP

50. Double triggering can cause what?

51. What is cycle asynchrony?
It occurs when the ventilator ends the breath at a time different from when the patient wants to.

52. What is the most common form of cycle asynchrony?
An inappropriately short inspiratory time

53. In what mode of ventilation is asynchrony less likely to occur?

54. What is the difference in ventilator dyssynchrony and asynchrony?
These two terms can be used interchangeably; therefore, there is no difference.

55. What is a patient-ventilator interaction?
A term that describes the connection and deliverance of a breath to a patient by the machine

Written by:

John Landry, BS, RRT

John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.


  • Faarc, Kacmarek Robert PhD Rrt, et al. Egan’s Fundamentals of Respiratory Care. 12th ed., Mosby, 2020.
  • Chang, David. Clinical Application of Mechanical Ventilation. 4th ed., Cengage Learning, 2013.
  • Rrt, Cairo J. PhD. Pilbeam’s Mechanical Ventilation: Physiological and Clinical Applications. 7th ed., Mosby, 2019.
  • “Patient-Ventilator Asynchrony.” PubMed Central (PMC), 2018,

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