Are you ready to learn about the ventilator modes of mechanical ventilation? If so, you’re in the right place because that is what this study guide is all about.

As you will see below, we have listed out pretty much everything you need to know about Ventilator Modes as a Respiratory Therapy Student. Not to mention, you’ll get access to some helpful practice questions as well. 

So if you’re ready to get started, let’s go ahead and dive right in.

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What is a Ventilator Mode?

A ventilator mode is a way of describing how the mechanical ventilator assists the patient with inspiration. The characteristics of a particular mode controls how the ventilator functions. 

Understanding the different ventilator modes is one of the most important aspects of mechanical ventilation.

What are the Primary Ventilator Modes?

Assist/Control (A/C) Mode

In this mode, a minimum number of preset mandatory breaths are delivered by the ventilator but the patient can also trigger assisted breaths. The patient makes an effort to breathe and the ventilator assists in delivering the breath.

With that said, this mode of ventilation does not allow the patient to take spontaneous breaths. In this mode, the operator can set either a controlled pressure or a controlled volume. 

Synchronous Intermittent Mandatory Ventilation (SIMV) Mode

In this mode, the ventilator delivers a preset minimum number of mandatory breaths. However, it also allows the patient to initiate spontaneous breaths in between the mandatory breaths.

This mode also allows the operator to set either a controlled pressure or a controlled volume. 

As a Respiratory Therapist (or student), SIMV and Assist/Control are the two ventilator modes that you should be most familiar with.

However, it’s also important to develop an understanding of some of the secondary modes of mechanical ventilation as well.

Ventilator Modes for Spontaneous Breathing:

Keep in mind that, in order to use any of the following modes, the patient must be breathing spontaneously.

Continuous Positive Airway Pressure (CPAP)

In CPAP, or continuous positive airway pressure, a continuous pressure that is above atmospheric pressure is maintained throughout the breathing cycle.

The patient must be breathing spontaneously to be in this mode because no mandatory breaths are given. This is a useful mode for weaning patients off of the ventilator. 

Pressure Support Ventilation (PSV)

A mode of mechanical ventilation is which the patient’s spontaneous breaths are supported by the ventilator during the inspiratory phase of breathing. As the patient triggers a breath, the ventilator assists by adding pressure to make breathing easier.

Volume Support (VS)

A mode of mechanical ventilation is which the ventilator delivers a supported breath to help the patient reach a set tidal volume. This mode is commonly used to wean patients from anesthesia. 

Other Modes of Mechanical Ventilation:

Airway Pressure Release Ventilation (APRV)

A mode of mechanical ventilation in which two levels of continuous positive airway pressure are applied with an intermittent release phase for spontaneous breaths. This mode is often recommended to improve oxygenation and treat refractory hypoxemia.

This mode is indicated for patients with an Acute Lung Injury (ALI), Acute Respiratory Distress Syndrome (ARDS), and atelectasis

Inverse Ratio Ventilation (IRV)

A mode of mechanical ventilation that uses an inverse I:E ratio to improve oxygenation and gas exchange. It’s been shown to decrease shunting, improve V/Q mismatching, and decrease deadspace ventilation.

This mode is commonly recommended for patients with Acute Respiratory Distress Syndrome (ARDS).

Pressure Regulated Volume Control (PRVC)

A mode of mechanical ventilation that provides volume-controlled breaths with the lowest pressure possible. It does so by altering the flow and inspiratory time. This mode is used to keep the peak airway pressure at the lowest possible level. 

Proportional Assist Ventilation (PAV)

A mode of mechanical ventilation where the machine uses variable pressure to provide pressure support for a patient’s spontaneous breaths. The level of pressure support is adjusts depending on the patient’s work of breathing. 

High-Frequency Oscillatory Ventilation (HFOV)

A type of mechanical ventilation that delivers very small tidal volumes at an extremely fast rate which minimizes the chances of a lung injury. 

This mode has been shown to improve oxygenation in severe cases, such as with refractory hypoxemia.

Practice Questions about the Ventilator Modes:

1. What are 5 examples of ventilator modes?

2. What type of pressure ventilation involves normal respirations, chest cuirass, and an iron lung?
Negative pressure

3. Positive pressure ventilators can be ____ vs ____ controlled.
Pressure, Volume

4. What are 2 example of nonconventional ventilator modes?

5. How does positive pressure ventilation create transairway pressure?
By increasing airway opening pressure above the alveolar pressure.

6. List the modes of positive pressure ventilation from the most support to the least support:

7. What is an advantage of a volume-controlled mode?
It ensures minimal minute ventilation.

8. What are some disadvantages of a volume-controlled modes?
The pressure is variable, there is a possibility of barotrauma/volutrauma, and the volume is limited by the high pressure alarm.

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9. What is an advantage of a pressure-limited mode?
There is less risk of barotrauma.

10. What are some disadvantages of pressure-controlled modes?
It doesn’t ensure minute ventilation, and the tidal volume is variable.

11. What two things are variable in pressure-controlled modes?
Volume (dependent on a set pressure) and Flow.

12. What are the four types of triggers?
Time, Patient, Pressure, and Flow.

13. What control is used to adjust the patient’s inspiratory effort?

14. What are the two types of sensitivity controls?
Pressure and Flow

15. How does a pressure trigger work?
The ventilator senses a drop in pressure below the baseline and senses the patient’s negative inspiratory effort.

16. Which trigger type is more sensitive, pressure or flow?

17. How does a flow trigger work?
When a patient initiates a breath, base flow returning to the ventilator is reduced, thus triggering an inspiration.

18. What is Controlled Mandatory Ventilation?
A mode that is time-triggered, gives machine breaths, and is volume or pressure cycled.

19. What are the indications for CMV?
The need to control minute ventilation completely. Also, the need to control chest expansion completely, for example, for a patient with flail chest.

20. What are some complications of CMV?
The patient is totally ventilator dependent, alarms are essential, you may be unable to assess weaning, and seizures may interrupt the delivery of a breath.

21. What are some indications for A/C mode?
The patient needs full ventilatory support, the need to support a high minute ventilation with low oxygen consumption, and the need for sedation after intubation.

22. What are some advantages of A/C mode?
Decreased work of breathing. The patient controls the respiratory rate, therefore the minute ventilation.

23. What are some complications of A/C mode?
Hyperventilation (i.e., respiratory alkalosis), pain/anxiety/CNS disease, Biot’s or Cheyne-stokes respirations.

24. What is the IMV mode?
It was the first widely used mode that allowed partial ventilatory support, facilitates weaning, and increases respiratory muscle strength. It is not widely used today.

25. What are some complications of IMV?
Breath stacking, which is a spontaneous effort immediately followed by a mechanical breath, which leads to an increased PIP; barotrauma; and cardiac compromise.

26. What is barotrauma/volutrauma?
A lung injury that occurs from hyperinflation of the alveoli past the rupture point. It usually occurs at a PIP > 50 and a Pplat > 35.

27. What is the synchronization window?
It is the time interval just prior to time triggering in which the ventilator is responsive to the patient’s spontaneous breath.

28. What are some indications for SIMV?
If the patient needs partial ventilatory support, and if the patient can actively contribute to their minute ventilation.

29. What happens if the rate is set high in SIMV mode?
This can provide total support (SIMV with no spontaneous rate is essentially the same as A/C)

30. What happens if the rate is set low in SIMV mode?
It facilitates weaning, strengthens respiratory muscles, decreases mean airway pressure making spontaneous breaths have a lower peak pressure than mandatory.

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31. What are some complications of SIMV?
A low rate can increase the patient’s work of breathing causing muscle fatigue/failure.

32. What mode has a positive baseline pressure continuously applied to the circuit and airway during both inspiration and expiration?

33. In this mode, the ventilator delivers a time-triggered breath and allows the patient to breathe at their own tidal volume between mechanical breaths?

34. In this mode, the ventilator delivers a set tidal volume or pressure at a time-triggered rate but the patient can trigger a mechanical breath above the preset rate?

35. In this mode of ventilation, the patient cannot trigger a mechanical or spontaneous breath so there is no negative deflection on graphics?
Controlled Mandatory Ventilation (CMV). The patient must be sedated or paralyzed. It is not as commonly used.

36. In order for this mode to be used, the patient must be spontaneously breathing, have adequate lung function to maintain normal PaCO2, and not be at risk for hypoventilation?

37. What does pressure support do?
It augments spontaneous tidal volume, decreases spontaneous respiratory rate, and reduces the patient’s work of breathing.

38. How does pressure support decrease the patient’s spontaneous respiratory rate?
An increased volume decreases the need for a high respiratory rate in order to achieve the required minute ventilation. Also, it decreases deadspace ventilation.

39. What is the desired respiratory rate?
Less than 25.

40. What is tidal volume dependent upon with a pressure support mode?
It is dependent on the set inspiratory pressure, lung compliance, and airway resistance.

41. What makes flow variable in pressure support?
It’s dependent upon the flow needed to maintain the plateau pressure.

42. What would be considered CPAP with pressure support?

43. CPAP with no pressure support would be considered what?

44. How do you manage pressure support?
Begin with 5 – 10 and increase in increments of 3 – 5.

45. You should titrate pressure support according to what 3 things?
(1) Spontaneous tidal volume of 5 – 7 ml/kg of IBW. (2) Respiratory rate of less than 25. (3) A decrease in work of breathing.

46. Is PEEP considered a standalone mode on ventilation?

47. What are some effects of PEEP?
They recruit alveoli, increase FRC (oxygenation), increase alveolar surface area (gas diffusion), and increase compliance.

48. What are some complications of PEEP?
Cardiac compromise, increased intrathoracic pressure, decreased venous return, decreased cardiac output and blood pressure.

49. What is an indication for PEEP?
Refractory hypoxemia

50. How do you manage PEEP?
The physiologic normal setting of PEEP is 5 cmH2O. Then you can increase in increments of 3 – 5 while also watching the patient’s blood pressure. You should decrease to the previous level or zero to lower blood pressure. You can treat low blood pressure with volume expansion or vasopressors, then increase PEEP again while continuing to monitor.

51. What is the definition of compliance?
It is the volume change per unit of pressure.

52. Inverse ratio ventilation is volume controlled or pressure controlled?
Pressure controlled

53. During breathing, a long inspiration and a short expiration causes what?
Air trapping, auto PEEP, and prevents alveolar collapse.

54. What is Auto-PEEP?
Air trapping that occurs when there is an incomplete expiration. 

55. How does IRV prevent alveolar collapse?
The critical opening pressure is reduced, the pressure needed for ventilation is less, and it improves ventilation.

56. What are some complications of IRV?
Barotrauma, requires paralysis sedation, and cardiovascular compromise.

57. When is mandatory minute ventilation activated?
When the patient’s spontaneous breathing is less than minimum set minute ventilation. When this occurs, the ventilator increases ventilation.

58. The method of increased ventilation with MMV varies upon what?
The ventilator model (some increases respiratory rate, some tidal volume, and some pressure support).

59. What should the minute ventilation be set to achieve?
A satisfactory PaCO2

60. What are some advantages of MMV?
It promotes spontaneous breathing, it requires minimal support but protects against hypoventilation and respiratory acidosis, and it permits weaning but compensates for apnea.

61. What are some disadvantages and complications of MMV?
It doesn’t protect against deadspace breathing. A high respiratory rate with a low tidal volume means the patient is breathing above minute ventilation (MMV remains inactive but PaCO2 increases, respiratory acidosis).

62. What does pressure control generate?
A flow in order to increase the airway pressure to a preset pressure limit.

63. When is inspiration terminated in Pressure Control?
When the preset I-Time is reached.

64. What are some indications for pressure control?
Low lung compliance, high PIP during volume ventilation, (PIP > 50, Pplat > 35), and ARDS.

65. What are some advantages of pressure control?
PIP is reduced while maintaining adequate oxygenation and ventilation. Also, there is a reduced risk of barotraumas.

66. How do you manage pressure control?
The PIP is set to achieve a desired tidal volume unless the patient is allowed to become hypercapnic in the interest of limiting PIP. Tidal volume and minute ventilation must be carefully monitored.

67. What is APRV?
A mode of ventilation that stands for: Airway Pressure Release Ventilation.

68. What happens during inspiration in APRV?
Positive airway pressure augments spontaneous breathing (High CPAP level, reduces WOB, Increases MAP to increase O2, allows spontaneous inspiration at any point during the breath-elevated pressure delivery).

69. What happens during exhalation with APRV?
Positive pressure is periodically released to allow exhalation (brief 1 – 2 seconds), decreases FRC and allows for exhalation and the release of CO2.

70. APRV is inappropriate for what kind of patients?
Those at risk for an inadequate spontaneous respiratory rate.

71. APRV can resemble IRV when?
The expiratory pressure release time is less than the spontaneous effort.

72. Why is APRV a beneficial alternative to IRV?
Because it does not require paralytics.

73. Describe APRV:
It is time-triggered but the patient is allowed to breathe spontaneously at any time; it is mandatory and spontaneous pressure limited; it is time-cycled with a preset I-time.

74. Describe HFOV:
It reduces the risk of lung destruction by keeping alveoli open at a constant pressure, oscillates very rapidly (high respiratory rate at small volumes); early intervention is key.

75. How do you manage oxygenation with HFOV?
Adjust the mean airway pressure, FiO2, and alveolar recruitment.

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76. How do you manage ventilation with HFOV?
Adjust the amplitude, Hertz, % I-time, cuff deflation, and permissive hypercapnia.

77. What is Amplitude in HFOV?
It is the change in stroke volume and the force delivered by the piston.

78. What are the trigger variables for VC/AC CMV?
Pressure, time, and flow

79. What are the limit variables for VC/AC CMV?
Volume and flow

80. What are the targeted variables for VC/AC CMV?

81. What are the cycle variables for VC/AC CMV?

82. What are the trigger variables for VC/SIMV?
Time, volume, and pressure

83. What are the limit variables for VC/SIMV?

84. What is Controlled Mandatory Ventilation (CMV)?
It is used in sedated, apneic, or paralyzed patients. All breaths are triggered, limited, and cycled by the ventilator. The patient has no ability to initiate their own breaths. If a patient tries to take a breath while in the CMV mode it is reported to sound like sucking on an empty bottle.

85. What is Synchronized Intermittent Mandatory Ventilation (SIMV)?
It is an assisted mechanical ventilation synchronized with the patient’s breathing. The ventilator senses the patient taking a breath then delivers the breath. Spontaneous breathing by patient occurs between the assisted mechanical breaths which occurs at preset intervals. If the patient fails to take a breath, the ventilator will provide a mechanical breath.

86. When is SIMV preferred?
When the patient has an intact respiratory drive.

87. How is SIMV is similar to CPAP and BIPAP?
Because they are all spontaneously triggered by patient.

88. How does Assist/Control Ventilation work?
The trigger for delivery of a breath can be either by the patient or by elapsed time.

89. What is the preferred mode for patients with respiratory distress?
Assist/Control Ventilation

90. What mode supports every breath whether its initiated by the patient or ventilator. Also, this mode delivers a full tidal volume regardless of the patient’s respiratory effort or drive?
Assist/Control Ventilation

91. This mode can be used in ARDS, paralyzed, or sedated patients?
Assist/Control Ventilation

92. During Assist/Control ventilation, what can happen to an anxious patient?
They can trigger the ventilator to hyperventilate which leads to breath stacking or auto-PEEP.

93. Which mode of mechanical ventilation can provide a precise I:E ratio?
Control Mode Ventilation (CMV)

94. What mode can make it easier for the patient to overcome the resistance of the ET tube and is often used during weaning because it reduces the work of breathing?
Pressure Support Ventilation

95. Describe Pressure Support Ventilation:
It supports ventilation during inspiration. The patient determines tidal volumes, rate, and minute volume. It requires consistent respiratory effort by the patient.

96. What is a component of CPAP/BPAP?
They are both spontaneously triggered by the patient.

97. What does CPAP stand for?
Continuous Positive Airway Pressure

98. What mode uses continuous positive pressure to maintain a continuous level of PEEP and uses mild air pressure to keep the airway open?

99. What does BiPAP stand for?
Bilevel Positive Airway Pressure

100. What mode uses alternating levels of PEEP to maintain oxygenation, commonly used in pneumonia, COPD, and asthma?

Final Thoughts

So there you have. That wraps up our study guide on the modes of mechanical ventilation. I hope that you found this information to be helpful. In fact, I’m confident that you can use this guide to boost your knowledge of the ventilator modes to a whole new level. 

And most importantly, this guide to give you a head start on preparing for the TMC Exam as well. Thank you so much for reading and as always, breathe easy my friend. 

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