Are you ready to learn about the ventilator modes of mechanical ventilation? If so, you’ve come to 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 mentioned, we topped it all off with some practice questions as well.

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

What is a Ventilator Mode?

A ventilator mode is a way of describing how the mechanical ventilator assists the patient with inspiration. Understanding the different ventilator modes is one of the most important aspects of mechanical ventilation.

What are the Primary Ventilator Modes?

Ventilator modes can be described as either a primary mode, secondary mode, or spontaneous mode. We’re going to discuss each type, but first, let’s cover the primary modes.

Assist/Control (A/C) Mode

In this mode, the ventilator delivers a set minimum number of mandatory breaths each minute. The patients can trigger assisted breaths by decreasing the volume, pressure, or flow below the established baseline value.

A/C mode can be used with either pressure control or volume control.

Synchronous Intermittent Mandatory Ventilation (SIMV) Mode

In this mode, the ventilator delivers a set minimum number of mandatory breaths each minute, but also allows the patient to breathe spontaneously in between the mandatory breaths.

It can also be used with either pressure control or volume control.

What are the Secondary Ventilator Modes?

Inverse Ratio Ventilation (IRV)

A form of pressure control (most often) or volume control ventilation with either a continuous mandatory or intermittent mandatory breath scheme.

This mode uses an inverse I:E ratio to improve oxygenation and gas exchange. It is recommended for patients needing a high FiO2 and high PEEP, a high PIP, or a low PaO2 with decreased compliance.

This is often the ventilator mode of choice for ARDS patients.

Airway Pressure Release Ventilation (APRV)

This is a mode similar to CPAP. APRV is an applied continuous positive airway pressure that at a set timed interval releases the applied pressure.

This mode improves oxygenation using a lower mean airway pressure.

Pressure Regulated Volume Control (PRVC)

This is a pressure-controlled mode, but adds a target tidal volume, so that the inspiratory pressure changes breath-by-breath up to a set point in order to maintain a stable tidal volume.

The breaths are patient or time-triggered, volume targeted, time cycled, and the rate and tidal volume are preset.

Proportional Assist Ventilation (PAV)

In this mode, a pressure is delivered but is dependent on the inspiratory flow and volume demands by the patient.

The pressure, flow, and volume are proportional to the patient’s spontaneous effort. The respiratory therapist (or operator) determines the amount of pressure support.

What are the Spontaneous Breathing Ventilator Modes?


In CPAP, or continuous positive airway pressure, the patient MUST be breathing spontaneously to be in this mode because no mandatory breaths are given.

This is a useful ventilator mode for weaning.

Pressure Support

This mode consists of spontaneous ventilation with all of the patient’s spontaneous breaths supported or augmented by the ventilator. In other words, a set pressure is added to each spontaneous breath.

The initial pressure support level is determined by measuring the patient’s airway resistance.

Volume Support

This mode consists of spontaneous ventilation that delivers a variable pressure to meet a target tidal volume. The ventilator adjusts the delivered pressure to meet that target volume.

What is High-Frequency Oscillatory Ventilation?

HFOV is a type of mechanical ventilation that uses a constant distending pressure with pressure variations oscillating around the MAP at very high rates. This creates small tidal volumes, often less than the dead space.

It’s an unconventional form of mechanical ventilation that maintains lung recruitment, avoids overdistention, and does not rely on bulk flow for oxygenation and ventilation.

It helps improve oxygenation in severe cases, such as ARDS.

This ventilator oscillates at very high frequencies in the 3 – 15 Hz range, and the tidal volumes are very low, typically in the 3 – 5 mL range.

Settings for HFOV:

  • Amplitude or power – the primary control for PaCO2
  • Frequency – the secondary control for the PaCO2
  • The lower the frequency, the higher the tidal volume. The higher the frequency, the lower the tidal volume. It is inversely proportional.
  • Mean airway pressure – the primary control for the PaO2.

Ventilator Modes Practice Questions:

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 types of nonconventional ventilation?

5. How does PPV 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 volume controlled mode?
It ensures minimal minute ventilation.

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

9. What is an advantage of pressure limited modes?
There is less risk of barotrauma.

10. What are some disadvantages of pressure controlled modes?
It doesn’t ensure minute ventilation; The tidal volume is variable.

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

12. What are the four types of triggers?
Time, patient, pressure, flow.

13. What is the control used to adjust the ventilator sensory of the patient’s inspiratory effort called?

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, machine breath, and 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, with 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, 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, Biots or Cheyne-stokes respirations.

24. Describe IMV mode?
It was the first widely used mode that allowed partial ventilatory support, facilitates weaning, increase 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. If the set rate is high (8-12) in SIMV mode?
This can provide total support (SIMV with no spontaneous rate is essentially the same as A/C)

30. Setting the rate low (<8) in SIMV does what?
It facilitates weaning, strengthens respiratory muscles, decreases mean airway pressure making spontaneous breaths have a lower peak pressure than mandatory.

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 pre-set rate?

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

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’s 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?

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), 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?
5 is the physiologic normal setting. 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 for 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 compliance?
It is the volume change per unit of pressure.

52. Inverse ratio ventilation is?
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?
Increased oxygenation, peep effects, increased FRC, PaO2, and surface area.

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 increase 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 d/t 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.

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?
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?
It is an assisted mechanical ventilation synchronized with the patients 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 the patient or 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?
CMV, or Control Mode Ventilation

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 list of practice questions all about ventilator modes for mechanical ventilation. Study these and there’s no doubt you’ll make a higher percentage on your next exam on ventilator modes.

And also, it will give you a head start on preparing for your board exams as well.