Volume-Controlled Ventilation: Mode of Ventilation (2025)

Volume-controlled ventilation is one of the most widely used modes in mechanical ventilation, particularly in critical care and surgical settings. It is a cornerstone of respiratory support for patients who cannot maintain adequate ventilation on their own.

This article explores how volume-controlled ventilation works, when it’s used, its benefits and limitations, and key considerations for clinical practice.

What Is Volume-Controlled Ventilation?

Volume-controlled ventilation is a mode in which the ventilator delivers a preset tidal volume with each breath. This means the clinician programs the ventilator to deliver a specific amount of air to the patient’s lungs during inspiration, regardless of the pressure required to do so.

Because the tidal volume remains constant, this approach ensures consistent minute ventilation, which is the total volume of air entering the lungs per minute. This is crucial for maintaining adequate oxygenation and carbon dioxide removal, especially in patients who are sedated, paralyzed, or otherwise unable to breathe effectively on their own.

How It Works

In volume-controlled ventilation, the following parameters are typically set:

• Tidal Volume (VT): The fixed amount of air delivered with each breath
• Respiratory Rate (RR): The number of breaths delivered per minute
• Inspiratory Flow Rate and Pattern: How fast the breath is delivered (e.g., square or decelerating flow)
• FiO₂ and PEEP: Oxygen concentration and positive end-expiratory pressure to support oxygenation

Note: Once these settings are programmed, the ventilator takes over the breath delivery. Each breath is guaranteed to deliver the exact volume set, whether triggered by the patient or the machine.

Clinical Applications

Volume-controlled ventilation is commonly used in:

• Postoperative patients under anesthesia
• Patients with acute respiratory failure
• Patients with neuromuscular diseases
• Initial ventilator setups in the ICU

Note: Because it offers predictable and reproducible ventilation, this mode is especially useful when strict control of ventilation is required—such as in cases of severe acid-base imbalance or elevated intracranial pressure.

Modes That Use Volume-Controlled Ventilation

• Assist/Control (A/C) Mode: In this mode, every breath, whether initiated by the patient or the ventilator, is delivered with the full preset tidal volume. This provides complete ventilatory support, making it ideal for patients who have little or no spontaneous breathing effort.
• Synchronized Intermittent Mandatory Ventilation (SIMV): In SIMV, mandatory breaths are delivered at set intervals, but the patient is allowed to take spontaneous breaths between them. These spontaneous breaths may be supported with pressure support ventilation (PSV) to reduce the work of breathing. SIMV is often used during weaning to gradually transition patients to spontaneous breathing.

Advantages of Volume-Controlled Ventilation

• Consistent Minute Ventilation: Ensures reliable delivery of set volumes and stable gas exchange
• Predictability: Useful during surgery and in patients with unstable conditions
• Ease of Use: Familiar mode for most respiratory therapists and ICU staff
• Better Control Over CO₂ Elimination: Because volume is constant, it simplifies management of ventilation goals

Key Limitations and Considerations

One of the major concerns in volume-controlled ventilation is the potential for high airway pressures, particularly in patients with:

• Decreased lung compliance (e.g., ARDS, pulmonary fibrosis)
• Increased airway resistance (e.g., asthma, COPD exacerbations)

Since the ventilator is focused on delivering the set volume, it will generate as much pressure as needed to achieve that target, raising the risk of:

• Barotrauma: Damage from high pressures
• Volutrauma: Lung injury from overdistention

Monitoring Is Essential

To manage these risks, it is crucial to:

• Monitor peak inspiratory pressure (PIP)
• Check plateau pressure (Pplat) regularly
• Set appropriate high-pressure alarms on the ventilator

If pressures become too high, the clinician may need to:

• Reduce the tidal volume
• Switch to a pressure-controlled ventilation mode
• Adjust the patient’s sedation or ventilator settings to improve synchrony

Patient-Ventilator Synchrony

Another important factor is patient comfort and synchrony. If the patient attempts to breathe against the ventilator or becomes asynchronous, this can result in:

• Discomfort and anxiety
• Ineffective ventilation
• Increased work of breathing
• Air trapping or breath-stacking

Strategies to improve synchrony include:

• Adjusting trigger sensitivity
• Using sedation appropriately
• Switching to a mode that better accommodates patient effort

When to Reassess the Patient

While volume-controlled ventilation is highly effective, it is not a one-size-fits-all solution. Continuous reassessment of the patient’s lung compliance, airway resistance, blood gas values, and comfort/synchrony is essential to determine whether this mode remains appropriate.

In some cases, switching to a pressure-targeted mode or utilizing advanced modes, such as PRVC (pressure-regulated volume control), may yield better results.

Volume-Controlled Ventilation vs. Pressure-Controlled Ventilation

Both volume-controlled and pressure-controlled ventilation are fundamental modes used in mechanical ventilation, but they differ significantly in how breaths are delivered and in the clinical situations where each is most appropriate:

Volume-Controlled Ventilation

In volume-controlled ventilation, the clinician sets a specific tidal volume to be delivered with each breath. The ventilator ensures that this exact volume reaches the lungs, regardless of the pressure required to do so. This provides predictable minute ventilation, making it easier to control carbon dioxide levels.

However, if the patient’s lung compliance decreases or airway resistance increases, the pressure needed to deliver that volume can rise significantly. This increases the risk of ventilator-induced lung injury, such as barotrauma or volutrauma.

Pressure-Controlled Ventilation

In pressure-controlled ventilation, the clinician sets the peak inspiratory pressure, and the tidal volume varies depending on lung mechanics. This approach limits the risk of high airway pressures and is particularly useful in patients with stiff lungs or acute lung injury, such as those with acute respiratory distress syndrome (ARDS).

The main drawback is that tidal volume is not fixed—it can fluctuate with changes in compliance or resistance, potentially leading to hypoventilation if not closely monitored.

The key distinction lies in what is being prioritized: volume control guarantees ventilation but allows pressure to vary, whereas pressure control guarantees limited pressure but allows volume to vary. Choosing the right mode depends on the patient’s condition, lung mechanics, and clinical goals.

Note: For patients requiring strict control of ventilation and carbon dioxide levels, volume control may be the preferred mode. For those at risk of pressure-related lung injury, pressure control may be the safer option. Ultimately, careful assessment and monitoring are essential regardless of the mode chosen.

Volume-Controlled Ventilation Practice Questions

1. During volume-controlled ventilation, an increase in airway resistance will result in which of the following?  
An increase in peak airway pressure.

2. A patient on VC-CMV is breathing at 25 bpm with an ABG showing pH 7.50, PaCO2 30 mmHg, and PaO2 98 mmHg. What is the most appropriate action?  
Change the mode to volume-controlled intermittent mandatory ventilation (VC-IMV).

3. A pressure-time scalar shows sharp rectangular pressure spikes with no dips between them. What ventilation mode is this most consistent with?  
Volume-controlled continuous mandatory ventilation (VC-CMV).

4. A pressure-time scalar shows a baseline pressure with dips indicating patient-triggered breaths. What mode does this suggest?  
Volume-controlled intermittent mandatory ventilation (VC-IMV) with pressure support.

5. Which ventilator mode is time-cycled, volume-targeted, and automatically adjusts pressure to ensure volume delivery?  
Pressure-regulated volume control (PRVC).

6. What are the three primary settings to configure in volume-controlled ventilation?  
Tidal volume, flow rate, and flow waveform (constant or ramp).

7. What is a potential effect of setting inspiratory flow too low in a patient breathing spontaneously?  
Increased work of breathing and patient discomfort.

8. What are potential consequences of setting inspiratory flow too high during volume-controlled ventilation?  
Increased peak pressure, shortened inspiratory time, and risk of uneven gas distribution.

9. Which ventilator mode is patient-triggered, pressure-limited, flow-cycled, and targets a set tidal volume?  
Volume support ventilation (VSV).

10. What is the purpose of performing an inspiratory pause during volume-controlled ventilation?
To measure plateau pressure and assess alveolar compliance.

11. What does plateau pressure reflect during volume-controlled ventilation?
Alveolar pressure and lung compliance.

12. What are the two most common types of breath triggers in mechanical ventilation?  
Pressure-trigger and flow-trigger.

13. In volume control, what defines the end of the inspiratory phase?  
When the preset tidal volume has been delivered.

14. What are two advantages of volume-controlled ventilation?  
Guaranteed tidal volume and the ability to set different flow waveforms.

15. What are two disadvantages of volume-controlled ventilation?  
It is not responsive to patient effort and does not guarantee a safe pressure.

16. A mode is set to deliver 500 mL, 12 times per minute, and each breath ends once 500 mL is delivered. What mode is being used?  
Volume control

17. If compliance drops from 50 to 20 mL/cmH2O and the set tidal volume is 500 mL, how much volume is delivered?  
500 mL (volume remains constant in volume control).

18. Patient #1 has compliance of 15 mL/cmH2O and Patient #2 has compliance of 50 mL/cmH2O. How much pressure is generated by delivering 400 mL?  
Patient #1 = 26.7 cmH2O; Patient #2 = 8 cmH2O.

19. With a flow rate of 60 L/min and a tidal volume of 500 mL, what is the inspiratory time (Ti)?  
0.5 seconds

20. With a flow rate of 60 L/min and a tidal volume of 750 mL, what is the inspiratory time (Ti)?  
0.75 seconds

21. With a flow rate of 60 L/min and a tidal volume of 1000 mL, what is the inspiratory time (Ti)?
1.0 seconds

22. With a flow rate of 30 L/min and a tidal volume of 1000 mL, what is the inspiratory time (Ti)?
2.0 seconds

23. Given RR = 15 bpm, VT = 400 mL, and flow = 50 L/min, how can inspiratory time be increased, and what are possible side effects?  
Decrease flow or increase volume; may cause short expiratory time and air trapping.

24. In a square waveform, what is the measured flow at the end of inspiration if set at 60 L/min?  
60 L/min (constant flow)

25. What are the four phases of a mechanical breath?  
Trigger, control (limit), cycle, and expiratory (baseline).

26. Which factors affect pressure during volume-controlled ventilation?  
Lung compliance, airway resistance (Raw), inspiratory flow pattern, tidal volume, set PEEP, and presence of auto-PEEP.

27. How long should an inspiratory pause last to accurately measure plateau pressure?  
Between 0.5 and 2.0 seconds.

28. In a severe asthma exacerbation requiring intubation, which flow pattern is preferred and why?  
Square flow pattern is preferred to allow for a longer expiratory time and reduce air-trapping.

29. In VC-AC mode, which of the following parameters are directly set by the clinician?  
Tidal volume, flow, flow waveform, oxygen concentration (FiO2), and PEEP.

30. What is the minimum ventilator rate considered to provide full ventilatory support?  
8 breaths per minute.

31. Which ventilator mode settings can provide partial ventilatory support?  
VC-IMV with a set rate of 4 breaths/min or VC-MMV with a minute volume of 8 L/min.

32. Setting a high inspiratory flow rate will have what effect on airway pressures?  
It will increase the peak inspiratory pressure (PIP).

33. What is a likely consequence of using slow inspiratory flow rates?  
Shortened expiratory time and potential air-trapping.

34. For a patient with acute asthma on VC-CMV, which flow waveform is recommended to improve gas distribution and lower PIP?  
Descending ramp waveform.

35. What is an appropriate initial tidal volume and rate for a 5’10” male with normal lungs on VC-CMV?  
VT = 525 mL, rate = 14 breaths per minute.

36. What tidal volume and rate should be recommended for a 5’2″ female with normal lungs on VC-CMV?  
VT = 364 mL, rate = 14 breaths per minute.

37. Which flow pattern improves gas distribution in volume-controlled ventilation?  
Descending ramp waveform.

38. Which mode uses pressure-limited, time-cycled breaths with tidal volume as a feedback control?  
Pressure-regulated volume control (PRVC).

39. In volume-controlled ventilation, which variable is held constant?  
Tidal volume.

40. In pressure-controlled ventilation, which variable is held constant?  
Peak inspiratory pressure.

41. In volume-controlled ventilation, how does peak inspiratory pressure change?  
It varies with changes in lung compliance and airway resistance.

42. In pressure-controlled ventilation, how does tidal volume respond to changes in impedance?  
Tidal volume varies based on compliance and resistance.

43. How is the flow pattern determined in volume-controlled ventilation?  
The clinician sets the flow pattern and waveform.

44. In pressure-controlled ventilation, what determines the inspiratory flow?
It is variable and depends on patient demand, resistance, compliance, and pressure.

45. How are breaths delivered in volume control ventilation?  
Breaths—whether machine or patient triggered—are delivered using the clinician’s preset parameters for tidal volume, flow, and rate.

46. How are breaths delivered in pressure control ventilation?  
Breaths have a fixed inspiratory pressure, but tidal volume and flow vary based on patient condition and ventilator settings.

47. What describes volume ventilation in terms of control variables?  
Tidal volume and flow are constant; inspiratory pressure varies with lung mechanics.

48. What describes pressure ventilation in terms of control variables?  
Inspiratory pressure is constant; volume and flow vary with patient impedance.

49. What is a major advantage of volume-controlled ventilation?  
It guarantees delivery of a consistent tidal volume for stable alveolar ventilation.

50. What is a major disadvantage of volume-controlled ventilation?  
Changes in compliance or resistance may cause harmful spikes in airway pressure.

51. What are two advantages of pressure-controlled ventilation?  
It maintains constant peak inspiratory pressure and allows flow to vary with patient demand.

52. What is a major disadvantage of pressure-controlled ventilation?  
Tidal volume varies with changes in compliance and resistance, potentially causing unstable blood gases.

53. What is the equation used to estimate mean airway pressure (MAP) in constant pressure ventilation?  
MAP = (PIP − PEEP) × (Ti/Ttot) + PEEP

54. What is the equation used to estimate MAP in constant flow ventilation?  
MAP = 0.5 × (PIP − PEEP) × (Ti/Ttot) + PEEP

55. What is PEEP and what are potential causes of auto-PEEP?  
PEEP is positive end-expiratory pressure. Auto-PEEP can result from air trapping, high minute ventilation, narrow airways, large tidal volumes, or inadequate expiratory time.

56. How is auto-PEEP detected?  
By performing an end-expiratory hold maneuver.

57. What effect does increased inspiratory time (Ti) have on MAP?  
It increases mean airway pressure without raising peak alveolar pressure.

58. In pressure-controlled ventilation, what happens beyond a certain inspiratory time?  
An end-inspiratory plateau develops as alveolar filling is complete.

59. In volume-controlled ventilation, how is plateau pressure measured?  
By applying an inspiratory pause at the end of inspiration.

60. What is the purpose of observing an expiratory plateau on a ventilator?  
To evaluate how well the lungs are emptying.

61. Which of the following settings is specific to volume-controlled ventilation?  
Flow — it affects inspiratory time and is set for patient comfort.

62. Which of the following settings is specific to pressure-controlled ventilation?  
Inspiratory Time (I-Time) — adjusted to aid comfort and oxygenation.

63. True or False: PC and VC modes are available in spontaneous modes of ventilation?  
False — They are used in control modes, not spontaneous ventilation modes.

64. Pressure control ventilation helps maintain what parameter to prevent barotrauma?  
Peak Inspiratory Pressure — limiting it helps reduce the risk of barotrauma.

65. True or False: Pulmonary pathology plays no role in the decision between PC and VC ventilation?
False — Lung pathology is a key factor in determining the appropriate mode.

66. What factors should be considered when deciding between PC and VC ventilation?  
Pulmonary pathology, patient comfort, hospital protocol, and acid-base status.

67. In volume-controlled ventilation, which variable is constant?  
Tidal Volume (Vt)

68. In volume-controlled ventilation, how does peak inspiratory pressure behave?  
It varies with changes in compliance and resistance.

69. In pressure-controlled ventilation, which variable is constant?  
Peak Inspiratory Pressure

70. In pressure-controlled ventilation, which variable is variable?  
Tidal Volume (Vt)

71. In volume ventilation, what causes changes in peak inspiratory pressure?
Impedance to ventilation, such as changes in lung compliance or airway resistance.

72. In pressure-controlled ventilation, what causes variation in tidal volume?
Changes in lung impedance (resistance and compliance).

73. In volume ventilation, who sets the flow pattern, and what are the common waveform options?  
The clinician sets it; common options include square, decelerating ramp, and sinusoidal waveforms.

74. How does the waveform in ventilation affect patient care?  
It impacts the mean airway pressure and distribution of ventilation.

75. What are the main parameters set by the clinician in volume-control ventilation?  
Tidal volume, flow rate and pattern, respiratory rate, and FiO2.

76. What characterizes pressure control ventilation in terms of flow and volume delivery?  
Flow delivery is decelerating and varies with patient demand; tidal volume varies based on compliance and resistance.

77. What is a key advantage of volume-controlled ventilation?  
It ensures delivery of a consistent tidal volume and alveolar ventilation.

78. What is a key disadvantage of volume-controlled ventilation?  
Rapid or harmful changes in airway pressure due to changes in lung mechanics.

79. Why might flow settings in volume control not meet patient demand?  
Because they are fixed and cannot adjust dynamically to spontaneous patient effort.

80. What are two main advantages of pressure-controlled ventilation?  
PIP and peak pressures are maintained at a constant level, and flow varies with patient demand.

81. What is a key disadvantage of pressure-controlled ventilation?  
Tidal volume fluctuates with changes in lung compliance and resistance, risking inconsistent gas exchange.

82. What does mean airway pressure represent?  
It is the average pressure applied to the lungs throughout the entire ventilatory cycle.

83. What is the formula for calculating mean airway pressure in constant pressure ventilation?  
MAP = (PIP − PEEP) × (Ti/Ttot) + PEEP

84. What is the formula for mean airway pressure in constant flow ventilation?  
MAP = 0.5 × (PIP − PEEP) × (Ti/Ttot) + PEEP

85. What is the effect of increasing inspiratory time (Ti) in volume-controlled ventilation?  
It increases mean airway pressure without raising peak alveolar pressure.

86. What effect does auto-PEEP have on patient breathing?  
It increases the work of breathing and can lead to patient-ventilator asynchrony.

87. In volume-oriented ventilation, what is the most important variable?  
Flow — it directly affects tidal volume delivery and patient comfort.

88. What are the three primary flow patterns available in volume-controlled ventilation?  
Square (constant), decelerating ramp, and adaptive flow.

89. What are the possible trigger variables in volume-controlled ventilation?  
Time-triggered by machine, patient-triggered by flow or pressure, or manually triggered by the operator.

90. What is the cycle variable in volume-controlled ventilation?  
Time — each breath cycles off after a set inspiratory time.

91. What is the limit variable in volume-controlled ventilation?  
Flow — it remains constant during the inspiratory phase.

92. How does flow behave in a square waveform pattern?  
It rapidly rises to the peak inspiratory flow rate (PIFR), holds steady, then drops abruptly to baseline.

93. How does flow behave in a decelerating ramp waveform?  
Flow rises quickly to PIFR, then gradually decreases throughout inspiration.

94. What is adaptive flow in volume-controlled ventilation?  
The ventilator dynamically adjusts flow based on patient demand, shortening Ti to maintain the set tidal volume.

95. What are signs that inspiratory flow rate is too high?  
Patient may cough against the flow, appear uncomfortable, and have uneven ventilation on a chest X-ray.

96. What can happen if the inspiratory flow rate is too high?  
The patient may look distressed and experience poor gas distribution in the lungs.

97. What are signs that inspiratory flow rate is too low?  
Increased work of breathing, visible neck muscle use, and suprasternal or intercostal retractions.

98. What are the independent variables set by the clinician in volume-controlled ventilation?  
Tidal volume, flow, and inspiratory time.

99. What is the dependent variable in volume-controlled ventilation?  
Airway pressure — it varies based on resistance and compliance.

100. How does a ventilator control exhalation in volume-controlled modes?  
It doesn’t — exhalation is passive and occurs once inspiratory flow stops.

Final Thoughts

Volume-controlled ventilation remains a reliable and essential tool in the management of critically ill or surgical patients requiring mechanical respiratory support. By delivering a consistent tidal volume with each breath, clinicians can maintain tight control over minute ventilation and gas exchange.

However, careful monitoring of airway pressures and patient-ventilator interaction is vital to avoid complications such as barotrauma or discomfort. Understanding when and how to use this mode—and when to transition to an alternative—is a critical skill for respiratory therapists and physicians alike.