Ventilator Initiation Overview and Practice Questions Vector

Ventilator Initiation: Overview and Practice Questions (2024)

by | Updated: Jun 30, 2024

Initiating mechanical ventilation is a critical process in managing patients with respiratory failure or those who require respiratory support during surgery and other medical conditions.

This procedure involves setting up a ventilator to ensure adequate oxygenation and ventilation, tailored to the individual needs of each patient.

Understanding the key initial settings and their adjustments is essential for optimizing patient outcomes and minimizing complications.

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What is Involved When Initiating Mechanical Ventilation?

The initiation of mechanical ventilation involves starting a mechanical ventilator to support or replace spontaneous breathing. This is done in cases of respiratory failure, severe hypoxemia, or inadequate ventilation. The process includes assessing the patient’s condition, setting appropriate ventilator parameters, and continuously monitoring to ensure effective respiratory support.

Initiation of mechanical ventilation vector illustration


Mechanical ventilation is a critical intervention in modern medicine, primarily used to support patients who are unable to breathe adequately on their own.

The goals of mechanical ventilation include:

Note: By achieving these goals, mechanical ventilation plays a vital role in the management of patients with severe respiratory conditions, ensuring that they receive the necessary respiratory support until they can breathe independently again.


Mechanical ventilation is indicated in various clinical situations where the patient’s spontaneous breathing is inadequate or absent.

The primary indications include:

  • Acute Respiratory Failure: When the patient cannot maintain adequate oxygenation or ventilation due to conditions such as acute respiratory distress syndrome (ARDS), pneumonia, or pulmonary edema.
  • Chronic Respiratory Failure: In cases where chronic lung diseases like chronic obstructive pulmonary disease (COPD) or neuromuscular disorders lead to a gradual decline in respiratory function.
  • Hypoxemia: When the patient has critically low levels of oxygen in the blood despite receiving supplemental oxygen. Causes can include severe asthma, severe pneumonia, or acute heart failure.
  • Hypercapnia: Elevated levels of carbon dioxide in the blood, often due to inadequate ventilation. This can result from conditions like COPD, drug overdose, or severe asthma exacerbations.
  • Surgical Procedures: Mechanical ventilation is commonly used during general anesthesia to control breathing and ensure adequate gas exchange during surgery.
  • Trauma: In cases of significant chest or head trauma, where breathing may be impaired due to injury or the need for sedation and pain control.
  • Neurological Impairment: Conditions such as stroke, traumatic brain injury, or spinal cord injury that impair the brain’s ability to regulate breathing.
  • Cardiac Arrest: During resuscitation, mechanical ventilation supports oxygenation and ventilation until the patient’s heart and breathing functions are stabilized.
  • Severe Sepsis: In severe infections, where the body’s response to infection leads to respiratory failure and the need for ventilatory support.
  • Postoperative Care: After major surgery, particularly in patients with pre-existing respiratory conditions or those who have undergone lengthy or complicated procedures, mechanical ventilation may be necessary to support recovery.
  • Protective Lung Strategies: In certain scenarios, mechanical ventilation is used proactively to prevent lung injury, such as in patients with a high risk of developing ARDS.

Note: These indications highlight the critical role of mechanical ventilation in supporting patients with compromised respiratory function, ensuring they receive the necessary respiratory support to stabilize their condition and promote recovery.


While adequate ventilation and oxygenation are critical for survival, there are no absolute contraindications for mechanical ventilation in emergencies where life support is needed.

However, there are considerations to be mindful of:

  • Patient Wishes: The primary contraindication is if a patient has legally and explicitly stated that they do not wish to be intubated or receive mechanical ventilation. This is typically documented in a Do Not Intubate (DNI) order.
  • Alternative Options: In cases where a DNI order is in place, the patient may opt for bilevel positive airway pressure (BiPAP), a form of noninvasive ventilation that can provide respiratory support without intubation.

Note: While mechanical ventilation is essential for patients who cannot maintain adequate breathing on their own, respecting patient autonomy and legally documented wishes is paramount.

Initial Ventilator Settings

When initiating mechanical ventilation, selecting appropriate initial settings is crucial to ensure patient safety and effective respiratory support.

Here are the key initial ventilator settings:


Any operational mode can be used when setting up the initial ventilator settings. The key is not to get overly concerned with selecting the perfect mode.

A simple guideline is to use assist-control (A/C) mode for patients requiring full ventilatory support and synchronized intermittent mandatory ventilation (SIMV) mode for those needing partial support.

Tidal Volume

Set the initial tidal volume at 6-8 mL/kg of the patient’s ideal body weight (IBW). Knowing the patient’s IBW allows you to calculate their initial tidal volume setting accurately.


Set the initial frequency (respiratory rate) at 10-20 breaths/min. This range helps maintain the patient’s pH and PaCO2 within normal limits.


Set the initial FiO2 at 30-60% unless the patient was previously receiving a higher percentage before intubation. For instance, if a patient in the emergency department was receiving 100% oxygen via a nonrebreathing mask prior to intubation, their initial FiO2 should be 100%.

The goal is to titrate the FiO2 below 60% as soon as possible while maintaining a normal PaO2, aiming to use the lowest concentration of oxygen necessary.

Flow Rate

Set the initial flow rate at 40-60 L/min. This range is typically sufficient to help the patient achieve an adequate minute ventilation.

I:E Ratio

Set the initial I:E ratio between 1:2 and 1:4. You can adjust the I:E ratio by modifying the flow rate, inspiratory time, expiratory time, tidal volume, and frequency settings.


Set the initial sensitivity between -1 and -2 cmH2O. This setting determines the amount of effort (negative pressure) the patient must generate to trigger a breath.


Set the initial PEEP between 4-6 cmH2O. Increase the PEEP in patients with refractory hypoxemia and severe oxygenation issues, such as ARDS.

Note: These settings serve as a starting point and should be adjusted based on the patient’s response, underlying condition, and arterial blood gas (ABG) results. Continuous monitoring and reassessment are essential to optimize ventilator settings and ensure patient safety.

Ventilator Initiation Practice Questions

1. When initiating mechanical ventilation, what mode should you choose?
The mode doesn’t matter as long as you can set a respiratory rate for the patient. Any mode is acceptable for initiating mechanical ventilation.

2. What are two full-support ventilator modes in which you can set a respiratory rate?
Controlled mandatory ventilation (CMV) and assist control (A/C).

3. What are two partial support ventilator modes in which you can set a respiratory rate?
Intermittent mandatory ventilation (IMV) and synchronized intermittent mandatory ventilation (SIMV).

4. What are the four methods of full ventilatory support?
1. Initiating mechanical ventilation, 2. Maintenance of mechanical ventilation, 3. Discontinuing/weaning mechanical ventilation, and 4. General considerations in mechanical ventilation.

5. What two settings on the ventilator allow you to manage the patient’s CO2?
Respiratory rate and tidal volume

6. What should the initial setting for respiratory rate be for a new mechanical ventilation patient?
10-20 breaths/min

7. What should the initial setting for tidal volume be for a new mechanical ventilation patient?
6-8 ml/kg of ideal body weight

8. What should the initial setting for pressure be for a new mechanical ventilation patient?
Less than or equal to 35 cmH2O

9. What should the initial setting for FiO2 be for a new mechanical ventilation patient?
40-60% (or set to the same level prior to ventilation)

10. What should the initial setting for PEEP be for a new mechanical ventilation patient?
2-6 cmH2O

11. Spontaneous tidal volume is driven by ________ and should not be considered on the initiation of mechanical ventilation.
Pressure support

12. What two options on the ventilator allow you to manage the patient’s O2 (SaO2)?
FiO2 and PEEP

13. Which patients should be set at 40% FiO2 during the initiation of mechanical ventilation?
Patient with non-cardiopulmonary issues

14. Which patients should be started at an FiO2 of 100% during the initiation of mechanical ventilation?
Patients with cardiopulmonary issues

15. What is the FiO2 exception rule for initiating mechanical ventilation?
A patient with a known FiO2 on a different device (i.e. CPAP or BiPAP) should be kept on that same FiO2 when put on the mechanical ventilator.

16. All patients being set up on mechanical ventilation must have what done?
An ABG within 30 minutes of being placed on the ventilator.

17. What should the tidal volume alarm be set at?
It should be set at +/- 100 mL of the patient’s exhaled tidal volume; or +/- 10% of the patient’s exhaled tidal volume.

18. What should the respiratory rate alarm be set at?
10-15 breaths/min above their observed rate.

19. What should the minute ventilation alarm be set at?
Greater than 10 L/min; or +/- 1 liter of the exhaled minute ventilation.

20. What should the PIP alarm be set at?
It should be set at +/- 10-15 cwp, but never greater than 50 cmH2O.

21. What should the plateau pressure alarm be set at?
It should be set at +/- 10, but never greater than 35 cmH2O.

22. What are some indications for mechanical ventilation?
Apnea, acute ventilatory failure, impending respiratory failure, severe hypoxemia, surgery, and  prophylactic support for pulmonary complications.

23. What constitutes acute ventilatory failure?
The patient cannot sustain spontaneous ventilation to provide adequate oxygenation and ventilation; pH < 7.25, PaCO2 > 50; COPD (uncompensated respiratory acidosis with PaCO2 above the patient’s normal value, which will be high).

24. What should you do for a patient with a NIF or MIP of less than 20 cmH2O?
Intubate the patient

25. What is the criteria for impending respiratory failure?
Tidal volume < 5 mL/kg of IBW, vital capacity < 10 mL/kg of IBW, respiratory rate >35 or < 10, minute ventilation > 10 L/min, NIF < -20 cwp, and RSBI > 105.

26. What is an absolute contraindication for initiating mechanical ventilation?
An untreated tension pneumothorax.

27. Why would you initially set tidal volumes lower than 8-12 mL/kg of ideal body weight?
Low compliance (ARDS 6-8mL/kg), increased compliance, air trapping; or the need for reduced lung volumes (pneumonectomy).

28. What type of ventilation only supports spontaneous breathing and is not needed during the initiation of mechanical ventilation?
Pressure support ventilation.

29. What two things should you monitor when using PEEP?
The patient’s blood pressure and their ABG results.

30. Why would you increase PEEP?
If the patient has refractory hypoxemia, or already at an FiO2 > 60%.

31. What is the most common method of I:E change?
Changing the flowrate

32. Changes in respiratory rate affect the length of what?

33. What are the complications of mechanical ventilation?
Barotrauma/volutrauma, decrease in cardiac output, blood pressure changes; pulmonary infection, tracheal damage, respiratory muscle fatigue, and poor nutrition.

34. What causes mechanical ventilation failure?
MIP < -20 cmH2O, respiratory rate < 8, minute ventilation < 10 L/min, vital capacity < 10 mL/kg, tidal volume < 5 mL/kg, MEP < 40 cmH2O, VD/VT > 60%, and QS/QT > 20%.

35. What other data may collectively indicate the need for mechanical ventilation?
No chest movement, absent breath sounds, hypoventilation (especially in the presence of a suspected drug overdose), and persistent hypoxemia (regardless of the FiO2).

36. What are the 9 things needed for the initiation of mechanical ventilation?
Rate, tidal volume, FiO2, PEEP, mode, peak flow, ideal body weight (IBW), type of ventilator, and complications associated with positive pressure ventilation.

37. What is the normal FiO2 to initiate mechanical ventilation for an adult?
Use the same FiO2 as the previous if it available. Don’t put the patient on room air (21%). Use 30-60% if the previous FIO2 is not known or if they were on room air. Initiate with an FiO2 of 100% if it’s an emergency situation.

38. What is the normal PEEP to initiate mechanical ventilation for an adult patient?
For PEEP, you should use the same as previous (CPAP values/the expiratory side of BIPAP). Or if no previous PEEP then any PEEP under 10 cmH20.

39. What is the normal mode that should be used to initiate mechanical ventilation on an adult patient?
Any mode is acceptable for initiating mechanical ventilation.

40 What is the normal peak flow to initiate mechanical ventilation on an adult patient?
For peak flow, you must calculate the appropriate flow.

41. What is the normal ideal body weight to initiate mechanical ventilation on an adult patient?
Use the given patient’s weight in kilograms. If it isn’t given, you can use this formula: IBW = 50 kg + (2 x # of inches over 5 ft. tall).

42. When should you use a volume-cycled ventilator during the initiation of mechanical ventilation?
If there is any problem with the lungs (e.g., ARDS, pneumonia, COPD, etc.).

43. When should you use a pressure-cycled ventilator during the initiation of mechanical ventilation?
If there is any problem other than with the lungs (e.g., neurological cases, drug overdose, myasthenia gravis, etc.).

44. What are the complications associated with positive pressure ventilation?
Decreased venous return, decreased urine output, loss of dignity, and development of ventilator dependency.

45. What should you monitor for a patient receiving mechanical ventilation?
The vital functions of the ventilator, oxygenation and ventilation, cardiac function, and changes in blood pressure.

46. What are the central objectives for a patient on mechanical ventilation?
Get them off of the ventilator and ensure adequate ventilation and oxygenation

47. How do you monitor the readiness to wean from mechanical ventilation?
The patient may be ready to wean if: 1) All vital signs are stable, 2) ABGs are good, 3) their spontaneous tidal volume is > 5 mL/kg, 4) their vital capacity is > 10 mL/kg, 5) their MIP is > 20 cmH20, 6) their QS/QT is < 20%, 7) their Vd/VT is < 60%, and 8) the underlying problem has been resolved.

48. What are the most common ventilator modes?
(1) SIMV, Assist/Control, Control Mode, Pressure Control Ventilation (PCV), Inverse Positive Pressure Ventilation Mode (IPPV), Inspiratory Plateau Mode, and High-Frequency Ventilation (HFPPV).

49. What is the SIMV mode?
SIMV (Synchronized Intermittent Mandatory Ventilation) mode is a type of mechanical ventilation where the ventilator delivers a set number of breaths in synchronization with the patient’s spontaneous breaths. It allows the patient to breathe spontaneously between the mandatory breaths.

50. What is the Assist/Control mode?
Assist/Control (A/C) mode is a mechanical ventilation setting where each breath is either assisted (patient-initiated) or controlled (ventilator-initiated) with a set tidal volume or pressure. Every breath, whether spontaneous or mandatory, receives full ventilatory support.

51. What is the Control mode?
Control mode (also known as Continuous Mandatory Ventilation or CMV) is a mechanical ventilation setting where the ventilator delivers a set number of breaths with a fixed tidal volume or pressure, independent of patient effort. The patient does not initiate breaths in this mode.

52. What is Pressure Control Ventilation (PCV)?
Pressure Control Ventilation (PCV) is a mode of mechanical ventilation where each breath is delivered with a preset pressure, maintaining that pressure throughout the inspiratory phase. The tidal volume varies depending on the patient’s lung compliance and resistance.

53. What is Inverse Positive Pressure Ventilation (IPPV)?
Inverse Positive Pressure Ventilation (IPPV) is a ventilation mode where the inspiratory time is longer than the expiratory time (inverse I:E ratio). This mode is used to improve oxygenation in patients with severe respiratory distress by increasing mean airway pressure.

54. What is the Inspiratory Plateau mode?
Inspiratory Plateau mode, also known as Inspiratory Pause, is a phase during mechanical ventilation where there is a brief pause at the end of inspiration before exhalation begins. This pause allows for measurement of plateau pressure, reflecting alveolar pressure, and helps in assessing lung mechanics.

55. What is the High-Frequency Ventilation (HFPPV) mode?
High-Frequency Positive Pressure Ventilation (HFPPV) is a mechanical ventilation mode that delivers very rapid respiratory rates (up to several hundred breaths per minute) with very small tidal volumes. It is used to minimize lung injury and improve gas exchange in certain clinical scenarios.

56. HFPPV is used on what patients?
It is typically use with ARDS patients or other problems with markedly decreased lung compliance.

57. What ventilator controls affect the patient’s PaCO2?
Mechanical deadspace, tidal volume, and respiratory rate

58. What should we do if the patient’s PaCO2 is in the normal range?
Do not make any changes to the ventilator settings.

59. What should you do if PaCO2 is high?
First, you should remove deadspace if the PaCO2 is only off by 1 point. Second, you should increase the tidal volume, but be sure to stay in the correct range. Third, you should increase the rate, which is the most common, but only choose it if the first two are not options or if the PaCO2 is 4 mmHg more than the target.

60. What should you do if PaCO2 is low?
First, add deadspace if the PaCO2 is only off by 1 point. Second, decrease the rate. Third, decrease the tidal volume but stay in the normal range.

61. What should you do if PaO2 is high?
You should decrease the FiO2 until it’s below 60%, then lower the PEEP. If the FiO2 is 60% or below, immediately focus on the PEEP. You should decrease the PEEP by decrements of 5 cmH2O. Then, you can move the FiO2 by 5-10% at a time.

62. What does it mean to add pressure support?
Pressure support helps to overcome the resistance of the circuit tubing during spontaneous breathing. Pressure support helps spontaneous breathing patients accomplish larger tidal volumes. It also helps to wean patient and keep their tidal volume above 5 mL/kg.

63. What are the two types of ventilator alarms?
High-pressure and low-pressure alarms

64. During the intubation for a patient who needs full ventilatory support, what are the three medications that should be given to this patient?
Anectine, Pavulon, and Curare.

65. To relieve pain and anxiety for a patient under full ventilatory support, what are the three medications that should be given?
Morphine, Valium, and Versed.

66. How should you position the patient while in full ventilatory support?
The semi-fowler’s position is the best for gas distribution during mechanical ventilation.

67. What are the most common diagnoses requiring mechanical ventilatory support?
Acute respiratory failure, COPD exacerbation, coma, and neuromuscular disease.

68. A brief inspiratory hold can improve what?
It can improve the distribution of ventilation and oxygenation.

69. A lung injury is caused by what during mechanical ventilation?
It is caused by repetitive opening and closing of unstable lung units. PEEP stabilizes in the open position, reducing the likelihood of injury.

70. Which ventilator mode must be used when setting up a patient with their initial ventilator settings?
Any operational mode is fine when setting up the initial ventilator settings.

Final Thoughts

The initiation of mechanical ventilation requires careful consideration of various settings to match the patient’s respiratory needs.

By appropriately selecting the mode, tidal volume, frequency, FiO2, flow rate, I:E ratio, sensitivity, and PEEP, healthcare providers can ensure effective and safe ventilatory support.

Continuous monitoring and adjustment of these settings are crucial for achieving optimal patient care and facilitating recovery.

John Landry, BS, RRT

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.


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  • Rrt, Cairo J. PhD. Pilbeam’s Mechanical Ventilation: Physiological and Clinical Applications. 7th ed., Mosby, 2019.
  • Faarc, Kacmarek Robert PhD Rrt, et al. Egan’s Fundamentals of Respiratory Care. 12th ed., Mosby, 2020.
  • Orebaugh SL. Initiation of mechanical ventilation in the emergency department. Am J Emerg Med. 2024.

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