Mechanical ventilation is the process of using a machine to move air into and out of the lungs. The goal is to provide breathing support long enough for the treatment of the underlying disease that caused the need for ventilatory support.
The initiation of mechanical ventilation is a complex process that requires the coordinated efforts of doctors and respiratory therapists.
In this article, we’ll provide an overview of the steps involved in initiating mechanical ventilation.
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What is Mechanical Ventilation?
Mechanical ventilation is a life-saving intervention for patients with respiratory failure. It involves the use of a machine that uses positive pressure to move air in and out of the lungs.
It’s a form of life support that can be used for a short period of time, or it can be used for long-term ventilatory support. The decision to use mechanical ventilation is based on the patient’s respiratory status and the underlying cause of the respiratory failure.
A mechanical ventilator will not cure a patient of their initial underlying condition. Instead, it’s meant to provide support until the disease is treated and reversed using other means.
The primary goals of mechanical ventilation include:
- To improve gas exchange
- To reverse hypoxemia
- To reverse acute respiratory failure
- To provide relief for respiratory distress
- To reverse respiratory muscle fatigue
- To improve pulmonary mechanics
- To prevent or reverse atelectasis
- To improve lung compliance
- To prevent lung injury
- To maintain lung and airway functionality
- To prevent respiratory muscular dystrophy
Each patient will have their own individualized goals based on their underlying health condition.
Some of the most common indications for mechanical ventilation include:
- Insufficient oxygenation
- Insufficient ventilation
- Acute Lung Injury (ALI)
- Severe asthma
- Severe hypotension
- Inability to protect the airway
- Upper airway obstruction
Mechanical ventilation is indicated whenever a patient’s spontaneous breathing is not adequate to sustain life.
In such a case, a ventilator would be needed to support the patient until their underlying condition is reversed.
A patient cannot survive without adequate ventilation and oxygenation. This means that there are no absolute contraindications for mechanical ventilation.
Therefore, if a patient needs help breathing and requires full ventilatory support, they are likely going to need mechanical ventilation.
The only true contraindication for mechanical ventilation is if a patient legally and specifically states that they do not wish to be intubated or receive life support.
This is referred to as a DNI order, which stands for do not intubate.
In such a case, the patient may opt to receive bilevel positive airway pressure (BiPAP) instead, which is a form of noninvasive ventilation.
Initial Ventilator Settings
Once it has been determined that mechanical ventilation is needed, the respiratory therapist must know how to properly select and input the patient’s initial ventilator settings.
Some of the most important ventilator settings include:
- Tidal volume
- Flow rate
- I:E ratio
Respiratory therapists must know the normal ranges for each setting in order to set up a new patient on the ventilator.
Any operational mode will work when setting up the initial ventilator settings. It’s important not to get too caught up in deciding on the correct mode.
This is especially true for students during the TMC Exam.
However, here’s a simple rule of thumb: You can select the A/C mode in patients who need full ventilatory support, and SIMV if they only need partial support.
The initial tidal volume should be set at 6-8 mL/kg of the patient’s ideal body weight (IBW).
Therefore, if you know the patient’s ideal body weight, you can easily calculate their initial tidal volume setting on the ventilator.
The initial frequency setting should be 10-20 breaths/min.
This is an adequate breathing rate that helps keep the patient’s pH and PaCO2 within their normal ranges.
The initial FiO2 setting should be set at 30-60% unless the patient was previously receiving a higher percentage before intubation.
For example, the physician elects to intubate a patient in the emergency department who is receiving 100% oxygen via a nonrebreathing mask. In this case, their initial FiO2 setting should be 100%.
Then, your goal should be to titrate the FiO2 below 60% as soon as possible. In general, you should strive to provide the lowest concentration of oxygen that’s possible to maintain a normal PaO2.
The initial flow setting should be 40-60 L/min.
This is typically what’s required to help a patient achieve an adequate minute ventilation.
The initial I:E ratio should be set between a range of 1:2 and 1:4.
The I:E ratio can be adjusted by making changes to the flow rate, inspiratory time, expiratory time, tidal volume, and frequency settings.
The initial sensitivity should be set between a range of -1 and -2 cmH2O.
This setting is what determines how much effort (negative pressure) the patient must generate in order to trigger a breath to be delivered.
The initial PEEP should be set between a range of 4-6 cmH2O.
This setting can be increased in patients with refractory hypoxemia and severe oxygenation issues, such as ARDS.
However, these are some general guidelines that can be used on most types of mechanical ventilators.
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. Name 2 full support ventilator modes in which you can set a respiratory rate:
Controlled Mandatory Ventilation (CMV); and Assist control (A/C)
3. Name 2 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 4 methods of full ventilatory support?
(1) Initiating mechanical ventilation (2) Maintenance of mechanical ventilation (3) Discontinuing/weaning mechanical ventilation (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 per minute
7. What should the initial setting for tidal volume be for a new mechanical ventilation patient?
5-10 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.
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 on initiation of mechanical ventilation?
Patient with non-cardiopulmonary issues
14. Which patients should be started at an FiO2 of 100% on 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?
+/- 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 per minutes above their observed rate
19. What should the minute ventilation alarm be set at?
> 10 L/min; or +/- 1 liter of the exhaled minute ventilation
20. What should the PIP alarm be set at?
+/- 10 – 15
21. What should the plateau pressure alarm 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, 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 patients normal value, which will be high)
24. For a patient with a NIF or MIP of less than 20 cmH2O, you should do what in this situation?
Intubate the patient
25. What is the criteria for impending respiratory failure?
Tidal volume < 5 mL/kg of ideal body weight, vital capacity < 10 mL/kg of ideal body weight, respiratory rate >35 or < 10, minute ventilation > 10 L/min, NIF < -20 cwp, RSBI > 105
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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
Changing the flowrate
32. Changes in respiratory rate affect the length of what?
33. Complications of mechanical ventilation include?
Barotrauma/volutrauma, decrease in cardiac output, blood pressure changes; pulmonary infection, tracheal damage, respiratory muscle fatigue, poor nutrition
34. What causes mechanical ventilation failure?
(1) MIP < -20 cmH2O, (2) respiratory rate < 8, (3) minute ventilation < 10 L/min, (4) vital capacity < 10 mL/kg, (5) tidal volume < 5 mL/kg, (6) MEP < 40 cmH2O, (7) VD/VT > 60%, (8) QS/QT >20%
35. What is the other data that may collectively indicate the need for mechanical ventilation?
(1) No chest movement, (2) Absent breath sounds, (3) Hypoventilation (especially in the presence of a suspected drug overdose), (4) Persistent hypoxemia (regardless of the FiO2)
36. In adults, what are the 9 things needed for the initiation of mechanical ventilation?
(1) Rate. (2) Vt. (3) FiO2. (4) PEEP. (5) Mode. (6) Peak Flow. (7) Ideal body weight. (8) Best type of ventilator. (9) 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
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 is ok.
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. All modes will ventilate.
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 initiating mechanical ventilation, when should you use a volume-cycled ventilator?
If there is any problem with the lungs. For example; ARDS, pneumonia , COPD etc.
43. When initiating mechanical ventilation, when should you use a pressure-cycled ventilator?
If there is any problem other than with the lungs, that’s when you should use a pressure-cycled ventilator. For example; neurological cases, drug overdose, myasthenia gravis, etc.
44. What are the complications associated with positive pressure ventilation to initiate a mechanical ventilation?
Decreased venous return, decreased urine output, loss of dignity, development of ventilator dependency.
45. How do you monitor a patient receiving mechanical ventilation?
(1) Maintain the vital function of ventilation, (2) Oxygenation and ventilation requires the need to monitor its clinical and lab areas, (3) Watch for a decrease in cardiac function (4) Changes in blood pressure needs to be monitored.
46. What are the central objectives for a patient on mechanical ventilation?
(1) Get them off of the ventilator, (2) Ensure adequate ventilation and oxygenation
47. How do you monitor the readiness to wean or to stop mechanical ventilation?
The patient may be ready to 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, Their MIP is > 20 cmH20, (6) the QS/QT is < 20%, (7) the Vd/VT is < 60%, (8) The underlying problem has been resolved.
48. What are the 7 Ventilator Modes?
(1) SIMV /
49. What is SIMV/IMV mode?
It is good for weaning, and also good for patients who breathe on their own to a small degree. This mode offers a less likelihood of barotrauma. Be sure to avoid hyperventilation. It is often used on anxious patients until sedation wears off, then a control mode can be used. It consists of a mandatory rate and also allows spontaneous breathing in between the mandatory breaths.
50. What is Assist/Control mode?
It provides a set tidal volume at a set rate. Also, the set tidal volume is delivered even when the patient spontaneously initiates breaths above the set rate. It’s a good mode and works with most patients. Alert patients tend to find it uncomfortable and may need sedation and anxiety controlling medications.
51. What is Control mode?
It is used for unconscious patients. It does not allow patients to determine the rate or tidal volume. For this mode, patients should be sedated or paralyzed. This mode is not common but will provide ventilation just as good as any other mode.
52. What is Pressure Control Ventilation (PCV) mode?
It is used when peak pressures are a primary concern above 50 cmH2O by volume ventilation. There is no tidal volume setting; only inspiratory pressure and inspiratory time. You must set exhaled tidal volume alarms. It is a good mode for high PIP and for
53. What is Inverse Positive Pressure Ventilation (IPPV)?
It’s not a good initial mode. It can be used on the same patients as those eligible for pressure control ventilation (ARDS). It may be useful for patients requiring high peak pressures due to low lung compliance.
54. What is Inspiratory Plateau mode?
It helps to improve gas distribution. Also, it can significantly increase mean airway pressure.
55. What is the High-Frequency Ventilation (HFPPV) mode?
Includes a rate at a high frequency. The main controls are drive pressure, inspiratory time, rate, injector line, PEEP, and FiO2. You can use the drive pressure, rate, and %IT to change ventilation.
56. HFPPV Is used on what patients?
Typically use with ARDS patient or other problems with markedly decreased lung compliance
57. What are the ventilator controls that affect the patient’s PaCO2?
58. What should we do if PaCO2 is between 35 – 45mmHg, which is the normal range?
Do not make any changes if the PaCO2 is in the normal range
59. What should you do if PaCO2 is high?
First, you should remove
60. What should you do if PaCO2 is low?
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61. What should you do if PaO2 is high?
You should decrease the FiO2 until it’s below 60%, then begin lowering the PEEP. If the FiO2 is 60% or below, then 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 alarm and low-pressure alarm
64. During an intubation for a patient that needs full ventilatory support, what are the three medications that should be given to this patient?
(1) Anectine, (2) Pavulon, and (3) Curare
65. If the patient is under full ventilatory support, in order to relieve pain and anxiety, what are the three medications that should be given?
(1) Morphine, (2) Valium, (3) Versed
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66. While in full ventilatory support, how should you position the patient?
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 may improve what?
The distribution of ventilation and oxygenation.
69. Lung injury is caused by?
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 ventilation settings.
Initiating mechanical ventilation can be a daunting task, but it is important to remember that any operational mode will work. The most important initial ventilator settings to remember include:
- Tidal volume
- Flow rate
- I:E ratio
Respiratory therapists play an important role in the initiation of mechanical ventilation. That is why this is such an important topic.
If you want to learn more, check out some of our other helpful guides on ventilator modes and settings. Thanks for reading!
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.
- 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.
- Faarc, Kacmarek Robert PhD Rrt, et al. Egan’s Fundamentals of Respiratory Care. 12th ed., Mosby, 2020.
- Orebaugh, S. “Initiation of Mechanical Ventilation in the Emergency Department.” PubMed, Jan. 1996, pubmed.ncbi.nlm.nih.gov/8630160.
- “Mechanical Ventilation.” National Center for Biotechnology Information, U.S. National Library of Medicine, 22 Apr. 2020, www.ncbi.nlm.nih.gov/books/NBK539742.
Ventilator Weaning: Overview and Practice Questions