Mechanical Ventilation: Standard Weaning Criteria (Respiratory Therapy)

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ALERT

If the patient shows signs of intolerance during standing weaning criteria procedures, STOP the test and return the patient to mechanical ventilation support.

OVERVIEW

The respiratory therapist (RT) should evaluate a patient’s readiness to wean or the ability to be liberated from mechanical ventilation at least once a day (preferably in the morning).^{undefined#ref4">4} The most common readiness to wean factors include, but are not limited to:^1,3

• Reversal or improvement of the condition that led to the need for mechanical ventilation
• Oxygen requirement of less than 40% or 50% fraction of inspired oxygen (FIO₂)^1,3
• Positive end-expiratory pressure (PEEP) of less than or equal to 5 to 8 cm H₂O^1,3
• Corrected ventilation and acid-base balance abnormalities
• Normalized cardiovascular and hemodynamic status
• Presence of spontaneous respiratory drive
• Minimal or no sedation

Standard weaning criteria (SWC) are used to evaluate the patient’s respiratory muscle strength and endurance and to predict the patient’s ability to successfully wean from mechanical ventilation. The most common and effective method is the spontaneous breathing trial (SBT). The SBT is a period that the patient breathes without any ventilatory support or minimal inspiratory pressure support.^2,3 The amount of time to remain on an SBT varies, but the typical range is 30 to 120 minutes.^1,3

During the SBT, the RT observes the patient’s vital signs and the spontaneous breathing parameters such as tidal volume (VT), respiratory frequency (f), minutes volume, and the rapid shallow breathing index (RSBI). Spontaneous tidal volume (VTS) is a measure of ventilation and respiratory muscle endurance. The threshold for VTS is greater than 5 ml/kg.¹ The threshold for minute volume is not clear, but most experts recommend that it be in the range of 10 to 12 L/min for successful weaning.³ The RSBI is the ratio of f/VT, and this value is used to gauge respiratory muscle fatigue during the SBT. If the RSBI is less than 105, it may indicate successful weaning.¹ If the RSBI is greater than or equal to 105, the patient may not be ready to wean from mechanical ventilation.³ These SWC are typically observed during the SBT performed on the mechanical ventilator.

Additionally, there are a variety of SWC that are performed off of the mechanical ventilator that may be helpful to further assess patients who have been on mechanical ventilation for an extended period or who have other conditions that make it more difficult to wean from the ventilator.¹ These SWC maneuvers may offer more information about respiratory muscle strength and endurance, especially in patients who are older, debilitated, or weak. These criteria may help determine the presence of respiratory muscle fatigue after a weaning period and predict a successful weaning and extubation outcome. A few of the most common additional SWC maneuvers include:

• Negative inspiratory force (NIF), also called maximum inspiratory force (MIF) or maximal inspiratory pressure (MIP). The measurement of NIF is effort-independent, meaning that the patient does not have to cooperate. The threshold used to predict mechanical ventilation weaning success is less than or equal to –20 to –30 cm H₂O.¹ Because this is an effort-independent measurement, the value is reliable with good technique, unless factors such as central respiratory drive impairment, sedation, a cuff leak, or respiratory muscle fatigue are present.
• Maximum expiratory pressure (MEP), also called positive expiratory pressure (PEP), may be measured to evaluate the patient’s ventilatory muscle strength. The threshold used to predict successful weaning is greater than 60 cm H₂O.³ It provides information about the patient’s ability to cough and clear secretions. It may be used in conjunction with the NIF to predict successful ventilator weaning and extubation.
• Vital capacity (VC) is also a measure of respiratory muscle endurance or reserve or both. A fatigued patient is unable to triple or even double the size of a breath. The threshold for VC is greater than or equal to 10 to 15 ml/kg (at least two to three times VTS).¹

Beyond SWC, other factors that may affect the patient’s ability to successfully wean from mechanical ventilation include sedation, psychologic status, level of consciousness, and nutrition factors.¹ All SWC are best used in combination with overall clinical assessment to determine the appropriateness of mechanical ventilation weaning and extubation.¹

SUPPLIES

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EDUCATION

• Give developmentally and culturally appropriate education based on the desire for knowledge, readiness to learn, preferred learning style, and overall neurologic and psychosocial state.
• Explain the need to measure respiratory muscle strength and endurance to be able to have the mechanical ventilator removed and potentially the artificial airway removed.
• Tell the patient, family, and caregivers that the patient may experience feelings of shortness of breath, anxiety, fatigue and the inability to take a breath during the testing.
• Explain to the patient the importance of cooperation and maximal effort to achieve valid and reliable measurements.
• Encourage questions and answer them as they arise.

ASSESSMENT AND PREPARATION

Assessment

1. Clean hands and don appropriate personal protective equipment (PPE) based on the risk of exposure to bodily fluids or infection precautions.
2. Determine if the patient has health literacy needs or requires tools or assistance to effectively communicate. Be sure these needs can be met without compromising safety.
3. Review the patient’s previous experience and knowledge of maneuvers and tests performed to determine weaning from mechanical ventilation and extubation readiness.
4. Verify the weaning or protocol to wean order from the authorized practitioner.
5. Assess the patient for readiness to wean from mechanical ventilation.
   1. Reversal or improvement of the condition that required mechanical ventilation.
   2. Oxygen requirement of less than 40% or 50% FIO₂^1,3
   3. PEEP of less than or equal to 5 to 8 cm H₂O^1,3
   4. Corrected ventilation and acid-base abnormalities
   5. Normalized cardiovascular and hemodynamic status
   6. Presence of spontaneous respiratory drive
   7. Minimal or no sedation
6. Assess the patient’s vital signs, breath sounds, and work of breathing.
7. Assess the patient’s need for a long-term artificial airway.

   The decision to extubate is separate from the patient’s ability to wean from mechanical ventilation.

Preparation

1. Ensure any effects from neuromuscular blocking agents are cleared from the patient’s body and the patient can spontaneously breathe.
2. Ensure that respiratory depressants, such as sedation or opioids, are off or minimal.
3. Suction the artificial airway, as needed.
4. Position the patient in a high semi-Fowler position.

PROCEDURE

1. Clean hands and don appropriate PPE based on the risk of exposure to bodily fluids or infection precautions.
2. Verify the correct patient using two identifiers.
3. Explain the procedure and ensure that the patient agrees to treatment.
4. Prepare and reassure the patient for the tests that may cause feelings of anxiety and shortness of breath.
5. Encourage and coach the patient throughout all measurements to achieve the best effort and reduce anxiety.
6. Perform the Spontaneous Breathing Trial (SBT).
   1. Set the ventilator at zero continuous positive airway pressure (CPAP) and zero pressure support. Pressure support of 5 to 8 cm H₂O may be used.^2,3,4
   2. Continuously monitor the patient’s vital signs and spontaneous breathing parameters, such as f, VTS, minute volume, and RSBI.
      1. If signs of SBT failure are sustained, return the patient to mechanical ventilation support.
         1. Respiratory rate greater than 35 breaths per minute¹
         2. Oxygen saturation less than 90%¹
         3. Significant change in vital signs, such as heart rate or blood pressure
         4. Agitation, diaphoresis, or severe anxiety
      2. If no signs of intolerance develop, continue the SBT for 30 to 120 minutes.^1,2,3
   3. Return the patient to previous mechanical ventilation support or lower support.
7. Perform additional SWC, such as volume (Box 1) or pressure (Box 2) measurements, to determine readiness to wean in patients who have been on mechanical ventilation for an extended period or who have other conditions that may make it more difficult to wean from the ventilator.
8. Discard supplies, remove PPE, and perform hand hygiene.
9. Document the procedure and measurements in the patient’s record.
10. Discuss all results and determine the plan to remove mechanical ventilation support and extubate.

EXPECTED OUTCOMES

• SBT completed for 30 to 120 minutes^4,3
• RSBI less than 105^1,3
• Additional SWC measurements, such as VTS, VC, and NIF, that meet patient’s individualized predicted threshold

UNEXPECTED OUTCOMES

• Invalid and unreliable measurements
• Decline in respiratory, physical, emotional, or hemodynamic status
• Stoppage of the procedure

DOCUMENTATION

• Education
• Best measurements obtained
• Patient’s tolerance of the tests
• Unexpected outcomes and related interventions
• Respiratory interventions

REFERENCES

1. Kaur, R., Vines, D.L. (2025). Chapter 53: Discontinuing ventilatory support. In J.K. Stoller and others (Eds.), Egan’s fundamentals of respiratory care (13th ed., pp. 1180-1207). St. Louis: Elsevier.
2. Ouellette, D.R. and others. (2017). Liberation from mechanical ventilation in critically ill adults: An official American College of Chest Physicians/American Thoracic Society clinical practice guideline: Inspiratory pressure augmentation during spontaneous breathing trials, protocols minimizing sedation, and noninvasive ventilation immediately after extubation. Chest, 151(1), 166-180. doi:10.1016/j.chest.2016.10.036
3. Proud, K. and others. (2020). Chapter 16: Ventilator discontinuance. In D.C. Shelledy, J.I. Peters (Eds.), Mechanical ventilation (pp. 637-666). Burlington, MA: Jones & Bartlett Learning.
4. Roberts, K.J. and others. (2024). AARC clinical practice guideline: Spontaneous breathing trials for liberation from adult mechanical ventilation. Respiratory Care, 11735. doi:10.4187/respcare.11735

ADDITIONAL READINGS

Girard, T.D. and others. (2017). An official American Thoracic Society/American College of Chest Physicians clinical practice guideline: Liberation from mechanical ventilation in critically ill adults. Rehabilitation protocols, ventilator liberation protocols, and cuff leak tests. American Journal of Respiratory and Critical Care Medicine, 195(1), 120-133. doi:10.1164/rccm.201610-2075ST

Hopkins, S. (2024). Procedure 30: Weaning mechanical ventilation. In K.L. Johnson (Ed.), AACN procedure manual for progressive and critical care (8th ed., pp. 275-282). St. Louis: Elsevier.

Schönhofer, B. and others. (2021). Prolonged weaning: S2k guideline published by the German Respiratory Society. Respiration, 99(11), 982-1084. doi:10.1159/000510085

Trudzinski, F.C. and others. (2022). Risk factors for prolonged mechanical ventilation and weaning failure: A systematic review. Respiration, 101(1), 959-969. doi:10.1159/000525604

Yi, L.J. and others. (2021). Comparative efficacy and safety of four different spontaneous breathing trials for weaning from mechanical ventilation: A systematic review and network meta-analysis. Frontiers in Medicine, 8, 731196. doi:10.3389/fmed.2021.731196

Clinical Review: Jennifer Elenbaas, MA, BS, RRT, AE-C

Published: July 2024