Indices that predict difficulty weaning
OVERVIEW
- Numerous objective indices have been studied to predict failure of ventilator liberation or weaning.
- None of these indexes alone are sufficiently sensitive and specific to be useful in predicting the success of ventilation discontinuation in an individual patient.
- Different studies use different cut offs, with different performance characteristics
- They are not recommended for routine use, the Spontaneous breathing trial (SBT) remains the de facto gold standard test.
INDICES THAT PREDICT SUCCESSFUL VENTILATOR DISCONTINUATION
- Respiratory rate <30 breaths per minute
- Tidal volume >5 ml/kg or >325 mL
- FVC >15 mL/kg predicts success
- Minute ventilation <15 L/min
— Normal 5 – 6 L/min
— Patient unlikely to wean if > 15 L/min - Maximum inspiratory pressure (PImax) < -30 cmH20
— Measure of respiratory muscle strength
— Normal -90 to -120 cmH2O - Rapid shallow breathing index (RSBI) = f/VT <105 breaths/min/L
— the ratio of respiratory rate : tidal volume
— often used in conjunction with SBT to determine if it should continue
— some evidence that its use in protocols delays ventilator discontinuation - P0.1/PImax > 0.3
— P0.1 is pressure at the airway opening 0.1 s after start of inspiratory flow
— Correlates with central respiratory drive - P0.1 x f/VT <300
- CROP index (dynamic compliance, respiratory rate, oxygenation, maximum inspiratory pressure index) >13
— Cdyn x PImax x (PaO2/PAO2)/f
— >13 good
— Cdyn = dynamic compliance - IWI (integrative weaning index) >25
— (CRS x SaO2)/(f/VT)
— CRS = static compliance of the respiratory system - CORE index (dynamic compliance, oxygenation, rate, effort) >8
— Cdyn x (PImax/P0.1) x (PaO2/PAO2)/f
OTHER CONSIDERATIONS
- the above indices focus on lung function
- successful ventilar discontinuation and extubation also depends on 2 other domains:
— general medical condition (e.g. disease resolution, nutrition, anaemia, conditioning, etc)
— ability to protect airway post-extubation (extubation assessment, separate from weaning assessment)
References and Links
CCC Ventilation Series
Modes: Adaptive Support Ventilation (ASV), Airway Pressure Release Ventilation (APRV), High Frequency Oscillation Ventilation (HFOV), High Frequency Ventilation (HFV), Modes of ventilation, Non-Invasive Ventilation (NIV), Spontaneous breathing and mechanical ventilation
Conditions: Acute Respiratory Distress Syndrome (ARDS), ARDS Definitions, ARDS Literature Summaries, Asthma, Bronchopleural Fistula, Burns, Oxygenation and Ventilation, COPD, Haemoptysis, Improving Oxygenation in ARDS, NIV and Asthma, NIV and the Critically Ill, Ventilator Induced Lung Injury (VILI), Volutrauma
Strategies: ARDSnet Ventilation, Open lung approach, Oxygen Saturation Targets, Protective Lung Ventilation, Recruitment manoeuvres in ARDS, Sedation pauses, Selective Lung Ventilation
Adjuncts: Adjunctive Respiratory Therapies, ECMO Overview, Heliox, Neuromuscular blockade in ARDS, Prone positioning and Mechanical Ventilation
Situations: Cuff leak, Difficulty weaning, High Airway Pressures, Post-Intubation Care, Post-intubation hypoxia
Troubleshooting: Autotriggering of the ventilator, High airway and alveolar pressures / pressure alarm, Ventilator Dyssynchrony
Investigation / Indices: A-a gradient, Capnography and waveforms, Electrical Impedance Tomography, Indices that predict difficult weaning, PaO2/FiO2 Ratio (PF), Transpulmonary pressure (TPP)
Extubation: Cuff Leak Test, Extubation Assessment in ED, Extubation Assessment in ICU, NIV for weaning, Post-Extubation Stridor, Spontaneous breathing trial, Unplanned extubation, Weaning from mechanical ventilation
Core Knowledge: Basics of Mechanical Ventilation, Driving Pressure, Dynamic pressure-volume loops, flow versus time graph, flow volume loops, Indications and complications, Intrinsic PEEP (autoPEEP), Oxygen Haemoglobin Dissociation Curve, Positive End Expiratory Pressure (PEEP), Pulmonary Mechanics, Pressure Vs Time Graph, Pressure vs Volume Loop, Setting up a ventilator, Ventilator waveform analysis, Volume vs time graph
Equipment: Capnography and CO2 Detector, Heat and Moisture Exchanger (HME), Ideal helicopter ventilator, Wet Circuit
MISC: Sedation in ICU, Ventilation literature summaries
LITFL
- CCC — Weaning from mechanical ventilation (Hot Case)
Journal articles
- El-Khatib MF, Bou-Khalil P. Clinical review: liberation from mechanical ventilation. Crit Care. 2008;12(4):221. PMC2575571.
- Haas CF, Loik PS. Ventilator discontinuation protocols. Respir Care. 2012 Oct;57(10):1649-62. PMID: 23013902. [Free Fulltext]
- Macintyre NR. Evidence-based assessments in the ventilator discontinuation process. Respir Care. 2012 Oct;57(10):1611-8. PMID: 23013898. [Free Fulltext]
- MacIntyre N. Discontinuing mechanical ventilatory support. Chest. 2007 Sep;132(3):1049-56. PMID: 17873200. [Free Fulltext]
- Yang KL, Tobin MJ. A prospective study of indexes predicting the outcome of trials of weaning from mechanical ventilation. N Engl J Med. 1991 May 23;324(21):1445-50. PMID: 2023603. [Free Fulltext]
Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the Clinician Educator Incubator programme, and a CICM First Part Examiner.
He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.
His one great achievement is being the father of three amazing children.
On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump.
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