Weaning: The art and science

1. Presenter: Dr. Sujay Halkur Shankar Resident Preceptor: Dr. Gogineni Ratnakar Faculty Preceptors: Dr. Ved Prakash Meena Dr. Animesh Ray Dr. Manish Soneja Weaning The art and science

2. Learning Objectives • Assess for the readiness for weaning • Understand the popular methods of weaning • Learn the approach to a patient difficult to wean

3. Topic Outline • Introduction • Steps in weaning • Post-extubation care • Factors in weaning difficulty • Tracheostomy and Long term care

4. Need not be gradual in all cases 80% of individuals needing temporary mechanical ventilation can be disconnected Liberation or discontinuation are now the preferred terms Weaning trials must be started for any patient who has been mechanically ventilated for 24 hours or more Definition Pilbeam's mechanical ventilation: physiological and clinical applications. 2012 The process of gradual discontinuation of ventilatory support from a patient

5. Problems with Mechanical Ventilation Sellares J. Intensive Care Medicine. 2011

6. Boles J-M. European Respiratory Journal. 2007 Stages of Weaning

8. Readiness Testing Weaning Methods Extubation Steps in Weaning

9. Readiness testing

10. Epstein S K. AJRCCM. 2000  Clinicians underestimate the ability of a patient to be weaned  50% of self-extubated patients do not require re-intubation  65 – 85% of patients are ready to be weaned on the first day of assessment  To prevent harms of premature weaning  Cardiac failure, respiratory failure, re- intubation To Wean Or Not to Wean That is the question

11. Clinical Criteria Weaning Predictors

12. Clinical Criteria Objective clinical values depicting the physiology of the patient to test readiness for weaning 30% patients who never satisfy conditions can also be weaned Subjective criteria Cause of respiratory failure has improved Objective criteria Adequate oxygenation PaO2 ≥ 60mmHg on FiO2 ≤ 40% PEEP ≤ 5 – 8 cmH2O PaO2/FiO2 ≥ 150 Stable cardiovascular system HR ≤ 140 bpm Stable blood pressure with minimal/no vasopressors Afebrile Temperature ≤ 38˚C Metabolic status No respiratory acidosis (pH ≥ 7.25) Acceptable electrolytes Adequate mentation Alert/Easily arousable No sedative infusions Adequate Hemoglobin Hb ≥ 8 g/dL MacIntyre N R. Chest. 2001

13. Weaning Predictors Physiologic tests to test readiness for weaning Study oxygenation and gas exchange, respiratory muscle capacity, load on the respiratory system May require special equipment for testing Best studied and most reliable – Rapid Shallow Breathing Index

14. Oxygenation and Gas Exchange • PaO2/FiO2 • PaO2/PAO2 • (A-a) gradient Respiratory system load and muscle capacity • Maximal Inspiratory Pressure (MIP) (< -20 cmH2O) • Compliance (Static and Dynamic) • Minute Ventilation (< 10L/min) • Respiratory frequency (< 35/min) • Tidal Volume (> 4 – 6mL/kg) Integrative Indices • RSBI (< 105 breaths/min/L) • CROP Index • CORE Index • Integrative Weaning Index (IWI) Respiratory Drive • P0.1 (> -6cmH2O) • P0.1/MIP Meade M. Chest. 2001 Weaning Predictors

15. PaO2 ≥ 60mmHg (FiO2 ≤ 40%) PEEP ≤ 5 – 8 cmH2O PaO2/FiO2 ≥ 150 PaO2/PAO2 > 0.47 (A-a) < 350mmHg (FiO2 = 100%) 𝑃𝐴𝑂2 = 𝐹𝑖𝑂2 × (𝑃𝑎𝑡𝑚 − 𝑃𝐻2𝑂) − 𝑃𝑎𝐶𝑂2 0.8 Adequacy of Oxygenation Pilbeam's mechanical ventilation: physiological and clinical applications. 2012

16. Respiratory system load and muscle capacity Vital Capacity > 15mL/kg (IBW) Minute Ventilation < 10 – 15L/min Tidal Volume > 4 – 6mL/kg (IBW) Respiratory rate < 35/min Ventilatory pattern – Synchronous and stable MIP < -20 to -30 cmH2O Pilbeam's mechanical ventilation: physiological and clinical applications. 2012

17. Others Dynamic Compliance > 25mL/cmH2O Static Compliance > 33mL/cmH2O P0.1 > -6 cmH2O Pilbeam's mechanical ventilation: physiological and clinical applications. 2012

18. RSBI RSBI (breaths/min/L) = Respiratory rate (f) / Tidal Volume in L (Vt) • Measured at least 1 minute after disconnecting from ventilator • Threshold for successful weaning < 105 breaths/min/L

19. How though?

20. Tobin MJ. Intensive Care Medicine. 2006

21. Preparation for weaning  Communicate with the patients  Explain the procedure and calm them  Record baseline parameters  Keep a calm environment  Position the patient upright in bed  Suction the ET tube to ensure patency

22. Weaning methods

23. Spontaneous Breathing Trial (SBT) Reduction in pressure support of PSV Reduction in IMV support Newer Methods

24. Spontaneous breathing trial Weaning Technique Relative rate of success P value Once daily SBT vs IMV 2.83 (1.36 – 5.89) < 0.006 Once daily SBT vs PSV 2.05 (1.04 – 4.04) < 0.04 Once daily SBT vs Intermittent SBT 1.24 (0.64 – 2.41) 0.54 130 of 546 patients failing a 2 hour SBT randomly assigned to wean via daily SBT (using a T-piece), IMV or PSV Esteban A. NEJM. 1995

25. 300 patients enrolled in a two arm RCT Shorter duration of weaning (4.5 vs 6 days; p = 0.003) Lower rates of post extubation respiratory failure (20% vs 40%; p = 0.001) Ely EW. NEJM. 1996

26. Types of SBT T-Piece trial Low levels of PSV (5 – 8 cmH2O) Low level CPAP (5 cmH2O) Automatic Tube Compensation (ATC)

27. 2017 ACCP/ATS Clinical Practice Guidelines • Based on a meta-analysis of 4 randomized trials • Higher extubation success (75.4% vs 68.9%; RR = 1.09, 95% CI 1.02 vs 1.18) SBT be conducted with inspiratory pressure augmentation (5-8 cm H2O) rather than without (T-piece or CPAP) Ouellette DR. Chest. 2017

28. Automatic Tube Compensation? Study/Year No of Patients Study Design Results Remarks Haberthur C et al/2002 90 RCT 1. PSV 2. T- Piece 3. ATC + CPAP 5 cm H20 Rate of successful extubation similar with modes Half the patients who failed with PSV or T- tube tolerated ATC - successfully extubated Cohen JD et al/2006 99 RCT 1. CPAP 2. CPAP + ATC Extubation 96% vs 85%, p = 0.08 Cohen JD et al/2009 180 RCT 1. ATC 2. PSV Extubation 94% vs 86% p = 0.12 Higher predictive value of RSBI in ATC

29. Duration of SBT Minimum of 30 minutes and can go up to 120 minutes 30 minutes and 120 minutes of T Piece trials have similar outcomes (526 patients, 75.9% vs 73.0%, p = 0.43) Patient’s failing an initial SBT or those requiring prolonged ventilation may require 120 minute SBT Esteban A. AJRCCM. 1997

30. Liang G. Respiratory Care. 2018

31. Subjective failure of SBT Agitation and anxiety Depressed mental status Diaphoresis Cyanosis Increased accessory muscle activity Facial signs of distress Esteban A. NEJM. 1995; Ely EW. AJRCCM. 1999

32. Objective failure of SBT Respiratory rate > 35 breaths/min (Or increase in 10 breaths/min or decrease in 8 breaths/min below baseline) Tidal volume < 250mL to 300mL Heart rate > 140bpm or > 20% from baseline Sudden onset VPC (more than 4 to 6 per minute) Significant change in blood pressure - Drop of 20 mmHg systolic - Rise of 30 mmHg systolic - SBP >180 mmHg - Change of > 10 mmHg of diastolic Desaturation with SO2 < 90% or PaO2 < 60mmHg (FiO2 ≤ 40%) Esteban A. NEJM. 1995; Ely EW. AJRCCM. 1999

33. SBT Success Extubation Failure Daily SBT Early extubation to NIV

34. Failed SBT Daily SBT vs Intermittent SBT – showed no difference in weaning success Diaphragmatic fatigue appears within the first 24 hours of mechanical ventilation Find the etiology for failure Laghi F. J Appl Physiol. 1995

35. Weaning with PSV SBT/Extubate PS 6 – 8 cmH2O and PEEP = 5cm H2O Reduce PS by 2 – 4 cmH2O twice daily Monitor clinically Set PS about 80% of Ppeak Record Vt and Ppeak More useful in prolonged weaning SBTs after reduction in PS by 50% IMV is not used for weaning

36. Extubation

37. Extubation Removal of the endotracheal tube Final step in liberating patient from mechanical ventilation Safety of extubation must be assessed prior to extubation

38. Assessment of airway protection Cough Consciousness Secretions

39. Consciousness: - Ideal - alert/arousable - Neck Holding: Hold neck off the bed for 5 seconds Secretions: - Thick secretions not a contraindication - Suctioning < 2 – 3 hours Cough: - Assessed during deep suctioning - PEF ≥ 60 L/min (Spirometry) - Index card – Ability to wet a card 1 – 2 cm from ETT Salam A. Intensive Care Medicine. 2004

40. Post-extubation stridor Incidence: <10% of cases Causes: Vocal cord edema, laryngeal injury, vocal cord dysfunction Risk factors: Jaber S. Intensive Care Medicine. 2003 Prolonged intubation Age > 80 years Female gender Ratio of ETT to laryngeal diameter > 45% (On CT) ETT size > 8mm in men and > 7mm in women Traumatic intubation History of asthma Excessive tube motility due to improper fixation

41. Cuff Leak Test Qualitative: Listening to air movement around the ETT Quantitative:  In Volume controlled ventilation  < 110mL or less than 12 – 24% of Vti – Negative cuff leak  Sensitivity: 15 – 85%; Specificity: 70 – 99% Vti – Vte > 110mL Associated with adequate patency of airway (Specificity 99%) Kriner EJ. Respiratory Care. 2005

42. Role of glucocorticoids Khemani RG. Cochrane Library. 2009

43. Selecting the right patient is more important than the number of doses administered Acceptable regimens: Role of glucocorticoids Khemani RG. Cochrane Library. 2009 IV Methylprednisolone 20mg Q4H for 4 doses IV Methylprednisolone 40mg Single dose 4 hours prior

45. Weaning success: 48 hours of unassisted breathing Hoarseness, sore throat and cough are common Post-extubation stridor:  Treat with nebulized racemic epinephrine (0.5mL, 2.25% epinephrine in 3mL NS)  Heliox treatment (70% Helium and 30% Oxygen)  Steroids  May require re-intubation Post-extubation care Pilbeam's mechanical ventilation: physiological and clinical applications. 2012

46. Post-extubation respiratory failure Risk factors • Age > 65 yr • > 1 SBT failure • Chronic heart failure • PaCO2 > 45 mmHg after extubation • Medical/surgical co-morbid illness • Poor cough reflex • BMI > 35 kg/m2 Fernando Frutos-Vivar,et al Chest 2006

47. All extubated patients must be oxygenated For patients at high risk for extubation failure who have been receiving mechanical ventilation for more than 24 hours, and who have passed a spontaneous breathing trial, we recommend extubation to preventative NIV (Strong recommendation, moderate grade of evidence). ACCP/ATS Guidelines High Risk Low Risk NIV is recommended Low flow oxygen High flow oxygen Ouellette DR. Chest. 2017

49. Weaning Failure Failure of SBT Re-intubation within 48 hours

50. Types of weaning Simple Weaning (70%) • Single SBT Difficult Weaning (10 – 20%) • 1 to 3 SBT • Weaned within 7 days Prolonged Weaning (10 – 15%) • More than 3 SBT • Weaning takes more than 7 days from first SBT Boles JM. Eur Respir J. 2007

51. PO4 Mg K Ca Weaning Failure

52. Respiratory factors RESPIRATORY LOAD Inappropriate ventilator settings – Increased WoB Reduced compliance • Pneumonia • Pulmonary edema • Pleural effusion Increased resistive load • Narrow ET tube • Bronchoconstriction • Increased airway secretions • Post-extubation: glottic oedema RESPIRATORY DRIVE • Sedation • Metabolic alkalosis • CVA, encephalitis, cerebral edema RESPIRATORY MUSCLE STRENGTH • Nutrition • Ventilator induced diaphragmatic dysfunction • Metabolic disturbances K/Ca/Mg/PO4 • Critical illness neuromyopathy Eskandar. Crit Care Clin. 2007

53. Cardiac Factors Weaning induced ischemia/failure: 20 – 60% cases of difficult weaning Difficult to identify if SBT is performed with PEEP Pro-BNP levels: Difficulty is expected if - Elevated levels before SBT - Elevated levels after an SBT - > 20% rise during an SBT 2D Echo: Helps identify systolic or diastolic dysfunction

54. Neuromuscular causes Central causes: OSA with hypoventilation, central apneas, stroke Critical illness myopathy/polyneuropathy - ≥ 25% of mechanically ventilated patients after 7 days - Risk Factors: Sepsis, Multi-organ failure, SIRS - Abrupt onset over 24 hours or progress over days - Aggressively treat the underlying cause

55. Metabolic causes PO4 Mg K Ca Raised pCO2 in chronic hypercapnia Bicarbonate excretion during MV Acute respiratory acidosis during SBT Falsely interpreted as failure of SBT Metabolic acidosis causes compensatory Respiratory alkalosis – Increase in the work of breathing Hypothyroidism

56. Drugs and sedatives Aminoglycosides – Neuromuscular blockade – Rare cause of weaning failure ATS Recommendation For acutely hospitalized patients ventilated for more than 24 h, we suggest protocols attempting to minimize sedation Strom T. Lancet. 2010

57. Nutrition Ventilated patients with severe infection can be given up to 35kcal/kg Undernutrition - Wasting of muscles (including diaphragm and cardiac) - Blunts central response to hypoxia and hypercapnia Overnutrition - Increased metabolic rate and increased workload on the respiratory system due to CO2 production

58. Psychological Depression, anxiety, delirium, pain Depression - 40% patients undergoing prolonged weaning Patients with delirium can be twice as hard to wean How to tackle? - Explain the process to the family and caregivers - Medications to treat psychiatric issues and adjustment of sedative doses - Reassurance - Adequate sleep and a stimulating environment

59. • 60 year old male • COPD and CAD • Admitted for CAP • Intubated in view of respiratory failure • Condition improved with antibiotics • Decided to be weaned • SBTs initiated – failed – Tachycardia; Tachypnea Ramu Re-admitted (A case scenario)

60. Vt Ppeak RR Pplat MVe PEEP 400 28 2522 8.8 6 SBT Vt Ppeak RR Pplat MVe PEEP 200 40 2944 8.8 6

61. Vt Ppeak RR Pplat MVe PEEP 400 28 2522 8.8 6 SBT Vt Ppeak RR Pplat MVe PEEP 200 40 3844 8.8 6

62. Vt Ppeak RR Pplat MVe PEEP 400 28 2522 8.8 6 SBT Vt Ppeak RR Pplat MVe PEEP 500 30 2630 15 6

64. Advantages: ◦ Easier airway management ◦ Improved patient comfort and communication ◦ Reduction in sedative use ◦ Earlier transition to oral feeding ◦ Reduced oropharyngeal trauma ◦ Prevention of VAP Disadvantages ◦ Long term risk of tracheal stenosis ◦ Procedure-related complication rate (4% - 36%) Tracheostomy Griffiths J. BMJ. 2005

65. Meta-analysis of the data from studies Significant effect on the duration of mechanical ventilation and the length of stay in intensive care Unable to confirm an effect of early (2- 10 days) tracheostomy in reducing the risk of pneumonia or death Strong consideration for those likely to need mechanical ventilation for more than 2 weeks Tracheostomy - timing Griffiths J. BMJ. 2005

66. Site where weaning and rehabilitation are the primary focus  Acute condition of the patient has to be resolved  Patient should be stable on a mechanical ventilator  Stable airway and a route for nutrition Consists of intensivists, internists, nurses and respiratory therapists who identify weaning goals and coordinate the weaning process Long term care facilities

67. Newer modes for weaning

68. NAVA – Neurally Adjusted Ventilator Assist Verbrugghe W. Respiratory Care. 2011

69. NAVA - Synchrony Problems of asynchrony • Increased need of sedation and muscle relaxants • Increased transpulmonary pressure – Barotrauma • Prolonged duration of ventilation Verbrugghe W. Respiratory Care. 2011

70. Respiratory Rate No trigger PCV Spont < Target PS/SIMV Spont > Target PSV Adaptive Support Ventilation Advantages Provides Automated weaning Fewer human resources are needed at bedside Fernandez J. Indian J Crit Care Med. 2013

71. Take Home Message  Test readiness before weaning  Daily SBT with inspiratory augmentation  Mechanical ventilation for > 2 weeks : Early tracheostomy  If weaning fails, look thoroughly for the cause and correct  NAVA and ASV are newer, more advanced modes for weaning

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