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Mvss part v weaning & liberation from mechanical ventilation


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Slides accompanying the Lecture/Review Mechanical Ventilatory support series part V/V: Weaning and liberation from mechanical ventilatory support. For medical students and residents in Internal medicine. Contents are including rationale of weaning, predictors of weaning success and failure, methods of weaning, and detection and management of weaning failure

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Mvss part v weaning & liberation from mechanical ventilation

  1. 1. Mechanical Ventilatory Support Series Part V: Weaning & Liberation from Mechanical Ventilation S a n t i S i l a i r a t a n a , M D Division of Pulmonary Medicine, Department of Medicine, Faculty of Medicine Vajira Hospital Navamindradhiraj University
  2. 2. Outlines Rationale of weaning Weaning failure Methods of weaning Predictors of weaning success/failure
  3. 3. Complications of Mechanical Ventilation Other complicationsET tube complications malfunction malposition self-extubation nasal/oral necrosis pneumonia laryngeal edema tracheal erosion sinusitis Ventilator-related complications Ventilator induced lung injury Diaphragm dysfunction Alveolar hypo/hyperventilation Atelectasis Hypotension Pneumothorax Diffuse alveolar damage GI hypomobility Stress gastropathy GI hemorrhage Arrhythmias Salt-water retention Malnutrition
  4. 4. Ventilator Days and Survival Chance Esteban A, Anzueto A, Frutos F, et al. More ventilation days, more deaths. Day Survival chance Asthma COPD ARF ARDS
  5. 5. Do patients need weaning? 19% 81% Brochard L, Rauss A, Benito S, et al. 456 patients were enrolled to study weaning methods 347 patients (81%) were successfully extubated within 48 hr
  6. 6. Metabolic Changes during Critical Illness Critical Illness Recovery Lung diseases Heart diseases Neuromuscular disease Mechanical ventilation Malnutrition Electrolyte disorders Sedation muscle relaxants Muscle breakdown, atrophy, weakness
  7. 7. Outlines Rationale of weaning Weaning failure Methods of weaning Predictors of weaning success/failure
  8. 8. Delayed vs Premature Extubation Delayed 
 extubation Premature 
 extubation Infection Diaphragm dysfunction Tracheal stenosis Infection Airway trauma Respiratory failure
  9. 9. Parameters Used in Prediction of Weaning Success PaO P: F ratio PaO A-a DO Pi FVC PaCO MV TV MVV RR P V C C RSBI CROP index P SWI
  10. 10. Predictors Based on Respiratory Physiology PaO P: F ratio P A-a DO Pi FVC PaCO MV TV MVV RR P V C C RSBI CROP index P SWI Oxygenation CombinedLoadStrengthDrive
  11. 11. Indicators of Muscle Performance Parameter of Oxygenation Weaning Threshold Pimax <-15 to -30 cm H2O FVC >10-15 mL/kg PaCO2 <50 mmHg Minute Ventilation (MV) <10-15 L/min Tidal volume (TV) >5 mL/kg Maximum voluntary ventilation (MVV) >20 L/min RR <35 breaths/min or >6 breaths/min f/Vt ratio <105 breaths/min/L Strength Stamina Ashfaq Hasan.
  12. 12. Respiratory Mechanics Mechanical Indices Weaning Threshold Dynamic compliance (Cdyn) >22 mL/cm H2O Static compliance >33 mL/cm/H2O Work of breathing 0.47 J/L or 33 J/min Ashfaq Hasan.
  13. 13. Indices of Oxygenation Parameter of Oxygenation Weaning Threshold PaO2 (on FiO2 0.5 and PEEP ≤5 cm H2O) >60 mmHg PaO2/FiO2 ratio (“PF”ratio) >200 PaO2/PAO2 ratio >0.35 Alveolo-arterial oxygen gradient (A-aDO2) <350 mmHg on FiO2 1.0 Shunt fraction (Qs/Qt ratio) 0.2 (<20% shunt) Ashfaq Hasan.
  14. 14. Composite Indices Composite Indices Weaning Threshold Failure Threshold RSBI (f/Vt) ratio <105 breaths/min/mL >105 breaths/min/mL CROP index >13 mL/breaths/min N/A P0.1/Pmax ≤0.9 N/A SWI <9/min >11/min RSBI CROP SWI Ashfaq Hasan.
  15. 15. Outlines Rationale of weaning Weaning failure Methods of weaning Predictors of weaning success/failure
  16. 16. Readiness to Wean The cause of respiratory failure has improved The patient is oxygenating adequately The arterial pH is >7.25 The patient is ale to initiate an inspiratory effort The patient is hemodynamically stable No myocardial ischemia
  17. 17. Methods of Weaning Spontaneous breathing with 
 T-piece Pressure support ventilation SIMV with PSV SIMV
  18. 18. Rate of Successful Weaning Weaning technique Relative rate of suscessful weaning (95% CI) P value Once daily SBT vs SIMV 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 SBTs 1.24 (0.64-2.41) 0.54 SBT Esteban, A, Frutos, F, Tobin, MJ, et al, SIMV PSV:
  19. 19. Assessment of Readiness to Wean Clinical assessment Objective measurements Good heart: HR ≤140 bpm SBP 90-160 mmHg No/minimal vasopressors Good oxygenation: SaO2 >90% on FiO2 ≤0.4 PEEP ≤8 mmHg ‘3 Cs’ Cough Clean Clear Good 
 consciousness Good pulmonary function: RR ≤35 bpm MIP ≤-20 to -25 cmH2O VT >5 mL/kg VC >10 mL/kg f/Vt <105 br/min/L No significant respiratory acidosis Stable metabolic status
  20. 20. Spontaneous Breathing with T-piece Trial
  21. 21. Weaning with PSV 1 2 3 4 5 6 Record Tidal volume P peak Set Level of PS 80-85% of P peak Monitor clinical signs periodically Gradual decrease PS 2 cmH2O twice per day PS 6-8 cmH2O PEEP ≤5 cmH2O T-piece trial or Extubation
  22. 22. Weaning with SIMV + PSV 1 2 3 4 5 6 Record spontaneous RR and P peak Set SIMV rate 75-80% of spontaneous rate and PS 80-90% of P peak Monitor clinical signs periodically Gradual decrease RR 1-2 bpm twice per day RR 0 bpm Gradual decrease PS 2 cmH2O twice per day 7 8 PS 6-8 cmH2O PEEP ≤5 cmH2O T-piece trial or Extubation
  23. 23. Modes of Weaning: Summary SIMV with PSV Progressive decrease of SIMV rate Progressive decrease of PSV PSV SB with PSV SB with T-piece SB without PSV Extubation
  24. 24. Outlines Rationale of weaning Weaning failure Methods of weaning Predictors of weaning success/failure
  25. 25. Weaning Failure Either the failure of Spontaneous breathing trial or the need for reintubation within 48 h following extubation J-M. Boles et al.
  26. 26. Classification of Patients with Weaning Failure Group/Category Description Simple weaning Success at the first attempt Difficult weaning 1-3 attempts of SBT Up to 7 days from the first SBT Prolonged weaning >3 attempts 7 days of weaning after the first SBT SBT J-M. Boles et al.
  27. 27. Causes of Weaning Failure Weaning
 failure LoadMetabolic Strength
 Drive Cardiac load: Pre-existing cardiac disease Increased workload Pulmonary load: Increased airway resistance Decreased lung compliance Patient-ventilator dyssynchrony Depressed central drive: Metabolic alkalosis Sedative-hypnotic medications Electrolyte abnormalities: Hypokalemia Hypophosphatemia Hypomagnesemia Ventilator induced diaphragm dysfunction Steroid-induced myopathy CINMA Malnutrition/Overweight Anemia Sleep deprivation Adrenal Insuffiency
  28. 28. Inadequate Central Drive Excess sedation Metabolic alkalosis: Nasogastric suctioning CNS diseases: Stroke Encephalitis Encephalopathy Sleep disordered breathing: central sleep apnea Obesity hypoventilation syndrome
  29. 29. Cardiogenic Weaning Failure Oxygen consumption by muscle Oxygen delivery by the heart = Oxygen delivery Stroke volume x HR (O + (0.0031 x PaO
  30. 30. Weaning-induced Pulmonary Edema Physiologic parameter Positive Pressure Ventilation Spontaneous breathing Preload Decrease Increase Afterload Decrease Increase Cardiac oxygen consumption Decrease Increase Cardiac output Increase Decrease
  31. 31. Pulmonary Causes of Weaning Failure Increased resistive load: Bronchoconstriction airway edema secretions Increased elastic load: Dynamic hyperinflation Alveolar filling Atelectasis Pleural disease Chest wall disease Abdominal distension Pulmonary vascular disease Pulmonary hypertension Pulmonary embolism
  32. 32. Critical Illness Polyneuropathy & Myopathy Microvascular alterations Vasodilatation Increased permeability Endoneural edema Hypoxemia Extravasation Cytokine production Metabolic alterations Hyperglycemia Hormone imbalance Hypoalbuminemia Amino acid deficiency Proteolysis Bioenergetic failure Antioxidant depletion Increased ROS Mitochondrial 
 dysfunction Apoptosis Electrical alterations Channelopathy Cell depolarization Cell inexcitability Altered Ca homeostasis Changes in 
  33. 33. Sleep Deprivation Ventilatory response to hypercapnia Ventilatory response to hypoxia Increased collapsibility of upper airway Negative nitrogen balance Decreased respiratory muscle endurance Increased oxygen consumption Increased carbon dioxide production
  34. 34. Signs and Symptoms of Weaning Failure Subjective indices Agitation and anxiety Depressed mental status Diaphoresis Cyanosis Accessory muscle use Facial signs of distress Dyspnea Objective measurements PaO2 ≤50-60 mmHg on FiO2 ≥0.5 SaO2 <90% PaCO2 >50 mmHg PaCO2 increase >8 mmHg pH <7.32 or decrease ≥0.07 f/Vt >105 br/min/L RR >35 bpm or increase ≥20% SBP ≥180 mmHg or increase ≥20% SBP <90 mmHg Cardiac arrhythmia RR ▲ >10/min HR ▲ >20 /min SBP ▲ >30 mmHg
  35. 35. Management of Weaning Failure Early detection Record V/S Physical Exam Obtain an ABG if possible Put back previous 
 settings Identify causes
  36. 36. Cause-specific Management Respiratory load Nerve impulse from brain Cardiac load Metabolic Daily Interruption of Sedation Correction of metabolic alkalosis Bronchodilators Diuretics Nutrition Diuretics Inotropics Antiarrhythmic drugs Nitrate/PCI Correct hypokalemia, hypomagnesemia, hypophosphatemia Correction of anaemia, blood transfusion Sleep deprivation Adjust environment Short-acting sedative/hypnotic drugs
  37. 37. Management of Weaning Failure Rest
 24 hours Correct the cause(s) Retry 
 weaning Retry with gradual modes Tracheostomy Long-term ventilation
  38. 38. Postextubation Laryngeal Edema: Risk Normal vocal cords Vocal cord edema Age >60 years Female Duration of intubation ≥3 days Severe disease (APACHE II, SAPS II score) Large tube size High cuff pressure History of self-extubation/reintubation Underlying DM, CKD, Liver disease
  39. 39. Postextubation Laryngeal Edema: Detection Suction and clearing airway Switch ventilator to VCV mode Set tidal volume to be inspired (Vti) Deflate ET tube cuff Record tidal volume of expiration (Vte) 5-10 breaths to calculate mean values Vti - Vte >110 mL associated with adequate patency of the airway (Specificity 99%)
  40. 40. Postextubation Laryngeal Edema: Management All intubated patients At risk: • Female • Longer duration of intubation • High APACHE II, SAPS II score • Large tube size • High cuff pressure • History of self-extubation • Negative cuff leak test Not at risk Consider: • Methylprednisolone 20 mg q 4 h 3-4 doses; at least 12 hr prior to extubation attempt • Place airway exchanger catheter Extubation with close observation Consider discharge Consider: • Prednisolone 0.5 mg/kg • Epinephrine 1 mg in NSS 5 mL NB • Helium 40% + O2 60% inhalation PES • Re-intubation • Continue steroids No improvement in 1 hr No symptom in 1 hr
  41. 41. Thank You