Mvss part v weaning & liberation from mechanical ventilation

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. Outlines Rationale of weaning Weaning failure Methods of weaning Predictors of weaning success/failure

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. 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. 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. 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

8. Delayed vs Premature Extubation Delayed   extubation Premature   extubation Infection Diaphragm dysfunction Tracheal stenosis Infection Airway trauma Respiratory failure

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. 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. 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. 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. 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. 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.

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. Methods of Weaning Spontaneous breathing with   T-piece Pressure support ventilation SIMV with PSV SIMV

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. 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. Spontaneous Breathing with T-piece Trial

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. 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. 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

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. 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. 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. Inadequate Central Drive Excess sedation Metabolic alkalosis: Nasogastric suctioning CNS diseases: Stroke Encephalitis Encephalopathy Sleep disordered breathing: central sleep apnea Obesity hypoventilation syndrome

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. 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. 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. 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   excitation-contraction   coupling

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. 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. Management of Weaning Failure Early detection Record V/S Physical Exam Obtain an ABG if possible Put back previous   settings Identify causes

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. Management of Weaning Failure Rest  24 hours Correct the cause(s) Retry   weaning Retry with gradual modes Tracheostomy Long-term ventilation

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. 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. 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. Thank You

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