Weaning and Discontinuation of Ventilatory Support

1. Weaning and Discontinuation of Ventilatory Support 215a

2. Educational Objectives • Differentiate between weaning, discontinuation, and extubation • List the causes of ventilator dependence • List the patient parameters evaluated and the values required prior to initiating weaning

3. Educational Objectives • Describe the various techniques of weaning, with the advantages and disadvantages of each • Describe the overall factors associated with successful weaning • List the steps of extubation

4. Definitions • Weaning • The process of gradually reducing ventilatory support and its replacement with spontaneous ventilation in an incremental manner • Discontinuation • The permanent removal of the ventilator

5. Definitions • Extubation • Removal of the artificial airway • Ventilatory Demand • The level of ventilation required to meet the patient’s need for elimination of carbon dioxide

6. Definitions • Ventilatory capacity • The level of the patient’s drive (CNS) to breathe and the ability of the respiratory muscles to maintain this drive (strength and endurance)

7. Causes of Ventilator Dependence • Ventilatory demand in excess of ventilatory capacity • Non-respiratory factors • Psychological factors • Nutritional needs

8. Ventilatory Demand in Excess of Ventilatory Capacity • Factors increasing ventilatory demand • Increased CNS drive • Hypoxia • Acidosis • Pain • Fear/anxiety • Stimulation of J receptors

9. Ventilatory Demand in Excess of Ventilatory Capacity • Factors increasing ventilatory demand • Increased metabolic rate • Increased carbon dioxide production • Fever • Shivering • Trauma • Infection/sepsis

10. Ventilatory Demand in Excess of Ventilatory Capacity • Factors increasing ventilatory demand • Decrease in lung compliance • Atelectasis • Pneumonia • Fibrosis • Pulmonary edema • ARDS

11. Ventilatory Demand in Excess of Ventilatory Capacity • Factors increasing ventilatory demand • Decreased thoracic compliance • Obesity • Ascites • Abdominal distention • Pregnancy

12. Ventilatory Demand in Excess of Ventilatory Capacity • Factors increasing ventilatory demand • Increased airway resistance • Bronchospasm • Mucosal edema • Secretions

13. Ventilatory Demand in Excess of Ventilatory Capacity • Factors increasing ventilatory demand • Artificial airways • Endotracheal tube • Tracheostomy tube

14. Ventilatory Demand in Excess of Ventilatory Capacity • Factors increasing ventilatory demand • Mechanical factors • Ventilator circuits • Demand flow systems • Inappropriate ventilator settings • Flow • Sensitivity

15. Ventilatory Demand in Excess of Ventilatory Capacity • Factors affecting ventilatory capacity • Decreased PaCO2 • Metabolic alkalosis • Pain • Electrolyte imbalance

16. Ventilatory Demand in Excess of Ventilatory Capacity • Factors affecting ventilatory capacity • Respiratory depressants • Narcotics • Sedatives

17. Ventilatory Demand in Excess of Ventilatory Capacity • Factors affecting ventilatory capacity • Fatigue • Overall fatigue • Malnutrition • Atrophy of respiratory muscles

18. Ventilatory Demand in Excess of Ventilatory Capacity • Factors affecting ventilatory capacity • Decrease in metabolic rate • Carbon dioxide retention • Neurologic or neuromuscular disease

19. Non-Respiratory Factors • Cardiovascular factors • Myocardial ischemia • Heart failure • Hemodynamic instability • Arrhythmias

20. Non-Respiratory Factors • Neurological factors • Decreased central drive • Decreased peripheral nerve transmission

21. Psychological Factors • Confusion/altered mental status • Fear and anxiety • Stress • Depression • Support from staff and family

22. Nutritional Needs • Preferably, patient is not on hyperalimentation • No excessive carbohydrates • Increased carbohydrate intake increases respiratory quotient > 0.8 • Results from increase in carbon dioxide production

23. Factors Affecting Readiness For Weaning • Reversal or stabilization of underlying disease causing initiation of support • Stable vital signs • Afebrile • Pulse, blood pressure within normal limits

24. Factors Affecting Readiness For Weaning • Adequate cardiovascular reserves • Absence of acute myocardial ischemia • Minimal requirement for vasopressors to maintain blood pressure • No significant arrhythmias

25. Factors Affecting Readiness For Weaning • Adequate blood gas results • PaO2 ≥ 60 mmHg with FIO2 < 0.5 and PEEP ≤ 5 cmH2O • pH > 7.25 • PaCO2 at patient’s normal level (may be greater than 45 mmHg for COPD patients)

26. Factors Affecting Readiness For Weaning • Adequate ventilatory status • Spontaneous respiratory rate < 30 breaths/min • Spontaneous tidal volume > 5 mL/kg • Vital capacity > 10 – 15 mL/kg

27. Factors Affecting Readiness For Weaning • Adequate respiratory muscle strength • Maximum inspiratory force • MIF < −30 cmH2O

28. Factors Affecting Readiness For Weaning • Adequate ventilatory reserve • Maximum voluntary ventilation • MVV > 20 L/min or two times minute ventilation

29. Factors Affecting Readiness For Weaning • Adequate ventilatory reserve • Rapid Shallow Breathing Index (RSBI) • Respiratory rate divided by tidal volume in liters (f/VT) • Calculated during one minute of unsupported, spontaneous breathing • Pressure support reduces predictive value

30. Factors Affecting Readiness For Weaning • Adequate ventilatory reserve • Rapid Shallow Breathing Index (RSBI) • Most predictive for patients on ventilatory support less than eight days • f/VT < 105 predictor of weaning success; < 80 associated with 95% success

31. Approaches to Weaning • Spontaneous breathing trials (SBT) • Synchronized intermittent mandatory ventilation • Pressure support ventilation • Extubation

32. Spontaneous Breathing Trials (SBT) • Method • Prepare the patient psychologically • Set FIO2either at the ventilator setting or 10% above setting • Patient placed on T piece or left on ventilator with no backup rate and CPAP set at zero

33. Spontaneous Breathing Trials (SBT) • Method • Start with five minutes off the ventilator (or less, if not tolerated by patient); may increase initial time up to 120 minutes if tolerated well

34. Spontaneous Breathing Trials (SBT) • Method • Response is monitored; trial discontinued if changes observed • f > 35 breaths/min • SPO2 < 90% • Heart rate > 140 beats/min or increase by 20%

35. Spontaneous Breathing Trials (SBT) • Method • Response is monitored; trial discontinued if changes observed • BP ≥ 20% change; systolic >180 mmHg and diastolic > 90 mmHg • Diaphoresis • Increased anxiety

36. Spontaneous Breathing Trials (SBT) • Method • If first trial unsuccessful and patient has auto-PEEP secondary to airway obstruction, may add 5 cmH2O • If patient has nasal ET tube or small ET tube, 5 to 7 cmH2O pressure support may be added • If patient fails SBT, patient replaced on ventilatory Support to rest for one to four hours

37. Spontaneous Breathing Trials (SBT) • Method • Increase duration of spontaneous breathing trials • Some patients may tolerate the procedure so well that they do not have to resume ventilator use at all

38. Spontaneous Breathing Trials (SBT) • When weaning is difficult, process can last weeks or months • Generally, ventilatory support is resumed overnight

39. Synchronized Intermittent Mandatory Ventilation • Method • Initially, respiratory rate and tidal volume set to provide full ventilatory support • Initiation of weaning by SIMV • May wait until patient’s condition has improved considerably • May begin as soon as patient’s condition allows

40. Synchronized Intermittent Mandatory Ventilation • Method • Rate decreased in increments of two with assessment of patient following each adjustment • May be reduced more rapidly as patient condition improves • Once rate is equal to 4 breaths/min and can be tolerated at least two to four hours, the patient may be extubated

41. Synchronized Intermittent Mandatory Ventilation • Decreases respiratory muscle atrophy and discoordination • Minimizes chance of barotrauma through rapid reduction of mean airway pressure

42. Pressure Support Ventilation • Mode of ventilatory support that assists the patient’s spontaneous inspiratory effort with a level of positive airway pressure

43. Pressure Support Ventilation • Mode works best for short-term weaning (< 72 hours); if used for long-term weaning, increase support to near maximum at night to allow patient to rest

44. Pressure Support Ventilation • Technique • Begin with pressure support level at which respiratory rate and tidal volume are close to full support • Gradually reduce support as tolerated by patient

45. Pressure Support Ventilation • Technique • Continue to reduce support until a minimum level of between 5 and 10 cmH2O can be tolerated • When patient can maintain this level for a minimum of two and four hours, the patient is considered weaned

46. Extubation • Decision to wean and decision to extubate are separate decisions

47. Extubation • Guidelines for extubation • No immediate need for mechanical ventilation • Achievement of adequate oxygenation and ventilation during spontaneous breathing

48. Extubation • Guidelines for extubation • Minimal risk of upper airway obstruction • Minimal upper airway edema; perform cuff leak test • Suction upper airway above cuff • Deflate cuff

49. Extubation • Guidelines for extubation • Minimal risk of upper airway obstruction • Minimal upper airway edema; perform cuff leak test • Briefly occlude endotracheal tube • If patient is unable to breathe around the occluded endotracheal tube with the cuff deflated, laryngeal edema may be present

50. Extubation • Guidelines for extubation • Minimal risk of upper airway obstruction • No evidence of mass obstructing airway • Minimal risk of aspiration • Adequate protection of airway • Adequate clearance of pulmonary secretions