Ventilatory strategies in the icu

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concise ventillator management

Ventilatory strategies in the icu

  1. 1. Ventilatory strategies in the ICU
  2. 2. Ventilatory strategies in the ICU  Need for mechanical ventilation  Modes of ventilation – VCV, PCV, DCV  Invasive vs Noninvasive ventilation  Weaning from mechanical ventilation  Extubation and failure to extubate
  3. 3. Ventilatory strategies in the ICU  Need for mechanical ventilation
  4. 4. Respiratory distressRS: • Mouth open • Alae nasi flaring • Pursed lips • Tracheal tug • Active accessory muscles • Breathlessness • Tachypnoea • Cyanosis • Paradoxical respiration CVS: • Cool extremities • Rising pulse • Falling BP • Anxiety • Drowsiness • Restlessness • Disorientation • Picking bedclothes CNS
  5. 5. “Inability to maintain either the normal delivery of O2 to the tissues ± removal of CO2 from the tissues” Type I vs Type II Respiratory failure
  6. 6. INDICATIONS FOR MECHANICAL VENTILATION • Ventilation abnormalities - Respiratory muscle dysfunction Respiratory muscle fatigue Chest wall abnormalities Neuromuscular disease Decreased ventilatory drive Increased airway resistance • Oxygenation abnormalities - Refractory hypoxaemia Need for PEEP Excessive work of breathing
  7. 7. INDICATIONS FOR MECHANICAL VENTILATION • Need for anaesthesia, sedation and/or neuromuscular blockade • Need to decrease systemic/myocardial oxygen consumption, e.g., low cardiac output states • Use of hyperventilation to reduce intracranial pressure
  8. 8.  Oxygen delivery  Adequate alveolar ventilation  Restore acid-base balance  Reduce work of breathing  Minimal side-effects Goals of ventilatory support
  9. 9. Ventilatory strategies in the ICU  Need for mechanical ventilation  Modes of ventilation – VCV, PCV, DCV
  10. 10. vs Man Machine
  11. 11. Inspiration 2 3 Expiration 4 1
  12. 12. SET TRIGGER1, Trigger 3, Cycling 4, Baseline P cmH2O 2, Limit Time
  13. 13. Basic Modes of Ventilation
  14. 14. VolumePressureFlow Insp Exp Volume limited Constant flow Time
  15. 15. VolumePressureFlow Insp Exp Volume limited Constant flow Pressure limitedVolume controlled Pressure controlled Time
  16. 16. Volume controlled vs Pressure controlled modes COMPARISON VCV PCV Volume Constant Varies Effect of low compliance Higher pressure Lower volume Effect of high airway resistance Higher pressure Lower volume Peak airway pressure High Lower Mean airway pressure Lower Higher
  17. 17. Case scenario 1 A 30 year old man, weighing 50 kg who had undergone laparotomy the previous day was complaining of pain at the incision. The postgraduate prescribed morphine 50 mg and phenergan 12.5 mg IM. The injections were given. Fifteen minutes later, he becomes apnoeic.
  18. 18. Case scenario 2 He was nicely settled on ventilator but now seems to have some respiratory efforts
  19. 19. Mechanical Ventilation Volume Controlled Ventilation Pressure Controlled Ventilation
  20. 20. Pressure Control Ventilation - CMV Pressure Flow Volume 0 30 Time
  21. 21. Pressure Control Ventilation - SIMV Pressure Flow Volume 0 30 Time
  22. 22. Case scenario 3 By 4 AM, the patient seems to be stable and breathing a lot better than before. You want to see whether you can encourage his spontaneous breaths and wean him by morning. What mode would you choose?
  23. 23. Pressure Support Ventilation (PSV)
  24. 24. Pressure Support Ventilation (PSV) Time 25 % 0 20 Time
  25. 25. Positive End-Expiratory Pressure (PEEP) PEEP is not a mode of ventilation per se 0 + PEEP with Mandatory breaths Alveolarpressure Time 5 Baseline variable
  26. 26. Continuous Positive Airway Pressure (CPAP) Appropriate for patients who have adequate spontaneous ventilation but persistent hypoxaemia due to physiological shunting Pressure (cmH2O) 0 + - Baseline
  27. 27. Ventilatory setting  Mode  Frequency  Tidal volume  I:E ratio  FIO2
  28. 28. Ventilatory strategies in the ICU  Need for mechanical ventilation  Modes of ventilation – VCV, PCV, DCV  Invasive vs Noninvasive ventilation
  29. 29. Mechanical Ventilation Invasive ventilation Noninvasive Ventilation
  30. 30. Noninvasive Ventilation – Advantages  Reduced need for sedation  Preservation of airway reflexes  Avoidance of upper airway trauma  Decreased ventilator associated pneumonia  Improved patient comfort  Shorter length of stay in the ICU and hospital  Improved survival
  31. 31. Noninvasive Ventilation – Disadvantages  Claustrophobia  Facial/nasal pressure lesions  Unprotected airway  Inability to suction deep airway  Gastric distension with face mask  Delay in intubation
  32. 32. Noninvasive Ventilation - Contraindications  Cardiac or respiratory arrest  Haemodynamic instability  Patients unable to co-operate  Inability to protect airway  High risk for aspiration  Active upper GI bleed  Severe hypoxaemia  Facial trauma, surgery or burns
  33. 33. Case scenario 4  This patient was doing fine for two days but developed abdominal distension, vomited and aspirated. He had to be reintubated and ventilated. He has stiff lungs now.
  34. 34. Case scenario 4 ABG FIO2 – 1 PaO2 – 100 mm Hg PaCO2 – 45 mm Hg pH – 7.3 SpO2 – 98%  Mode  Frequency  Tidal volume  I:E ratio  FIO2
  35. 35. PaO2PvO2P50 a v PO2 (mm Hg) Haemoglobinsaturation(%)
  36. 36. Oxygenation status PaO2/FIO2 ratio 500 – Normal 250 – Good 100 – 250: Poor 100 - Critical
  37. 37. 10% shunt 10040 60 800 20 Air 600 400 200 Assume normal QT, VO2, Hb, C(a-v)O2 20% shunt 30% shunt 40% shunt 50% shunt FIO2 (%) Nunn JF: Oxygen. In Nunn JF (ed): Applied Respiratory Physiology, 3rd ed. London: Butterworths,1987,109 Normal
  38. 38. NormalShunt Dead space
  39. 39. Case Scenario 4  Mode - PCV  Frequency - Higher  Tidal volume - Lower  I:E ratio – 1:2 to 1:1 or even inverse ratio ventilation  FIO2 – As required  PEEP Avoid • Barotrauma • Volutrauma • Atelectrauma • Biotrauma • Oxygen toxicity
  40. 40. Mean airway pressure
  41. 41. Increase mean airway pressure by  Increasing peak airway pressure  Increasing plateau pressure  Increase duration of inspiration (I:E ratio)  Increase PEEP
  42. 42. Bilevel Positive Airway Pressure Ventilation (BiPAP)
  43. 43. Mechanical Ventilation Volume Controlled Ventilation Pressure Controlled Ventilation Dual Controlled Ventilation
  44. 44. Case Scenario 5 A 20 year old man, known asthmatic, was admitted to the Casualty with severe wheeze. He is tachypnoeic, hypoxic and restless. He was sedated and intubated but his lungs are very stiff. What would you do?
  45. 45. Case scenario 5  Mode - PCV  Frequency - Slower  Tidal volume – 7 ml/kg  I:E ratio – Longer I:E  FIO2 ABG FIO2 – 1 PaO2 – 250 mm Hg PaCO2 – 50 mm Hg pH – 7.3
  46. 46. Auto-PEEP DetectionFLOW INCREASED RESISTANCE NORMAL TIME LINEAR DECAY EXPONENTIAL DECAY Flow –time graph
  47. 47. Auto-PEEP Reduction  Low respiratory rate  Lower tidal volume  Large endotracheal tube  Higher inspiratory flow rate  Longer expiratory time  Permissive hypercapnia
  48. 48. Watch • Gas exchange • Lung mechanics –Volumes, pressures • CVS • The complete picture!
  49. 49. Ventilatory strategies in the ICU  Need for mechanical ventilation  Modes of ventilation – VCV, PCV, DCV  Noninvasive ventilation  Weaning from mechanical ventilation
  50. 50. “Weaning” is … gradual discontinuation of ventilatory support
  51. 51. When to wean? Early withdrawal Vs Premature discontinuation
  52. 52. Has there been a significant improvement or reversal in the primary pathology ?
  53. 53. Assessment of patients Are they ready for weaning?
  54. 54. Is the respiratory function adequate?
  55. 55.  FIO2 < 0.4 – 0.5  PaO2 (mmHg) > 60  SaO2 (%) > 90  SvO2 (%) > 60  PaO2/PAO2 ratio > 0.35  PaO2/FIO2 ratio > 350 Oxygenation
  56. 56. PaCO2 < 50 mmHg pH > 7.35 Ventilation  Respiratory rate < 35.min-1  Minute volume < 10 L.min-1  Maximum inspiratory pressure > - 20 cmH2O  Vital capacity > 10 ml.kg-1  VD / VT < 0.6
  57. 57. Rapid shallow breathing index (RSBI) * * Yang KL, Tobin MJ. N Engl J Med 1991,324:1445-50 f / VT < 105 (b.min-1L-1) Where, f = Respiratory rate in breaths.min-1 VT = Tidal volume in Litres
  58. 58. Are his other systems functioning adequately?
  59. 59. Spontaneous Breathing Trial (SBT)
  60. 60.  Low levels of CPAP (e.g., 5 cmH2O)  Low levels of pressure support (e.g., 5 – 7 cmH2O) or  Simply as “T-piece breathing”  Screening phase (5 min)  Assessment phase (30 – 120 min) Ref: MacIntyre NR. Chest 120, December 2001 375S – 395S
  61. 61. Monitoring during weaning
  62. 62. Monitors do not substitute for an ever vigilant clinician !
  63. 63.  The patient  Oxygenation  Ventilation  Cardiovascular status
  64. 64. Failed Spontaneous Breathing Trial (SBT) Why ? What next ?
  65. 65. The most common cause of failure to wean is an imbalance between ventilatory capability and ventilatory demand.
  66. 66.  Patients who fail an SBT should receive a stable, nonfatiguing, comfortable form of ventilation  Attempts at weaning can continue with once daily SBTs.  Twice daily SBTs offer no advantage over once daily SBT.
  67. 67. Ventilatory strategies in the ICU  Need for mechanical ventilation  Modes of ventilation – VCV, PCV, DCV  Noninvasive ventilation  Weaning from mechanical ventilation  Extubation and failure to extubate
  68. 68. The decision to discontinue ventilatory support must be distinct from the decision to extubate !
  69. 69. Those who will be successfully extubated will have i) the resolution of the disease ii) haemodynamic stability iii) absence of sepsis iv) adequate oxygenation status v) adequate ventilatory status…. etc, etc
  70. 70. and also will have…. the ability to maintain patency of the airway
  71. 71. Upper airway obstruction Excess respiratory secretions Inability to protect airway Cardiac failure or ischaemia Encephalopathy Respiratory failure GI bleeding, sepsis, seizures Causes of failure to extubate
  72. 72. Maziak DE, Meade MO, Todd RJ. Chest 1998;114:605-9 Insufficient evidence exists to support the idea that the timing of tracheotomy alters the duration of mechanical ventilation in critically ill patients. ROLE OF TRACHEOSTOMY IN WEANING
  73. 73. Ventilatory strategies in the ICU  Need for mechanical ventilation  Modes of ventilation – VCV, PCV, DCV  Noninvasive ventilation  Weaning from mechanical ventilation  Extubation and failure to extubate
  74. 74. Thank you

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