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Respiratory atef

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Respiratory atef

  1. 1. Acute respiratory failure
  2. 2. Topics Definition of acute respiratory failure Basic respiratory physiology Pathophysiology Respiratory monitoring Treatment
  3. 3. Definitions acute respiratory failure occurs when: – pulmonary system is no longer able to meet the metabolic demands of the body hypoxaemic respiratory failure: – PaO2 60 mmHg when breathing room air hypercapnic respiratory failure: – PaCO2 50 mmHg
  4. 4. Basic respiratory physiology
  5. 5. CO2 O2
  6. 6. Pulmonary Ventilation and pressures
  7. 7. Oxygen in• Depends on – PAO2 – Diffusing capacity – Perfusion – Ventilation-perfusion matching
  8. 8. Oxygen Carbon dioxide Water vapour NitrogenAlveolar pressure PAO2 PACO2 PAH2O PAN2
  9. 9. Alveolar Oxygen tensionPAO2= (PB-PH2O)FIO2 – CO2/0.8PAO2= (760-47)0.21 -40/0.8=100
  10. 10. How much oxygen is in the blood PaO2 SaO2 Oxygen content (CaO2)
  11. 11. How much oxygen is in the bloodPaO2• The amount of dissolved oxygen in the plasma phase -- and hence the PaO2 -- is determined by alveolar PO2 and lung architecture onlySaO2• The percentage of hemoglobin molecule bounded with oxygen.Oxygen Content CaO2• CaO2 = Hb (gm/dl) x 1.34 ml O2/gm Hb x SaO2 + PaO2 x (.003 ml O2/mm Hg/dl)
  12. 12. Oxygen dessociation Curve
  13. 13. Oxygen in• Depends on – PAO2 • FIO2 • PACO2 • Ventilation • Alveolar pressure – Ventilation-perfusion matching – Perfusion – Diffusing capacity
  14. 14. Carbon dioxide out Largely dependent on alveolar ventilation Alveolar ventilatio n RR x (V - V )T D Anatomical dead space constant but physiological dead space depends on ventilation-perfusion matching
  15. 15. Carbon dioxide out• Patient Vt f Ve Description –A (400) (20) = 8.0 L/min slow and deep –B (200) (40) = 8.o L/min fast/shallow• Patient Va-Vd f Va Description –A (400-150)(20) = 5.0 L/min slow and deep –B (200-150)(40) = 2.0 L/min fast/shallow
  16. 16. Acute Lung Compromise Increase work of breathing Muscle fatigue Shallow breathing followed by increase in RRIncrease PaCO2
  17. 17. Carbon dioxide out Respiratory rate Tidal volume Ventilation-perfusion matching
  18. 18. Ventilation-perfusion matching
  19. 19. Dead space
  20. 20. Shunt
  21. 21. Pathophysiology
  22. 22. Pathophysiology• Low inspired Po2• Hypoventilation• Ventilation-perfusion mismatch – Shunting – Dead space ventilation• Diffusion abnormality
  23. 23. PAO2=105 mmHg PACO2=37 mmHg75% 100%
  24. 24. Pathophysiology• Low inspired oxygen concentration• Hypoventilation• Shunting• Dead space ventilation• Diffusion abnormality
  25. 25. F I O2 Ventilation without perfusion Hypoventilation (deadspace ventilation) Diffusionabnormality Normal Perfusion withoutventilation(shunting)
  26. 26. Brainstem Spinal cord Airway Nerve root Lung Nerve Pleura NeuromuscularChest wall junction Respiratory muscle Sites at which disease may cause ventilatory disturbance
  27. 27. Causes of respiratory failure Respiratory Center in Brain Brain
  28. 28. Causes of respiratory failure Respiratory Center in Brain Brain Neuromuscular Connections (peripheral nervous system) Nerves
  29. 29. Causes of respiratory failure Respiratory Center in Brain Brain Neuromuscular Connections Thoracic Bellows (intact rib cage and chest wall musculature) Nerves Bellows
  30. 30. Causes of respiratory failure Respiratory Center in Brain Brain Neuromuscular Connections Thoracic Bellows Airways (upper & lower) Nerves Bellows Airways
  31. 31. Causes of respiratory failure  Respiratory Center in Brain Brain  Neuromuscular Connections  Thoracic Bellows  Airways (upper & lower) Nerves  AlveoliAll the links are disrupted ! Bellows Airways Alveoli
  32. 32. Shunting• Intra-pulmonary – Pneumonia – Pulmonary oedema – Atelectasis – Collapse – Pulmonary haemorrhage or contusion• Intra-cardiac – Any cause of right to left shunt • eg Fallot’s, Eisenmenger, • Pulmonary hypertension with patent foramen ovale
  33. 33. Respiratory monitoring
  34. 34. Clinical• Respiratory compensation• Sympathetic stimulation• Tissue hypoxia• Haemoglobin desaturation
  35. 35. Clinical• Respiratory compensation – Tachypnoea – Accessory muscles – Recesssion – Nasal flaring• Sympathetic stimulation• Tissue hypoxia• Haemoglobin desaturation
  36. 36. Clinical• Respiratory compensation• Sympathetic stimulation – HR – BP (early) – sweating• Tissue hypoxia• Haemoglobin desaturation
  37. 37. Clinical• Respiratory compensation• Sympathetic stimulation• Tissue hypoxia – Altered mental state – HR and BP (late)• Haemoglobin desaturation
  38. 38. Summary• worry if • RR > 30/min (or < 8/min) • unable to speak 1/2 sentence without pausing • agitated, confused or comatose • cyanosed or SpO2 < 90% • deteriorating despite therapy• remember • normal SpO2 does not mean severe ventilatory problems are not present
  39. 39. Treatment
  40. 40. Treatment• Treat the cause• Supportive treatment – Oxygen therapy – CPAP – Mechanical ventilation
  41. 41. Oxygen therapy• Fixed performance devices• Variable performance devices
  42. 42. Variable performance device 30 100% O2Flow 6 l/min O2 6 0 Time
  43. 43. Variable performance device 30 24 l/min air 37% O2Flow 6 l/min O2 6 0 Time
  44. 44. Fixed performance device Venturi mask 30 60% O2 60% O2 30 l/minFlow 15 l/min air 100% O2 15 l/min 0 Time
  45. 45. Other devices Reservoir face mask • Bag valve resuscitator •
  46. 46. CPAP• reduces shunt by recruiting partially collapsed alveoli
  47. 47. Mechanical ventilation• Decision to ventilate – Complex – Multifactorial – No simple rules
  48. 48. Ventilate?• Severity of respiratory failure• Cardiopulmonary reserve• Adequacy of compensation – Ventilatory requirement• Expected speed of response – Underlying disease – Treatment already given• Risks of mechanical ventilation
  49. 49. Ventilate?• 43 year old male• Community acquired pneumonia• Day 1 of antibiotics• PaO2 60 mmHg, PaCO2 30 mmHg, pH 7.15 on 15 l/min via reservoir facemask• Respiratory rate 35/min• Agitated No Yes
  50. 50. Yes• 43 year old male• Community acquired pneumonia• Day 1 of antibiotics• PaO2 60 mmHg, PaCO2 30 mmHg, pH 7.15 on 15 l/min via reservoir facemask• Respiratory rate 35/min• Agitated
  51. 51. Yes• 43 year old male• Community acquired pneumonia• Day 1 of antibiotics• PaO2 60 mmHg, PaCO2 30 mmHg, pH 7.15 on 15 l/min via reservoir facemask• Respiratory rate 35/min• Agitated
  52. 52. Yes• 43 year old male• Community acquired pneumonia• Day 1 of antibiotics• PaO2 60 mmHg, PaCO2 30 mmHg, pH 7.15 on 15 l/min via reservoir facemask• Respiratory rate 35/min• Agitated
  53. 53. Yes• 43 year old male• Community acquired pneumonia• Day 1 of antibiotics• PaO2 60 mmHg, PaCO2 30 mmHg, pH 7.15 on 15 l/min via reservoir facemask• Respiratory rate 35/min• Agitated
  54. 54. Yes• 43 year old male• Community acquired pneumonia• Day 1 of antibiotics• PaO2 60 mmHg, PaCO2 30 mmHg, pH 7.15 on 15 l/min via reservoir facemask• Respiratory rate 35/min• Agitated
  55. 55. Ventilate?• 24 year old woman• Presents to ER with acute asthma – SOB for 2 days• Salbutamol inhaler, no steroids• PFR 60 L/min, HR 105/min• pH 7.25 PaCO2 51 mmHg, PaO2 315 mmHg on FiO2 0.6• RR 35/min• Alert No Yes
  56. 56. No• 24 year old woman• Presents to A&E with acute asthma – SOB for 2 days• Salbutamol inhaler, no steroids• PFR 60 L/min, HR 105/min• pH 7.25 PaCO2 51 mmHg, PaO2 315 mmHg on FiO2 0.6• RR 35/min• Alert
  57. 57. No• 24 year old woman• Presents to A&E with acute asthma – SOB for 2 days• Salbutamol inhaler, no steroids• PFR 60 L/min, HR 105/min• pH 7.25 PaCO2 51 mmHg, PaO2 315 mmHg on FiO2 0.6• RR 35/min• Alert
  58. 58. No• 24 year old woman• Presents to A&E with acute asthma – SOB for 2 days• Salbutamol inhaler, no steroids• PFR 60 L/min, HR 105/min• pH 7.25 PaCO2 51 mmHg, PaO2 315 mmHg on FiO2 0.6• RR 35/min• Alert
  59. 59. No• 24 year old woman• Presents to A&E with acute asthma – SOB for 2 days• Salbutamol inhaler, no steroids• PFR 60 L/min, HR 105/min• pH 7.25 PaCO2 51 mmHg, PaO2 315 mmHg on FiO2 0.6• RR 35/min• Alert
  60. 60. No• 24 year old woman• Presents to A&E with acute asthma – SOB for 2 days• Salbutamol inhaler, no steroids• PFR 60 L/min, HR 105/min• pH 7.25 PaCO2 51 mmHg, PaO2 315 mmHg on FiO2 0.6• RR 35/min• Alert
  61. 61. No• 24 year old woman• Presents to A&E with acute asthma – SOB for 2 days• Salbutamol inhaler, no steroids• PFR 60 L/min, HR 105/min• pH 7.25 PaCO2 51 mmHg, PaO2 315 mmHg on FiO2 0.6• RR 35/min• Alert
  62. 62. Thank you

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