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Respiratory atef
- 2. Topics Definition of acute respiratory failure Basic respiratory physiology Pathophysiology Respiratory monitoring Treatment
- 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
- 5. CO2 O2
- 6. Pulmonary Ventilation and pressures
- 7. Oxygen in • Depends on – PAO2 – Diffusing capacity – Perfusion – Ventilation-perfusion matching
- 8. Oxygen Carbon dioxide Water vapour Nitrogen Alveolar pressure PAO2 PACO2 PAH2O PAN2
- 9. Alveolar Oxygen tension PAO2= (PB-PH2O)FIO2 – CO2/0.8 PAO2= (760-47)0.21 -40/0.8=100
- 10. How much oxygen is in the blood PaO2 SaO2 Oxygen content (CaO2)
- 11. How much oxygen is in the blood PaO2 • The amount of dissolved oxygen in the plasma phase -- and hence the PaO2 -- is determined by alveolar PO2 and lung architecture only SaO2 • 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)
- 13. Oxygen in • Depends on – PAO2 • FIO2 • PACO2 • Ventilation • Alveolar pressure – Ventilation-perfusion matching – Perfusion – Diffusing capacity
- 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. 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. Acute Lung Compromise Increase work of breathing Muscle fatigue Shallow breathing followed by increase in RR Increase PaCO2
- 17. Carbon dioxide out Respiratory rate Tidal volume Ventilation-perfusion matching
- 19. Dead space
- 20. Shunt
- 21. Pathophysiology
- 22. Pathophysiology • Low inspired Po2 • Hypoventilation • Ventilation-perfusion mismatch – Shunting – Dead space ventilation • Diffusion abnormality
- 23. PAO2=105 mmHg PACO2=37 mmHg 75% 100%
- 24. Pathophysiology • Low inspired oxygen concentration • Hypoventilation • Shunting • Dead space ventilation • Diffusion abnormality
- 25. F I O2 Ventilation without perfusion Hypoventilation (deadspace ventilation) Diffusion abnormality Normal Perfusion without ventilation (shunting)
- 26. Brainstem Spinal cord Airway Nerve root Lung Nerve Pleura Neuromuscular Chest wall junction Respiratory muscle Sites at which disease may cause ventilatory disturbance
- 27. Causes of respiratory failure Respiratory Center in Brain Brain
- 28. Causes of respiratory failure Respiratory Center in Brain Brain Neuromuscular Connections (peripheral nervous system) Nerves
- 29. Causes of respiratory failure Respiratory Center in Brain Brain Neuromuscular Connections Thoracic Bellows (intact rib cage and chest wall musculature) Nerves Bellows
- 30. Causes of respiratory failure Respiratory Center in Brain Brain Neuromuscular Connections Thoracic Bellows Airways (upper & lower) Nerves Bellows Airways
- 31. Causes of respiratory failure Respiratory Center in Brain Brain Neuromuscular Connections Thoracic Bellows Airways (upper & lower) Nerves Alveoli All the links are disrupted ! Bellows Airways Alveoli
- 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
- 34. Clinical • Respiratory compensation • Sympathetic stimulation • Tissue hypoxia • Haemoglobin desaturation
- 35. Clinical • Respiratory compensation – Tachypnoea – Accessory muscles – Recesssion – Nasal flaring • Sympathetic stimulation • Tissue hypoxia • Haemoglobin desaturation
- 36. Clinical • Respiratory compensation • Sympathetic stimulation – HR – BP (early) – sweating • Tissue hypoxia • Haemoglobin desaturation
- 37. Clinical • Respiratory compensation • Sympathetic stimulation • Tissue hypoxia – Altered mental state – HR and BP (late) • Haemoglobin desaturation
- 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. Treatment
- 40. Treatment • Treat the cause • Supportive treatment – Oxygen therapy – CPAP – Mechanical ventilation
- 41. Oxygen therapy • Fixed performance devices • Variable performance devices
- 42. Variable performance device 30 100% O2 Flow 6 l/min O2 6 0 Time
- 43. Variable performance device 30 24 l/min air 37% O2 Flow 6 l/min O2 6 0 Time
- 44. Fixed performance device Venturi mask 30 60% O2 60% O2 30 l/min Flow 15 l/min air 100% O2 15 l/min 0 Time
- 45. Other devices Reservoir face mask • Bag valve resuscitator •
- 46. CPAP • reduces shunt by recruiting partially collapsed alveoli
- 47. Mechanical ventilation • Decision to ventilate – Complex – Multifactorial – No simple rules
- 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. Thank you