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Respiratory atef
Acute respiratory failure occurs when the pulmonary system can no longer meet the body's metabolic demands. It can be hypoxaemic, with an oxygen level below 60 mmHg, or hypercapnic, with a carbon dioxide level over 50 mmHg. Respiratory failure results from issues in oxygen intake and carbon dioxide removal, due to problems in ventilation, perfusion matching, gas exchange, or other pathologies. It is monitored clinically and with blood tests, and treated by addressing the underlying cause, providing supportive oxygen therapy or ventilation support like CPAP or mechanical ventilation if needed.
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Respiratory atef
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- 2. Topics Definition of acute respiratory failure Basic respiratory physiology Pathophysiology Respiratory monitoring Treatment
- 3. Definitions acute respiratoryfailure 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
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- 5. CO2 O2
- 6. Pulmonary Ventilation andpressures
- 7. Oxygen in • Dependson – 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 oxygenis in the blood PaO2 SaO2 Oxygen content (CaO2)
- 11. How much oxygenis 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)
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- 13. Oxygen in • Dependson – 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
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- 22. Pathophysiology • Low inspiredPo2 • 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 respiratoryfailure Respiratory Center in Brain Brain
- 28. Causes of respiratoryfailure Respiratory Center in Brain Brain Neuromuscular Connections (peripheral nervous system) Nerves
- 29. Causes of respiratoryfailure Respiratory Center in Brain Brain Neuromuscular Connections Thoracic Bellows (intact rib cage and chest wall musculature) Nerves Bellows
- 30. Causes of respiratoryfailure Respiratory Center in Brain Brain Neuromuscular Connections Thoracic Bellows Airways (upper & lower) Nerves Bellows Airways
- 31. Causes of respiratoryfailure 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
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- 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
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- 40. Treatment • Treat thecause • Supportive treatment – Oxygen therapy – CPAP – Mechanical ventilation
- 41. Oxygen therapy • Fixedperformance 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 shuntby recruiting partially collapsed alveoli
- 47. Mechanical ventilation • Decisionto ventilate – Complex – Multifactorial – No simple rules
- 48. Ventilate? • Severity ofrespiratory failure • Cardiopulmonary reserve • Adequacy of compensation – Ventilatory requirement • Expected speed of response – Underlying disease – Treatment already given • Risks of mechanical ventilation
- 49. Ventilate? • 43 yearold 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 yearold 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 yearold 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 yearold 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 yearold 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 yearold 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 yearold 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 yearold 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 yearold 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 yearold 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 yearold 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 yearold 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 yearold 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
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