Patho-Physiology of Respiratory Failure.  John KOLBE Respiratory Services Green Lane Hospital, & Faculty of Health Science...
<ul><li>Someone told me that each equation I included in the book would halve the sales. </li></ul>Stephen Hawking “ A Bri...
RESPIRATORY FAILURE Def: When the lungs fail to adequately  oxygenate the arterial blood and/or fail to  prevent undue CO ...
Relationship of PaCO 2  and (Alveolar) Ventilation PaCO 2 = Vco 2  k VA i.e. PaCO 2  1   VA
Relationship of PaCO 2  and (Alveolar) Ventilation VT = VA + VD
<ul><li>I could never make out what those damned dots meant. </li></ul>Lord Randolph Churchill (referring to decimal point...
Respiratory Drive Neuromuscular Transmission Load
HYPOVENTILATION   Drive   Neuromuscular    Transmission  Muscle weakness/ (fatigue = reversible) +  LOAD.
HYPERCAPNIA  Hypoventilation -   Respiratory Drive - Neuro-muscular (in)competence (-    Drive) -    Neuromuscular Tra...
HYPOXIA <ul><li>Reduced F 1 o 2 </li></ul><ul><li>Hypoventilation </li></ul><ul><li>Diffusion </li></ul><ul><li>V/Q mismat...
Alveolar-Arterial Oxygen Gradient. <ul><li>Adequacy of Gas Exchange! </li></ul>
 
 
Alveolar-Arterial Oxygen Gradient. ie, at sea level, breathing air; PAO2 = 20 - PaCO2/0.8 A-a Gradient = 20 - PaCO2/0.8 -P...
ALVEOLAR GAS EQUATION PaO 2  = (P b  - PH 2 O)    F I O 2  -  PaCo 2  + k   R    20 kPa - PaCo 2   0.8 (Normal A-a gradi...
 
DIFFUSION <ul><li>Depends on </li></ul><ul><ul><li>- gas </li></ul></ul><ul><ul><li>- diffusion distance/thickness </li></...
V/Q = 00 V/Q = 1 V/Q = 0 V/Q mismatch - most important cause - 3 compartment model of Lung Dead Space  “Ideal”  Shunt
V/Q =   V/Q = 1 V/Q = 0 Co2 - N              Cco2 - N   N    Compensatory   Hyperventilation (of V/Q = 1)
 
 Worsening Disease  Unable to Undertake compensatory Hyperventilation   Pa CO 2   (pH is normalised by rental (and oth...
 
Relationship of PaCO 2  and (Alveolar) Ventilation Ve = Va + Vd Ve = k    Vco 2 PaCo 2  (1 - Vd/Vt)
RIGHT TO LEFT SHUNTS - distinguish from V/Q mismatch by  administration of 100% O 2 - normally Pao 2  rises to >600 mmHg -...
 
 
 
<ul><li>Science is built up of facts, as a house is built of stones; but an accumulation of facts is no more a science tha...
 
 
 
 
 
 
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Patho Physiology Of Respiratory Failure

  1. 1. Patho-Physiology of Respiratory Failure. John KOLBE Respiratory Services Green Lane Hospital, & Faculty of Health Sciences University of Auckland.
  2. 2. <ul><li>Someone told me that each equation I included in the book would halve the sales. </li></ul>Stephen Hawking “ A Brief History of Time”: 1988.
  3. 3. RESPIRATORY FAILURE Def: When the lungs fail to adequately oxygenate the arterial blood and/or fail to prevent undue CO 2 retention. In practical Terms; PaO 2 < 8kPa (60 mmHg) (Hypoxic,TypeI) PaCo 2 > 6.6 kPa (50mmHg) (Hypercapnic, Type II)
  4. 4. Relationship of PaCO 2 and (Alveolar) Ventilation PaCO 2 = Vco 2  k VA i.e. PaCO 2  1 VA
  5. 5. Relationship of PaCO 2 and (Alveolar) Ventilation VT = VA + VD
  6. 6. <ul><li>I could never make out what those damned dots meant. </li></ul>Lord Randolph Churchill (referring to decimal points).
  7. 7. Respiratory Drive Neuromuscular Transmission Load
  8. 8. HYPOVENTILATION   Drive   Neuromuscular Transmission  Muscle weakness/ (fatigue = reversible) + LOAD.
  9. 9. HYPERCAPNIA  Hypoventilation -  Respiratory Drive - Neuro-muscular (in)competence (-  Drive) -  Neuromuscular Transmission - Muscle weakness/fatigue - Abnormal load  V/Q mismatch (Multi-factorial)
  10. 10. HYPOXIA <ul><li>Reduced F 1 o 2 </li></ul><ul><li>Hypoventilation </li></ul><ul><li>Diffusion </li></ul><ul><li>V/Q mismatch </li></ul><ul><li>R-L Shunt </li></ul>
  11. 11. Alveolar-Arterial Oxygen Gradient. <ul><li>Adequacy of Gas Exchange! </li></ul>
  12. 14. Alveolar-Arterial Oxygen Gradient. ie, at sea level, breathing air; PAO2 = 20 - PaCO2/0.8 A-a Gradient = 20 - PaCO2/0.8 -PaO2 (Normal A-a gradient = 1-2 kPa)
  13. 15. ALVEOLAR GAS EQUATION PaO 2 = (P b - PH 2 O)  F I O 2 - PaCo 2 + k R  20 kPa - PaCo 2 0.8 (Normal A-a gradient = 1-2 kPa)
  14. 17. DIFFUSION <ul><li>Depends on </li></ul><ul><ul><li>- gas </li></ul></ul><ul><ul><li>- diffusion distance/thickness </li></ul></ul><ul><ul><li>- surface area </li></ul></ul><ul><ul><li>- (Hb) </li></ul></ul><ul><ul><li>- capillary volume </li></ul></ul><ul><li>Use of CO </li></ul><ul><li>- diffusion (and not perfusion) limited </li></ul><ul><li>- soluble </li></ul><ul><li>- avidly binds to Hb  zero back pressure </li></ul>
  15. 18. V/Q = 00 V/Q = 1 V/Q = 0 V/Q mismatch - most important cause - 3 compartment model of Lung Dead Space “Ideal” Shunt
  16. 19. V/Q =  V/Q = 1 V/Q = 0 Co2 - N      Cco2 - N   N  Compensatory Hyperventilation (of V/Q = 1)
  17. 21.  Worsening Disease  Unable to Undertake compensatory Hyperventilation   Pa CO 2 (pH is normalised by rental (and other) mechanisms) Dangers: - High inspired O 2 - Monitoring O 2 saturations only
  18. 23. Relationship of PaCO 2 and (Alveolar) Ventilation Ve = Va + Vd Ve = k  Vco 2 PaCo 2 (1 - Vd/Vt)
  19. 24. RIGHT TO LEFT SHUNTS - distinguish from V/Q mismatch by administration of 100% O 2 - normally Pao 2 rises to >600 mmHg - role of - absorption atelectasis - relaxation of hypoxic vasoconstriction
  20. 28. <ul><li>Science is built up of facts, as a house is built of stones; but an accumulation of facts is no more a science than a heap of stones is a house. </li></ul>Henri Poincare “ Science and Hypothesis”: 1905 .
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