Oxygen delivery-systems

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Oxygen delivery-systems

  1. 1. Oxygen Therapy & O2 Delivery Systems Dr. J. S Dali MAMC www.anaesthesia.co.in anaesthesia.co.in@gmail.com
  2. 2. Oxygen Therapy ?
  3. 3. Oxygen Therapy Partial Pr of O2 in insp. gas (Pi o2)
  4. 4. Oxygen Therapy Partial Pr of O2 in insp. gas (Pi o2) Conc. of O2 (Fi o2) (Orthobaric) Total Pressure (Hyperbaric)
  5. 5. Father of modern O2 Therapy ?
  6. 6. Father of modern O2 Therapy O2 lack not only stops the machine, but totally ruins the supposed machinery J.S Haldane-1917
  7. 7. Aim of O2 Therapy ?
  8. 8. Aim of O2 Therapy To restore tissue O2 towards normal
  9. 9. O2 Cascade Air mitochondria
  10. 10. O2 Cascade 159mm Hg Atm. Air (20.95 % of 760) (dry) ? Lower Resp. Tract (moist 37 c) o 149mm Hg (20.95 % of 713)
  11. 11. O2 Cascade 159mm Hg Atm. Air (20.95 % of 760) (dry) Humidification 6 Vol % (47mm Hg) Lower Resp. Tract (moist 37 c) o 149mm Hg 20.95 % of 713 (760-47)
  12. 12. O2 Cascade Lower Resp. Tract (moist 37oc) 149mm Hg (20.95 % of 713) ? ? Alveolar air 101mm Hg (14 % of 713) or (15 % of 673) 673 = 760 – 47 – 40 PA O2 = FI O2 (Pb – 47) – PaCo2 x F R.Q = PI O2 – PaCo2 = PI O2 – PaCo2 if breathing 100% O2
  13. 13. O2 Cascade Lower Resp. Tract (moist 37oc) O2 consumption 149mm Hg (20.95 % of 713) Alv. ventilation Alveolar air 101mm Hg (14 % of 713) or (15 % of 673) 673 = 760 – 47 – 40 PA O2 = FI O2 (Pb – 47) – PaCo2 x F R.Q = PI O2 – PaCo2 = PI O2 – PaCo2 if breathing 100% O2
  14. 14. O2 Cascade Alveolar air 101mm Hg (14 % of 713) or (15 % of 673) 673 = 760 – 47 – 40 ? Arterial blood 97mm Hg Pa O2 = 100 – 0.3 x age (years) mm Hg A – a = 4 – 25 mmHg
  15. 15. O2 Cascade Alveolar air 101mm Hg (14 % of 713) or (15 % of 673) 673 = 760 – 47 – 40 Venous admixture Arterial blood 97mm Hg Pa O2 = 100 – 0.3 x age (years) mm Hg A – a = 4 – 25 mmHg
  16. 16. O2 Cascade Venous admixture (physiological shunt) Low VA/Q Normal True shunt (normal anatomical shunt)
  17. 17. O2 Cascade Venous admixture (physiological shunt) Low VA/Q Normal True shunt (normal anatomical shunt) Pulmonary (Bronchial veins) Extra Pulm. (Thebesian veins)
  18. 18. O2 Cascade Venous admixture (physiological shunt) Low VA/Q Normal True shunt (normal anatomical shunt) Pulmonary (Bronchial veins) Extra Pulm. (Thebesian veins) Normal = upto 5 % of cardiac output
  19. 19. O2 Cascade Alveolar air PA O2 = 101mm Hg (14 % of 713) or (15 % of 673) 673 = 760 – 47 – 40 ? ? Venous admixture Arterial blood Pa O2 = 97mm Hg Pa O2 = 100 – 0.3 x age (years) mm Hg A – a = 4 – 25 mmHg
  20. 20. O2 Cascade Alveolar air PA O2 = 101mm Hg (14 % of 713) or (15 % of 673) 673 = 760 – 47 – 40 PI O2 PV O2 Venous admixture Arterial blood Pa O2 = 97mm Hg Pa O2 = 100 – 0.3 x age (years) mm Hg A – a = 4 – 25 mmHg
  21. 21. O2 Cascade Arterial blood Pa O2 = 97mm Hg (Sat. > 95 %) Utilization by tissue Cell Mitochondria PO2 7 – 37 mmHg Mixed Venous blood PV O2 = 40mm Hg Sat. 75% – The critical level for aerobic metab. to continue
  22. 22. O2 Cascade Arterial blood Pa O2 = 97mm Hg (Sat. > 95 %) Utilization by tissue Cell Mitochondria PO2 7 – 37 mmHg Mixed Venous blood PV O2 = 40mm Hg Sat. 75% Pasteur point – The critical level for aerobic metab. to continue (1 – 2 mmHg PO2 in mitochondria)
  23. 23. Which patient is better placed – ? A B Hb 14gm (normal) 7gm (Anaemic) C.O. 5 L (normal) 4 L (Low) PaO2 O2 Flux 23 mm 375ml 60 mm 350ml
  24. 24. Which patient is better placed – ? A B Hb 14gm (normal) 7gm (Anaemic) C.O. 5 L (normal) 4 L (Low) SPO2 40 % 90 % PaO2 O2 Flux 23 mm 375ml 60 mm 350ml Min. gradient for O2 transfer from cap. to cell (app. 20 mm Hg) = sat. 20 – 30% = 200 – 300ml O2 flux Critical Level for O2 delivery / critical O2 flux
  25. 25. O2 Cascade Arterial blood Pa O2 = 97mm Hg (Sat. > 95 %) Utilization by tissue Cell Mitochondria PO2 7 – 37 mmHg Mixed Venous blood PV O2 = 40mm Hg Sat. 75% Pasteur point – The critical level for aerobic metab. to continue (PO2 1-2 mmHg in mitochondria, 22mmHg in capillary)
  26. 26. O2 Cascade Pa O2 = 97mm Hg Arterial blood ? ? Utilization by tissue Cell Mitochondria PO2 7 – 37 mmHg (Sat. > 95 %) Mixed Venous blood PV O2 = 40mm Hg Sat. 75% Pasteur point – The critical level for aerobic metab. to continue (PO2 1-2 mmHg in mitochondria, 22mmHg in capillary)
  27. 27. O2 Cascade Arterial blood (Sat. > 95 %) Perfusion O2 content (Hb Conc.) Utilization by tissue Cell Mitochondria PO2 7 – 37 mmHg Pa O2 = 97mm Hg Mixed Venous blood PV O2 = 40mm Hg Sat. 75% Pasteur point – The critical level for aerobic metab. to continue (PO2 1-2 mmHg in mitochondria, 22mmHg in capillary)
  28. 28. O2 content Per 100 ml Art. blood 14g x 1.39 x 100% = 20 ml Ven. blood 14g x 1.39 x 75% = 15ml Tissue extraction 25% = 5ml
  29. 29. O2 content Per 100 ml Art. blood 14g x 1.39 x 100% = 20 ml Ven. blood 14g x 1.39 x 75% = 15ml Tissue extraction 25% = 5ml 1% = 0.2ml Art. blood 7g x 1.39 x 100% = 10 ml Ven. blood 7g x 1.39 x 50% = 5ml Tissue extraction 50% = 5ml 1% = 0.1ml
  30. 30. PO2 97mm 40mm O2 content Per 100 ml Art. blood 14g x 1.39 x 100% = 20 ml Ven. blood 14g x 1.39 x 75% = 15ml Tissue extraction 25% = 5ml 1% = 0.2ml 97mm ? Art. blood 7g x 1.39 x 100% = 10 ml Ven. blood 7g x 1.39 x 50% = 5ml Tissue extraction 50% = 5ml 1% = 0.1ml
  31. 31. PO2 97mm 40mm O2 content Per 100 ml Art. blood 14g x 1.39 x 100% = 20 ml Ven. blood 14g x 1.39 x 75% = 15ml Tissue extraction 25% = 5ml 1% = 0.2ml 97mm 27mm Art. blood 7g x 1.39 x 100% = 10 ml Ven. blood 7g x 1.39 x 50% = 5ml Tissue extraction 50% = 5ml 1% = 0.1ml
  32. 32. Oxygen Therapy Indications
  33. 33. Oxygen Therapy Indications FIO2 Barometric Pressure PIO2
  34. 34. Oxygen Therapy Indications FIO2 - Barometric Pressure - High altitude FIO2 during anaes. - Rebreathing PIO2
  35. 35. Oxygen Therapy Indications FIO2 - Barometric Pressure - High altitude FIO2 during anaes. - Rebreathing PIO2 O2 Consumption Alveolar Ventilation PAO2
  36. 36. Oxygen Therapy Indications FIO2 - Barometric Pressure - High altitude FIO2 during anaes. - Rebreathing PIO2 O2 Consumption Alveolar Ventilation -convulsions -resp. depression -thyrotoxicosis -Resp. muscle paresis -shivering -pyrexia PAO2 - resp.effort (trauma) -airway obstruction
  37. 37. Oxygen Therapy Indications FIO2 - Barometric Pressure - High altitude FIO2 during anaes. - Rebreathing PIO2 O2 Consumption Alveolar Ventilation -convulsions -resp. depression -thyrotoxicosis -Resp. muscle paresis -shivering -pyrexia (7 % / o C) PAO2 - resp.effort (trauma) -airway obstruction
  38. 38. Oxygen Therapy Indications Low VA/Q Normal Anat. shunt PaO2
  39. 39. Oxygen Therapy Indications Low VA/Q Normal Anat. shunt Abn. Pulmonary shunt Abn.extra Pulm. Shunt •cong. heart disease - pneumonia -lobar atelectasis -ARDS PaO2 (R L)
  40. 40. Oxygen Therapy Indications Low VA/Q Normal Anat. shunt Abn. Pulmonary shunt Abn.extra Pulm. Shunt •cong. heart disease - pneumonia -lobar atelectasis PaO2 -ARDS Hypoxic hypoxia (R L)
  41. 41. Simple Rule Hypoxia due to hypoventilation Slight increase in O2 conc. (Thus the importance of ventimask) Higher O2 conc. – –
  42. 42. Simple Rule Hypoxia due to hypoventilation Slight increase in O2 conc. (Thus the importance of ventimask) Higher O2 conc. – hypercapnoea – absence of cynosis
  43. 43. Oxygen Therapy Indications Low VA/Q Normal Anat. shunt Abn. Pulmonary shunt Abn.extra Pulm. Shunt •cong. heart disease - pneumonia -lobar atelectasis PaO2 (R L) -ARDS Perfusion Hb concentration Cell PO2
  44. 44. Oxygen Therapy Indications Low VA/Q Normal Anat. shunt Abn. Pulmonary shunt Abn.extra Pulm. Shunt •cong. heart disease - pneumonia -lobar atelectasis PaO2 (R L) -ARDS Perfusion local - PVD, thrombosis gen – shock, Hypovol., card. Failure arrest cardiac Hb concentration -Anaemia Cell PO2 -CO poisoning
  45. 45. Which patient is better placed – ? A Anaemic patient Hb = 7gm % B Patient with Hb 14gm% Normal Hb 7gm% Hb Co 7gm%
  46. 46. Which patient is better placed – ? A B Anaemic patient Hb = 7gm % 2,3 DPG Shift to R Patient with Hb 14gm% Normal Hb 7gm% Hb Co 7gm% Shift to L unloading of O2 (blood PVO2 – ? tissue) unloading of O2 (blood PVO2 – ? tissue)
  47. 47. Which patient is better placed – ? A B Anaemic patient Hb = 7gm % 2,3 DPG Shift to R unloading of O2 (blood tissue) PVO2 – 27 mm Hg Patient with Hb 14gm% Normal Hb 7gm% Hb Co 7gm% Shift to L unloading of O2 (blood PVO2 – ? tissue)
  48. 48. Which patient is better placed – ? A B Anaemic patient Hb = 7gm % 2,3 DPG Shift to R unloading of O2 (blood tissue) PVO2 – 27 mm Hg Patient with Hb 14gm% Normal Hb 7gm% Hb Co 7gm% Shift to L unloading of O2 (blood tissue) PVO2 – 14mmHg
  49. 49. Hypoxia in co poisoning is out of proportion to degree of anemia
  50. 50. Which patient is better placed – ? A Anaemic patient Hb = 7gm % B Patient with Hb 14gm% Normal Hb 7gm% Hb Co 7gm% 2,3 DPG Shift to R Shift to L unloading of O2 (blood tissue) unloading of O2 (blood tissue) PVO2 – 27 mm Hg PVO2 – 14mmHg Cardiac Output
  51. 51. Dissolved O2 in plasma 0.003ml / 100ml of blood / mm PO2 Breathing Air (PaO2 100mm Hg) 0.3ml / 100ml of blood
  52. 52. Dissolved O2 in plasma 0.003ml / 100ml of blood / mm PO2 Breathing Air (PaO2 100mm Hg) 0.3ml / 100ml of blood Breathing 100% O2
  53. 53. Dissolved O2 in plasma 0.003ml / 100ml of blood / mm PO2 Breathing Air (PaO2 100mm Hg) 0.3ml / 100ml of blood Breathing 100% O2 (PaO2 600mm Hg) 1.8ml / 100ml of blood
  54. 54. Dissolved O2 in plasma 0.003ml / 100ml of blood / mm PO2 Breathing Air (PaO2 100mm Hg) 0.3ml / 100ml of blood Breathing 100% O2 (PaO2 600mm Hg) 1.8ml / 100ml of blood Breathing 100% O2 at 3 Atm. Pressure
  55. 55. Dissolved O2 in plasma 0.003ml / 100ml of blood / mm PO2 Breathing Air (PaO2 100mm Hg) 0.3ml / 100ml of blood Breathing 100% O2 (PaO2 600mm Hg) 1.8ml / 100ml of blood Breathing 100% O2 at 3 Atm. Pressure 5.4ml / 100ml of blood
  56. 56. Dissolved O2 in plasma 0.003ml / 100ml of blood / mm PO2 Breathing Air (PaO2 100mm Hg) 0.3ml / 100ml of blood Breathing 100% O2 (PaO2 600mm Hg) 1.8ml / 100ml of blood Breathing 100% O2 at 3 Atm. Pressure 5.4ml / 100ml of blood
  57. 57. Benefit of O2 therapy in Hypoxia Hypoxic hypoxia (gas phase) +++ Anaemic hypoxia (fluid phase – const.) + Stagnant hypoxia (fluid phase – flow) + Histotoxic hypoxia (tissue phase) -
  58. 58. Benefit of O2 therapy in Hypoxia Hypoxic hypoxia (gas phase) +++ Anaemic hypoxia (fluid phase – const.) + Stagnant hypoxia (fluid phase – flow) + Histotoxic hypoxia (tissue phase) Normal Person (breathing 100% O2) 14gm x 1.34ml = 18.7ml + 1.8ml = 20.5ml (1.8 is 9% 20.5)
  59. 59. Benefit of O2 therapy in Hypoxia Hypoxic hypoxia (gas phase) +++ Anaemic hypoxia (fluid phase – const.) + Stagnant hypoxia (fluid phase – flow) + Histotoxic hypoxia (tissue phase) Normal Person (breathing 100% O2) 14gm x 1.34ml = 18.7ml + 1.8ml = 20.5ml (1.8 is 9% 20.5) Anaemic patient (breathing 100% O2) 4gm x 1.34ml = 5.4ml + 1.8ml = 7.2 ml (1.8 is 25% of 7.2)
  60. 60. Oxygen Therapy Indications Physical effects of O2
  61. 61. Oxygen Therapy Indications Physical effects of O2 “Air in the body – where it should not be”
  62. 62. Oxygen Therapy Indications Physical effects of O2 “Air in the body – where it should not be” Surgical emphysema Pneumothorax Air embolism Bowel decompression
  63. 63. Gas Tensions mmHg Art. blood Ven. blood Breathing air PO2 100 40 PCo2 40 46 PN 2 570 570 PO2 600 ? PCo2 40 46 PN 2 0 0 Breathing 100% O2
  64. 64. Gas Tensions mmHg Art. blood Ven. blood Breathing air PO2 100 40 PCo2 40 46 PN 2 570 570 PO2 600 50 PCo2 40 46 PN 2 0 0 Breathing 100% O2
  65. 65. Tissue requirement per 100ml = 5ml Dissolved Fraction = 1.8 ml Balance = 3.2 ml 0.2ml x 16% = 3.2ml 84% saturation = PO2 50mm Hg
  66. 66. Oxygen Therapy Pre oxygenation / ? Indications
  67. 67. Oxygen Therapy Indications Pre oxygenation / denitrogenation To the O2 reserve in the body – ?
  68. 68. O2 stores in the body Breathing air Breathing 100% O2 Lungs (FRC) 450 ml 3000 ml Blood 1000 ml 1090 ml + + Tissue fluids / myoglobin
  69. 69. O2 Delivery systems
  70. 70. O2 Delivery systems Ambient pressure – Variable performance devices – Fixed performance devices
  71. 71. O2 Delivery systems Ambient pressure – Variable performance devices – Fixed performance devices Positive pressure ventilation – Non invasive (BIPAP, CPAP) – Invasive
  72. 72. O2 Delivery systems Ambient pressure – Variable performance devices – Fixed performance devices Positive pressure ventilation – Non invasive (BIPAP, CPAP) – Invasive ECMO
  73. 73. O2 Delivery systems Ambient pressure – Variable performance devices (Pt. dependent) low flow  No capacity system – no rebreathing nasal catheter / cannulae  Capacity system – chance of rebreathing – Small – (mass shell only) – Large – (with reservoir bag) – Fixed performance devices (Pt. independent) high flow  HAFOE (ventimask)  Anaesthesia circuits
  74. 74. High flow system The gas flow is sufficient to meet all inspiratory requirement Low flow system The gas flow is insufficient to meet all inspiratory requirement. Part of tidal volume is provided by room air.
  75. 75. Variables O2 flow rate Patient factors – – Device factors – –
  76. 76. Variables O2 flow rate Patient factors – Inspiratory flow rate – Expiratory time (active exp. flow + exp. pause) Device factors – –
  77. 77. Variables O2 flow rate Patient factors – Inspiratory flow rate – Expiratory time (active exp. flow + exp. pause) Device factors – Physical volume (capacity) – Vent resistance (tight fit)
  78. 78. Variable O2 flow rate Patient Insp. Flow rate Factors Exp. time Device Physical volume No cap. Devices FIO2 += –= + – + – + – + – Capacity devices FIO2 FICO2
  79. 79. Variable O2 flow rate Patient Insp. Flow rate Factors Exp. time Device Physical volume No cap. Devices FIO2 += –= + – + – + – + – Capacity devices FIO2 FICO2
  80. 80. Variable O2 flow rate Patient Insp. Flow rate Factors Exp. time Device Physical volume No cap. Devices FIO2 += –= + – + – + – + – Capacity devices FIO2 FICO2
  81. 81. Variable O2 flow rate Patient Insp. Flow rate Factors Exp. time Device Physical volume No cap. Devices FIO2 += –= + – + – + – + – Capacity devices FIO2 FICO2
  82. 82. Variable O2 flow rate Patient Insp. Flow rate Factors Exp. time Device Physical volume No cap. Devices FIO2 += –= + – + – + – + – Capacity devices FIO2 FICO2
  83. 83. Variable O2 flow rate Patient Insp. Flow rate Factors Exp. time Device Physical volume No cap. Devices FIO2 += –= + – + – + – + – Capacity devices FIO2 FICO2
  84. 84. Variable O2 flow rate Patient Insp. Flow rate Factors Exp. time Device Physical volume No cap. Devices FIO2 += –= + – + – + – + – Capacity devices FIO2 FICO2
  85. 85. Variable O2 flow rate Patient Insp. Flow rate Factors Exp. time Device Physical volume No cap. Devices FIO2 += –= + – + – + – + – Capacity devices FIO2 FICO2
  86. 86. Nasal Catheter O2 Flowrate (L/min) Fi O2 1 2 3 4 5 6 0.24 0.28 0.32 0.36 0.40 0.44
  87. 87. Normal Anatomic Reservoir (50ml) 6 Ltr/min = 100ml/sec = 50ml/1/2 Sec
  88. 88. Nasal Catheter Merits Easy to fix  Keeps hands free  Not much interference with further airway care  Useful in both spont. breathing and apnoeic 
  89. 89. 10-15 Ltr/min flow rate ----------- 50-60 % O2 conc.
  90. 90. Nasal Catheter Merits      Easy to fix Keeps hands free Not much interference with further airway care Useful in both spont. breathing and apnoeic Small but definite rise in FiO2 (dose not critical) Demerits Mucosal irritation (uncomfortable)  Gastric dilatation (especially with high flows) 
  91. 91. For higher O2 Concentration gadgets with storage capacity (reservoir) problem of re-breathing minimized / avoided by higher flows
  92. 92. Simple Face Mask – ? Simple face mask
  93. 93. Simple Face Mask Simple face mask NO YES
  94. 94. Simple face mask O2 Flowrate (L/min) Fi O2 5-6 6-7 7-8 0.40 0.50 0.60
  95. 95. Partial Rebreathing mask (polymask)
  96. 96. Partial Rebreathing mask (polymask) O2 Flowrate (L/min) Fi O2 6 7 8 0.60 0.70 0.80
  97. 97. Poly mask What type of circuit it is – ?
  98. 98. Poly mask What type of circuit it is – ? Modified T – Piece
  99. 99. Non Rebreathing mask Non Rebreathing Mask
  100. 100. 10 – 15 Ltr/min flow rate – 50-100 O2 conc.
  101. 101. Face Masks Merits  Higher Oxygen Conc. Demerits  Rebreathing (if O2 flow is inadequate)  Interfere with further airway care  Proper fitting is required  Uncomfortable (sweating, spitting)
  102. 102. Bag – Valve – Mask assembly (Ambu Resuscitator) Bag – Valve – Mask assembly (Ambu Resuscitator)
  103. 103. Bag – Valve – Mask assembly (Ambu Resuscitator)  Delivers  O2 O2 during BOTH spont. & artf. Vent concentration – 30 – 50% (without reservoir) – 80 – 100% (with reservoir)  To deliver 100% O2
  104. 104. Bag – Valve – Mask assembly (Ambu Resuscitator)  Delivers  O2 O2 during BOTH spont. & artf. Vent concentration – 30 – 50% (without reservoir) – 80 – 100% (with reservoir)  To deliver 100% O2 – Reservoir – as large as bag vol – O2 flow rate > minute volume (10 l/m)  Drawback – keeps rescuer’s hands engaged
  105. 105. Pocket Mask  Delivers O2 in BOTH spont. & aponeic  Allows use of both hands – for maintaining airway  Upto 4 ltr reserve vol. (rescuer’s vital capacity) O2 Flowrate (L/min) 5 10 15 Fi O2 0.40 0.50 0.80 (Spont.) 0.54 (M - mask)
  106. 106. Incubator  Small infants – not on ventilator  Works on venturi principle  Complete air change – 10 times / hour  Control of humidity & temperature  O2 conc. falls rapidly when access ports are open
  107. 107. O2 tents  For children – not tolerating mask / catheter  Large capacity system  Upto 50% O2 concentration  Large tent cap. and leak port – limited CO 2 build up.  Disadvantage – Limited access – Risk of fire – Conflict in O2 therapy / nursing care
  108. 108. Can You name the device ? Written over it – 28 % @ 4 L P M – ? If flow is doubled (8 LPM) – what will the %age of O2 delivered by the device ? If flow is halved (@ 2 LPM) – what will be the %age of O2 received by the patient ? What is the likely entertainment ratio of this device ? 1 2 4 8 16 What precaution to be taken for humidification of gases while using this device ?
  109. 109. F ix e d P e r fo r m a n c e D e v ic e C o n s ta n t I n s p ir a t o r y m ix tu re I n s p ir a to r y f lo w w a v e fo rm C o n t in o u s f lo w > P I F R R oom A n . C ir c u it w it h c o lla s ib le r e s e r v o ir HAFO E V e n t u ri X A p p. D e a d S pa ce R e b r e a t h in g K n o w n , fix e d & s e le c ta b le
  110. 110. •Works on principle of constant pressure jet – mixture. •O2 jet entrains air as per entrain. ratio. •Total flow > PIFR (30 – 35 L/min) •Eliminates the problem of dead space & leak free connection.
  111. 111. Ventimask
  112. 112. Simple Face Mask Simple face mask NO YES
  113. 113. •Works on principle of constant pressure jet – mixture. •O2 jet entrains air as per entrain. ratio. •Total flow > PIFR (30 – 35 L/min) •Eliminates the problem of dead space & leak free connection. •Upper limit is 60 %. •Humidification of O2 supply is not sensible.
  114. 114. If conc. of O2 which a patient is getting is not known then the situation is similar to a drug being administered without knowing the dose which can do harm if given more or provide insufficient effect if given less
  115. 115. O2 Toxicity 100% - not more than 12hrs 80% - not more than 24hrs 60% - not more than 36hrs
  116. 116. Rest (read it yourself)
  117. 117. www.anaesthesia.co.in anaesthesia.co.in@gmail.com

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