1. Principles of Mechanical Ventilation Mazen Kherallah, MD, FCCP

2. Oxygenation Parameters Alveolar P O2 Arterial P O2 Tension-based indices –P (A-a)o2 –P aO2 /P AO2 –P aO2 /F iO2 Respiratory index Pulmonary Shunt

3. Distribution of Normal Ventilation-Perfusion Ratios 1 10 0.10

4. Oxygenation Status Monitoring Alveolar - arterial Oxygen Tension Difference P (A-a)o2 PAo2 = Fio2 (PB-P H2O ) - Pa co2 /R = (Fio2  713) - (Pa co2 /0.8) at sea level = 150 - (Pa co2 /0.8) at sea level on room air A-a Gradient = PAo2 - PaO2 Normal Value: 5-25 mmHg

5. Oxygenation Status Monitoring A-a Gradient Increased: –Decreased Fio2 –V/Q mismatch –Shunting process –Diffusion abnormalities Decreased –Hyperventilation –Increased Fio2

6. Pa O2 /PA O2 Remains stable when FiO2 changes Can be used to determined FiO2 needed for desired PO2 –FiO2 needed=[(desired PaO2)/(PaO2/PAO2)+Paco2]/(PB-47) Value of less than 0.75 indicates pulmonary dysfunction due to V/Q abnormality, shunt or diffusion abnormality

7. Pa O2 /FI O2 Oxygenation index Value of less than 200 is associated with severe shunt in patients with acute respiratory failure Easy to calculate

8. Respiratory Index P(A-a) O2 /PaO2 Normal value 0.1 Values higher than 0.1 indicate respiratory abnormality Better indicator of oxygenation dysfuntion

9. Pulmonary Shunt Q S /Q T = (CcO2-CaO2)/(CcO2-CvO2) Q S /Q T = (CcO2-CaO2)/(3.5+ CcO2-CaO2) when pulmonary catheter is not in place

10. Oxygenation Status Monitoring Oxygen Delivery Do2 = CI  Ca O2 CaO2 = SaO2  1.36  Hgb + (0.0031  PaO2) CI = CO/ BSA Normal Value: 800-1200 mL/min

11. Oxygenation Dissociation Curve

12. Oxygenation Status Monitoring Oxygen Consumption Vo2=CI (CaO2-CvO2) CaO2 = SaO2  1.36  Hgb + (0.0031  PaO2) CvO2 = SvO2  1.36  Hgb + (0.0031  PvO2) Normal Value: 225-275 mL/min

13. Oxygenation Status Monitoring Oxygen Extraction O2 ext = Vo2 / Do2 Normal value: 27%

14. Oxygenation Status Monitoring Relationship between Vo2 and Do2

15. Oxygenation Status Monitoring Oxygen Transport Variables

16. Anatomic and Capillary Shunts

17. Dead Space

18. Ventilation-Perfusion Inequality Acute Exacerbation of COPD 0.01 0.1 1 10 100

19. Ventilation-Perfusion Inequality Asthma 0.01 0.1 1 10 100

20. Ventilation-Perfusion Inequality Pulmonary Embolism 0.01 0.1 1 10 100

21. Shunting Process ARDS 0.01 1 10 100

22. The Effect of Increasing Ventilation- Perfusion Inequality on Arterial Po2 and Pco2

23. The effect of changing the inspired oxygen concentration on arterial Po2 for lung’s shunts of 10 to 50%

24. Assessment of Hypoxia

25. Ventilation Status Monitoring Tidal Volume: Vt Minute ventilation: Vm Respiration Rate: RR CO2 production: Vco2 Dead Space: V DS /V T

26. Dead Space Ventilation V D /V T =(Pa CO2 -PE CO2 )/Pa CO2 Normal is 0.2-0.4 PEco2 is measured by collecting condensate from the water trap on the expiratory limb of the ventilator circuit and the measure PCO2 using blood gas analyzer

27. Causes of Increased Dead Space Ventilation Pulmonary embolism pulmonary hypoperfusion positive pressure ventilation High rate-low tidal volume ventilation

28. Arterial CO2 Pa CO2 = V CO2. 0.863/V E.(1-Vd/Vt)

29. High Minute Ventilation Increased CO2 production –Sepsis –Fever –Thyrotoxicosis –High carbohydrate feeding Increased ventilation: –Agitation –Pain –Central hyperventilation –Increased dead space

30. Low Minute Ventilation Decreased CO2 production –Hypothermia –Hypothyroidism –Severe sedation –Low carbohydrate feeding –Paralysis Decreased ventilation: –Sedation –Central hypoventilation –Decreased dead space

31. Airway Pressure Waveform

33. Pulmonary Mechanics Peak pressure Plateau pressure I E Airway Resistance

34. Mean Airway Pressure Paw= (PIP-PEEP).(T I /T T )+PEEP.(T E /T T )

35. Methods to Increase Mean Airway Pressure Increase in tidal volume Increase in respiratory frequency Reduction in T E Decrease in respiratory flow rate: increase in T I Addition of end-inspiratory pause Addition of PEEP

36. Equation of Motion

37. Work of Breathing Mechanical work is performed when a force moves its point of application through a distance In the case of three dimensional fluid system, work is done when a pressure (P) changes the volume (V) of the system W = P.V: {PIP-(0.5). (Pplat)/100}.v T 0.5 J/L

38. Static Pressure-volume curve in ARDS

39. Ventilatory System

40. Control Variables during Inspiration

41. Phase Variables

42. Modes of Ventilation

43. Breath Type during Mechanical Ventilation

44. Pressure Waveforms

45. Flow, Pressure, and Volume Waveforms with Constant Flow, Volume Ventilation

46. Flow, Pressure, and Volume Waveforms with Decelerating Ramp Flow, Volume Ventilation

47. Waveforms for Decelerating and Accelerating Ramp Flows

48. Full and Partial Decelerating Ramp Flow with Volume Ventilation

49. Flow, Pressure, and Volume Waveforms with Pressure Ventilation

50. Full and Modified Sine-flow Waveforms during Volume Ventilation

51. Flow, Pressure, and Volume Waveforms with Pressure Support Ventilation

52. Active Inspiration during Positive Pressure Ventilation

53. Airway Flow Waveform during Mechanical Ventilation

54. Airway Volume Waveform during Mechanical Ventilation

55. Flow-Volume and Pressure-Volume loops with COPD

56. Changes in Flow-Volume and Pressure- Volume loops with Bronchodilators

57. Pressure-Volume Loop Work Performed to Trigger the Ventilator

58. Pressure-Volume Loop Lung/Chest Wall Compliance

59. Dynamic Pressure-Volume LOOP Restrictive Work

60. Inspiratory Work of Breathing

61. Pressure-Volume Loop Deflection Points

62. Modes of Mechanical Ventilation Volume-Cycled Control Mode Ventilation

63. Modes of Mechanical Ventilation Assist-Control Ventilation

64. Indications: – for patients who are awake, moderately sedated or paralyzed and able to initiates ventilation –increase metabolic demands: infection, burns, multisystem organ failure –Respiratory muscle strengthening and weaning Limitations: –patient-ventilator dysynchrony –ventilator assisted hyperventilation in agitated patients with increased inspiratory drive –auto-PEEP in COPD patients

65. Modes of Mechanical Ventilation Intermittent Mandatory Ventilation

66. Modes of Mechanical Ventilation Synchronized Intermittent Mandatory Ventilation

67. Pressure Waveform for SIMV

68. Synchronized Intermittent Mandatory Ventilation Indications: –patients with minimal spontaneous respiratory efforts –respiratory muscle conditioning –ventilator weaning Limitations: –patient-ventilator dysynchrony especially in agitated patients –nonphysiologic way of respiratory muscle conditioning

69. Modes of Mechanical Ventilation Pressure Support Ventilation

70. Indications: –weaning –more physiologic conditioning of respiratory muscles: low pressure-high volume load –improved patient- ventilator dysynchrony Limitations:

71. Modes of Mechanical Ventilation Inverse Ratio Ventilation

72. Auto-PEEP

74. Normal Lung Mechanics and Gas Exchange

75. Severe Airflow Obstruction

76. Acute on Chronic Respiratory Failure

77. Acute Hypoxemic Respiratory Failure