Basic Pulmonary Mechanics during Mechanical Ventilation

1. Basic Pulmonary Mechanics during Mechanical Ventilation

2. Points of Discussion Basics , scalars and loops Abnormalities Air Leak Auto PEEP and air trapping Active Exhalation Inadequate insp flow Obstruction Trigger sensitivity Increased airway resistance Inadequate flow support Inadequate sensitivity Atelectasis Inadequate PEEP Over-distension • Equation of motion • Airway pressures • Compliance • Resistance • Pressure-Time • Flow-Time • Pressure-volume loop • Flow-volume loop • Work of breathing • Hysterexis

3. Spontaneous Breathing Exhalation Inspiration

4. Precondition of Inspiration Gas Flow Pa • Pa<Pb • Spontaneous breath • Pb>Pa • Mechanical ventilation Pa<Pb Pb

5. Spontaneous Inspiration Volume Change Pressure Difference Gas Flow

6. Mechanical Ventilation Pressure Difference Gas Flow Volume Change

7. Airway Resistance “The Feature of the Tube” D P R = D F Pressure Difference = Flow Rate x Resistance of the Tube

8. Compliance Volume D V D P Pressure D V C= D P Volume Change= Pressure Difference x Compliance of the Balloon

9. Tube + Spring Model Resistive Forces Elastic Forces

10. Basic Calculations dP = R x Flow + dV / C st Pressure Pplat PEEP time Cst = dV / (Pplat-PEEP) R = (PIP-Pplat) / Flow

11. Lung Mechanics transairway pressure transrespiratory pressure transthoracic pressure volume elastance = Dpressure / Dvolume resistance = Dpressure / Dflow flow

12. Pressure vs TimeSpontaneous Breath Expiration Paw (cm H20) Time (sec) Inspiration

13. Pressure vs TimeMechanical Breath Peak Inspiratory Pressure PIP PEEP Paw (cm H2O) Inspiration Expiration TI TE } Time (sec)

14. Spontaneous vs. Mechanical Mechanical Inspiration Paw (cm H2O) Spontaneous Expiration Expiration Inspiration Time (sec)

15. Assisted vs Controlled Assisted Controlled Pressure (cmH20) Time (sec)

16. Components of Inflation Pressure Pplateau (Palveolar) Begin Inspiration PIP } Transairway Pressure (PTA) Paw (cm H2O) Inspiratory Pause Expiration Time (sec) Begin Expiration

17. Exhalation Valve Opens Begin Inspiration Inflation Hold (seconds) Pplateau (Palveolar Paw (cm H2O) Time (sec) PIP } Transairway Pressure (PTA) Paw (cm H2O) Expiration Time (sec) Begin Expiration PIP Distending (Alveolar) Pressure Airway Resistance Expiration Begin Inspiration Begin Expiration

18. PIP vsPplat PIP High Raw Normal PIP PPlat PPlat Paw (cm H2O) Low Compliance PIP PIP PPlat High Flow PPlat Time (sec)

19. Mean Airway Pressure Lengthen Inspiratory Time Increase peak pressure Increase PEEP Increase Rate Increase Flow

20. Increasing Mean Airway Pressure 1. Increase flow 2. Increase peak pressure 3. Lengthen inspiratory time 4. Increase PEEP 5. Increase Rate

21. Flow vs Time Inspiration Time (sec) Flow (L/min) Expiration

22. Flow Patterns SQUARE DECELERATING ACCELERATING SINE

23. Flow Patterns and Effects of Volume ACCELERATING SINE DECELERATING SQUARE

24. Inspiratory Flow Pattern Total cycle time TCT Beginning of expiration exhalation valve opens Peak inspiratory flow rate PIFR Inspiration Inspiratory Time TI Expiratory Time TE Flow (L/min) Time (sec) Beginning of inspiration exhalation valve closes Expiration

25. Expiratory Flow Pattern Beginning of expiration exhalation valve opens Duration of expiratory flow Peak Expiratory Flow Rate PEFR Inspiration Expiratory time TE Time (sec) Flow (L/min) Expiration

26. Spontaneous Breath Inspiration Time (sec) Flow (L/min) Expiration

27. Mechanical vs Spontaneous Mechanical Spontaneous Inspiration Expiration

28. Increased Expiratory Resistance Flow Time Normal Resistance Increased Resistance

29. Response to Bronchodilator After Before Time (sec) Flow (L/min) Long TE PEFR Shorter TE Higher PEFR

30. Insufficient Expiratory Time Flow Time End-Expiratory Flow

31. Air Trapping Air Trapping Auto-PEEP Normal Patient Inspiration Time (sec) Flow (L/min) } Expiration

32. Excessive Secretions Normal Patient Inspiration Time (sec) Flow (L/min) Expiration

33. Air Leak (Flow Trigger, autotriggering) Inspiration Time (sec) Flow (L/min) Leak in LPM Expiration

34. Active Inspiration or Asynchrony Patient’s effort Normal Abnormal Time (sec) Flow (L/min)

35. Excessive Inspiratory Time Air Trapping Auto-PEEP Normal Patient Inspiration Increase WOB and “Fighting” of the ventilator Time (sec) Flow (L/min) } Expiration

36. Obstruction vs Active Expiration Obstruction Active Expiration Time (sec) Flow (L/min) Normal Abnormal

37. Trigger Sensitivity Sensitivity level Pressure Time Flow Time

38. Volume vs. Time Inspiratory Tidal Volume Volume (ml) Inspiration Expiration TI Time (sec)

39. Active Exhalation Volume (ml) Time (sec)

40. Inadequate Inspiratory Flow Adequate Flow Inadequate Flow Paw (cm H2O) Time (sec)

41. Air Leak Air Leak Volume (ml) Time (sec)

42. Air Leak Pressure Flow Expiratory flow area less than inspiratory flow area Expired volume Inspired volume Volume Leak

43. FRC and PV Loop Normal Compliance TLC VOLUME FRC FRC Negative Positive 0 DISTENDING PRESSURE

44. Components of Pressure-Volume Loop VT Expiration Volume (mL) Inspiration PIP Paw (cm H2O)

45. Pressure-Volume Loop(Type of Breath) E E Vol (ml) E I I I Paw (cm H2O) Spontaneous Controlled Assisted I: Inspiration E: Expiration

46. PEEP and P-V Loop VT PEEP PIP Volume (mL) Paw (cm H2O)

47. Inflection Points Upper Inflection Point Lower Inflection Point • Upper Inflection Point: Represents pressure resulting in regional overdistension • Lower Inflection Point: Represents minimal pressure for adequate alveolar recruitment Volume (mL) Pressure (cm H2O)

48. Decreased Compliance Normal Patient Volume(ml) Pressure (cm H2O)

49. Lung Compliance Changes and the P-V Loop Volume Targeted Ventilation Preset VT Increased Normal Decreased Volume (mL) Paw (cm H2O) PIP levels

50. Lung Compliance Changes and the P-V Loop VT levels Increased Normal Pressure Targeted Ventilation Decreased Volume (mL) Preset PIP Paw (cm H2O)