Basic Pulmonary Mechanics during Mechanical Ventilation

Basic Pulmonary Mechanics during Mechanical Ventilation

Basic Pulmonary Mechanics during Mechanical Ventilation

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Presentation Transcript

1. Basic Pulmonary Mechanics during Mechanical Ventilation Equation of Motion dP=Rx Flow +dV / C st

2. Points of Discussion • Equation of motion • Airway pressures • Compliance • Resistance • Pressure-Time • Flow-Time • Pressure-volume loop • Flow-volume loop

3. Spontaneous Breathing Exhalation Inspiration

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

5. Lung Mechanics transairway pressure transrespiratory pressure transthoracic pressure volume compliance= Dvolume/ Dpressure resistance = Dpressure / Dflow flow

6. Tube + Spring Model Resistive Forces Elastic Forces

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

8. Compliance Volume D V D P Pressure D V Cs= D P Pressure Difference = Volume Change/ Compliance

9. Compliance and Resistance D P R = D F D V Cs= D P

10. Equation of Motion DYNAMIC CHARACTERISTICS: dP = dV / Cdyn RESISTANCE: dPresistive= R x Flow STATIC COMPLIANCE: dPdistensive = dV / Cst dP = dPresist. + dP dist. dP = R x Flow + dV / C st

11. Equation of Motion dP=Rx Flow +dV / C st

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

13. 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

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

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

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

17. Inspiratory Flow Pattern Total cycle time TCT Peak Expiratory Flow Rate PEFR 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

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

19. Flow Patterns SQUARE DECELERATING ACCELERATING SINE

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

21. Mechanical vs Spontaneous Mechanical Spontaneous Inspiration Expiration

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

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

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

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

26. Thank You