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Pulmonary Mechanics

Pulmonary Mechanics. Pulmonary mechanics describes the bellows function of the lung It describes the forces and resistances that determine the flow of gas in and out of the lung Mechanical properties include both elastic and resistive properties

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Pulmonary Mechanics

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  1. Pulmonary Mechanics • Pulmonary mechanics describes the bellows function of the lung • It describes the forces and resistances that determine the flow of gas in and out of the lung • Mechanical properties include both elastic and resistive properties • Elastic properties determine volume capacities • Resistive properties determine flow characteristics

  2. Inspiratory Reserve Volume Inspiratory Capacity Vital Capacity Total Lung Capacity Tidal Volume Expiratory Reserve Volume Functional Residual Capacity Residual Volume Spirometry

  3. Boundary Conditions TLC VT ERV FRC RV VOLUME RV TIME Which of these can be measured with a spirometer ? Answer: NONE

  4. Lung Mechanics: Elastic Properties Law of Laplace P = 2T R Hysteresis

  5. Surface Tension is Not All Bad

  6. Lung Mechanics: Elastic Properties Paw=Pcw + Pel

  7. Lung Mechanics: Regional Lung Volumes

  8. Lung Mechanics: Regional Lung Volumes

  9. Lung Mechanics: Closing Volume Expired Nitrogen Conc.

  10. Lung Mechanics: Resistance Properties Viscosity dependent Density dependent

  11. Lung Mechanics: Resistance Properties Cond = 1/AWR

  12. Lung Mechanics: Resistance Properties

  13. Lung Mechanics: Resistance Properties 5 23

  14. The Problem of Measuring Airway Pathology • Earliest changes in COPD occur in small airways (respiratory bronchioles) • Measurements of airway resistance evaluate the diameter of large conducting airways

  15. Lung Mechanics: Pressure Flow Relationships

  16. Lung Mechanics: Pressure Flow Relationships

  17. Lung Mechanics: Pressure Flow Relationships If you're not confused, you're not paying attention.

  18. Pel - Ptm' Vmax = Rus • Elastic Recoil Pressure (Pel) • Upstream airway Resistance (Rus) • Airway closing pressure (Ptm′)

  19. Emphysema Asthma Bronchitis, Bronchiolitis

  20. Body Plethysmography

  21. MP BP MP BP . V Lung Mechanics: Body Plethysmography Mouth P Volume Mode Flow Shutter Assembly X Y Resistance Mode Box P

  22. MP BP Pressure Flow Slope 2 Slope 1 Raw = = Body Plethysmography: Resistance Mode . V BP Shutter Closed Slope 2 = Mouth Pressure  Box Pressure Shutter Open Slope 1 = Flow  Box Pressure 1 / Raw = Gaw Gaw / Vtg = SGaw

  23. Measuring Lung Volume by Body Plethysmography DuBois, AB, Botelho, SY, Bedell, GN, Marshall, R, Comroe (Jr), JH. A rapid plethysmographic method for measuring thoracic gas volume: a comparison with a nitrogen washout method for measuring functional residual capacity in normal subjects. J. Clin. Invest. 1956. 35:322-326. DuBois, AB, Botelho, SY, Comroe (Jr), JH. A new method for measuring airway resistance in man using a body plethysmograph; values in normal subjects and in patients with respiratory disease. J. Clin. Invest. 1956. 35:327-335.

  24. What is the best definition of Lung Mechanics? • The bellows properties of the lungs that determine air flow • People who repair lungs • God’s version of “Trust me” • Chaos and complexity • All of the above

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