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IPHY 3430 9-27-11

IPHY 3430 9-27-11. Review: During inhalation/exhalation at rest: pressure differential of about 1 mm . 760. 759 mmHg. 761. 760. Exhalation at rest. Inhalation at rest.

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IPHY 3430 9-27-11

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  1. IPHY 3430 9-27-11

  2. Review:During inhalation/exhalation at rest:pressure differential of about 1 mm 760 759 mmHg 761 760 Exhalation at rest Inhalation at rest

  3. Review:During exercise, pressure differentials greater than 1 mm generated due to greater numbers of muscles contracting with greater force, resulting in larger expansion of thoracic cavity and lungs. Inhalation Exhalation 760 750 770 760 mmHg

  4. So,…..Quiet breathing: 500 ml x 12 b/m = 6 L/minExercise: 2300 ml x 40-50 b/m = 100-120 L/ min

  5. Factors that can affect gas exchange by influencing flow and lung volumeVentilation: Air Flow = P/ resistance SNS --bronchodilationPNS--bronchoconstrictionChronic obstructive pulmonary disease (COPD)Asthma,emphysema, chronic bronchitisFactors that reduce lung volume: pneumonia, cancer, tuberculosis

  6. Gas exchangeBetween outside air and lungs= ventilationBetween alveolar air and blood = diffusionDiffusion rate = P x surface area x solubility coefficient distance x M.W.1/2

  7. Physical principles governing diffusion1. Gases diffuse down partial pressure gradient (PO2, PCO2, PN2, etc)2. Diffusion of one gas unaffected by diffusion of another3. In lungs, all gases diffuse through water 4. The bigger the partial pressure gradient, the faster the rate of diffusion.

  8. Partial pressures of gases (mm Hg)Gas Air AlveolarN2 597 (78.6%) 569 (74.9%)O2 159 (20.8%) 104 (13.6%)CO2 0.3 ( 0.04%) 40 (5.3%)H20 3.7 (0.5%)47 (6.2%) 760 760

  9. Oxygen Diffusion at restAir--> alveoli-->arteriolar blood--> cells(159) (100) (100) (40) 100  PO2 = 60 arteriolar lungs cells 100 40 40  PO2 = 60 venous

  10. Oxygen Diffusion during exerciseAir--> alveoli-->arteriolar blood--> cells(159) (100) (100) (20) 100  PO2 = 80 arteriolar lungs cells 100 20 20  PO2 = 80 venous

  11. CO2 Diffusion during restAir<-- alveoli <--venous blood <-- cells (.3) (40) (46) (46) 40  PCO2 = 6 arteriolar lungs cells 40 46 46  PCO2 = 6 venous

  12. CO2 Diffusion during exerciseAir<-- alveoli <--venous blood <-- cells (.3) (40) (55) (55) 40  PCO2 = 15 arteriolar lungs cells 40 55 55  PCO2 = 15 venous

  13. During exercise:Alveolar PO2 (104) and PCO2 (40) MUSTbe maintained at those levels by increased rate and depth of ventilation in order to ensure that partial pressure gradients are as large as possible.Air<-- alveoli <--venous blood <-- cells (.3) (40) (55) (55) 40  PCO2 = 15 arteriolar lungs cells 40 55 55  PCO2 = 15 venous CO2 must rise

  14. High AltitudeAltitude Pb PO2 Alveolar PO2sea level 760 159 104 10,000 523 110 67 20,000 349 73 40

  15. At 10,000 ftAir--> alveoli --> arteriolar blood --> cells (110) (67) (67) (40) 67  PO2 = 27 arteriolar lungs cells 67 40 40  PO2 = 27 venous

  16. At 20,000 ftAir--> alveoli --> arteriolar blood --> cells (73) (40) (40) (must be >40) 40  PO2 = 20 arteriolar lungs cells 40 20 20  PO2 = 20 venous

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