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

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IPHY 3430 9-27-11

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

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. 750 760 mmHg 770 760 Exhalation Inhalation

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

Factors that can affect gas exchange by influencing flow and lung volume Ventilation: Air Flow = P/ resistance SNS --bronchodilation PNS--bronchoconstriction Chronic obstructive pulmonary disease (COPD) Asthma,emphysema, chronic bronchitis Factors that reduce lung volume: pneumonia, cancer, tuberculosis

Gas exchange Between outside air and lungs= ventilation Between alveolar air and blood = diffusion Diffusion rate = P x surface area x solubility coefficient distance x M.W. 1/2

Physical principles governing diffusion 1. Gases diffuse down partial pressure gradient (P O2, P CO2, P N2, etc) 2. Diffusion of one gas unaffected by diffusion of another 3. In lungs, all gases diffuse through water 4. The bigger the partial pressure gradient, the faster the rate of diffusion.

Partial pressures of gases (mm Hg) GasAirAlveolar N 2 597 (78.6%) 569 (74.9%) O 2 159 (20.8%)104 (13.6%) CO 2 0.3 ( 0.04%)40 (5.3%) H 2 03.7 (0.5%)47 (6.2%) 760760

Oxygen Diffusion at rest Air--> alveoli-->arteriolar blood--> cells (159) (100)(100) (40) lungs venous arteriolar cells 100 40 PO2 = 60

Oxygen Diffusion during exercise Air--> alveoli-->arteriolar blood--> cells (159) (100)(100) (20) lungs venous arteriolar cells 100 20 PO2 = 80

CO 2 Diffusion during rest Air<-- alveoli <--venous blood <-- cells (.3) (40)(46) (46) lungs venous arteriolar cells 40 46 PCO2 = 6

CO 2 Diffusion during exercise Air<-- alveoli <--venous blood <-- cells (.3) (40)(55) (55) lungs venous arteriolar cells 40 55 PCO2 = 15

During exercise: Alveolar PO2 (104) and PCO2 (40) MUST be 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) lungs venous arteriolar cells 40 55 PCO2 = 15 CO2 must rise

High Altitude AltitudePbPO2 Alveolar PO2 sea level 760 159104 10,000523 11067 20,000349 7340

At 10,000 ft Air--> alveoli --> arteriolar blood --> cells (110) (67)(67) (40) lungs venous arteriolar cells 67 40 PO2 = 27

At 20,000 ft Air--> alveoli --> arteriolar blood --> cells (73) (40)(40) (must be >40) lungs venous arteriolar cells 40 20 PO2 = 20

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