Presentation on theme: "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."— Presentation transcript:
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.
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