1、麻醉通氣（英文）Ventilation麻醉通氣（英文）Ventilation麻醉通氣（英文）Measurement of GasesTotal Pressurecombined pressure of all atmospheric gases760 mm Hg or torr at sea levelPartial PressurePressure exerted by each gas of a mixtureAtmosphericNitrogen 597.0 torr (78.62%); Oxygen 159.0 torr (20.84%); Carbon Dioxide 0.3 tor

2、r (0.04%); Water 3.7 torr (0.5%)麻醉通氣（英文）Measurement of GasesPartial PressuresAlveolar Nitrogen 569.0 torr (74.9%); Oxygen 104.0 torr (13.7%); CO2 40.0 torr (5.2%); Water 47.0 torr (6.2%)麻醉通氣（英文）RespirationVentilation vs. RespirationExchange of gases between a living organism and its environmentExter

3、nal Respirationexchange between lungs & blood cellsInternal Respirationexchange between blood cells & tissues麻醉通氣（英文）RespirationHow are O2 and CO2 transported?Diffusiondefinitiongases dissolved in water and pass through alveolar membraneFiO2% of oxygen in inspired air (e.g. FiO2 = 0.95)麻醉通氣（

4、英文）RespirationOxygen Content of Blooddissolved O2 crosses pulm cap membrane and binds to Hgb of RBCTransport = O2 bound to hemoglobin (97%) or dissolved in plasmaO2 Saturation: % of hemoglobin saturated with oxygen (usually carries 96% of total)O2 content divided by O2 carrying capacity麻醉通氣（英文）Respi

5、rationOxygen saturation affected by:low Hgb (anemia, hemorrhage)inadequate oxygen availability at alveolipoor diffusion across pulm membrane (pneumonia, pulm edema, COPD)Ventilation/Perfusion (V/Q) mismatch blood moves past collapsed alveoli (shunting)alveoli intact but blood flow impaired麻醉通氣（英文）Re

6、spirationCarbon Dioxide content of bloodByproduct of work (cellular respiration)Transported as bicarbonate (HCO3- ion) 20-30% bound to hemoglobinPressure gradient causes CO2 diffusion into alveoli from bloodincreased level - hypercarbia麻醉通氣（英文）Anatomy of the Lower Airway麻醉通氣（英文）Alveoli PO2 100 & PCO2 40PO2 40 & PCO2 46 - Pulmonary circulation - PO2 100 & PCO2 40 HeartPO2 40 & PCO2 46 - Systemic circulation - PO2 10