人工通气参数的变化对FETCO_2和mean PACO_2的影响

EFFECT OF CHANGES IN VENTILATING PARAMETERS ON FETCO2 AND MEAN PACO2

推导出了人体在稳定的呼吸过程中，一次呼吸周期内肺泡气的瞬时ＣＯ２浓度，以及本周期内肺泡气的平均ＣＯ２分压（ｍｅａｎＰＡＣＯ２）和呼吸末ＣＯ２百分比浓度（ＦＥＴＣＯ２）的计算公式。在保持相对稳定的代谢率和肺泡通气量的条件下，模拟计算一组不同通气频率和潮气量时的ｍｅａｎＰＡＣＯ２和ＦＥＴＣＯ２。在通气频率增加（或降低）后，１）调节潮气量以维持ｍｅａｎＰＡＣＯ２值在正常通气时的水平将引起ＦＥＴＣＯ２的降低（或上升）；２）调节潮气量以维持ＦＥＴＣＯ２值在正常通气时的水平将引起ｍｅａｎＰＡＣＯ２的降低（或上升），这意味着此时肺泡通气不足（或通气过度）发生了，从而导致体内化学环境的不稳定。

athematical formulas for calculating instantaneous concentration, mean PACO2 and endtidal FCO2(FETCO2) of alveolar carbon dioxide during breathing cycle were derived. The mean PACO2 and FETCO2 with different simulated ventilating parameters, such as ventilating frequency f and ventilating volume VT, were calculated under the conditions of relatively stable metabolic rate and minute alveolar ventilation. After f was increased(or decreased),1) adjusting VT to maintain mean PACO2 constant at its reference value in normal ventilation would caused FETCO2 descend (or rise); 2) adjusting VT to maintain FETCO2 constant at its reference value in normal ventilation would result in rise (or fall) of mean PACO2, which implied that alveolar hypoventilation (or hyperventilation) occurred at that time.