Scheller M S, Jones B R, Benumof J L
Department of Anesthesiology, University of California, San Diego 92103.
J Cardiothorac Anesth. 1989 Oct;3(5):564-7. doi: 10.1016/0888-6296(89)90153-1.
The relative importance of fresh gas flow and inspiratory/expiratory ratio in determining delivered tidal volume and PaCO2 was studied in anesthetized adult patients ventilated with a fixed ventilator bellows volume. The fresh gas flows studied were 2, 6, and 10 L/min, and inspiratory/expiratory ratio was either 1:2 or 1:4.5. Bellows volume and respiratory rate were held constant throughout the study. At the lowest fresh gas flow and smallest inspiratory/expiratory ratio, PaCO2 was 43 +/- 2 mm Hg. The PaCO2 decreased progressively and significantly with each increase in fresh gas flow during ventilation with either inspiratory/expiratory ratio setting. PaCO2 averaged 30 +/- 3 during ventilation with the highest fresh gas flow and largest inspiratory/expiratory ratio. As fresh gas flow increased, PaCO2 and tidal volume changed to a significantly greater degree in response to changes in inspiratory/expiratory ratio. These data demonstrate that altering either fresh gas flow or inspiratory/expiratory ratio can produce clinically significant perturbations in PaCO2 and tidal volume during anesthesia. These perturbations occur even if bellows volume is held constant. Furthermore, changes in inspiratory/expiratory ratio will affect these parameters to a greater degree as fresh gas flow is increased.
在使用固定通气皮囊容量对成年麻醉患者进行通气的过程中，研究了新鲜气体流量和吸呼比在决定潮气量和动脉血二氧化碳分压（PaCO2）方面的相对重要性。所研究的新鲜气体流量为2、6和10升/分钟，吸呼比为1:2或1:4.5。在整个研究过程中，皮囊容量和呼吸频率保持恒定。在最低的新鲜气体流量和最小的吸呼比时，PaCO2为43±2毫米汞柱。在任何一种吸呼比设置下进行通气时，随着新鲜气体流量的每次增加，PaCO2均逐渐且显著下降。在最高的新鲜气体流量和最大的吸呼比通气时，PaCO2平均为30±3。随着新鲜气体流量增加，PaCO2和潮气量对吸呼比变化的反应程度显著增大。这些数据表明，在麻醉期间，改变新鲜气体流量或吸呼比均可导致PaCO2和潮气量出现具有临床意义的波动。即使皮囊容量保持恒定，这些波动仍会发生。此外，随着新鲜气体流量增加，吸呼比的变化对这些参数的影响程度会更大。
