Artru A A, Katz R A
Department of Anesthesiology, University of Washington School of Medicine, Seattle 98195.
Can J Anaesth. 1987 Sep;34(5):484-8. doi: 10.1007/BF03014355.
A new breathing circuit (the Humphrey A.D.E., double lever model) was evaluated in adults to determine (1) the fresh gas flow (FGF) needed to achieve normocapnia during controlled ventilation and to just induce rebreathing during spontaneous ventilation, (2) end-expired CO2 (PECO2) at those FGF values, (3) the standard deviation of FGF requirements for controlled and spontaneous breathing (reliability of recommended FGF settings) and (4) the magnitude of change in PECO2 produced by varying FGF from the recommended values (sensitivity of the system). The FGFs that provided normocapnia with controlled ventilation and just induced rebreathing with spontaneous ventilation were 67 +/- 10 and 52 +/- 7 ml . kg-1 . min-1 (mean +/- SD), respectively. PECO2 values were 36.0 +/- 0.3 and 41.6 +/- 3.9 mmHg respectively. During controlled ventilation low reliability was offset by low sensitivity so that PECO2 changed little when FGF was raised or lowered from recommended values (0.2 mmHg/ml . kg-1 . min-1). In contrast, during spontaneous ventilation low reliability was additive with high sensitivity when using FGFs lower than the mean value that just induced rebreathing. A threshold was reached where lowering FGF from recommended values caused large changes in PECO2 (1.1 mmHg/ml . kg-1 . min-1). It is concluded that the FGF recommended by Humphrey for controlled ventilation is satisfactory. However, the FGF recommended by Humphrey for spontaneous ventilation may result in hypercapnia in some patients. This can be prevented either by using a higher FGF of 66 ml . kg-1 . min-1 routinely in all patients or by using lower flows with CO2 monitoring.
对一种新型呼吸回路（汉弗莱A.D.E.双杠杆模型）在成人中进行了评估，以确定：(1) 在控制通气期间实现正常碳酸血症以及在自主通气期间刚好引起重复呼吸所需的新鲜气体流量（FGF）；(2) 这些FGF值时的呼气末二氧化碳（PECO2）；(3) 控制呼吸和自主呼吸时FGF需求的标准差（推荐FGF设置的可靠性）；以及(4) 将FGF从推荐值改变所产生的PECO2变化幅度（系统的敏感性）。在控制通气时提供正常碳酸血症且在自主通气时刚好引起重复呼吸的FGF分别为67±10和52±7 ml·kg-1·min-1（平均值±标准差）。PECO2值分别为36.0±0.3和41.6±3.9 mmHg。在控制通气期间，低可靠性被低敏感性所抵消，因此当FGF从推荐值升高或降低时，PECO2变化很小（0.2 mmHg/ml·kg-1·min-1）。相比之下，在自主通气期间，当使用低于刚好引起重复呼吸的平均值的FGF时，低可靠性与高敏感性相加。当FGF从推荐值降低时，会达到一个阈值，此时PECO2会发生较大变化（1.1 mmHg/ml·kg-1·min-1）。结论是，汉弗莱推荐的用于控制通气的FGF是令人满意的。然而，汉弗莱推荐的用于自主通气的FGF在某些患者中可能导致高碳酸血症。这可以通过在所有患者中常规使用66 ml·kg-1·min-1的较高FGF来预防，或者通过在有二氧化碳监测的情况下使用较低流量来预防。
