Chakrabarti M K, Stacey R G, Holdcroft A, Whitwam J G
Department of Anaesthetics, Royal Postgraduate Medical School, Hammersmith Hospital, London.
Anaesthesia. 1990 Apr;45(4):314-7. doi: 10.1111/j.1365-2044.1990.tb14741.x.
A circle breathing system was connected by deadspace tubing to an open system valveless ventilator. The minimum volume of this tubing, required to prevent dilution of anaesthetic gas in the breathing system by the driving gas of the ventilator, was determined at frequencies of 15, 30, 60, 100 and 150 breaths/minute, with tidal volumes that ranged from 100 to 1100 ml and a fresh gas supply to the circle system of 1, 2 and 4 litres/minute. At 15 breaths/minute, tidal volumes equal to or less than the deadspace volume could be used safely without any mixing with the ventilator driving gas, when a fresh gas flow of 2 litres/minute or above is supplied to the circle system. At 1 litre/minute of fresh gas flow, mixing occurred at tidal volumes less than the deadspace volume. Mixing of gas occurred in the system at frequencies greater than 30 breaths/minute even when the tidal volume was much less than the deadspace volume. However, at high frequencies of ventilation, since the tidal volume requirement decreases, deadspace tubing with a safe internal volume, that is greater than 600 ml, may be used up to 100 breaths/minute.
一个环形呼吸系统通过无效腔管道连接到一个开放式无阀呼吸机。在呼吸频率为15、30、60、100和150次/分钟时，潮气量范围为100至1100毫升，向环形系统的新鲜气体供应量为1、2和4升/分钟，测定了防止呼吸机驱动气体稀释呼吸系统中麻醉气体所需的该管道的最小容积。在呼吸频率为15次/分钟时，当向环形系统供应2升/分钟或更高的新鲜气体流量时，等于或小于无效腔容积的潮气量可以安全使用，而不会与呼吸机驱动气体混合。在新鲜气体流量为1升/分钟时，潮气量小于无效腔容积时会发生混合。即使潮气量远小于无效腔容积，在呼吸频率大于30次/分钟时系统中也会发生气体混合。然而，在高频通气时，由于潮气量需求降低，内部安全容积大于600毫升的无效腔管道在呼吸频率高达100次/分钟时仍可使用。
