Anesthesia Machine Evaporator

Anesthesia Machine Evaporator

The Function of Evaporator 

Anesthesia machine evaporation tank, also known as evaporator, is generally divided into several types: enflurane, isoflurane, halothane, sevoflurane, desflurane, etc. The commonly used ones in China are enflurane tanks, isoflurane tanks, and sevoflurane, and the use of enflurane has been banned domestically. Its function is to convert liquid inhaled anesthetics into gas, and then mix them with oxygen to a certain proportion concentration before delivering them to the patient. Therefore, the evaporator is a particularly important component of the anesthesia machine, and the accuracy directly affects the overall quality of the anesthesia machine.

Can different evaporation tanks be used interchangeably?

Each type of evaporator actually uses the corresponding anesthetic calibration scale, so the concentration scale of the corresponding evaporator when paired with the corresponding anesthetic is relatively accurate. The volatile concentration is difficult to control, and each jar is paired with a volatile coefficient. When manufacturers make jars, the volatile coefficients for different anesthetics are different internally. For example, the concentration of enflurane added to the evaporation tank of enflurane is accurate. Different inhaled anesthetics should not be mixed with the evaporation tank because their boiling points are different, and mixing can cause the actual inhaled concentration to deviate from the indicated concentration on the turntable. If you put in the medication of isoflurane, it's not that it can't be used, it's just that the concentration will be inaccurate. The scale of the volatile tank indicates that under certain conditions (within the compensation range), the volume concentration of anesthetic gas flowing out of the volatile tank can reach the nominal value, but it does not represent the actual inhalation concentration of the patient. The actual inhalation concentration of patients is not only related to the scale of the volatile tank, but also to factors such as fresh air flow rate, minute ventilation volume, and dead space volume in the circuit.

What is the difference between a single tank and a double tank?

There is a difference in the configuration of anesthesia machines between single tank and double tank, which refers to the number of evaporation tanks equipped on the anesthesia machine. When it is actually working, there will only be one evaporation tank, and the double tank machine will be equipped with a bypass valve. Its function is that when you open this evaporator, the other one cannot be used because anesthesia cannot be used with each other. In addition, there are two commonly used evaporation tanks now: the purple evaporation tank is specifically designed for isoflurane, while the yellow evaporation tank is specifically designed for sevoflurane.

Advantages and disadvantages of mechanical and electronic evaporation tanks

The mechanical evaporation tank is widely used now, especially during low flow anesthesia, due to the influence of temperature, pressure, and flow rate, the output accuracy is not ideal. Compared to traditional mechanical evaporators, electronic evaporators perform better in terms of precision in outputting anesthesia. However, electronic evaporation tanks can only be used on characteristic models, unlike most mechanical evaporation tanks that can be used interchangeably. The sensors and other components used in electronic evaporation tanks have a higher failure rate and maintenance cost compared to mechanical flow meters.