The vast majority of inhaled general anesthesia drugs are volatile liquids at room temperature and pressure. This type of liquid drug must be converted into gas before it can be applied clinically. This requires the use of an evaporator to evaporate liquid drugs and turn them into usable gas anesthetics. Gas anesthetics are easy to enter the human body with breathing, achieving the purpose and effect of general anesthesia.
According to the principle of material motion, molecules that make up liquid matter undergo irregular collisions with each other at all times due to the presence of internal energy. As the temperature increases, the intramolecular energy increases, and the number of collisions and the speed of molecular motion also increase. When the internal energy of certain molecules increases enough to overcome the mutual attraction between molecules, the molecules that make up liquid substances will break free from the constraints of liquid substances and form gaseous substances. This process is called the vaporization of liquids. The vaporization of liquid substances is not unrestricted in a closed container. It is subject to the dual effects and constraints of pressure and temperature inside the container.
When the temperature is constant, as the liquid material continuously vaporizes and the number of gas molecules increases, a pressure that increases with the number of molecules will be generated in the container. When the molecules in the liquid are under pressure inside the container and their internal energy is insufficient to overcome this pressure, the liquid molecules in the liquid cannot become gas molecules, thus achieving a relative equilibrium state. The concentration of gas molecules is relatively balanced. The temperature at this point is called saturation evaporation temperature; Pressure is called saturated vapor pressure.
When the pressure is constant, as the liquid material continuously vaporizes, the temperature of the medicine will gradually decrease and the evaporation rate will slow down. When it drops to a certain level, the temperature will not be sufficient to support the vaporization of the liquid. Make the concentration of gas molecules relatively balanced.
When either of the pressure or temperature conditions change, the evaporation process will continue until a new equilibrium is reached.
Evaporators are generally divided into two categories; One type is called liquid level evaporator; Another type is called evaporator for specific drugs. A liquid level evaporator is a carrier that passes a certain amount of gas, usually a mixture of oxygen and laughing gas, from the space above a container containing volatile anesthetics to the evaporation chamber. When this gas flows through the evaporation chamber, it will become a gas containing saturated anesthetic vapor, forming the safe concentration of anesthetic gas required in clinical practice.