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  • design and ergonomics of anesthesia machines

  • electrical safety features

  • anesthesia machine


Although early anesthesia machines did not require any electrical power, those made in the last several decades do rely on electricity for various functions. As machines have changed and become more complex, more and more systems on anesthesia machines depend on an external power source. Fortunately for us and our patients, the most vital functions of most anesthesia machines still do not require electricity. Do you know what parts of the anesthesia machine or machines that you commonly use would still work if electrical power were lost?


In this chapter, we will discuss things in generalities because not all anesthesia machines will operate the same way in case of a power outage. When electrical power is lost, what may work on one model of machine may not work on another model even from the same manufacturer. We will discuss the basic components of the electrical system of an anesthesia machine and what to do in the event of a power loss during an anesthetic.


The basic components of the electrical system of an anesthesia machine include a master switch, electrical outlets, circuit breakers, and (in most cases) a backup power source. The most modern machines also have data ports that allow information to pass between the machine display and various monitors.


Master Switch


This switch does two things: it turns on the electrical system, and it activates the pneumatic system. Although we call it a switch, it can be a knob, a switch, or even a button, depending on the model. When turned on, all of the electrical components of the machine are powered up. (This may or may not include patient monitors, again, depending on the model and setup.) In addition, the pneumatic system of the machine is activated. There is an electronic valve in the pneumatic system that, when opened by the master switch, allows communication between the gas sources (pipeline or cylinders) and the rest of the machine. The reason for this is that when you turn off the machine, gas is not left on and wasted.


The important thing to remember about the master switch is that even if there is no electricity, as long as the master switch is turned on, the pneumatic system will work. On some more modern machines, however, if you have been on backup battery power for long enough to drain the batteries, the machine’s pneumatic system will cease to function when the batteries in fact go dead. In any circumstance, if the master switch is not turned on, the pneumatic system will not work, with one exception: the oxygen flush button bypasses the master switch pneumatic control, so even if the machine master switch is not turned on, the oxygen flush will work (Figure 12-1).


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