I got my start in the biomedical field maintaining and repairing anesthesia machines right after graduating from college. With eight years of experience, I have worked on just about every make and model of anesthesia machine currently on the market throughout the United States. I have received training from all of the major anesthesia machine manufacturers. Over the past eight years, I have seen just about every type of malfunction. I know anesthesia machines inside and out and they are, still to this day, my favorite equipment to work on because they are what started my career in the biomedical field.
FUNDAMENTALS OF ANESTHESIA
James Swandol, CBETBaylor Scott & White McKinney
To be successful with an anesthesia machine you must learn the fundamentals. The easiest way to begin is to start with the gas supplies. Today’s anesthesia machines use Oxygen (O2), Air, and Nitrogen Oxide (N2O). These gases are color coded for identification purposes. Understanding the color code for these three gases is extremely important. First thing you must learn are these three colors: Green for O2, Yellow for Air, and Blue for N20. These gases enter the anesthesia machine from pipeline supply or cylinder supply.
Pipeline is the facility supplied gases and connect to the back of the anesthesia machine using a safety system called Diameter Index Safety System (DISS). DISS prevents the connection of the wrong type of gases making it impossible to connect N2O where the O2 is supposed to connect and likewise. Cylinders use a safety system called Pin Index Safety System (PISS). PISS works just like DISS in the manner that it prevents the operator from connecting the cylinders incorrectly on the anesthesia machine.
Once the gases enter the anesthesia machine they go through a pressure regulator. Pipeline pressure from the facility is set at 50psi. The cylinder pressure varies based on the size of the cylinder and the type of gas. The regulator steps the pressure down to 25psi to prevent damage to the anesthesia unit.
Gases are controlled on the front of the anesthesia machine with knobs that are labeled not only with gas name but also by the color code mentioned earlier. This part of the anesthesia machine is known as the gas blender. An important thing to know about the blender is the Hypoxia prevention device. Every manufacturer uses a different approach here so it is important to learn the terminology each manufacturer uses. For example, GE Healthcare uses the Link25 system where as Draeger uses a system called the SORC. Regardless of how the manufacturer goes about insuring this safety measure they all prevent O2 levels from dropping below 21 percent oxygen which can be fatal for the patient.
The absorber of an anesthesia machine works like a circle, the fresh gas supply comes from the mixer and enters the absorber where it is routed to the patient through a disposable patient circuit with a wye connection. When the patient inspires the gas mixture is delivered to the patient’s lungs, then the patient’s exhaled gases enter the wye connection and go to the expiratory side of the absorber where it is routed to the soda lime. Soda lime is a material that scrubs the CO2 from the exhaled gases of the patient. Once the CO2 has been scrubbed the gases are routed to the Bellows or the breathing bag depending on which mode of operation is being used. Once the gases have reached this point they can be used again on the patient completing the circle. The soda lime plays a very important role in this operation, the soda lime crystals will turn purple when they have absorbed all the CO2 they can hold. Once this happens, it is time to replace the soda lime.
“There are too many steps during preventive maintenance to go off of memory. Keep in mind this machine is keeping the patient alive during surgery, cutting corners with anesthesia maintenance should never be done.”
KEY TO SUCCESSFULLY COMPLETING PREVENTIVE MAINTENANCE
The best advice I can give when completing preventive maintenance is to have your service manual with you. It doesn’t matter if it is a hard copy or a digital copy on a tablet just make sure to use it. There are too many steps during preventive maintenance to go off of memory. Keep in mind this machine is keeping the patient alive during surgery, cutting corners with anesthesia maintenance should never be done. One tip I have used for every anesthesia machine I’ve worked on is that; before I sign off that it is ready for cases I asked myself if I would want my kids or wife to use this anesthesia machine during a surgery.
Use proper test equipment. Every service manual explains what test equipment is necessary to complete maintenance for a particular anesthesia unit. Let’s face it, test equipment is expensive and management will frown upon another expense, but using the proper test equipment is the only way to ensure that the unit is performing the way the manufacturer designed the unit to work.
Last piece of advice, not all anesthesia machines are created equal. Different manufacturers have different approaches to how to ventilate a patient. Just because you have been trained on one model does not mean you can work on any anesthesia machine. Request to be manufacturer trained on your anesthesia machines. Take the time and study the manuals, learn your anesthesia machines.
I’ve spent the majority of my biomedical career working on anesthesia machines. I’ve learned that without the fundamentals it is difficult to completely understand how anesthesia machines are supposed to perform. Proper training is key. Do not attempt to work on an anesthesia machine without proper training; the patient’s life depends on it. Take your time, complete the maintenance properly and always in accordance with the manufacturer’s recommendations. Never skip steps and never sign off on a unit unless you feel comfortable with your loved ones using it during a surgery.
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