Medical Gas Supply Systems

KEYWORDS

medical gas cylinders

oxygen supply systems

There are many things that are a part of our lives, both personal and professional, that we take for granted. When we turn on the faucet, we expect water to come out; when we turn on the TV, we expect there is electricity flowing through the wires in the room so the TV comes on; and when we turn on an oxygen flowmeter, we expect oxygen to be there as well. But how does the medical facility in which you train or practice ensure that there is oxygen available when you turn on the flowmeter? Many of us might understand how we get the water to the tap or the electricity to the outlet better than we understand where the oxygen we use in great quantities every day comes from.

As a clinician, you will use much more oxygen in a day than you use water—did you ever think of that? So, it is a good idea to talk about where the medical gases we use get to the outlet for us and what would happen and what you would do if that supply was interrupted. Don’t assume that somebody else will know what to do. It’s your responsibility.

When we discuss medical gases, the big one is, of course, oxygen. We have the ability on our anesthesia machines to use oxygen from two different sources—cylinders and the hospital pipeline (wall) source. But you should remember that unless you always use cylinders of nitrous oxide and medical air, these two gases for your anesthesia machine come from the hospital supply as well.

In this chapter, we will discuss the systems that facilities use to supply oxygen, nitrous, and air via pipelines as well as some potential problems that can happen. We will also talk about how medical suction is generated and distributed throughout a building.

OXYGEN

Oxygen supplied through a medical pipeline system can have two sources: it can originate from a collection of large cylinders, or it can come from a liquid oxygen storage system. Smaller facilities, such as an outpatient surgery center that is not a part of a larger health care campus, will likely have a group of large oxygen cylinders as the source of pipeline oxygen. Hospitals, which will use thousands of liters of oxygen a day, use bulk liquid oxygen to supply their needs. We will discuss both kinds of sources.

Cylinder

In this setup, a group of “H” cylinders of oxygen will be attached to each other through a common manifold. The number of cylinders involved depends on the oxygen consumption of the facility—there can be as few as two or as many as the facility needs. There is a one-way valve between each tank and the common manifold, so if a tank has a leak or is empty, there will be no retrograde flow. From the manifold, the oxygen goes to a pressure regulator to take the pressure down to 50 to 55 psig, which is what pressure the oxygen is when it comes out of the wall pipeline. This setup is the primary supply. Some places also have a secondary supply as a backup.

The location of such a supply can be a small closet-sized area, a supply room, or an outdoor pen. It needs to be accessible to medical gas company workers for the cylinders to be changed out. Remember that an “H” cylinder holds 6900 L of oxygen at a pressure (when full) of 2200 psig, the same pressure as a full “E” cylinder. For a small hospital or surgery center, five to 10 “H” cylinders can supply several days’ worth of oxygen. If a facility had five “H” tanks, that would be:

So if a surgery center had five rooms, and we say the average oxygen use per anesthesia machine is 3 L/min:

And then

Are you comfortable with that supply of oxygen? A facility has to figure in how much the delivery costs are for the gas distributor to come out every 4 days. More cylinders might be better. Also keep in mind that oxygen consumption goes on not only in the operating room (OR) but also in the recovery room, intensive care units, or anywhere procedures are done such as the cath lab, endoscopy, and interventional radiology.

This is also a good place to discuss actual oxygen use of your anesthesia machine. Does anything else on your anesthesia machine use oxygen besides what you dial in with your flowmeter? This is an example of why it is important to know as much about the anesthesia machine as you can. As discussed in the chapter on anesthesia ventilators, the type of anesthesia machine you use makes an incredible difference in oxygen usage. A piston ventilator uses no oxygen other than what is dialed into the flowmeter. A Datex-Ohmeda bellows ventilator uses a quantity of oxygen more or less equal to the patient’s minute ventilation in addition to what is going through the flowmeter (a Draeger bellows ventilator uses a mixture of oxygen and air, but Draeger no longer makes bellows ventilators). If oxygen supply is a consideration, you might want to consider piston drive ventilators the next time the facility purchases new machines.

Liquid Oxygen

This is the manner in which most large hospitals store oxygen. It is more economical than using dozens of cylinders a day. Liquid oxygen is powerful stuff; it is used in rocket propulsion. Fortunately, it has been learned over the years how to handle and store it relatively safely.

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