About Oxygen Equipments, Part 1 Print E-mail



Oxygen equipment has two basic components. One is the container that holds the oxygen. The other is the means for getting the oxygen from that container into your lungs. There are alternatives for each.

The Oxygen Container

If you beginor are already onoxygen therapy, you should have two types of oxygen sources. One is a large stationary unit you use in your home. The other is a small portable unit that goes everywhere with you when you leave your home. Three oxygen-supplying systems are currently available: high pressure compressed gas cylinders, liquid oxygen storage flasks, and oxygen concentrators. Some are easily portable, some are not.

The high pressure compressed gas cylinderlarge, green, and uglywas the first home oxygen system. Although currently inexpensive and the most easily available system, these tall green cylinders have drawbacks. Both the home and portable cylinders (called E-cylinders) run out of gas fairy quickly. And the portable gas cylinders are both heavier than would be ideal, and dangerous to refill (or "transfill," as the lingo goes) at home from the large cylinders. So for the stationary and portable cylinders, you need either the room to keep an ample supply on hand, or you need frequent replacement deliveries.

Liquid oxygen storage flasks hold oxygen in its liquidrather than its gaseousstate. (Whether a particular element is in its solid, liquid, or gaseous form depends on the temperature of its environment. The most familiar example is water, which freezes at 32F, becomes steam at 180F, and is liquid between the two.) Extreme cold is needed to condense oxygen into liquid. Stationary and portable storage units, which resemble giant and extra-large thermoses, respectively, maintain the super-cold temperature needed to liquefy oxygen. As the liquid is drawn out it meets room air, which warms it, returning it to its gaseous state so it can be breathed.

These liquid storage flasks have two advantages over gas tanks. First, because you get the same amount of oxygen in a much smaller, lighter container, the stationary unit takes up less space and the portable unit is much easier to carry around. (The same volume of oxygen takes up significantly less space as a liquid than as a gas, so it needs a smaller, less weighty container. And since liquid oxygen doesn't build up the pressure that a gas does, the container doesn't need to be as strong. This makes it lighter still.)

Second, refilling your portable flask from the large one is safe and easy. Your DME dealer refills this large tank at regular intervals. You can breathe directly from it when you are at home and reserve your portable unit for your time away. Or you can use your portable unit full-time, treating the large tank simply as your storage facility.

These advantages make liquid oxygen particularly suitable for patients who go to work every day, and those whose desire to be on the go a lot takes them away from their stationary oxygen source for prolonged periods of time. In fact, these small units revolutionized the lives of advanced COPD patients by enabling them to participate in activities outside the home. There are devices to help you carry or wheel it around with you.

Continued improvements in both design (minimizing oxygen waste) and materials (making flasks lighter and stronger) have made the portable units even more mobile. The current state of the art is the new HELiOS oxygen system manufactured by Mallinckrodt. It features a portable oxygen unit weighing less than 3.4 lbs.worn on a waist belt or shoulder strap or in a backpackand provides 10 hours of use (at the standard flow rate of 2 liters/minute) between fillings. Filling is easily accomplished from your home reservoir in about 40 seconds, and the reservoir itself needs only 8 to 10 refills a year.

But the liquid oxygen is not perfect. Like a pressure cooker, the storage flasks need a built-in leak to prevent buildup of explosive pressures, so some oxygen is lost from the tank when the patient isn't using it. A bigger problemparticularly if you travel out of townis that none of the several brands of liquid oxygen are compatible. You cannot refill your flask from a larger container of a different brand. Also, liquid oxygen is typically more expensive than compressed gas oxygen. But all these disadvantages are usually outweighed by the ease of mobility liquid oxygen provides. If you are going to use liquid oxygen, it is essential that your doctor specify it in your oxygen prescription.

If you choose an oxygen concentrator, your DME dealer will provide you with equipment only. This electrically powered machine makes its own oxygen supply by separating it out of the surrounding air. It is cheaper and more convenient than compressed gas and liquid oxygen systems. More than 20 different devices currently exist for filtering oxygen out of room air. The major drawback of all these commercially available concentrators is their reliance on electricity. For starters, this means that patients using a concentrator must also keep a compressed gas system on hand in case the power fails. The need for electricity also precludes portability. And since a portable liquid gas flask cannot be refilled from a concentrator, the portable alternative is usually one of the precautionarily stored compressed gas canisters. Finally, although a concentrator's rental is subsidized by medical insurance, the cost of the electricity that runs it is not.

The one caution with concentrators is their need for regular servicing to assure proper oxygen purity and flow rate. Do not consider renting an oxygen concentrator from a DME dealer who will not include an adequate servicing arrangement in your contract. Purchasing your own concentrator rather than renting doesn't seem to solve any problems, while it can add the burden of responsibility for repairs further complicated by a serious lack of service facilities.

Although little significant progress has been made in developing portable concentrators, a cryocooler system now in prototype form is being developed by InX for home use. The systemwhich will function as a middleman between your oxygen concentrator and whatever portable liquid oxygen system you useis designed to divert a liter of oxygen per minute from any concentrator to the cryocooler, where it is cooled sufficiently to change from gas to liquid. This system will generate 0.8 lbs. of liquid oxygen daily in your home, enough to give you 8 to 10 hours away from homedepending, of course, on the rate of flow you require and whether or not you use a conserving system. If the engineering challenges presented by some of its components are solved, this equipment will dramatically reduce the need for oxygen deliveries and thus produce huge savings to suppliers.

Because a concentrator is not dependent on a preset oxygen supply, a portable device provides unlimited freedomas long as you have a battery supply on hand. A patient can, for example, go on vacation without needing to establish a network of oxygen suppliers.


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