PERF, The Pulmonary Education and Research Foundation, is a small but vigorous non-profit foundation.  We are dedicated to providing help for those with chronic respiratory disease through education, research, and information.  We hope this newsletter is worthy of our efforts.

Demand Oxygen Conserving Devices for Compressed Gas Cylinders

By Craig Murga, RCP, Center Manager of the Torrance, CA Lincare

We received an e-mail recently asking us to recommend the best oxygen-conserving device (OCD) available.  Five years ago, with so few devices on the market, this would have been a much easier question to answer.  Today, many manufacturers are producing quality devices and, of course, each one will lay claim to having the best product on the market.  We should congratulate all the manufacturers for their efforts in the research and development of new products that allow oxygen dependent patients to enjoy a better quality of life.

Almost all the manufacturers that currently produce OCDs uses the demand mode rather than time cycled pulse dose method of delivery.  The demand mode enhances the ability of the OCD to maintain proper oxygen saturation while also allowing greater ease in detecting a problem. The most important consideration when selecting an OCD is to be sure that the device will allow the user to maintain adequate O2 saturation, while also providing the longest duration of oxygen use per cylinder.

No OCD should ever be placed on a patient without a doctor’s order, or without testing the user on the device using oximetry to verify effectiveness. Any oxygen provider that carries these units should have a respiratory therapist or nurse on staff who will provide this service without any extra cost.  If an oxygen provider does not maintain a respiratory therapist or nurse on staff to provide this service, it’s time to change oxygen companies.

The test should be performed with oximetry while walking the patient for an extended period of time, during normal conditions of exertion, while carrying the system.  If the user fails the test because of oxygen desaturation, the procedure should be repeated while on a continuous flow of oxygen.  If a continuous flow provides adequate saturation, you may find that using a device with a lower ratio of saving may provide better results.

All manufacturers test their devices to determine the ratio of savings.  In other words, if the manufacture has rated the device as having 2:1 savings, oxygen should last twice as long with the conserving device as it would with continuous flow oxygen while maintaining the same oxygen satur-ation. 

Some manufacturers have engineered their device to provide a larger pulse of oxygen at the beginning of inspiration, attempting to mimic the flow curve of diseased lungs.  This may serve to meet the needs of a larger portion of the general population but each individual’s lungs are unique.  The saving ratio gives the user a rule a thumb when selecting a device, but this does not always translate into true savings.  The best way to know how long any given cylinder will last is by having the user time their individual length of use with the equipment.

I am of the belief that when it come to OCDs, simpler is better. In other words, the fewer bells and whistles, the less that can go wrong with the device.  Some users will gain added confidence with a device that provides a visual response.  In most cases, however, adding components to the unit also increases the weight of the device.  Some other suggestions to consider when using conserving devices:

• Never use an OCD while sleeping.

• Never use extension tubing on an OCD.

• If the device uses a battery, have an extra battery ready to change if necessary.

• If the user has a cold, flu, upper airway obstruction, or exacerbated disease process, use a standard regulator until the problem has passed.

• If the user’s respiratory rate dramatically increases, retest using oximetry.

• If someone feels the device is not operating properly, retest with oximetry.

• If the OCD does not have the continuous flow option, have a standard flow meter ready for emergencies.

If the user’s oxygen saturation is not supported by the OCD, try a device with a lower savings ratio.

Demand Oxygen Conserving Device Comparison 
gotten from the manufacturers

The oxygen savings ratio is based on information supplied by each manufacturer with a 20 breath per minute cycle vs. the equivalent continuous liter flow setting.

Many thanks to Craig Murga for this informative article.  He will be writing a companion piece on other types of conserving devices for a forth coming newsletter.

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