Oxygen Conserving Devices

These devices are designed to provide the right amount of oxygen when needed, and therefore reducing waste and conserving oxygen.

For most people breathing is something we do unconsciously. It just happens and we rarely concentrate on it.

For people with COPD who are on long term oxygen therapy the respiratory process is a major factor. Perhaps the most fearsome part of it is breathlessness. That feeling of suffocation and insufficient air coming in.

The act of breathing is not something static and doesn´t have a precisely fixed time frame. During the day we have variations in our breathing cycle. When we are active, when resting or sitting down, when talking, when eating. During each of these activities our breathing cycle varies. When eating, for example, many COPD patients find themselves short of breath. This is because you cannot swallow and breath at the same time as the well know "it went the wrong way" exemplifies.

An increase in activity has a direct response to our respiration. Similarily when sleeping our breathing rate has changed as it is reduced because our body is demanding less oxygen.

Oxygen therapy means that a patient receives, at specific rates and flows, supplemental oxygen. Therefore as our breathing requirements vary, it does not make much sense to receive oxygen at a continuous flow rate. When oxygen is delivered continuously it is quite obvious that the supplemental oxygen is wasted when we are breathing out.

At one time this was the normal practice as oxygen in itself is not expensive. What is expensive is the refilling service as well as the oxygen machines. Another factor is the length of time, not only between refills, but also how it affects the freedom of movement. If you have oxygen for one hour, that is it. It is one hour and you have to take appropriate measures and adjust accordingly.

These are perhaps the primary reasons why oxygen conserving devices are used.

1. To deliver the right amount of oxygen when it is needed. This implies both the breathing rhythms at different times and the correct amount.
2. Reduce waste and increase the oxygen´s supply time frame. For both tanks (liquid oxygen) and cylinders (gas oxygen) the costs involved in refilling and service can be high. A longer lasting supply means less refills.

A quick look at three aspects of the breathing process help highlight the effects of a properly set up conserving device.

1. The breathing process implies inhalation and exhalation (breathing in and breathing out). During the first part of the inhalation the air goes straight to the alveoli (damaged in cases of COPD). Oxygen delivered during this first part of the inspiration is vitally important and so the conserving device should be delivering oxygen exactly on time.
2. During the second half of the inhalation process, air coming in occupies other space such as the upper airways. This helps create a reservoir of oxygen allowing pooling of oxygen. The same thing happens with reservoir cannulas.
3. When the breathing rate is higher the time engaged in breathing in is shorter and this dilutes the oxygen dose. When short of breath or after strenuous activity the typical reaction is quick shallow breathes.

One of the conclusions from this breathing process and conserving devices is that the response time to the inspiration signals is important.

• A slow response will affect the amount of oxygen delivered to the alveoli. As mentioned earlier our breathing patterns vary according to activity and circumstance. When sleeping or when there is shortness of breath, the inspiration signals we emit are weaker.
• If the conserving device´s response is slow the delivery will be less effective.

The Two Oxygen Conserving Device Systems.

              Conserving devices can be mechanical or electrical, and the conserving aspect is to reduce oxygen waste.

Oxygen Conserving Pulse Systems

Pulse systems are made to deliver a higher rate of oxygen when inhalation begins

• and this means more oxygen is delivered to the alveoli.
• The second part of the operation is when the oxygen flow stops, during the latter part of inhalation, and this is at a preset limit.
• These systems are very effective for patients with stable oxygen needs (however remember that the breathing process does vary).

 Oxygen Conserving Demand Systems

Demand systems deliver oxygen for the whole breathing-in process, the inhalation.

• The delivery begins at the start of the inspiration and continues all the way through. This in turn means that the flow rate is usually lower and not as precise.
• One of the effects is that oxygen delivered to the alveoli is less.
• Demand oxygen conserving devices are usually targeted at patients with greater levels of activity.

More sensitive oxygen devices are being developed that adjust the flow and timing of the delivery according to the breathing rate, allowing the patient to receive the correct amount of oxygen (the required flow rate) at the right time.

An example of this is the LifeChoice Portable Oxygen Concentrator with Auto Mode Technology.