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Understand POC settings

  1. Aug 19,2019
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POC settings and continuous L/min flow setting are not comparable

Large stationary concentrators put out a specific adjustable continuous flow of oxygen that is measured in litres per minute (L/min). The oxygen produced by portable units cannot be measured in L/min since they do not produce constant oxygen for one minute. The output of a POC is determined by the size of the individual pulse (called a bolus) and is measured in mL per breath. There is no standard pulse size. Each POC model has a different pulse volume.

The numbers on a pulse unit are settings NOT equal to the litre flow from continuous flow devices or the oxygen conserving devices used with medical oxygen cylinders. So, don’t think that a setting of 3 is necessarily the same as 3 L/min on your continuous machine or number 3 on your oxygen conserving device powered by a medical oxygen cylinder. The only way for you to determine if you are being properly saturated by a particular unit, be it pulse or continuous, is to check your saturations with your doctor using a pulse oximeter during rest and exertion whilst using the POC you intend to purchase. Many people respond differently to different POCs.

Another feature of POC models/units is when and how the pulse is released. In some cases. the bolus is released immediately when it senses your breath, and in other cases, it is spread out longer or occurs later in your breathing cycle. All of this affects how saturated you are with oxygen. If the bolus is released late and you are taking short breaths, some of the oxygen could be wasted.

Over-breathing a POC

Another thing that must be taken into account with POCs is the number of pulses of oxygen they are able to produce in a minute. As a general rule, the more breaths you take and trigger a POC, the lower the percentage of oxygen delivered to you, as the machine cannot keep up with your higher breathing rate. This is called ‘over-breathing’ the device.

It is very easy to ‘over-breathe’ these units by trying to take more breaths than they are capable of producing. Many POCs do not have a low oxygen alarm to warn you to slow your breathing down.

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