Portable Oxygen: A User's PerspectiveWhat Do the Numbered Settings
Mary in PA and a number of others who use portable oxygen have written to me as follows:
I have a question about the pulse settings on my portable oxygen system. I have heard that the numbers on the pulse dial are not the same as the numbers on my concentrator. Do you know what the equivalent is for say 2 Lpm continuous flow and setting 2 on a pulse dial?
You have raised an interesting question, one that I have heard often from other users of pulse-based systems, I usually get these questions when these users discover that, even when set to the same number, their concentrators supports them better than do their pulse-based systems. I offer these users three recommendations.
The amount of oxygen delivered by a pulse system on each inhalation may be as little as 1/6 that of a continuous flow system at the same settings. For this, both oxygen providers and users are happy. Oxygen providers make fewer trips to deliver less oxygen to pulse system users and these users change or refill their portables less frequently.
To make pulse system this efficient, manufacturers of pulse systems use technology to improve the efficiency of oxygen delivery while trying to maintain its efficacy. Pulse systems sense when you begin to inhale and try to deliver as much oxygen as possible within the first several hundredths of a second. Some pulse systems stop oxygen deliver at that point whereas other systems continue delivery until exhalation is detected.
Manufacturers established the efficacy of their pulse systems through clinical studies whose subjects were oxygen users who were participating in rehab programs at the time. These subjects are typically on 2 Lpm prescriptions and have breathing rates of about 20 bpm. You should not be surprised if folks on a 2 Lpm prescriptions who have breathing rates of 20 bpm are ones who are more likely than not to set both their concentrators and pulse systems to the 2 setting.
Recently, a study was conducted to determine the effectiveness of pulse flow as compared with a continuous flow at different breathing rates and different settings. The study used several piece of equipment to emulate a human lung. Measurements were taken of the percent of oxygen that was in the air during each inhalation.
The following table shows the results of this study at three breathing rates.
Oxygen concentration in simulated
lung at three breathing rates
(setting = 2)
The above table shows that average and fast breathers are likely to use the same settings on their concentrators and portable systems. The table also shows that slow breathers may not. Slow breathers may have prescriptions with pulse settings one or two positions higher than continuous flow settings.
The second comparison of the study is between different settings at the breathing rate of 20 bpm. The results are reported in the following table.
Oxygen concentration in simulated
lung at three settings
(breathing rate = 20 bpm)
The implication of the above table is that 20 bpm users with 2 Lpm prescriptions will probably have the same continuous and pulse flow settings and that users with higher prescribed rates will not.
You can read the original study by going to Valley Inspired Products. The study was conducted by Peter Bliss and Bob McCoy of Valley Inspired Products and presented at AARC International Congress in 2000.
What should you glean from this discussion? There are some users whose prescriptions call for the different settings on concentrators and pulse flow systems. These differences may be related to breathing rate or to flow settings. It may be related to other factors not covered here.
In closing, let me paraphrase the recommendations from the above study, as follows:
© 2003 Copyright
Peter M. Wilson, Ph.D.
Founder of PortableOxygen.org
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