Portable Oxygen: A User's Perspective

What Do the Numbered Settings Really Mean?




Portable Oxygen: A User's Perspective

What Do the Numbered Settings
Really Mean?

IMPORTANT: 
The information here provided is for educational purposes only and it is not intended nor implied to be a substitute for professional medical advice. Always consult your own physician or healthcare provider with any questions you may have regarding a medical condition.   

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?

Hi, Mary,

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.
  • Slow down! Recognize that by simply walking out the door increases the need for oxygen to manage the weight of a coat and the oxygen system, and to face real, and sometimes unpleasant weather.

  • Ask yourself if you have any impediments that might decrease the effectiveness of a pulse system. Are you a mouth breather?  Do you have a deviated septum or any blockage in a nostril?  Is your breathing rate at rest slower than normal 20 bpm (breaths per minute), thus providing you with fewer pulses than normal? Which of the following two ways do you compensate when you perform activities requiring more oxygen--do you maintain your at-rest breathing rate and increase the depth of breathing or do you increase your breathing rate, causing it to be more shallow?

  • Validate the settings you use on both systems if you believe one of the two is not supporting your requirements. A respiratory therapist (RT) should evaluate the efficacy of your equipment, both when you initially receives it and thereafter when reevaluation appears to be required. To those folks I suggest they get a prescription from their physician requesting their oxygen provider's RT test them on the equipment they are using in the environment where they use it.
You have asked if the flow settings of continuous flow systems, like your concentrator, are the same as the settings on pulse systems. If you are asking if at the same setting the flow of oxygen from each is the same, the answer is no.

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.
  • The first row shows that, with no supplementary oxygen, the oxygen concentration of air entering the lung is 21 perecent at all breathing rates .

  • The second row of the table shows that pulse flow increases the oxygen concentration from 21 percent to about 27 percent on each breath. This concentration is constant across the three breathing rates.

  • The third row of the table shows that, when oxygen is provided in continuous flow, the concentration of oxygen on each breath is affected by the breathing rate. The concentration ranges from 30 percent at 15 bpm to 25 percent at 26 bpm. 
Table 1
Oxygen concentration in simulated
lung at three breathing rates
(setting = 2)
Source of
Supplementary
Oxygen
Percent of oxygen in the air
that is entering the lung when the
rate of breathing is:

15 bpm
20 bpm
26 bpm
   None
21
21
21
   Pulse Flow
27*
27*
26*
   Continuous Flow
30
27
25
*average of 5 pulse flow systems

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.
  • The first row shows that, with no supplementary oxygen, the oxygen concentration of air entering the lung is 21 perecent.

  • The second row shows that supplementary oxygen provided by pulse flow raises the oxygen concentration  from between 27 and 35 percent, depending on the setting.

  • The third row shows that supplementary oxygen provided by continuous flow raises the oxygen concentration from between  27 and 39 percent, depending on the setting.
Table 2
Oxygen concentration in simulated
lung at three settings
(breathing rate = 20 bpm)
Source of
Supplementary
Oxygen
Percent of oxygen in the air
that is entering the lung when the
flow/pulse dial is at::

Setting 2
Setting 4
Setting 6
    None
21
21
21
    Pulse Flow
27*
31*
35**
    Continuous Flow
27
33
39
*average of 5 pulse flow systems
**average of 4 pulse flow systems

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:
  • Settings on all oxygen equipment must be made to meet therapeutic goals rather than on comparisons between pulse flow devices or to continuous O2 use.

  • There are other factors not addressed in this study which may affect patient's therapy, such as individual breathing patterns and the triggering sensitivity of each pulse flow device.

  • Patients should be titrated at rest and activity levels on the specific device they will use.



Click here

to see a list of other feature stories.

© 2003 Copyright 
Peter M. Wilson, Ph.D. 
Founder of PortableOxygen.org

You have permission to print this document for your personal use. You also have permission to print, copy, and distribute this document to oxygen users and their caregivers.

Title and buttons courtesy of Ben Ledet,  <benledet@parkermedical.com> Creative Director, Parker Medical, Englewood, CO. 80112