This article was reviewed by Senior Director of Community Engagement and COPD360social Community Manager, Bill Clark, as well as certified staff Respiratory Therapists on January 29, 2020.
Dear COPD Coach,
I have had idiopathic pulmonary fibrosis (IPF) since 2009. I was an athlete. I did not smoke. I have been told I am de-saturated at night and have a concentrator for night use.
Based on my latest 6 minute walk test, my clinician’s impressions are the following: With treadmill titration, patient required 3L to maintain an oxygen saturation (SpO2) of 91% at a metabolic (MET) level of 4.8. Decrease in walk distance compared to January by over 350 feet. However, still with excellent effort on 6 minute walk test, but severe desaturation to 75% on 3 liters per minute of oxygen. With significant oxygen needs for higher exertion levels. Discussed paced activity, monitoring SpO2 with activity.
Is there any portable concentrator that is preferred (flow and weight) for moving around NYC on foot generally (walking, and going up and down subway stairs)? I realize that these questions, and my situation, are perhaps an anomaly, but hope the questions can be answered from your experience/knowledge base. Is there any portable concentrator OR other oxygen apparatus that is preferred/usable (flow and weight) for outdoor exercise (put of bike rack) that permits 6-8 liter per minute flow exercise (which was my use at rehab gym on treadmill, etc.)?
Thank you for any advice.
- Concentrator Questions
Dear Concentrator,
You pose some interesting questions. It is apparent that you are having a more difficult time keeping your saturations up during exertion as time goes on. However, increasing your ability to exert by using a portable concentrator becomes a little complicated. The problem is that it appears you are looking towards finding a smaller concentrator that will provide sufficient output to increase your saturations to an acceptable level, and there is a very real possibility that the concentrator you are looking for does not exist.
First off, there are two delivery systems for portable concentrators, “pulse” and “continuous flow.” The pulse machines deliver a specific dose (called a bolus) each time you breathe. This sounds like it would work well, other than two factors: As you increase the size of the bolus, you decrease the number of breaths that the unit is able to produce per minute. As a result, each breath past a certain number of breaths (usually in the 20’s) decreases the purity of the oxygen dose. A simple way of putting this is that by breathing faster (as you usually do when exerting) you might “over breathe” the unit.
Secondly, oxygen concentrators work by pulling in room air and forcing that air through a sieve bed containing a substance that separates oxygen (which is around 21% of the air we breathe) from the other gases (mostly nitrogen). The output of the unit as far as pure oxygen being delivered is controlled by the size of the sieve beds and the compressor. The pulse units are smaller and lighter weight because the sieve beds are smaller as are the compressors that fill the sieve beds. And, since the units are not running continuously, they can use smaller batteries.
A third factor with pulse units is that their output cannot be measured in liters per minute as they do not run continuously for an entire minute. The industry uses a measure called “equivalent liters per minute” which denotes the approximate size of one bolus as it relates to the amount of oxygen you might get with one breath using a continuous flow unit. But, it’s important to remember that the pulse unit is only able to deliver that bolus a certain number of times per minute before the oxygen dose becomes diluted.
That sounds complicated, but there’s actually more.
There is no standardization as to how the bolus is delivered; if it is extended over time or delivered in one burst.
The settings on the vast majority of pulse units do not denote their equivalent liter flow. For example, a pulse unit might have a setting of six but that does not mean six equivalent liters, when instead it might only deliver three equivalent liters at that setting (as I said, there are no standardizations). It also does not indicate the purity of the oxygen at that setting or how many boluses per minute the unit provides.
Some people are not able to use a pulse dose system because they require more breaths than the unit produces (they then over breathe the unit with means they are taking in larger amounts of room air as opposed to pure oxygen) or the size of the bolus is not sufficient for their needs. If this is the case, they simply cannot maintain their oxygen saturations at a safe level.
As far as continuous flow goes, the same restraints apply. In order to produce a constant flow, the sieve beds and compressor must be larger which then also means much larger batteries that don’t last as long. Because of these limitations, there are NO continuous flow portables that produce more than 3 liters per minute. The units that are out there are much larger and heavier than any of the pulse units. Most continuous flow portables also deliver pulse and can be used in both modes.
I know I haven’t answered your question totally as there is no definitive answer I can give you. The following is the best I can do:
Q: Is there any portable concentrator that is preferred (flow and weight) for moving around NYC on foot generally (walking, and going up and down subway stairs)? I realize that these questions, and my situation, are perhaps an anomaly, but hope the questions can be answered from your experience/knowledge base).
A: That would depend on the amount of exertion you plan on doing. I don’t believe any portable will be able to provide you with unlimited saturation without pacing yourself. I do not know if you would be able to use pulse or would require continuous flow. I use only use oxygen for sleeping and also have a home concentrator. However when traveling, walking long distances, or other situations where I do more than simple short distance walking, I use a portable oxygen concentrator. I use a pulse unit but in pretty much every case, I still must pace myself and still get out of breath. At times I over-breathe the unit.
Q: Is there any portable concentrator OR other oxygen apparatus that is preferred/usable (flow and weight) for outdoor exercise that permits 6-8 liter per minute flow exercise (which was my use at rehab gym on treadmill, etc.)?
A: As I said earlier, there are no portable units that put out that much oxygen. If there was, as technology stands, it would be too large to carry.
The best advice I can give you is to talk with your doctor and oxygen provider, and if possible try a couple different units to find what works best for you. I would NOT buy a unit before trying it first. I really believe that in your case you will have to end up settling for the unit that offers the best result for you even if that result is not what you hoped for as far as mobility. Make sure you get a pulse oximeter that you can carry with you as you measure your saturations!
One last thing: The larger the unit you have to carry, the more desaturated you will become. When I first started traveling with oxygen, the only unit available was a pulse unit that weighed 14 pounds and had to be pulled on a cart. I desaturated so badly that the unit could not keep up so it was pretty much useless.
Sorry I couldn’t be more help but please reach out if you have any additional questions.
-The COPD Coach
Coaches Corner is aimed at providing information for individuals with COPD to take to your doctor, and is not in any way intended to be medical advice. If you would like to submit a question to the Coaches Corner email us at coachescorner@copdfoundation.org. We would love to hear your questions and comments. You can address your emails to The COPD Coach.