At some point in ALS progression the question of using oxygen to ease breathing difficulty
will come up. Getting enough oxygen is not a the problem in ALS. There is nothing wrong with the
lungs. The problem is muscle weakness that prevents inhaling
deeply enough to get enough air in. If a machine such as BiPAP or a ventilator is used to push
enough air in, the lungs can absorb oxygen from room air without difficulty. Therefore the
treatment for breathing problems in ALS is mechanical support, not oxygen. For people with ALS
who also have lung problems that directly affect the ability of the lungs to absorb oxygen (such
as pneumonia, COPD, emphysema or asthma) in addition to ALS, oxygen may be necessary.
Often the response to the use of oxygen is that it is dangerous for ALS patients. That is
both true and false!
Respiratory drive runs on CO2 levels. Oxygen levels contribute very little to the process
of stimulating breathing. CO2 is produced by working cells and sent through the blood to the
lungs to be removed during the process of breathing. The CO2 is exchanged for oxygen and the CO2
is exhaled. When that exchange is impaired, CO2 levels rise and the respiratory regulatory
center in the brainstem coordinates an increase in breathing rate and depth to blow it off. An
ALS patient with weak respiratory muscles can't breathe deeper so the CO2 levels are harder to
The risk of giving oxygen to an ALS patient who has high CO2 levels is not recognized by some doctors and respiratory therapists. If you develop breathing problems and call for an ambulance or go to the Emergency Room, protect yourself by wearing a Medic Alert bracelet. They are available online from several companies. This site offers a range of styles.
Over time body chemistry allows the respiratory system compensate and to work with these
levels as the "new normal". When the compensatory measures are maxed out by increased weakness
of the respiratory muscles or lung congestion or pneumonia, that small amount of respiratory
drive from oxygen becomes very helpful. But if oxygen is given and the O2 Saturation increases
to about 90%, that part of the respiratory drive stops because the O2 level is near normal. Loss
of that small part of respiratory drive is enough to tip the drive from "barely enough" to "not
enough". The rate of failure begins to increase and the patient may stop breathing entirely. The
risk of adding O2 is therefore very real -- but only if the patient is retaining CO2 enough to
rely on compensatory body chemistry.
So when does this risk begin with ALS? It is a basic rule in medicine that you don't
automatically give more than 2 liters per minute of oxygen to anyone. This amount is considered
low enough to be safe for anyone, but a check of an ALS patients CO2 levels should be done regardless.
O2 Saturation (monitored with a simple fingertip monitor) does not reflect CO2 levels and O2 levels remain
normal until CO2 levels are very high. The person's CO2 levels have
to be checked to see if he is retaining CO2. This can be done using a device that tests exhaled air
(Capnometer), or with a check of blood drawn from a vein, the same as for most blood work.
The results of these methods correlate well (within 95% in most breathing problems) with the
"gold standard" of respiratory tests, ABG's (Arterial Blood Gasses). ABG's require drawing
blood from an artery. ABG's are often preferred by doctors because they show not only the CO2 level,
but also if the body is already using compensatory chemistry.
The issue of using oxygen frequently comes up when the insertion of a feeding tube is
suggestion is that anyone who is planning a PEG insertion have their CO2 levels checked a few
days before to determine the degree of risk from oxygen and a consult between the Pulmonologist
and GI doctor inserting the tube concerning the need for BiPAP and use of oxygen versus changes
to the BiPAP settings if sedation and pain meds slow respirations.