Annie's Phil is correct. The main problem with giving oxygen is his possibly high CO2 levels, but it requires a blood sample to determine that. The risk of respiratory arrest from giving oxygen ONLY occurs if the CO2 level is high. However, oxygen at 2 liters per minute or less is considered safe even if the CO2 is high. If he is so congested, there is a risk of respiratory slow down simply from fatigue of the respiratory muscles. You would expect to see the signs of labored breathing if he is in respiratory distress, but with ALS you won't see the usual deeper breaths. You will see rapid shallow breathing. The Trilogy will prevent that. So, on the Trilogy to help blow off the CO2. If he is not willing to "let nature take its course" just yet, a CO2 level, Chest X-ray, sputum culture and antibiotics if indicated are necessary. If not, extra water to keep the mucus thin and the cough assist are best. Low level oxygen will make him more comfortable even though it won't reduce the CO2 if it is actually high.
From my website:
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 contributing 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 bring down.
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.
