Brian Tiep, MD

If someone had an oxygen level (SpO2) of 69% during the night and was told to use oxygen at night, and yet did not use it, could this cause the person to have a heart attack or to possibly die while sleeping?  Why is a person’s breathing worse when they lay on their back?

This level of oxygen drop at night or any other time is damaging to the body. Damage may occur acutely, but it also causes deterioration in health over time. In the British Medical Research Council (MRC) study done in the 1970's, patients whose oxygen level was low but received nighttime oxygen had significantly better survival. Looking at it the other way, those who did not use their oxygen were much more likely to die sooner. It has also been discovered that patients who desaturate at night were more likely to have abnormal heart rhythms. So, it is important to use oxygen not only for wakeful rest, but also during exercise and sleep.

In the second part of this question, when a person lies on their back, several changes occur. First, their tongue may go to the back of the throat and temporarily block airflow. This happens mainly at night (during sleep) in people with obstructive sleep apnea. Also, laying on your back enables the diaphragm to move upward in the chest due to the abdominal contents pushing on the diaphragm. Thus, there is less room inside the chest to inhale. This does not bother most people but some with COPD become noticeably short of breath. For many COPD patients, sitting upright and leaning forward with arms straight and braced on the knees (in a tripod position) gives them more breathing room.

Are there any positive or negative consequences to using oxygen at a higher flow setting than prescribed - what and why? Is there a way to determine the optimum on-demand flow rate?  By turning up the flow rate, do you run the risk of carbon dioxide poisoning?

A reasonable target for your oxygen setting is to assure that your oxygen saturation (SpO2) is greater than 90%. We recommend 92%. Turning the oxygen higher than you need while sitting at rest provides no added benefit. In contrast, a higher setting during exercise or activity may help you to comfortably maintain a higher activity level for a longer period of time. It also may help you to derive greater benefit from your exercise program. This will help you to live a more active life filled with quality.

In the second part to this question, concern about giving oxygen causing CO2 retention (poisoning) is very much overstated. There is an occasional build up of CO2 upon providing oxygen, but it is usually not dangerous. It is best to assure that your SpO2 is running at 92% or higher.  

I've heard that if you have too long an extension tube from your concentrator, that it reduces the O2 that reaches you. So, if you have it set at 3LPM but have 60 feet of tubing that when it actually gets to you it is no longer 3LPM. Is this true?

It is true that a long oxygen tube may create a high resistance to the flow of oxygen and thereby reduce the flow coming from the concentrator. However, this occurs more commonly at higher flows. Most concentrators will handle 5 L/m going through the cannula tubing plus the extension tubing very well. If there is any question, your oxygen supplier has a flow meter to check the actual flow coming from the concentrator.  The bottom line is to check your SpO2 to assure that you are saturating adequately.

I'm on oxygen at night only.  Often after I wake up in the morning, take a shower and start getting ready for the day, I feel the need for it again, so I use it for a little while, maybe half an hour, and it seems to give me the boost I need to make it through the day. Is it okay to do this?   

First of all, please be sure that you need oxygen only at night. A lot of people who are prescribed oxygen at night also need oxygen during their daily activities and their exercise program. In regard to a boost to get through the day, you may be one of those people who need it during the day. If not, a boost may help you to feel better throughout the day – and that’s a good thing. However, you may not be deriving a physiological benefit from this short-term oxygen. You cannot store oxygen taken in the AM for the rest of the day. Sorry!