image181-1Ask Mark

Tom asks how low can you let your oxygen saturation drop before you get into trouble?

Mark replies, That is a loaded question and not easily answered with a simple, straightforward response.

A one­time drop in saturation will rarely cause any direct harm, in and of itself, as long as it is limited in duration and severity. One can drop to a saturation in the 35% range (like climbing Mt. Everest or hiking in the Chilean Andes at 20,000 feet). But that can only be for a very short time before you feel the ill effects. If saturation repeatedly drops, all bets are off for what is the lowest, how long and how many times it can drop before harm ensues. Therapists like to keep your oxygen saturation about 92% in active people with COPD.

What usually happens in COPD is that for up to a few years, one’s saturation dips below 85% during activity and maybe also during sleep. Much of the time, no ill effects are noted, so the person is unaware that it is happening, except that during activity, they may become inordinately short of breath. After so many occurrences of such drops occurring over time, and how many and how long is very individualized, at some point the body – especially the heart – says: “I’ve had enough!” and begins to fail in function. The heart works harder to pump blood through the diseased lungs trying to get more oxygen in or the heart muscle stretches out against the back pressure that is created by constricted blood vessels in the lungs. Blood ves­ sels in the lungs constrict in response to low oxygen levels. The heart then loses its strength to contract effec­ tively. In either case, heart failure develops.

If not corrected by use of supple­ mental oxygen to normalize oxygen levels, total failure will eventually occur.

John was looking at the GOLD guidelines at and where his pulmonary function results fell in the classification chart. His results were in both Stage II Pre- Bronchodilator and Stage I Post- Bronchodilator. John asks if this means as long as he uses prescribed inhalers, he is in Stage I, but that he is in Stage II if he doesn’t?

Mark explains, It is upon the “post­bronchodilator” PFT measure­ ments that we base the diagnosis and staging of one’s COPD. Your response to the bronchodilators may change over time.

Pat from EFFORTS wondered if eating a large pasta meal would be good for her.

Mark says, Pasta contains very long chain carbohydrates which don’t tend to drive up blood sugar (and therefore do not cause rapid loading of carbon dioxide) like short chain sugars do in the sweet things we eat. As with potatoes, pasta is a

image093-1good component to one’s diet if you have COPD. You just have to eat it in modest servings – four ounces or less of cooked pasta. It is the type of carb and the quantity it represents in one’s diet that is important!

When you eat a ‘full­sized’ meal, your diaphragm is being pushed downward, compressing the contents of your abdomen. A full stomach competes for that space increas­ ingly wanting to be occupied by the increasingly distended lungs. Only one can win, and it’s usually the stomach, since it is filled with matter more dense than the air in the lungs, so breathing is impeded.

By reducing the size of each meal and increasing the number of times you eat, you lessen ‘the competition’. When you split your ‘usual’ total calorie intake between several meals, it can ‘seem’ like you are eating less, when you are actually eating the same, or even more. Counting calo­ ries and watching weight changes is really the best way to determine what you are doing with regard to calorie intake.

Mark Mangus RRT, BSRC, is a member of the Medical Board of EFFORTS (the online support group, Emphysema Foundation For Our Right To Survive, www.emphysema. net). He generously donates his time to answer members’ questions.