let me try and explain it in the best way that I can, based on my own experience and theoretical knowledge.

first, breathing is essential for life, so therefore our biological "alarm" system is very sensetive and takes a very large margin. this is why we can experience shortness of breath, even when there is only a mild impairment of our respiratory system and we have a good respiratory reserve.

the breathing center in our brain is very sensetive to the absolute level of CO2 in our blood and also to changes in it. kids that have contests of breath holding learn to "hyperventilate" before and then their CO2 levels go down and they can hold their breath longer. but if you hyperventilate too much you will start feeling dizzy and tingling in your extremities, the reason for that is a change in the acidity of your blood and a decrease in the level of calcium.

if you hold your breath, your level of CO2 will start rising and reach a level in which your respiratory drive will be so high that you will be unable to keep on holding your breath any more. this senseation is a horrible feeling of suffocation. and that is why if you can't breath enough to correct it you may feel like you are about to die.

this is different from one person to the other. some people are extremely sensetive to very small changes in their CO2 level and others can tolerate much higher levels. also, people that have chornically high levels of CO2 (such as patients with COPD) will become less sensetive to it.


at this stage of CO2 retention you may feel very agitated,

if the CO2 levels keep on going up, you will start to feel more and more solmnolent. this may almost be a feeling of euphoria, at some point. and this is really dangerous, because then you just gradually sink.

if your CO2 levels are constantly higher then your normal, you may just feel totally wiped out, physically and mentally. you may also experience morning head aches, as when you sleep your CO2 retention becomes worse.

the O2 levels may be slightly decreased or even near normal, as the gas exchange of oxygen is dependent on many other factors, and you need much less ventilation in order to keep it intact.

all the consequences of CO2 retention are basically reversible once the level is corrected. as opposed to significant hypoxemia, which can easily lead to irreversible brain damage, within a few minutes.

the use of oxygen, can sometimes make the CO2 retention worse, due to complex processes, and therefor most neuromuscular pulmonologists do not recomend its use.

a respirator, allows the respiratory muscles to rest (as obviously you can't let them rest, like you would your arms or legs, by stopping to breath for a while). sometimes no more then 15 minutes are required and sometimes an entire day. sometimes every few hours and sometimes no more then once a week, all depends on the various factors that affect the activity of this illness.

I have learned, the hard way, that even excellent pulmonologists, with a very good understanding of neuromuscular disease, can be totally ignorant when it comes to non-invasive respiratory support.

and it was quite funny, because at one point I had a pulmonologist that had a good understanding in neuromuscular disease and another that had no understanding in that, but had a good understanding of NIV. and none was interested in communicating with the other. at some point I realized that this just doesn't work and eventually found one that understands both.

I hope this has been of some help,

as I have said neuromuscular pulmonology is very complicated and in a fluctative illness like MG even more, and my knowledge in that is limited.

alice