June 29, 2008 Close to fifty years is a long time for drive to breathe 'myth' to be perpetuated
Posted Jun 29 2008 4:05pm
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Close to fifty years is a long time for drive to breathe 'myth' to be perpetuated
Mark Mangus replies:
question as to why the general medical pulmonologists seem to feel that there could be a problem with too much oxygen and are hesitant to approve a higher flow.
"You ask a very good question. I can't deny that there are a LARGE number of physicians AND other health care professionals who still adhere/clingto the 'myth' that "too much oxygen can cause those who retain CO2 to stop breathing or to at least decrease their ventilation enough to put them at risk for 'acute respiratory failure'".That is a premise that was birthed out of our misunderstanding of how human beings breathe going back to the late 1950's - early 1960's; hence why I call it a 'myth'. It was based on what we NOW know to be fallacious understanding of respiratory physiology and the mechanisms - - - chemical and neurological - - - that drive breathing.In the 1990's and on into this century, a mounting number of studies (some impressive and audacious, done by the Japanese!) have attempted to invoke the phenomenon - - - 'apnea' - cessation of breathing - - - in CO2-retaining COPD'ers, several studies using subjects that were in full blown 'acute respiratory failure' with extremely high CO2's, by having them breathe 80 % oxygen and higher. In not one instance have they been able to stop one's breathing. In several studies, breathingINCREASED. The fact of the matter is thatwe have only empiric, reproducible evidence to show that the myth is NOT truewhile we have not a single shred of reproducible or empiric evidence to support the 'myth'!
Close to fifty years is a long time for a 'myth' to be perpetuated. It literally pervades ALL levels of health care training. You know the old adage: "Tell a lie long enough and it becomes the reality, but not necessarily the 'truth'." That sums up the gist of the debate. Today, in most respiratory care training materials, it is taught as a "historical misunderstanding" in contrast with the correct - - - and scientifically verifiable - - - explanation.As evidenced by revisions of recent textbooks by our nation's prominent pulmonologists (Barry Make, Brian Tiep, Thomas Petty, to name a few)to include partial revisions of the old 'myth' to work towards denying that it exists at all. They are tiptoeing toward the truth while trying not to totally upset the thinking ship of the greater medical community! While they have not flatly said it's bogus, they are saying that even if it does affect a rare individual , to practice using the 'just enough oxygen' therapy approach - - - where they allow one's oxygen to be raised only to above 88 %, but not above, say, 92 %,notonly robs those with hypoxia and CO2-retention of a decent level of comfort,but it drives them to right heart failure and an earlier death while robbing them of considerable function and livelihood in the meantime.
The concern is mounting to such a degree that our NIH/NHLBI recently initiated a long term study to evaluate (1) earlier intervention with oxygen therapy when hypoxia below 92 % is FIRST detected, so as to assess survival statistics and (2) to assess the affect on physical function, right heart function and length survival by attempting to correct hypoxia to a more "normal" level of >/= 94 % saturation. Another fallacy that is being studied is the notion that detrimental effects on function and the right heart are directly influenced by "paO2" and NOT by "saturation". Yet, with more study of 'dynamic hyperinflation' and the discovery that desaturation resulting from this factor does NOT lower paO2 as much as it causes 'respiratory acidosis' (increased CO2 with decreased pH) suggests that it is indeed saturation and acidosis that is responsible for secondary pulmonary hypertension and quicker onset right heart failure, while paO2 can be "adequate" according to clinical evidence.When you see me responding to folks who talk about their CO2 being elevated, or being CO2-retainers and they are concerned about oxygen use, you will always see me asking about their pH on their blood gas.That is because the pH is the ALL IMPORTANT factor in whether or not we need to worry about what the CO2 is. A CO2 that is elevated in the presence of a pH that is equally decreased spells trouble, regardless of what the oxygen is.The saturation will ALWAYS be decreased with that combination. On the other hand, a CO2 that is increased in the presence of a normal pH is NOT a problem and saturation remains high/normal. Further, 99 % of those who retain CO2 have a NORMAL pH, which is WHY there is NO fear that they will breathe any different, much less worse, if given enough oxygen to run their saturation up to 96 % and higher
The bottom line is that those clinicians who are still adamant about restricting oxygen use by CO2-retainersare, (1) not informed/up to date or (2) simply are not convinced of the evidence, so far. I am confident that with the work going on and the voices in the wilderness, like me, that we will come to a point when folks will slap their foreheads and figure it out. Until then, you must do what your conscience and your doctor agree is best for you. We know that the likelihood of avoidable mishap exists as long as they withhold adequate oxygen. But, it is the accepted standard by a large segment of the medical community and we haven't convinced enough of the medical community to act accordingly."
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