A few reasons not too rooted in the delivery of 02 (do2) and o2 extraction.
intubation with excessive ventilaton is more harmful than compressions only. If you read the AHA position, it states intrathoracic pressure increases during ventilation
Another off hand point is there is a physiologic reserve of oxygen, so it is not the most important treatment.
back to Do2, if there is a clot blocking blood flow, or bleeding reducing flow, then excess o2 isn't getting anywhere.
There is also the issue of reperfusion injury and the secondary effects of free radical generation.
Furthermore, since CPR and defib are the only proven treatments, those take priority over o2 delivery.
Not a complete or indepth post by any means.
If I might respectfully suggest something?
Read up on physiology.
This topic is explained very well in this book:
http://www.amazon.com/Physiologic-B...1382/ref=sr_1_2?ie=UTF8&qid=1328282027&sr=8-2
or if you have a medical library at hand:
http://www.amazon.com/Millers-Anest...=sr_1_1?s=books&ie=UTF8&qid=1328282073&sr=1-1
The two bolded statements, are the main reason for AHA not wanting airway to be your primary concern.
The cause of cardiac arrest in adults, is rarely due to respiratory arrest. This being the case, that means that the blood statically sitting in the body during arrest still has sufficient oxygen in it to initially perfuse vital organs. Not until we start doing CPR does that oxygen reserve get utilized.
Its like holding your breath underwater. Though you aren't breathing for an extended period of time, your body does still receive oxygen and hence you retain consciousness and a heartbeat.
On the other hand, if you note that AHA recommends 15:2 for kids when more than one provider is present, this is based on the idea that when kids go into cardiac arrest, it is usually related to respiratory arrest. If respiratory arrest is the cause, then the body will not have this remaining cache of oxygen in the blood to utilize as soon as you begin compressions. The thing is that we don't know for sure if respiratory arrest is the cause, so to play it safe they kept compressions first, but split the time until ventilation started down the middle. Hence 15:2.
Also as stated above, intubating has its fair share of complications. First of all, not everyone is the most skilled in intubation. The AEMT (sort of like intermediate here) in my volunteer department, most of have never intubated a real person. The AEMT class here, does not require intubations on anything but a manikin. (paramedic does)
So, you now have someone who truly doesn't know what they are doing, but thinks they do and wastes all this time trying to intubate 10 times.
Next up is the fact that is is MUCH easier to cause an increase in thoracic pressure when a patient has an advanced airway in place vs mask to face. 9/10 the mask wont make a perfect seal with the face, but it will be adequate to ventilate. This allows for overpressure to have at least some route of escape vs. directly over-inflating the lungs. An ET tube gives you one way in and one way out. If the provider is still pressing in on that bag, the air inst coming out. Pop-off valves aren't set to each patient. A 21 year old kid won't have the same tolerance to over-inflation as an 80 year old. Through this, not only have you caused potential damage to the lungs, you may not be letting enough air to escape the lungs. This causes respiratory acidosis, and more importantly has the potential to cause obstruction to the inferior vena cava and Aorta, decreasing the return of blood to the heart and thereby decreasing cardiac output, the exact thing we are trying to repair. Patients should receive absolutely no more than enough volume of air to see the chest rise. (hard to tell when you are doing them in sync with compressions)
AHA has a very strong emphasis on HIGH QUALITY CPR. BLS before ALS every time. Always remember that no pressor drugs or anything but HIGH QUALITY CPR and early defibrillation has been proven by any studies to increase our chances of ROSC. CPR itself is the only proven method. As long as that patient is getting enough air to perfuse the alveoli and slightly expand the chest, your job is done. Gastric inflation is of course a concern, but there are bigger things in the picture to focus on than a potential secondary or tertiary problem.
(I am an BLS AHA instructor)
