By Marc Minkler
Marc Minkler is a 30-year paramedic, educator, and student. He is the owner of mainelyems.com and seeks out finely crafted beer. He recommends a slice of tomato on an English muffin, covered with a slice of Swiss cheese and Italian seasoning and then gently toasted.
“Knowledge is knowing that a tomato is a fruit. Wisdom is not putting it in a fruit salad.” Miles Kington, a quirky British journalist, probably never thought his quote could be used for EMS. You may have missed the textbook chapter on this Tomato Philosophy, as it is known, yet it could be the basis of much of what we do as care providers.
Oxygen is really good. All of our patients need it. Our atmosphere provides what we need most of the time, and at 20.95%, it’s plenty good enough. Except when it is not. As oxygen is the most common medication administered by EMS providers, it must be good for our patients. Right?
Pause the playlist for a moment.
Oxygen is bad.
Oxygen is also good.
So which is it? Does your fruit salad have tomato in it? And, if tomatoes are fruit, is ketchup a fruit smoothie?
As medical providers, we know that oxygen is good. We know that it is a medication as well. But ALL medications have side effects and sometimes they are harmful effects. Textbooks often list the adverse effects of oxygen as “can cause a decreased level of consciousness, and respiratory depression in patients with chronic CO2 retention” or something similar. Feels like I was just told a tomato is a fruit. Technically accurate, but not entirely useful. Let’s look at something a bit more useful.
Gas moves other gas.
When we fill our lungs with high levels of O2, we wash out nitrogen. Since we don’t use all the alveoli with each normal breath, 78% (or so) fill with nitrogen. Nitrogen is inert, doesn’t absorb easily and “splints” alveoli open that is not currently being used. If the alveoli fill with O2 instead of nitrogen, O2 is quickly absorbed, but since we are not releasing the equivalent amount of CO2, the alveoli deflate and stick together like a deflated balloon. This is called atelectasis. Now if we later need to use those alveoli for distress or shock, they are no longer available. Bummer.
Oxygen is a terrorist.
Not really, but it is a free radical. That means it is highly reactive and damaging to cells. Antioxidants normally balance it, and everyone lives in peace. However, when flooded with O2, the antioxidants have not had time to ramp up and prepare for the flood of oxygen. Thus, cell damage occurs. Remember, cell damage = tissue damage = tissue death. Bummer.
Oxygen is a vasoconstrictor.
This is a double whammy. When we think of the “big calls” – an MI, stroke, massive trauma and the like, we routinely administer high-flow O2. Studies have shown that 5 minutes of high flow O2 can decreases coronary blood flow by 30% due to coronary artery constriction, and can also blunt the vasodilation effect of nitroglycerin. Now we just made the patient worse. Double bummer.
Despite all of this, oxygen remains important. When a patient is hypoxic (gasping for breath, poor skin color, etc.), have signs of heart failure (rales, or wet, lung sounds) and/or reliable pulse oximetry readings below 94%, oxygen is certainly beneficial. Everything discussed above will still occur, but the underlying problem is a bigger issue. The American Heart Association and the ECC guidelines reflect this. Proactive medical directors, EMS protocols, and providers also understand this. We can no longer just “give ‘em high-flow O2”. Every medication has good and bad effects. Every patient should be evaluated for the need for oxygen. You gained the knowledge through classes and continuing education about oxygen. Now use the wisdom to correctly administer it.
No one wants a tomato in their fruit salad.
References
Guy, Jeffrey. (2011). Pharmacology for the Prehospital Professional, St. Louis: Mosby.
Harten JM, Anderson KJ, Kinsella J, et al. (2005). Normobaric hyperoxia reduces cardiac index in patients after coronary artery bypass surgery. J Cardiothorac Vasc Anesth, 19, 173–175.
McEvoy, Mike. (2012, June 30). Can oxygen really hurt our patients? Retrieved from https://www.ems1.com/ems-products/medical-equipment/airway-management/articles/1308955-Can-oxygen-hurt-our-patients/
McNulty PH, et al. (2005). Effects of supplemental oxygen administration on coronary blood flow in patients undergoing cardiac catheterization. Am J Physiol Heart Circ Physiol, 288, H1057-H1062.
Sheldrake, Philip. (2011). The Business of Influence: Reframing Marketing and PR for the Digital Age, Chichester: Wiley.