O2 sats and asthma attacks revisited

After 9 years of blogging about life with severe asthma, I still get a lot of traffic from people searching the internet for specific information about O2 saturation and how it relates to asthma or the severity of an asthma attack. So for those who might have missed my earlier posts, here’s a recap of that topic.

O2 saturation by itself IS NOT a good indicator of how severe an asthma flare is. There are many factors involved in accurately assessing the severity of an attack, the biggest one being how well you respond to treatment, not your O2 sat readings! In fact, when it comes to assessing the severity of an attack, I would place O2 sat readings near the bottom of the list. While they’re useful as a rough guide to see which way you’re heading, they don’t paint the entire picture.

As with all vital sign monitoring, numbers that are higher or lower than normal usually get the most attention, and since breathing problems are often equated with oxygen levels, patients and medical staff alike tend to focus on the pulse ox reading and often place too much importance on it. But here’s the deal, you can be in the middle of a pretty severe asthma attack and still have a normal, or near normal O2 sat readings. How is this possible? Well, you have to remember that asthma is a disease of the airways, not the alveoli where gas exchange take place (such as the case with COPD or Emphysema). So unless your airways are completely blocked (which is rare unless you had some sort of massive anaphalatic reaction), or you have a secondary infection or a pneumonia going on, at least a little bit of air still gets through those tight lungs, and that little bit of air is usually enough to keep the blood oxygen level within the lower limits of the normal range. It’s usually not until you’ve been working really hard to breath over a period of several hours, or sometimes even days, that your body can no longer compensate and that’s when your O2 sats will start to drop.

So what’s a typical O2 saturation reading for someone experiencing a bad attack? Everyone is different, but based on my observations as an RT working in a hospital ER and also as a person with really severe asthma, Id say a pulse ox reading of 87-95% on room air or low flow oxygen is pretty common in the ER. As an example, you can see in the photo above, that even though I was in the middle of a pretty severe flare, I was still able to maintain my sat at 95% while breathing 40% oxygen).

Now, that doesn’t mean that if you’re sat is higher than 95%, that you’re not sick. It just means that you’re still able to oxygenate your body. A super high saturation (99-100%) could also indicate some hyperventilaton, which btw almost always happens at the very beginning of an acute flare.
Naturally , if someone’s saturation is trending lower that’s a much bigger concern, as it could possibly indicate impending respiratory failure or full blown respiratory arrest. Thankfully in the vast majority of asthma attacks, that rarely happens.

Bottom line, if you’re an asthmatic having a difficult time breathing and it seems to be getting worse despite taking your medications, what you need to do is contact your doctor and/ or get to a hospital. Don’t waste time by fixating on your O2 sat numbers and trying to figure out if they’re too high to warrant a trip to the ER. Base your decision on how you feel, not your numbers.

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