Hypoxia and Medicine

"Pulse-ox" reading inaccurate?

Hi, I've been having some pretty bad asthma symptoms lately (bad enough where I went into the hospital last night). I was put on Prednisone 40 mg 2X daily. Anyway, my oxygen saturation was fine, and I'm wondering if my over-compensating breathing (i.e. I was trying to make up for my shallow breaths by taking more and taking them as deeply as possible, even though my chest was sore) would have highered it, when, if I had just let myself breathe without physically straining during the attack, would it have made my oxygen levels drop lower? There have also been times when I have a bad attack and my oxygen is close to normal, whereas with a mild one, the reading is much lower. Could this be caused by my rapid breathing (in a desperate attempt to get more air in)? Thanks! Would the nail polish, poor circulation, and cold hands cause a LOWER reading than normal, or a higher reading? (If you don't mind, can you hit the "edit" on your answer and add that in please? I don't think you can reply to a question twice. :) Thank you so much!) Oh my gosh! That could explain why it read normal ... I'm very anemic (Ferritin was 7 I believe). Thank you so much!

Public Comments

1. Hyperventilation will make your 02 sat go down because you are actually not getting enough 02 to your body. Breathing deeply but not rapidly will make your sat go up because your body is actually able to use the oxygen when its not rapid in excess. Regardless the things than can cause a inaccurate 02 sat is cold hands poor circulation to the hands fingernail polish bad battery in the machine itself Fingernail polish, cold hands, poor circulation will make it lower To respond to the ER nurses comment: I did not say that hyperventilation was a lack of oxygen. It is too much C02 (carbon dioxide) therefor it does you no good to do so becasue your body cant use it due to the carbon dioxide. Yes, your 02 sat during hyperventilation will most likely be within normal limits. Hope this helped, I hope you get better soon.
2. Im sure you know that with Asthma its not taking in deep breaths that is going to get you relief.. but your Albuterol Inhaler. Because your bronchioles are tightning in which wheezing would take place.. it wouldnt benfit you to take in deeper breaths until you are able to. It would seem like with a bad attack.. your O2 levels would be lower then a mild one.. but everyone is different. My suggestion is to always carry your peak flow meter to let you know how your lungs are doing.. and always use a spacer with your inhaler. 80% of the medicine will hit the back of your throat without a spacer no matter how good you are at doing it :)
3. A pulse oximetry machine measures the percentage of your RBC's (red blood cells) that are carrying oxygen. Many things can affect the reading such as anemia. If your RBC count is too low then even if your pulse oximetry reading is 100%, you may still not be getting enough oxygen to your tissues because there isn't enough RBC's to carry it. The reading simply means all the RBC's you do have are carrying oxygen. As far as your respiratory effort affecting the reading yes it could. If you had breathing very shallow and very rapid you might not have been taking in as much air as you were when you were forcing yourself to deep breathe. As far as the different readings with a mild attack vs. a serious one, this is something that could have been because of your breathing patttern, or your RBC count at the different times, like I talked about earlier. And yes, fingernail polish, cold hands, and poor circulation can cause "false readings". These would cause the pulse oximetry machine to read your oxygen saturation as lower than it actually was. This is why healthcare proffesionals are taught to "treat the patient, and not the monitor". While a pulse oximetry is a valuable tool, we also look for things like cyanosis (blue lips, fingers, etc), wheezing, retractions (where you are using muscles not usually involved with breathing, in an attempt to get in more air) and respiratory rate (normal is 12-20 breathes a minute). The best way to determine a patients blood oxygen level is with an ABG (arterial blood gas). This is where a small sample of blood is taken from an artery and tested. I also wanted to respond to one of the other answers you recieved which is incorrect.: Hyperventilation is caused by a carbon dioxide defecit, not a lack of oxygen. When you hyperventilate (breathe to fast and shallow) you blow off to much carbon dioxide, not oxygen, and a hyperventilating person almost always has a normal oxygen saturation. Also use your fast ating inhaler such as Albuterol when you have an attack as this will help relieve the constriction of the bronchials. Hope this helps!