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Is it possible to have an oxygen saturation of 100% on room air?

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Question
Is it possible to have an oxygen saturation of 100% on room air? Why or why not?
Posted Sun, 22 Sep 2013 in Medicines and Side Effects
 
 
Answered by Dr. Kerry Pottinger 43 minutes later
Brief Answer:
Yes, in a healthy person at sea level.

Detailed Answer:
Hi,
Thank you for using Healthcare Magic.
A healthy person with normal lungs breathing air at sea level will have an arterial oxygen saturation of 95% – 100%.
The oxygen saturation is the percentage of hemoglobin associated with oxygen. This is dependent on both the percentage of oxygen in the atmosphere breathed and the barometric pressure.
Therefore, if you are at altitude, the pressure of oxygen will be less although still 21%. Due to this, the normal range of saturation will be slightly lower than at sea level.
I hope this helps you. If you have any further questions, please do not hesitate to contact me.
regards,
Dr K A Pottinger,
MBChB FRCA
Above answer was peer-reviewed by
 
Follow-up: Is it possible to have an oxygen saturation of 100% on room air? 1 hour later
Hi, ok great thank you! What is the effect of barometric pressure on O2 Saturation? Or can you simply explain why pressure of oxygen will be less, though still 21%?

Thank you, I am a new RN trying to understand the concept fully. A friend recently told me "you can't approach 100% O2 saturation on room air," which I felt wasn't entirely true.
 
 
Answered by Dr. Kerry Pottinger 30 minutes later
Hi,
Thank you for the further question which I will try to answer as fully as possible.
At higher altitudes, the barometric pressure is less. So, although the percentage of oxygen in air will be the same as at sea level, 21%, the pressure of this 21% oxygen will be lower as the total barometric pressure is lower.
At the alveolus, this will result in a lower partial pressure of oxygen in the alveolar gas and therefore the blood. A lower partial pressure of oxygen in the blood equates to a lower saturation of hemoglobin with oxygen in the blood. This can be seen from the oxyhemoglobin dissociation curve.
Perhaps an example may help. At the top of XXXXXXX the air contains 21% oxygen but the barometric pressure is much lower than at sea level. Aterial blood has very low saturations in normal healthy mountaineers at these altitudes. Sometimes saturations as low as 75% have been recorded.
I hope this has explained it adequately. If anything is not clear please let me know.
Regards,
Dr K A Pottinger,
MBChB FRCA
Above answer was peer-reviewed by
 
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