How Much Oxygen Should I Use?
Target Oxygen Saturation is 92%
Dear Dr. Mahler:
I am 71 years old and have severe COPD for several years, but am doing fine and have adjusted to my situation. I use oxygen 24/7 from a stationary concentrator at home and from a POC with activities and travel. I fly (at least before COVID-19) to visit my children/grandchildren in Wisconsin.
However, I am confused about my oxygen flow rate. My doctor told me that 2 liters/minute is what I need at rest, and my oxygen saturation level is usually 91-92%. However, I turn up the oxygen to 4 liters/min because I feel better when my saturation level is 94-95%.
My POC has pulse flow and I use the highest number – 5 – which maintains a saturation around 91% when I am active.
What are your thoughts on this?
Jim in Austin, TX
Dear Jim:
Thanks for a common question that can be confusing for many individuals using supplemental oxygen.
Everyone knows that oxygen (O2) is essential for life. The air we breathe contains 21% O2 and 78% nitrogen with the remainder being trace gases. How does oxygen get to the cells? O2 in the air is inhaled into the lungs, reaches the air sacs (alveoli), and transfers across a thin membrane into the blood. In the blood, it is carried by red blood cells throughout the body and moves from blood into cells and mitochondria.
Oxygen is a fuel that combines with nitrogen and hydrogen in mitochondria to produce proteins to build new cells. In addition, it combines with carbon and hydrogen to produce carbohydrates – a major source of energy for the body. It also activates the immune system to help kill bacteria and defend against viruses.
What Is The Oxyhemoglobin Saturation Curve?
In the curve shown below, PaO2 refers to the partial pressure of oxygen as determined by a sample of arterial blood. Note that the curve is S-shaped. For mitochondria and cells to function normally, the PaO2 should be 60 mmHg or higher
(dashed vertical line). This corresponds to a SpO2 of 90% (dashed horizontal line). Thus, the goal when using oxygen is to use a flow rate that achieves a SpO2 of at least 90%. A target of 92% is often used to allow for possible inaccuracies of pulse oximetry in the measurement of SpO2. For example, oximeters may give a reading 2% over or 2% under what your saturation would be if obtained by an arterial blood gas (the gold standard). Anything higher than 92% is generally unnecessary unless you are having a sudden or acute medical problem.
What Is A Normal Saturation?
A normal SpO2 is 95 to 100%. A value below 95% is reduced but considered adequate if it is above 88%. In fact, for oxygen to be paid by an insurance company, the SpO2 needs to be 88% or below. The oxygen saturation is normally measured by a pulse oximeter placed on a finger, but a Wrist Bracelet can also be used.
Jim – even though you might feel better at a SpO2 of 94-95%, there is no evidence that your mitochondria or cells work any better at a level above 92% .
What Is Oxygen Titration?
Usually, a nurse, respiratory therapist, or pulmonary function technician will measure your SpO2 with an oximeter and then adjust the flow rate to determine how much oxygen you need at rest and/or with walking to achieve a SpO2 of 92%. This is called titration. Typically, a higher flow rate is required during physical activities/exercise than at rest.
Please note, the advice provided is not a substitute for asking your health care professional about your specific situation.
Sincerely,
Donald A. Mahler, M.D.