Pulse Oximeter

A Pulse Oximeter is a device for checking how much oxygen is in your blood (Blood Oxygen Saturation or SpO₂). They work by shining two different colored lights through your finger and seeing how much of each color is absorbed. A healthy person at sea level should have a SpO₂ of 96-99%. A pulse oximeter is primarily used in Altitude Training or when traveling to altitude, but it is also handy for measuring Resting Heart Rate. I recommend two Pulse Oximeters – the cheap ($30) Octive Tech CEN and the more expensive CMS-60C.

1 Getting an Accurate Reading

Because a Pulse Oximeter is indirectly measuring SpO₂ via the light traveling through your skin, there are a number of factors that can impact the accuracy of the reading.

• Fingernail polish. Any polish or covering over the fingernail can create problems for the Pulse Oximeter. If you can use a finger that is clear, that is ideal, but you can twist the Pulse Oximeter sideways to get a reading across the finger rather than down through the nail.
• Skin color. Dark skin pigmentation can result in an over-estimated SpO₂ reading when it the levels are below 80%. Try to find an area of lighter skin color if possible.
• Movement. Any movement tends to disrupt the measurement, so stay as still as possible.
• Bright lights. A good Pulse Oximeter will tend to shield out any external light, but try to keep light levels reasonably low and avoid shining a light onto the Pulse Oximeter.
• Carbon monoxide poisoning. The pulse Oximeter will show the overall saturation of the blood, without telling the difference between oxygen and carbon monoxide.
• Blood insufficiency. Low blood volume, anemia or poor circulation can all cause problems with the reading.

2 Positioning the Oximeter

These pulse oximeters can be positioned on the finger or the toe. While the toe is the most accurate location there is a delay in the reading that makes it unsuitable for Intermittent Hypoxic Exposure.

3 Recommended Pulse Oximeters

3.1 Octive Tech CEN

This is one of the cheapest pulse oximeters I found, and provides the basic functions adequately. It will display current SpO₂ and Heart Rate, and is easy to use. It doesn't have the more advanced features of the CMS-60C or CMS-50E, such as values overnight or interfacing to a computer. I use a similar pulse oximeter to record my Resting Heart Rate each morning.

3.2 CMS-60C

This is a significantly more expensive and more sophisticated pulse oximeter. Unlike most pulse oximeters the main unit and the fingertip sensor are separate. I find this makes it much easier to use for Altitude Training as there is little weight on the fingertip. Like cheaper pulse oximeters, the CMS-60C will display current SpO₂ and Heart Rate, but it will also record the values for up to 24 hours. However, the biggest advantage of the CMS-60C is that it will interface to a computer. I have written some custom software, the Hypoxic Timer, that helps record and evaluate Intermittent Hypoxic Exposure training. The CMS-60C sensor is also easily replaceable, which is nice.

3.3 CMS-50E

Before I got the CMS-60C I used the CMS-50E with my Hypoxic Timer software. I upgraded to the CMS-60C for convenience and the price is not radically different, so I would not recommend the CMS-50E unless you particularly want the compact form factor. Note that this is the only pulse oximeter other than the CMS-60C that I know will work with my Hypoxic Timer software.