SAFA Skysailor Magazine

50 SKY SAILOR September-October-November | SPRING 2025 of different wavelengths on the upper side, through the fingernail. These are received on the lower side of the of the device. From the signals received, the character- istics of the Reductive Haemoglobin and Oxyhaemoglobin are determined using the Lambert Beer Law (nothing to do with beer). The monitor provides an Oxygen saturation value as a percentage. This type of device is really the gold standard for measuring SPO2. So what devices are available that we can buy to do the same thing? There is actually a heap of them out there and they are pretty cheap. They also come in a couple of distinct shapes and modes of operation. Back in 2019 I purchased three of them and gave them a go. Let’s recap those and then get an update. First up, what is there that operates as per the hospital model? Back in 2019 I went for a Contec CMS-50D. There are several versions of this unit which will have either no download capability or download to software via USB cable or Bluetooth. I went basic with this one (Figure 1). The link for that unit will now take you to the latest version of the device. Figure 1: Contec CMS-50D It’s easy to use, just slip it on your finger, press the white button and wait 5-10 seconds. Keep pressing the white button to change how the data is displayed. The display is clear and easy to read. To turn off remove your finger. It’s powered by two AAA batteries. The downside is that for our Hypoxia – 2025 Refresh