NOTE: Try Before You Buy. This app supports most pulse oximeters, but not all models are supported.
Step 1:
First, you need a pulse oximeter hardware. Such as CMS50D +. (https://www.amazon.com/Blue-Finger-Pulse-Oximeter-Sofware/dp/B00B8L8ZXE)
Step 2:
Install the pulse oximeter driver software. Such as CP210x USB to UART Bridge VCP Drivers. (https://www.silabs.com/products/development-tools/software/usb-to-uart-bridge-vcp-drivers)
Step 3:
Connect the pulse oximeter to the USB port.
* Set the COM serial port parameters according to the pulse oximeter manual.