Blood Oxygen Saturation (SpO2)

Last modified by Iris Spruit on 2024/07/26 12:38

Contents

Introduction

Blood oxygen saturation can be measured on the fingertip or earlobe. A finger or ear clip with LEDs, one red and one infrared, is used. Because light absorption differs between oxygenated and deoxygenated hemoglobin, the percentage of oxygenated hemoglobin can be measured.

Availability, Support and Use-case

SpO2 equipment from BIOPAC (OXY100E) can be borrowed from SOLO through the Helpdesk (reservations tile) or by contacting labsupport@fsw.leidenuniv.nl. 

Protocol

Below, a general protocol for measuring SpO2 is described. Note that an adequate training is required before working with physiological data acquisition equipment and collecting such data from participants. If you are uncertain about the procedure, please contact your supervisor or lab coordinator. 

Setup

Equipment

Oxygen saturation can be measured with the BIOPAC OXY100E module.

Transducer

The OXY100E uses an ear clip SpO2 transducer (TSD124B) or finger clip SpO2 transducer (TSD124D). Currently, only an ear clip transducer is available at SSH Leiden.

Materials

For SSH researchers, supplies can be picked up at SOLO 1B11 in PdlC or 2.5.01 in Sylvius, see lab supplies for more info.

  • SpO2 equipment (see Setup)
  • Gloves
  • Incidin OxyWipe

OXY100E calibration

See the Pulse Oximetry product sheet for more information about the calibration. The calibration needs to be done once, when the module is connected to a Biopac MP system and a PC. Make sure to create a template (.gtl file) that you can use for each participant. Perform the calibration again when the setup changes (i.e. connected to a different PC or different Biopac MP system).

  • Connect the OXY100E to the Biopac MP system and the MP system to the data acquisition PC.
  • Go to MP150/160 > Set Up Data Acquisition.
  • Add an OXY100E module (Add New Module > OXY100E).
  • Click View by Channels (in the bottom left). Select the OXY100E channel and click Setup. A warning will pop up, click Yes. You are now in the Scaling analog channel menu for the OXY100E module.
  • On the OXY100E module, use a paperclip or pen tip to press the Cal button. Press and hold the Cal button for ~1.5 seconds to switch between modes. Once the mode has switched, release the Cal button. The modes are indicated by the Status LED states on the OXY100E module.
    • Normal status: yellow occasionally flickers
    • Calibration low: Constant green
    • Calibration high: Constant yellow
  • Press and hold the Cal button to switch from Normal to Calibration Low (constant green). Then click the Cal2 button in the Scaling analog channel menu in AcqKnowledge.
  • Press and hold the Cal button to switch from Calibration Low to Calibration High (constant yellow). Then click the Cal1 button in the Scaling analog channel menu in AcqKnowledge.
  • Press an hold the Cal button to switch from Calibration High to Normal (yellow occasionally flickers).
  • Make sure to save the calibration in a template, go to Options > Save as Graph Template to save the calibrated OXY100E channel. Make sure to use this template each time you are collecting data.

Contact labsupport@fsw.leidenuniv.nl if you need help with the calibration.

Placement

Always wear disposable gloves (see gloves protocol) when you place the ear clip. After use, remove the gloves and dispose of them.

Skin preparation is not required.

Place the ear clip on the participant:

  • Make sure the participant does not wear earrings.
  • Put on disposable gloves.
  • Place the ear clip on one of the earlobes.

Note that the ear clip should be properly placed on the earlobe. Make sure the light shines through the earlobe, not under it. When the light shines under the earlobe, oxygen saturation levels of > 100% are measured. When the participant has small earlobes, attaching the clip can be difficult. Try carefully stretching the earlobe a bit with one hand, while placing the ear clip with the other hand. Make sure you always communicate with the participant about what you are doing and ask them to indicate when it hurts.

Cleaning up

  • Put on disposable gloves.
  • Remove the ear clip from the participant’s ear.
  • Disconnect the ear clip from the OXY100E module.
  • Gently clean the ear clip with Incidin Oxywipe (make sure the wipe is not too wet). Let the clip dry before using it again.

Tips & Tricks

  • Do not let the participant move much with their head, to make sure the ear clip stays properly attached.
  • Check the oxygen saturation and pulse signal before starting actual data collection. When the oxygen saturation level is > 100% (around 125%) the ear clip is probably not attached properly, and the light is shining under the earlobe. This can be because the participant has small earlobes. Try reattaching the ear clip.

Resources