Case1 Where is the Optimum Measurement Site of SpO2 for PICU/NICU Patients?

Our brochures and operation manuals indicate body weight of the patient as a yardstick when selecting a SpO2 probe. We also state that an ideal thickness of measurement site is 6 to 18 mm in Case 2. Nonetheless, there are cases that it is difficult to stably measure an accurate SpO2 value especially for neonates and infants.

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NIHON KOHDEN’s SpO2 probes are designed for 6 to 18 mm of thickness of the recommended attachment sites*. The optimum attachment sites for neonates and/or infants are instep/sole/finger or toe, depending on their sizes.


Even said so, if the value is unstable, here are some points to confirm.

Point 1: Thickness of the Attachment site

When the SpO2 value is not stable, isn’t it attached to a site thicker than 18 mm? Or, even it is attached within our recommended range that is 6 to 18 mm, isn’t there any bones between a light emitter and a photo detector of SpO2 probe?
When a probe is attached, there are bones in between a light emitter and a photo detector, thus the light do not transmit properly which results in inaccurate measurement. Because bones of neonates are cartilaginous, the light might transmit through the bones and be able to detect SpO2 but if you cannot stably measure an accurate SpO2, avoid attaching a probe to a bony part.

Attach probes avoiding bonesAvoid attaching on bones or bony part

Attach probes avoiding bonesAvoid attaching on bones or bony part

Point 2: Where the Probe is Attached

In addition to attach a probe to instep/sole/finger or toe, we also suggest to attach a probe on the big toe or the base of the 4th toe for neonates/infants, in Case 2. With these area, relatively larger pulsation can be detected in these sites thus more stable measurement can be measured.

6-18 mmbig toebase of the 4th toe


Point 3: How the Probe is Attached

Make sure that the light emitter and the photo detector face each other at all times. For more information in how to attach correctly, please read Case 3.

Good attachmentBad attachment

Use NIHON KOHDEN’s genuine probes with our monitors!

*The thickness of the recommended attachment site may differ depending on the connected monitor and/or cable. If you would like to know the detail, please contact your NIHON KOHDEN representative.