Case6 Where is the optimum measurement site of SpO2 for PICU/NICU patients?

Our brochures and operation manuals recommend using the body weight of the patient as a yardstick when selecting an SpO2 probe. We also state that the ideal thickness of the measurement site is 6 to 18 mm in Case 2. Nonetheless, there are cases where 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 attachment to the recommended attachment sites with a thickness of between 6 and 18 mm*. The optimum attachment sites for neonates and/or infants are the instep, sole, finger or toe, depending on a thickness of attachment site.

indstepsole fingertoe

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

Point 1: Thickness of the Attachment site

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

Attach probes avoiding bonesAvoid attaching on bones or bony part

Attach probes away from bonesAvoid attaching on bones or bony parts

Point 2: Where the Probe is Attached

In addition to attaching a probe to the instep, sole, finger or toe, we also suggest attaching a probe to the big toe or the base of the 4th toe for neonates/infants, as in Case 2. Relatively larger pulsation can be detected at these sites, thus more stable measurement can be obtained.

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 on how to attach them 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 more details, please contact your NIHON KOHDEN representative.


SpO2 Probe Attachment Guide (for Neonate)