Need Advice- Cosmed K4B2- CO2 sensor adjustment

[Justus Ortega]

We have a Cosmed K4b2 in the lab. O2 sensor was replaced 6 months ago ($1500). We do not use the K4b2 very much (one study and 16 subjects). Now the Co2 sensor is showing good values but the trimmer is out of "normal range" (shows 0). We have technical notes to adjust the trimmer, but Cosmed Support sayswe need to send the unit in and that the O2 sensor should be replaced again and they will adjust the CO2 sensor at the same time.

1. Even thought the unit has not been used very much, does it seem right that the O2 sensor already needs to be replaced (even though it gives good calibration values).?
2. What is the rationale for replacing the O2 sensor every 6 months; such a short period of time and use (6 month, 16 subjects and only ~12 hours of use)?
3. Do you think it is fine to simply adjust the trimmer according to the technical notes? it seems straight forward but am I missing somethings.

Any insights are greatly appreciated.

Justus Ortega (HSU Biomechanics Lab)