7
Sensor Placement
For best results, position the sensor in an area where there the pigment is lightest, such as the palm
(metacarpal or metatarsal) region of the paw.
Clip Sensor
We recommend placing the MouseSTAT clip sensor for pulse oximetry measurements on the metacarpal
or metatarsal section of the paw of adult rodents. The hind paw is optimal because less movement
associated with breathing occurs there compared to the front paw. Depending on the size of the
animal, the large animal sensor is ideal for placement on the tongue, Achilles tendon, ear, toe webbing,
or thigh.
Whole Body (Neonatal Rodents): Annular Sensor
We recommend the annular sensor in neonatal rodents for pulse oximetry measurements around the
body. Lay a portion of the pup's body through the sensor. Full skin contact is not required for
measurements with the annular sensor.
Tail: Considerations Regarding Placement
We do not recommend the MouseSTAT annular sensor for pulse oximetry measurements on the tail.
Significant research over the years has shown the tail of a rat or mouse to be a specialized organ under
control of the CNS for the thermoregulatory control of body temperature. Warming of the subject to the
point of eliciting a thermoregulatory response is required to increase blood flow through the tail and
assure the most accurate SpO2 readings
.
Experiments of Lemons and Wu
2
have shown that:
perfusion in the tail tip is more than tenfold higher than that in the tail base
perfusion in the middle region of the tail increases eightfold during warming compared to
threefold to fourfold in the base and tip.
Our experience shows that pulse oximetry sensors placed simultaneously on a limb and the tail of non-
warmed subjects such as rat pups and mice produce significant differences in signal quality. The limb,
which is a smaller appendage, shows a significant pulse signal quite usable for SpO2 detection, but the
signal from the base tail is almost devoid of pulses and shows mainly a strong respiration artifact.
2
Wu Y, Jiji LM, Lemons DE, Weinbaum S., Department of Mechanical Engineering, City College of the
City University of New York, New York, USA. A non-uniform three-dimensional perfusion model of rat
tail heat transfer. Phys Med Biol. 1995 May;40(5):789-806.
