Toe gangrene in an infant subsequent to application of adult-type pulse oximeter probe for 10 min.

We present a case of ischemic changes after application of an adult pulse oximeter probe in an infant for a short period of only 10 min. To understand the physiology behind this mishap, we studied pressure exerted by the adult pulse oximeter probe on simulated fingers (fluid-filled pouches), which were filled under gravity through the three-way stopcock. A catheter was placed inside the pouch to continuously measure the pressure. The experiment was performed on different sizes of the finger-shaped pouches and by varying the positioning of the pouches in the pulse oximeter. It was observed that pressure exerted by the pulse oximeter was directly proportional to the extent to which it was stretched after placement on the fluid-filled pouches of different sizes. In the fully extended position, the pressure exerted was higher (up to 30 mmHg) than in the fully collapsed position (4 mmHg). Higher pressures were caused by greater stretch of the probe. This could occur due to larger fingers and closer placement of fingers to the hinge of the probe.