In Reply:

—Datex-Ohmeda concurs with the authors conclusions that extremely intense lights can affect the readings of the volume monitoring function of the Datex-Ohmeda Modulus CD anesthesia system. Similar affects can be expected on other Datex-Ohmeda products that use the same infrared light/turbine vane volume measurement technique.

Datex-Ohmeda became aware of this unlikely potential condition in the late 1980s. Since that time, revised subject Operation and Maintenance  manuals include an additional warning in the precaution section:“WARNING: Exposure of the sensor clip to a direct beam of light may cause erroneous monitor readings. Shield the sensor clip with opaque material if the readings are suspect.”

It is interesting to note that newer surgical lights are generally designed to filter the amount of infrared light. This is intended to reduce the heating effect on the patient and operating room personnel. Malfunctioning lights, lights missing infrared filters, or older designs of lights may increase the possibility of this potential condition.