Merck Manual

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Open-mouth breathing in an oxygen cage, cat
Open-mouth breathing in an oxygen cage, cat
Open-mouth breathing in an oxygen cage, cat

A cat with open-mouth breathing that is being administered oxygen using an oxygen cage. Note the environmental monitors of oxygen, CO2, temperature, and humidity. CO2, measured in parts per million (ppm), should be lowered by ventilating the unit or using a unit with CO2 scavenging when levels are >2,500 ppm.

Courtesy of Dr. Andrew Linklater.