What technology does a capnograph use to measure gas levels?

A capnograph utilizes infrared light technology to measure the concentration of carbon dioxide (CO2) in exhaled gas. This method relies on the principle that different gases absorb specific wavelengths of infrared light. As the exhaled air passes through the capnograph, the infrared sensor detects the absorption of light at these specific wavelengths, which corresponds to the level of CO2 present in the sample. This allows for real-time monitoring of a patient’s respiratory status and can provide valuable information during anesthesia or critical care scenarios.

The other options, while they represent different scientific principles, do not pertain to the function of a capnograph in measuring gas levels. For instance, ultrasound waves are used in imaging technologies, thermal conductivity can be applied in certain respiratory measurements but isn't the primary mechanism for capnography, and electrical impulses are more relevant to other medical technologies such as electrocardiograms or nerve conduction studies. Thus, infrared light is the correct and specific technology utilized in capnography.