Infrared absorption provides the measurement basis for most capnographs. As exhaled air is analyzed, carbon dioxide absorbs infrared radiation, allowing the device to track CO₂ during each breath. The resulting measurements are displayed over time, so investigators can examine respiratory changes continuously rather than relying on isolated observations.
The waveform represents successive phases of exhalation, making its shape informative beyond a single numerical value. By following the pattern breath by breath, an observer can identify altered breathing patterns and relate them to ventilation or airway patency. This graphical view is especially useful when respiratory behavior changes during monitoring.
End-tidal CO₂ focuses attention on the concentration measured at the end of expiration, when a breath has reached its terminal exhalation point. Tracking this value alongside the waveform helps assess changes in ventilation and respiratory physiology. In biological studies, its trend can complement observations of respiratory rate and breathing pattern.
Respiratory rate describes how often breaths occur, while the end-tidal CO₂ value adds information about the carbon dioxide level at the end of expiration. The waveform supplies a third view by showing successive exhalation phases. Considering all three observations helps investigators characterize ventilatory activity more fully than rate alone.
During a respiratory study, the instrument is followed continuously as each breath produces a CO₂ measurement and waveform. The observer can compare respiratory rate, end-tidal CO₂, and waveform changes over time, then relate those patterns to ventilation, airway patency, gas exchange, or metabolic and ventilatory activity. This supports structured interpretation of changing physiology.
Capnography is relevant in anesthesia, experimentation, and respiratory investigations because it provides a continuous respiratory readout. Investigators can follow breathing patterns, ventilation, airway patency, and gas exchange as conditions change. In biology, this makes the method useful for connecting observed CO₂ dynamics with broader respiratory or metabolic activity.