capnografi

Capnografi, or capnography, is the continuous monitoring of carbon dioxide (CO2) in respiratory gases, providing both a numerical value for the end-tidal CO2 (EtCO2) and a graphical waveform known as the capnogram. The capnogram reflects CO2 concentration throughout the breathing cycle and is used to assess ventilation and airway status. Capnometry refers to the numeric measurement of CO2, while capnography combines this value with the graphical display.

Capnography relies on infrared absorption of CO2. There are two main sensor configurations: mainstream sensors place the detector directly in the airway path, while sidestream (or sampling) sensors divert a small flow of gas to an external analyzer. Both methods yield real-time CO2 information and can be connected to ventilators, anesthesia machines, or dedicated capnographs.

Clinical use is common in anesthesia, critical care, emergency medicine, and prehospital settings. It helps confirm endotracheal tube placement, monitor adequacy of ventilation, detect apnea or hypoventilation, identify sudden changes in circuit integrity or airway obstruction, and trend CO2 over time to guide therapy. The EtCO2 value typically reflects alveolar CO2 and is normally about 35–45 mmHg in healthy adults, with lower values suggesting hypoventilation, poor perfusion, or disconnection, and higher or rising values indicating hypoventilation or increased CO2 production.

Limitations include potential discrepancy between EtCO2 and arterial PaCO2, especially in cases of poor perfusion, large dead space, pulmonary embolism, or significant ventilation–perfusion mismatch. Sampling delays, sensor calibration, and interference from other gases can also affect readings. Capnography is a valuable, noninvasive tool when interpreted in context with clinical status and other monitoring data.

---