Endotracheal intubation is a medical procedure where a flexible tube is placed through the mouth into the trachea, or windpipe, to maintain an open airway. This allows a patient to breathe during anesthesia or when they are unable to breathe on their own. During this process, a carbon dioxide (CO2) detector is used to help confirm that the breathing tube has been inserted into the correct location.
The Purpose of CO2 Detection During Intubation
When a breathing tube is inserted, it can travel down one of two paths: the trachea, which leads to the lungs, or the esophagus, which leads to the stomach. Correct placement in the trachea is necessary for oxygen to reach the lungs and be distributed throughout the body. If the tube is mistakenly placed in the esophagus, the patient will not receive any oxygen, which can lead to severe complications or death.
The CO2 detector provides immediate feedback on the tube’s location. By confirming the presence of exhaled carbon dioxide, it tells the medical team that the tube is in the airway. This verification is a standard part of the intubation process to ensure patient safety.
Without this confirmation, a misplaced tube might not be discovered immediately, and the lack of oxygen delivery can have lasting consequences. The use of a CO2 detector offers a reliable method to avoid such an error, acting as a safety check for the procedure.
The Science Behind CO2 Detection
The science behind CO2 detection is based on respiration. The lungs perform gas exchange, where inhaled oxygen enters the bloodstream and carbon dioxide, a waste product from metabolism, is removed from the blood and exhaled. Consequently, the air that a person breathes out is rich in carbon dioxide.
In contrast, the stomach and digestive tract do not participate in gas exchange. The amount of carbon dioxide present in the stomach is very low to nonexistent. This physiological difference makes CO2 detection effective. If a breathing tube is correctly placed in the trachea, the air passing through it will contain a measurable amount of CO2.
A CO2 detector is designed to identify this gas. The presence of CO2 serves as a direct indicator that the tube is connected to the respiratory system. If the tube is in the esophagus, there will be no significant CO2 to detect, allowing medical professionals to confirm the tube’s position.
Common CO2 Detector Devices
There are two main types of CO2 detectors used in medical settings. The first is a colorimetric CO2 detector, a small, single-use device. It attaches to the endotracheal tube and contains pH-sensitive paper that changes color when it contacts carbon dioxide. The detector is purple and will turn yellow upon detecting CO2 from exhaled air.
This color change provides a quick, qualitative confirmation of tube placement. Because these devices are simple and disposable, they are often used for initial confirmation, offering a straightforward “yes” or “no” answer regarding the presence of CO2.
A more advanced option is waveform capnography. This electronic monitor provides continuous, real-time measurements of CO2 levels. It displays the concentration of exhaled CO2 as a number, known as end-tidal CO2 (EtCO2), and as a waveform. This monitoring is used for initial placement and ongoing assessment of the patient’s ventilation.
Understanding Detector Readings
Interpreting the readings from a CO2 detector is direct. A positive confirmation of correct tracheal placement is indicated by a sustained color change from purple to yellow on a colorimetric device. With waveform capnography, a consistent waveform and a numerical EtCO2 reading confirms the tube is in the airway, showing CO2 is exchanged with each breath.
A negative reading is a significant warning sign. If the colorimetric detector remains purple or if the capnography monitor shows a flat line, it suggests the tube has been placed in the esophagus. This requires immediate removal of the tube and a re-attempt at intubation to establish a proper airway.
In cases of cardiac arrest, a CO2 reading might be falsely negative. This can happen because poor blood circulation prevents CO2 from being transported to the lungs to be exhaled. For this reason, CO2 detection is used with other confirmation methods, such as listening for breath sounds.