Last Updated On: December 26, 2024
Capnography refers to a non-invasive measurement for checking end-tidal carbon dioxide (EtCO₂). EtCO2 is defined as the level of carbon dioxide exhaled at the end of each breath. This measurement is important for checking how CO₂ is produced by your body and transported through blood circulation. The current Advanced Cardiac Life Support (ACLS) guidelines recommend using Capnography during CPR to analyze chest compressions and the duration of cardiopulmonary resuscitation (CPR). It ensures effective airway management by monitoring the compression rate and depth in patients. This guide will discuss in detail the importance of capnography during CPR and emergency care.
CPR is an effective technique performed on patients experiencing cardiac arrest to provide adequate blood flow to the heart, brain, and other parts of the body. Capnography is performed to monitor and improve CPR outcome optimization during this time. Here’s how the tool helps healthcare providers perform effective chest compressions in emergencies:
Higher EtCO2 levels indicate good blood flow to organs like the brain and heart, which means CPR is effective. Low levels of <10 mmHg suggest poor outcomes and may guide decisions about advanced interventions.
A sudden rise in EtCO₂ during CPR often signals the return of spontaneous circulation (ROSC). This means the heart resumes an effective rhythm and begins pumping blood again after cardiac arrest. A change in the heart’s rhythm usually signals an improvement in the patient’s condition.
Capnography during CPR ensures the breathing tube (endotracheal tube) is placed correctly by detecting CO₂ in exhaled air. ETCO₂ levels help decide whether patients need specialized treatments in prolonged cardiac arrest cases.
Drugs like adrenaline and ventilation changes can impact ETCO₂ levels. End-tidal CO₂ capnography helps interpret these readings carefully to analyze the effectiveness of CPR in reviving the patient. It provides real-time insights into the effectiveness of CPR by reflecting changes in blood flow and gas exchange. This enables healthcare providers to assess the likelihood of resuscitation and make adjustments to CPR techniques.
Proper capnography equipment setup is the key to monitoring ETCO₂ levels during CPR and ensuring adequate resuscitation. The process begins by preparing the equipment and providing the capnography monitor in working condition. Further steps include:
Make sure that the capnography monitor is fully functional and ready for use. Select the CO₂ sampling line based on the patient’s condition. For non-intubated patients, you must use a nasal cannula or face mask with integrated capnography capability. However, an inline adaptor is required for all intubated patients. Ensure that all components are compatible with the monitor.
For intubated patients, place the inline adaptor between the endotracheal tube and the ventilator bag or mechanical ventilator. This setup ensures continuous CO₂ measurement during ventilation. For non-intubated patients, attach the nasal cannula or face mask to capture exhaled air effectively. Proper connection helps avoid leakage and provides accurate readings when using capnography in emergency care.
Turn on the capnography monitor and follow the manufacturer’s instructions to perform calibration. This ensures that the device provides correct ETCO₂ measurements and avoids errors during situations like CPR.
After setting up the equipment on the monitor, start the capnography waveform interpretation process. Make sure that the waveform corresponds to the patient’s ventilation. Analyze the readings to assess the quality of CPR and make adjustments as needed. Pay attention to any abrupt rise in ETCO₂ because it indicates the return of spontaneous circulation (ROSC).
Ensure the capnography equipment is correctly positioned and unobstructed during CPR. If the readings appear abnormal, check the sampling line for blockages or disconnections. Based on the monitor’s feedback, adjust ventilation and chest compressions to optimize resuscitation efforts.
4 Phases of Capnography Readings
Capnography readings are interpreted as waveforms, which you must understand adequately to ensure correct CPR efforts. Every waveform indicates four distinct key indicators which are in the form of phases. These include:
The first phase of a waveform occurs during inhalation. Since you cannot release carbon dioxide while breathing in, this phase shows a flat line at or very close to zero on the monitor screen. Phase I forms the baseline of capnography waveform interpretations.
Phase II begins when the patient transitions from inhaling to exhaling phases. The rapid increase in CO₂ pressure trips the capnograph’s sensors. This may appear as a sudden uptick in the graph and often forms the first side of the rectangle.
This phase represents dead space air being exhaled on the capnography monitor. Phase III is also called the alveolar plateau and forms the top of the waveform rectangle. It maintains a constant pressure as your patient breathes out. The peak pressure that you get at the end of phase III is your end-tidal carbon dioxide value.
Phase IV is the final indicator, which witnesses the patient transitioning from exhaling to inhaling. Please note that CO₂ is not released during inspiration. This phase witnesses a sharp drop in the end-tidal CO₂ on the monitor.
Capnography during CPR helps detect the return of spontaneous circulation (ROSC) effectively. The measurement of end-tidal CO₂ (ETCO₂) provides real-time feedback on blood flow and ventilation, which are indicators of cardiac activity.
A sudden and sustained rise in ETCO₂ levels during CPR is one of the most reliable signs of ROSC. This increase occurs because the heart has resumed effective pumping. It helps improve the blood flow to the lungs and enables the elimination of CO₂. ETCO₂ levels after ROSC may often be higher than during cardiac arrest, where levels frequently remain below ten mmHg.
Capnography waveforms are also helpful in identifying ROSC. A sharp change in the waveform pattern during CPR suggests that spontaneous circulation is restored, which encourages a reassessment of the patient’s condition.
Capnography allows healthcare providers to confirm ROSC early by providing immediate and noninvasive feedback. This ensures timely treatment adjustments to optimize patient outcomes.
Capnography in emergency medicine is an excellent assessment tool that helps analyze the condition of patients. However, simply relying on its interpretations is not enough because the tool has its own set of challenges, such as:
Improper placement of the CO₂ sampling line, especially in intubated patients, can lead to inaccurate readings or no waveform detection. For example, a misplaced endotracheal tube can result in a flat capnography waveform. To overcome this, always verify correct tube placement immediately after intubation using the initial waveform and ensure the sampling line is securely connected. Routine checks during CPR help maintain proper equipment setup.
Blockages caused by mucus, blood, or condensation in the CO₂ sampling line can interfere with accurate monitoring. These obstructions can cause erratic waveforms or sudden drops in ETCO₂ levels. To address this, inspect the sampling line regularly during resuscitation and clear any visible blockages. Using anti-condensation sampling lines or replacing the line when needed can prevent disruptions.
ETCO₂ readings can be influenced by factors such as altered ventilation rates, low cardiac output, or drug administration (e.g., adrenaline). Misinterpreting these variations may lead to inappropriate decisions during CPR. Overcoming this challenge requires integrating capnography data with clinical assessments and understanding how external factors impact ETCO₂ levels. Healthcare providers can train themselves in Capnography waveform interpretation for accurate decision-making and effective use of the tool.
If you are a healthcare professional, you may have to use capnography during CPR in several cases. Make sure that you understand how to run the equipment before setting it up for ETCO₂ analysis. The best way to learn more about capnography is to pursue a CPR re-certification. Approach a recognized organization of your choice and enroll in a course that teaches you in detail about using various equipment to help patients in cardiac emergencies. This will help you acquire efficient skills as a healthcare provider and assist individuals in real-life scenarios.
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