Cardiopulmonary Resuscitation (CPR) is a life-saving technique used when breathing or heart stops. Effective CPR maintains blood flow to vital organs, improving patient outcomes. Modern CPR integrates advanced monitoring tools to guide rescuers and enhance care quality. Capnography is a primary tool in this process, providing real-time insights into resuscitation effectiveness.
What Capnography Measures During CPR
Capnography is a non-invasive method that measures carbon dioxide (CO2) in a patient’s exhaled breath. It focuses on End-Tidal Carbon Dioxide (ETCO2), representing the CO2 level at the end of each exhalation. This measurement is obtained using a sensor placed in the patient’s breathing circuit.
The physiological basis for ETCO2 monitoring during CPR is linked to blood circulation and metabolism. CO2 is a byproduct of cellular metabolism, transported by blood to the lungs for exhalation. During CPR, effective chest compressions generate artificial blood flow, carrying CO2 from tissues to the lungs. The ETCO2 level therefore reflects the adequacy of blood flow produced by these compressions. A higher ETCO2 value indicates better blood flow and more effective CPR.
Identifying Effective CPR with Capnography
During CPR, specific ETCO2 values indicate the quality of chest compressions and resulting circulation. The ideal range for ETCO2 is between 10 and 20 mmHg, with some suggesting 20 mmHg or higher for better effectiveness. Achieving and maintaining these values indicates that chest compressions produce sufficient blood flow to deliver carbon dioxide to the lungs for exhalation.
These ETCO2 values provide a reflection of the cardiac output generated during CPR. Higher ETCO2 readings correlate with improved blood flow to vital organs and better patient outcomes. If ETCO2 levels fall below this range, it suggests compressions may be ineffective or the patient’s overall circulation is poor.
Interpreting Capnography Trends
Beyond single readings, dynamic changes and trends in ETCO2 provide real-time information during CPR. A sudden and sustained increase in ETCO2, often rising to normal values or increasing by at least 10 mmHg, indicates Return of Spontaneous Circulation (ROSC). This spike occurs because the heart has resumed effective pumping, leading to a sudden flush of CO2 from tissues to the lungs.
Conversely, a gradual decline in ETCO2 during ongoing CPR may signal decreasing quality of chest compressions or a worsening patient condition. Persistently low ETCO2 values, especially below 10 mmHg, can indicate a poor prognosis and minimal blood flow. A complete loss of the waveform or a zero reading may indicate issues like esophageal intubation or complete circulatory arrest.
Capnography’s Role in Resuscitation Decisions
Medical professionals utilize capnography data to make real-time decisions and guide resuscitation efforts. Capnography helps assess CPR quality, as persistently low ETCO2 values prompt immediate feedback and adjustments to compression depth and rate. Adjusting compression technique based on these readings can optimize cardiac output.
Capnography is also considered a reliable method for confirming proper placement of a breathing tube in the trachea. A sudden, sustained increase in ETCO2 predicts ROSC, signaling the need for a pulse check. Persistently very low ETCO2 values can be a factor when deciding to terminate resuscitation efforts, as it suggests minimal to no cerebral or coronary perfusion.