Capnography is a critical tool in the field of emergency medical services (EMS), providing crucial information on the respiratory system and its functions. Despite its importance, there is still a stigma surrounding the use of capnography in EMS culture. However, learning and using this tool and understanding capnography waveforms can greatly improve treatment and care for patients.
The Four Pillars of Respiratory Physiology
The Four Pillars of Respiratory Physiology are ventilation, perfusion, oxygenation, and diffusion. Ventilation refers to the movement of air in and out of the lungs, while perfusion is the delivery of blood to tissues. Oxygenation involves the delivery of oxygen to the tissue, and diffusion refers to the movement of oxygen and carbon dioxide (CO2) between the lungs and the bloodstream.
There are several tools for capturing CO2, including the EZ cap, nasal capnography, and in-line capnography with a bag-valve-mask (BVM). The anatomy of a reading includes the end-tidal CO2 (ETCO2), which is the maximum amount of exhaled air at the end of a breath, and the capnogram, which is a graph that shows the waveform of CO2 over time.
Capnography Waveforms
Capnography waveforms have several sections, including exhaling, the expiratory plateau, inhaling, and shape changes. Hyperventilation and hypoventilation can also be detected through capnography, and changes in waveform shape can indicate respiratory disorders such as asthma.
Capnography is a valuable tool for recognizing irregular respiratory patterns and detecting respiratory depression and airway disorders, especially during sedation. It is also useful in understanding ventilation-perfusion and metabolism of breathing and acid-base balance. The ROME mnemonic, which stands for Respiratory Opposite, Metabolic Equal, is often used to explain the relationship between CO2 and pH.
End-Tidal CO2
The accuracy of ETCO2 readings can be affected by factors such as the accuracy of the endotracheal tube placement and the effectiveness of CPR compressions. ETCO2 readings above 10 can indicate the return of spontaneous circulation (ROSC) during resuscitation.
In conclusion, capnography is a crucial tool for EMS providers in understanding respiratory physiology, recognizing irregular respiratory patterns, and detecting respiratory depression and airway disorders. Despite any stigma surrounding its use, EMS providers need to learn and use capnography to improve treatment and care for their patients.
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