8/5/2023 0 Comments Normal end tidal co2 waveformKnowing how to read capnography waveforms gives you a surface understanding of your patient’s ventilation status. Abnormal Capnography Waveforms and Their Interpretation As such, phase IV appears as a sharp drop from the end-tidal CO2 peak back down to baseline, forming the last side of the rectangle. Remember that CO2 isn’t released during inspiration. Phase IV takes place when your patient transitions from exhaling to inhaling. The peak pressure at the very end of the plateau is your end-tidal carbon dioxide value. It should maintain a mostly constant pressure between 35-45 mm hg as your patient breathes out. Phase III forms the top of the waveform rectangle. Which phase of the capnography waveform represents dead space air being exhaled? That would be phase III, also called the alveolar plateau. This appears as a sudden uptick in the graph, forming the first side of the rectangle. The rapid increase in CO2 pressure trips the capnograph’s sensors. Phase II begins at the point where your patient transitions from inhaling to exhaling. Phase I forms the baseline of your waveform. Since you don’t release carbon dioxide while breathing in, this phase is a flat line at or very close to zero (the horizontal axis). The first phase of a waveform takes place during inhalation. When someone is breathing normally, these take the shape of a rectangle with rounded corners. When they inhale, it falls toward zero.Įvery waveform displays four distinct phases of ventilation. When the patient exhales, the line goes up. The part that takes getting used to is reading the graph in terms of how much carbon dioxide is present instead of oxygen. They’re nothing more than a type of line graph that illustrates a patient’s breathing pattern. Capnography Waveform PhasesĬapnography waveforms may look difficult to read, but once you understand what they’re trying to tell you, you’ll find that it’s fairly simple. Keep these letters in mind as we move on to look at the different phases of a capnography waveform. Trend: is the patient’s ventilation improving, stabilized, or worsening?.Shape: does the waveform display the typical shape or one associated with a specific problem?.Rate: how fast is the patient breathing, is it within the normal range, and is the rate changing?.Quantity: what is the patient’s EtCO2, and is it within the normal range?.Proper: what are the normal or “proper” readings we’re looking for?.The letters PQRST will help you remember what you’re watching for when looking at a waveform: proper, quantity, rate, shape and trend. When you’re learning to read an EtCO2 waveform, it’s best to start with the alphabet. Even so, you can read the waveforms displayed on a capnography device the same way no matter what machine is used or what condition the patient is in. The end-tidal CO2 monitoring standard of care varies based on your environment and the situation-paramedics in the field, for example, may use slightly different methods than anesthesiologists in an OR. You’ll use the waveform shape to interpret general ventilation patterns. In this case, the exact EtCO2 value will be shown elsewhere on the screen. The horizontal axis shows the time elapsed.Ī live capnography display scrolls in real-time and is often unlabeled. When you look at a waveform diagram, you’ll notice that the vertical axis measures the EtCo2 value. The normal values for patients regardless of age, sex, race, or size range between 35-45 mm Hg, or about 5% CO2. EtCO2 values are recorded in mm Hg (millimeters of mercury), a unit of pressure. Introduction to Capnography WaveformsĬapnography measures ventilation through a metric known as end-tidal carbon dioxide (EtCO2). Want to learn how to track a patient’s ventilation on your own? In need of a capnography waveform cheat sheet? In this guide, we’ll teach you how to read a capnography monitor and interpret the results. As such, these devices are as valuable for triage as they are for long-term monitoring. Did you know, though, that measuring the carbon dioxide they exhale is often just as important? You can read this vital sign with a device called a capnograph, which produces a waveform diagram much like an EKG.Ĭapnography waveforms can give you information on anything from whether your airway placement was successful to whether a patient suffered respiratory damage. Knowing a patient’s oxygen levels provides crucial information about their respiratory status.
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