8/6/2023 0 Comments Normal end tidal co2 waveform![]() ![]() Use of Capnography to Optimize Prehospital VentilationĬapnography is an efficient means of maximizing a patient’s ventilatory status during prehospital care and transport (14). Close the window to return to this section.Ĭapnographs can be main stream or side stream (as described in the physiology section). Most of the commonly used devices use infrared absorption of CO 2 as principle of operation.įor an understanding of the physics behind capnography, click here to open a new window. The digital reading for end-tidal CO 2 is often displayed as mm Hg (partial pressure of CO 2 in exhaled gas) or as % in exhaled gas. The device will not provide a reading if it is clogged with secretions or brokenĬapnographs provide both a waveform and digital reading of end-tidal CO 2.The membrane can turn ‘yellow’ (implies end-tidal CO 2 > 2%) when the device is contaminated with acidic substances such as gastric acid, lidocaine, or epinephrine.Confirmation of endotracheal tube placement in non-cardiac arrest patients is not always reliable.Limitations of colorimetric devices include: Normal end-tidal CO 2 is >4% hence, the device should turn yellow when the endotracheal tube is inserted in patients with intact circulation. When cardiac output increases, end-tidal CO 2 provides information about adequacy of ventilation and circulation.Ĭolorimetric devices provide continuous, semiquantitative end-tidal CO 2 monitoring. esophageal intubation) or there is an absent or decreased presentation of CO 2 to the lungs (i.e. When CO 2 is absent as measured by devices used to detect these parameters, either the endotracheal tube is not correctly placed (i.e. The end-tidal CO 2 is detected and measured by colorimetry, capnometry, and capnography. PetCO 2 can be used to estimate PaCO 2 in patients with essentially normal lungs. The gradient between the blood CO 2 (PaCO 2) and exhaled CO 2 (end-tidal CO 2 or PetCO 2) is usually 5-6 mm Hg. The normal values of end-tidal CO 2 is around 5% or 35-37 mm Hg. End-tidal carbon dioxide reflects CO 2 concentration of alveoli emptying last. This maximum concentration is called end-tidal carbon dioxide concentration or tension depending on whether it is expressed in fractional concentration or mm Hg. In low cardiac output states such as shock, cardiac arrest, or cardiopulmonary resuscitation (CPR) with inadequate chest compressions, end-tidal CO 2 may not be detected.Īs explained in the physiology section, the CO 2 concentration reaches a maximal level at the end of exhalation. A normal-appearing waveform and a digital numeric display will confirm that the endotracheal tube is in trachea. Tube / cuff palpation in the neck or suprasternal notchĬapnography can be used to confirm successful endotracheal intubation.Absence of breath sounds / gurgling over the stomach / epigastrium.Correct placement of the endotracheal tube is suggested by, but not confirmed by the following methods: The most catastrophic complication of endotracheal intubation is inadvertent esophageal intubation. When CO 2 is absent as measured by end-tidal capnography, it means either the endotracheal tube is in the wrong position (esophageal) or there is an absent or decreased presentation of CO 2 to the lungs. Despite these recommendations, capnography is not always widely available nor consistently applied (3).Īpplication of Capnography in the Prehospital Arena Numerous national organizations, including the American Heart Association, now endorse capnography and capnographic methods for confirming endotracheal tube placement (2). In patients with hemorrhage, capnography provides information regarding tissue perfusion and may help guide fluid resuscitation (1). In the prehospital environment, it is used primarily for confirmation of successful endotracheal intubation, but it may also be a useful indicator of efficient ongoing cardiopulmonary resuscitation (CPR). Capnography is a non-invasive monitoring technique that allows fast and reliable insight into ventilation, circulation, and metabolism (1). Indirectly, it indicates changes in the production of C02 at the tissue level and in the delivery of C02 to the lungs by the circulatory system. Chief Resident, Department of Anesthesiology, Perioperative, and Pain Medicine, Brigham and Woman’s Hospital, Harvard Medical School, Boston, MA The measurement of carbon dioxide (CO 2) in expired air directly indicates changes in the elimination of C02 from the lungs. Use of Capnography in Emergency Medicine and Prehospital Critical Care ![]()
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