Without the use of capnography, signs of a defective unidirectional valve could easily go unnoticed. Rebreathing could also occur if the inhalation valve is not functioning as intended.Ī misaligned, warped, or cracked flutter disk also increases the risk of rebreathing of CO 2. If the exhalation valve is incompetent-which means the flutter disk on the exhalation valve is open during inhalation-the patient is able to rebreathe CO 2 from the expiratory limb of the breathing circuit. This component, which is commonly referred to as the flutter disk, should lay completely flat, closing off the exhalation valve during inhalation and only opening to allow expired gas to move through to the absorber canister or vent out to the adjustable pressure limiting (APL) valve during expiration. How do unidirectional valves work? Circle anesthesia machines have a light, thin disk that is seated at the top of the exhalation and inhalation valves. Malfunctioning unidirectional valves, exhausted or faulty CO 2 absorbent/channeling, and excessive dead space can all be seen with capnography. It also picks up faults with the anesthesia machine in real time. Within a couple of breaths, alterations in the shape of a previously normal waveform appear. A CO 2 reading can signal a leaking or deflated cuff, kinked or obstructed tube, bronchial intubation, accidental endotracheal extubation, or inadvertent disconnection of the breathing circuit from the endotracheal tube. Eliminating accidental esophageal intubation is one, but monitoring CO 2 can alert staff to several other complications that occur at the endotracheal site. Retried from BIT.LY/2X2GĬapnography can detect a multitude of equipment problems and malfunctions. l Equipment mistakes and malfunctions Figures Courtesy Respironics Inc. Changes in rate and tidal volume are displayed immediately as changes in the waveform and ETCO 2. Capnography also measures and displays the respiratory rate. The capnograph is the waveform that shows how much CO 2 is present at each phase of the respiratory cycle, and it normally has a rectangular shape (Figure 1). This is end-tidal CO 2 (ETCO 2) which is normally 35 to 45 mm Hg in dogs and 28 to 32 mm Hg in cats. The number represents capnometry, which is the partial pressure of CO 2 detected at the end of exhalation. Waveform capnography represents the amount of carbon dioxide (CO 2) in exhaled air, which assesses ventilation. What is capnography?Ĭapnography 2 is the measurement of carbon dioxide in a patient’s breath over time. For instance, just as the anesthesiologists found in their study, monitoring CO 2 in a patient’s breath instantly confirms whether tracheal intubation was successful. For some of these problems, both physiologic and equipment-related, there is no other parameter that will alert you of trouble before the patient is adversely affected. Equipment-related anesthetic problems can be promptly detected and corrected when using capnography. Capnography reflects changes in circulation resulting from poor cardiac output, variations in ventilation frequency and rate, or restrictive disease. It can pick up changes in metabolism that result from factors such as fluctuation in a patient ’s temperature that causes an increase or decrease in CO 2 excretion. 1 Some of those reported cases included death or injury from intubation error.Ĭapnography, which is the measurement of carbon dioxide in a patient’s breath, provides a good picture of the respiratory process, which comprises metabolism, circulation, and ventilation. In a closed claim study, anesthesiologists who reviewed 1,175 anesthetic-related closed malpractice claims found capnography and pulse oximetry could have potentially prevented 93 percent of avoidable anesthetic mishaps. The association’s guidelines include ensuring adequate ventilation to patients receiving general anesthesia, providing continuous evaluation of ventilation, and verifying correct positioning of an endotracheal (ET) tube by measuring CO 2 in the expired gas. The American Society of Anesthesiologists (ASA) considers monitoring CO 2 a standard of basic anesthetic protocol. By Jenny Flynn, LVT Capnography provides a good picture of the respiratory process.
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