![]() Lack of pulmonary blood flow (cardiac arrest, air embolis).Failed intubation, airway disconnection, or airway occlusion.Most commonly the end-tidal CO 2 reading changes because of: New technology has overcome these problems. The main disadvantages were cost, size sensors increasing dead space, and fragility. This has been made possible by improved optics and miniaturisation. Mainstream sampling sensor systems are electronically complex with the optical sensor being located at the ET tube adapter. This technology is mechanically complex, expensive to maintain (requires a vacuum pump, dehumidification, and real time measurement of pressure drops in the system), and causes waste gas pollution. Side-stream sampling sensor systems are continuously drawing gas via a length of small tube from the airway (ET tube adapter) to an infrared spectrometer located in a distant monitor. Physical signs of high CO 2 include high HR, RR, BP and injected, pink mm's. ![]() ETCO 2 values (mm Hg) during anaesthesia with spontaneous ventilation Monitors display the peak ETCO 2 value, respiratory rate, and usually inspired CO 2 value. D = the next inspiration - inspired gas should not contain CO 2. An alveolar gas "plateau" may not be obtained in animals with small tidal volumes (e.g., cats). This should correspond to the arterial PaCO 2 in animals that don't have lung disease. A continuous wave form can be generated which will demonstrate three phases of expiration during each respiratory cycle: A = dead space gas with no CO 2 B = mixed gas with rising CO 2 C = alveolar gas with a CO 2 plateau from which the ETCO 2 peak value is read. End tidal CO 2 (ETCO 2) monitors continuously sample gas at the endotracheal connector and measure the CO 2 partial pressure using proportional absorption of infra-red light. Methodology: As anaesthetic depth increases, ventilatory function (minute ventilation = respiratory rate x tidal volume) decreases and therefore CO 2 increases in a dose-dependent fashion.
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