Ch 15 what points on a capnographic waveform represens a misture of alveolar gas and dead space gas2/24/2024 The end-tidal peak is occasionally referred to as the end-tidal point. Expiration itself consists of three successive phases: (1) a latency phase (phase 1), corresponding to the expiration of the anatomical dead space (P expCO 2 equals zero), which is indistinguishable from the preceding inspiration (2) slope phase (phase 2) marked by a very rapid rise in P expCO 2, corresponding to expiration of mixed air and (3) plateau phase (phase 3), reflecting the elimination of alveolar air (slightly increasing P expCO 2) resulting in a peak at the end of tidal expiration (P etCO 2 close to alveolar carbon dioxide tensions P ACO 2). ![]() 1), marked by alternating inspiratory (P inspCO 2 equals zero) and expiratory phases. The normal capnogram has an almost square wave pattern (Fig. Its role has spread beyond the realms of anaesthesia and capnography is now used in emergency medicine to confirm and verify endotracheal tube placement, monitor ventilatory status of patients with impaired respiratory function, monitor ventilation of patients during sedation/analgesia, evaluate ventilator settings and circuit integrity, assess effectiveness of cardiopulmonary resuscitation, and for early detection of changes in airway resistance and circulatory collapse. Today, capnography is considered to be essential in monitoring metabolic and respiratory functions during anaesthesia. But it was only in the early 1980s that capnometry became widely used mainly in anaesthetic practice. In the 1950s, capnometers were used experimentally during anaesthesia to measure expired CO 2. Capnometry, discrete measurements of carbon dioxide concentrations, was first developed during the Second World War as a means of monitoring the internal environment of submarines.
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