A carbon dioxide monitor that does not show the waveform has value

The author argues that a simple analog needle display can provide the anesthesiologist with the essential information he or she needs when monitoring carbon dioxide in the patient airway. He argues that essentially the most important information is virtually a binary, or all or none, phenomenon; in other words, carbon dioxide is either continuously present in the breathing circuit or is absent. Thus, circuit disconnects and undesirable endotracheal tube locations are readily identified. He relates the analog display of information to that of an automobile speedometer or the hands of a standard wrist watch. The author also compares analog meters with those used by pilots in aviation. He concludes with the argument that the carbon dioxide analyzer provides necessary information without the need to resort to expensive microprocessed displays that would include the waveform and trending, but would substantially increase the cost of the instrument.