Journal of clinical monitoring
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Most patients receiving spinal narcotics can be monitored adequately by well-trained nurses on postoperative or postdelivery wards. Patients at high risk (e.g., those with preexisting lung disease or many elderly patients) do need monitoring in the intensive care unit. Also requiring special monitoring are patients for whom epidural narcotics alone will not cover their pain, such as young patients with multiple trauma. Patients without these restrictions, however, can be monitored successfully outside the intensive care unit, although the dose of epidural narcotic should be kept as low as possible.
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Current alarms protect the manufactures of medical equipment from liability but do little to improve the quality of patient care. Existing alarms are so intrusive that the response of the anesthesiologist and others in the operating room is to want the offensive noise to go away, rather than to address potentially life-threatening situations. Alarms need to be refined so that only those whose attention is required (e.g., the anesthesiologist) are disturbed. It should always be immediately clear which particular variable is outside accepted limits, and alarms for different variables should operate independently so that if one alarm fails, others will still work.
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The administration of anesthesia may be viewed as a closed-loop control system consisting of three major components: the anesthesia system, the patient, and the system operator. A monitoring and alarm system during anesthesia should not be limited to only one of the three major components but must include monitoring of the patient, the performance of the anesthesia system, and the action of the system operator. ⋯ The authors describe the characteristics of a structured alarm system that maximizes the time available to correct a potential problem before injury begins, that clearly identifies the cause of the problem, and that prioritizes alarms according to the urgency of the required response. Alarms should be easy to temporarily silence, have built-in alarm default settings to prevent the inadvertant use of settings meant for a previous patient, and have a graphic display that enables the operator to detect problems or trends before an alarm sounds.
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Respiratory oxygen, carbon dioxide, and nitrous oxide concentrations were recorded in 20 patients breath-by-breath during general anesthesia and early recovery, using the Cardiocap multiparameter monitor. Several approved maneuvers were performed to demonstrate the usefulness of endtidal oxygen measurement. "Oxygrams" provided by the fast paramagnetic oxygen sensor confirmed the capnometric information in the diagnosis of hypoventilation, apnea, and disconnections. In one patient, the alarm for inspiratory oxygen concentration, set at 18%, appeared to prevent alveolar hypoxia and low arterial saturation from occurring when oxygen instead of nitrous oxide was turned off. ⋯ Changes in nitrous oxide concentration often complemented oxygen-related information obtained in our observations. In the recovery room, a decrease in end-tidal oxygen concentration preceded low pulse oximetry readings. Therefore, it is suggested that all three gases should be monitored continuously to prevent mishaps related to insufficient ventilation and inappropriate gas concentrations during anesthesia and immediate recovery.
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An alarm algorithm was developed to monitor the ventilator on the National Aeronautics and Space Administration space station. The algorithm automatically identifies and interprets critical events so that an untrained user can manage the mechanical ventilation of a critically injured crew member. The algorithm was tested in two healthy volunteers by simulating 260 critical events in each volunteer while the volunteer breathed via the ventilator. ⋯ The alarm textual messages were correct 98% (505 of 516 messages) of the time. The alarm algorithm is an improvement over current alarms found on most ventilators because its alarm messages specifically identify failures in the patient breathing circuit or ventilator. The system may improve patient care by helping critical care personnel respond more rapidly and correctly to critical events.