Effectiveness of enhanced pulse oximetry sonifications for conveying oxygen saturation ranges: a laboratory comparison of five auditory displays.

Background: Anaesthetists monitor auditory information about a patient's vital signs in an environment that can be noisy and while performing other cognitively demanding tasks. It can be difficult to identify oxygen saturation (SpO2) values using existing pulse oximeter auditory displays (sonifications). Methods: In a laboratory setting, we compared the ability of non-clinician participants to detect transitions into and out of an SpO2 target range using five different sonifications while they performed a secondary distractor arithmetic task in the presence of background noise. The control sonification was based on the auditory display of current pulse oximeters and comprised a variable pitch with an alarm. The four experimental conditions included an Alarm Only condition, a Variable pitch only condition, and two conditions using sonifications enhanced with additional sound dimensions. Accuracy to detect SpO2 target transitions was the primary outcome. Results: We found that participants using the two sonifications enhanced with the additional sound dimensions of tremolo and brightness were significantly more accurate (83 and 96%, respectively) at detecting transitions to and from a target SpO2 range than participants using a pitch only sonification plus alarms (57%) as implemented in current pulse oximeters. Conclusions: Enhanced sonifications are more informative than conventional sonification. The implication is that they might allow anaesthetists to judge better when desaturation decreases below, or returns to, a target range.

The cognitive aids in medicine assessment tool (CMAT) applied to five neonatal resuscitation algorithms.

OBJECTIVE: The International Liaison Committee on Resuscitation (ILCOR) provides recommendations on neonatal resuscitation training and practice, which includes a template for a decision-making algorithm. We evaluated the design properties of the ILCOR algorithm and four adaptations by member resuscitation organizations using the validated Cognitive Aids in Medicine Assessment Tool (CMAT). STUDY DESIGN: Two experts rated five neonatal resuscitation algorithms against the CMAT and against medical device design criteria. RESULTS: The ILCOR algorithm scored 32 of a possible 60 CMAT points, showing an adherence rate to CMAT of 53%. The ILCOR algorithm scored higher than the design variations by member organizations. Nonetheless, there are design limitations in the ILCOR algorithm. CONCLUSION: In principle, cognitive aids can improve neonatal resuscitation team performance; however, a considered design process that incorporates the full complexity of the 'procedure as performed' is needed to improve future versions of the algorithm for incorporation in international guidelines.

The effectiveness of pulse oximetry sonification enhanced with tremolo and brightness for distinguishing clinically important oxygen saturation ranges: a laboratory study.

UNLABELLED: Our study examined the effectiveness of pulse oximetry sonification enhanced with acoustic tremolo and brightness to help listeners differentiate clinically relevant oxygen saturation ranges. In a series of trials lasting 30 s each, 76 undergraduate participants identified final oxygen saturation range ( TARGET: 100% to 97%; Low: 96% to 90%; Critical: 89% and below), and detected threshold transitions into and out of the target range using conventional sonification (n = 38) or enhanced sonification (n = 38). Median (IQR [range]) accuracy for range identification with the conventional sonification was 80 (70-85 [45-95])%, whereas with the enhanced sonification it was 100 (99-100 [80-100])%; p < 0.001. Accuracy for detecting threshold transitions with the conventional sonification was 60 (50-75 [30-95])%, but with the enhanced sonification it was 100 (95-100 [75-100]%; p < 0.001. Participants can identify clinically meaningful oxygen saturation ranges and detect threshold transitions more accurately with enhanced sonification than with conventional sonification.

Comparison of the identification and ease of use of two alarm sound sets by critical and acute care nurses with little or no music training: a laboratory study.

The melodic alarm sound set for medical electrical equipment that was recommended in the International Electrotechnical Commission's IEC 60601-1-8 standard has proven difficult for clinicians to learn and remember, especially clinicians with little prior formal music training. An alarm sound set proposed by Patterson and Edworthy in 1986 might improve performance for such participants. In this study, 31 critical and acute care nurses with less than one year of formal music training identified alarm sounds while they calculated drug dosages. Sixteen nurses used the IEC and 15 used the Patterson-Edworthy alarm sound set. The mean (SD) percentage of alarms correctly identified by nurses was 51.3 (25.6)% for the IEC alarm set and 72.1 (18.8)% for the Patterson-Edworthy alarms (p = 0.016). Nurses using the Patterson-Edworthy alarm sound set reported that it was easier to distinguish between alarm sounds than did nurses using the IEC alarm sound set (p = 0.015). Principles used to construct the Patterson-Edworthy alarm sounds should be adopted for future alarm sound sets.

Prospective memory in the ICU: the effect of visual cues on task execution in a representative simulation.

Despite the potential dangers of clinical tasks being forgotten, few researchers have investigated prospective memory (PM) - the ability to remember to execute future tasks - in health-care contexts. Visual cues help people remember to execute intentions at the appropriate moment. Using an intensive care unit simulator, we investigated whether nurses' memory for future tasks improves when visual cues are present, and how nurses manage PM demands. Twenty-four nurses participated in a 40-minute scenario simulating the start of a morning shift. The scenario included eight PM tasks. The presence or absence of a visually conspicuous cue for each task was manipulated. The presence of a visual cue improved recall compared to no cue (64% vs. 50%, p = 0.03 one-tailed, η(p)(2) = 0.15). Nurses used deliberate reminders to manage their PM demands. PM in critical care might be supported by increasing the visibility of cues related to tasks. PRACTITIONER SUMMARY: Nurses must remember to execute multiple future tasks to ensure patient safety. We investigated the effect of visual cues on nurses' ability to remember future tasks. Experimental manipulation of cues in a representative intensive care unit simulation indicated that visual cues increase the likelihood that future tasks are executed.

Learnability and discriminability of melodic medical equipment alarms.

Melodic alarms proposed in the IEC 60601-1-8 standard for medical electrical equipment were tested for learnability and discriminability. Thirty-three non-anaesthetist participants learned the alarms over two sessions of practice, with or without mnemonics suggested in the standard. Fewer than 30% of participants could identify the alarms with 100% accuracy at the end of practice. Confusions persisted between pairs of alarms, especially if mnemonics were used during learning (p = 0.011). Participants responded faster (p < 0.00001) and more accurately (p = 0.002) to medium priority alarms than to high priority alarms, even though they rated the high priority alarms as sounding more urgent (p < 0.00001). Participants with at least 1 year of formal musical training identified the alarms more accurately (p = 0.0002) than musically untrained participants, and found the task easier overall (p < 0.00001). More intensive studies of the IEC 60601-1-8 alarms are needed for their effectiveness to be determined.

The effects of ambient music on simulated anaesthesia monitoring.

We examined the effect of no music, classical music or rock music on simulated patient monitoring. Twenty-four non-anaesthetist participants with high or low levels of musical training were trained to monitor visual and auditory displays of patients' vital signs. In nine anaesthesia test scenarios, participants were asked every 50-70 s whether one of five vital signs was abnormal and the trend of its direction. Abnormality judgements were unaffected by music or musical training. Trend judgements were more accurate when music was playing (p = 0.0004). Musical participants reported trends more accurately (p = 0.004), and non-musical participants tended to benefit more from music than did the musical participants (p = 0.063). Music may provide a pitch and rhythm standard from which participants can judge changes in vital signs from auditory displays. Nonetheless, both groups reported that it was easier to monitor the patient with no music (p = 0.0001), and easier to rely upon the auditory displays with no music (p = 0.014).

Anesthesia alarms in context: an observational study.

This paper surveys current work on the design of alarms for anesthesia environments and notes some of the problems arising from the need to interpret alarms in context. Anesthetists' responses to audible alarms in the operating room were observed across four types of surgical procedure (laparoscopic, arthroscopic, cardiac, and intracranial) and across three phases of a procedure (induction, maintenance, and emergence). Alarms were classified as (a) requiring a corrective response, (b) being the intended result of a decision, (c) being ignored as a nuisance alarm, or (d) functioning as a reminder. Results revealed strong effects of the type of procedure and phase of procedure on the number and rate of audible alarms. Some alarms were relatively confined to specific phases; others were seen across phases, and responses differed according to phase. These results were interpreted in light of their significance for the development of effective alarm systems. Actual or potential applications of this research include the design of alarm systems that are more informative and more sensitive to operative context than are current systems.

A comparison of post mortem findings with post hoc estimated clinical diagnoses of patients who die in a United Kingdom intensive care unit.

OBJECTIVE: To determine the accuracy of clinical diagnosis compared to post mortem findings in intensive care patients. DESIGN: A retrospective and blinded review of medical records. SETTING: A nine-bed combined high dependency and intensive care unit in a district general hospital in Gloucester, England. PATIENTS AND PARTICIPANTS: Ninety-seven patients who died on the intensive care unit and subsequently underwent post mortem examination. RESULTS: Suspected cause of death and main clinical diagnoses were determined and compared with findings at post mortem examination. All patients in whom a discrepancy was found had their cases reviewed to determine the significance of the discrepancy using the Goldman classification of post mortem discrepancies. Between June 1996 and May 1999 there were 1718 admissions with 252 deaths (14.7%), where 102 post mortem examinations were performed (40.5%). Five patients were not studied. Of the 97 patients, 4 (4.1%) had Goldman I discrepancies and 19 (19.6%) had Goldman II discrepancies. Complete agreement between pre and post mortem diagnosis was found in 74 (76.3%). Discrepancies fell into four main groups; unrecognised haemorrhage (7 patients), myocardial infarction (5), thromboembolic disease (5) and infectious complications (4). CONCLUSIONS: This study reveals that in an intensive care unit important diagnostic discrepancies were found in 19.6% of patients who underwent a post mortem examination. In a fifth of these (4.1%), survival may have been adversely affected. Haemorrhage was the most commonly missed diagnosis. Despite technological advances in intensive care medicine the post mortem examination continues to have an important role in auditing clinical practice and diagnostic performance.

Evaluating design proposals for complex systems with work domain analysis.

In this paper we propose a new framework for evaluating designs based on work domain analysis, the first phase of cognitive work analysis. We develop a rationale for a new approach to evaluation by describing the unique characteristics of complex systems and by showing that systems engineering techniques only partially accommodate these characteristics. We then present work domain analysis as a complementary framework for evaluation. We explain this technique by example by showing how the Australian Defence Force used work domain analysis to evaluate design proposals for a new system called Airborne Early Warning and Control. This case study also demonstrates that work domain analysis is a useful and feasible approach that complements standard techniques for evaluation and that promotes a central role for human factors professionals early in the system design and development process. Actual or potential applications of this research include the evaluation of designs for complex systems.

Acute airway obstruction in a child with acute lymphoblastic leukaemia during central venous catheterization.

We report the case of a seven-year-old girl with recently diagnosed acute lymphoblastic leukaemia (ALL) who suffered acute airway obstruction during insertion of a central venous catheter under general anaesthesia. The central airway obstruction was due to a mixture of leukaemic cells, blood clot and fibrin. There is discussion about airway obstruction both as a complication of central line insertion and secondary to ALL. The pulmonary complications of ALL, with particular reference to pulmonary haemorrhage, are detailed. The management of blood clot obstructing the central airway is discussed.

The role of clonidine in anaesthesia.

Clonidine is an alpha 2-adrenoceptor agonist which has been used for over 20 years to treat hypertension. It has recently, however, found a new and possibly significant role in anaesthesia and the treatment of pain. This article discusses the premedicant, perioperative and postoperative uses of clonidine.

The effectiveness of clonidine as an analgesic in paediatric adenotonsillectomy.

PURPOSE: To compare the analgesic effects of preoperative oral clonidine with intraoperative intravenous fentanyl in children undergoing tonsillectomy or adenotonsillectomy. METHODS: This randomized, controlled, double-blind study of 36 ASA I-II children, age 7-12 yr undergoing adenotonsillectomy was conducted at a tertiary care paediatric teaching hospital. Either 4 micrograms.kg-1 clonidine po was given 60-90 min preoperatively or 3 micrograms.kg-1 fentanyl i.v. was given intraoperatively. Postoperatively visual analog pain scores (VAS) were recorded at rest and on swallowing every 10 min for the first 30 min and then every 15 min for two hours. Morphine 0.05 mg.kg-1 i.v. was given for VAS > or = 5. If > 3 doses were required, 1.5 mg.kg-1 codeine po and 20 mg.kg-1 acetaminophen po were given. Sedation and anxiety scores were recorded preoperatively. Haemodynamic changes, blood loss, recovery scores, and the incidence of vomiting, hypotension, and airway obstruction were recorded. RESULTS: Children who received clonidine had a higher incidence of preoperative sedation (63%) than those receiving fentanyl (6%). Preinduction mean arterial pressure was lower in the clonidine group but required no intervention. VAS scores were similar throughout the observation period. There was no difference either in the number of morphine or codeine rescue doses administered or in the incidence of side effects. CONCLUSION: Oral clonidine is an effective analgesic and sedative for children undergoing tonsillectomy or adenotonsillectomy.

A survey of pentobarbital sedation for children undergoing abdominal CT scans after oral contrast medium.

Radiologists have traditionally been responsible for the sedation of children undergoing radiological investigations. Anaesthetists are becoming increasingly involved in providing sedation and/or anaesthesia in this environment. The sedation of a child for a CT scan who has recently been given oral contrast medium (OCM) may pose anaesthetists a number of dilemmas. This is a retrospective survey of 149 intravenous pentobarbital sedations administered by radiologists to children (age range three months to seven years three months, weight range 5 kg to 28.9 kg) undergoing upper abdominal CT after recent ingestion of OCM. The average patient received pentobarbital 4.6 mg.kg-1. 141 patients (94.6%) received pentobarbital as the only sedative agent, whereas eight patients (5.4%) required supplementary sedation (midazolam +/- fentanyl). There were no failed sedations. 36 complications occurred during 22 sedations (14.7% of total), with the most common being desaturation, vomiting, airway secretions, airway obstruction, coughing and bronchospasm.

Acceleromyography improves detection of residual neuromuscular blockade in children.

PURPOSE: To determine whether detection of residual blockade is improved by using the accelerograph. A secondary objective was to compare acceleromyographic measurements with those obtained by electromyography. METHODS: In a prospective, randomized, double-blind investigation, 22 anaesthetized children were studied during recovery from neuromuscular blockade following 0.1 mg.kg-1 vecuronium i.v.. Assessments of depth of block began 10 min after injection and were repeated at one minute intervals using electromyography (Datex, Relaxograph) in one hand, and acceleromyography (Biometer, Tofguard) in the other, to measure response of the adductor pollicis to train-of-four (TOF) stimulation of the ulnar nerve. Monitoring was stopped when no fade was visible and TOF ratio > or = 0.7. The electromyographic (EMG) and acceleromyographic (AMG) data were compared with corresponding observations of the number of twitches and TOF fade in the visible responses of the thumb, made by the attending anaesthetist. The method of Bland and Altman was used to compare differences between AMG and EMG data. RESULTS: During recovery from neuromuscular blockade, fade was no longer visible clinically 38.6 +/- 10.4 min (mean +/- SD) after the administration of vecuronium. This corresponded to TOF ratios of 0.04 +/- 0.23 by AMG and 0.34 +/- 0.21 by EMG. Usually, two twitches were visible before AMG detected the first twitch. The time to TOF ratio > or = 0.7 by AMG and EMG was similar at 49.1 +/- 10.5 and 50.9 +/- 9.0 min, respectively. The bias between AMG and EMG was one minute, with limits of agreement from -10 to nine min. CONCLUSION: AMG is superior to visual assessment in detecting residual neuromuscular block and provides similar estimates of recovering block as the more cumbersome EMG.

A comparison of the priming properties of two central venous catheters and one pulmonary artery catheter.

The time taken to prime the individual lumina of two multilumen central venous catheters (Viggo-Spectramed 14G 20 cm Hydrocath and Vialon 14G 20 cm Deltacath) and one pulmonary artery catheter (Viggo-Spectramed 110 cm 7.5F Pentacath) at flows between 5 ml.h-1 and 99 ml.h-1 is reported. The catheters supplied by different manufacturers but of identical length and gauge have significantly different priming times (p < 0.001). A protocol which may be used to prime the individual lumina of the three catheters studied is described. By means of an in vitro test the accuracy of this protocol is validated.

The complex role of perceptual organization in visual display design theory.

Two experiments were performed to test and extend the current 'emergent features' approach to display design for dynamic failure detection tasks. It was predicted that a display whose emergent features were well-mapped to goal-relevant task invariants would lead to better failure detection performance than either of two alternative displays. Contrary to prediction. Experiment 1 showed no differences in failure detection speed or accuracy across displays. The reason for this may have been that subjects did not discover the mapping between the mathematical properties of the task and the emergent feature, so in Experiment 2 subjects were explicitly instructed about the mapping and were advised on how to use the display geometry to help their performance. A significant difference in failure detection speed emerged, but the display supporting fastest performance was not the one with the well-mapped emergent feature. These results suggest that alternative perceptual organizational factors were at work which overpowered the intended effect. The results also underscore the difficulty of developing a theory of display design, and their impact on current theories is outlined.

Emergent features in visual display design for two types of failure detection tasks.

Visual display design for dynamic systems may be helped by exploiting emergent features that allow subjects to easily distinguish different states of the system. Three different types of displays were compared--two object displays and one separated display--each in a version that had a salient emergent feature that distinguished normal and failed states and in a version that did not have such an emergent feature. Subjects monitored for global and local failures simultaneously, which presented demands similar to integrated and separated tasks, respectively. Displays with salient emergent features supported superior global failure detection and may also have helped local failure detection. An object display with a salient emergent feature supported both types of failures better than or at least as well as the other displays. This advantage was attributed to the fact that the display had a salient emergent feature rather than to the fact that it was an object display. This research shows that emergent features can be effectively exploited to support tasks involving both integration of information and attention to individual data sources.