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.

Tailoring reveals information requirements: the case of anaesthesia alarms

We discuss the phenomenon of system tailoring in the context of data from an observational study of anaesthesia. We found that anaesthetists tailor their monitoring equipment so that the auditory alarms are more informative. However, the occurrence of tailoring by anaesthetists in the operating theatre was infrequent, even though the flexibility to tailor exists on many of the patient monitoring systems used in the study. We present an influence diagram to explain how alarm tailoring can increase situation awareness in the operating theatre but why factors inhibiting tailoring prevent widespread use. Extending the influence diagram, we discuss ways that more informative displays could achieve the results sought by anaesthetists when they tailor their alarm systems. In particular, we argue that we should improve our designs rather than simply provide more flexible tailoring systems. because users often find tailoring a complex task. We conclude that properly designed auditory displays may benefit anaesthetists in achieving greater patient situation awareness and that designers should consider carefully how factors promoting and inhibiting tailoring will affect the end-users' likelihood of conducting tailoring. (C) 2004 Elsevier B.V. All rights reserved.

Testing new alarms for medical electrical equipment

This paper reports the first of several tests of new auditory alarms originally proposed by Block et al. [1] and formalized in IEC 60601-1-8 for use in medical electrical equipment. We test whether participants who are supplied with the IEC-recommended mnemonics while learning label-alarm associations can more accurately identify the alarms after short periods of learning. Results for 18 participants strongly indicate that there is a mutual confusability between certain alarm pairs in both learning conditions, but that mnemonics may strengthen rather than diminish certain key confusions.

The multimodal world of medical monitoring displays

A vision of the future of intraoperative monitoring for anesthesia is presented-a multimodal world based on advanced sensing capabilities. I explore progress towards this vision, outlining the general nature of the anesthetist's monitoring task and the dangers of attentional capture. Research in attention indicates different kinds of attentional control, such as endogenous and exogenous orienting, which are critical to how awareness of patient state is maintained, but which may work differently across different modalities. Four kinds of medical monitoring displays are surveyed: (1) integrated visual displays, (2) head-mounted displays, (3) advanced auditory displays and (4) auditory alarms. Achievements and challenges in each area are outlined. In future research, we should focus more clearly on identifying anesthetists' information needs and we should develop models of attention in different modalities and across different modalities that are more capable of guiding design. (c) 2006 Elsevier Ltd. All rights reserved.

Auditory lexical decisions in children with specific language impairment

This study examined spoken-word recognition in children with specific language impairment (SLI) and normally developing children matched separately for age and receptive language ability. Accuracy and reaction times on an auditory lexical decision task were compared. Children with SLI were less accurate than both control groups. Two subgroups of children with SLI, distinguished by performance accuracy only, were identified. One group performed within normal limits, while a second group was significantly less accurate. Children with SLI were not slower than the age-matched controls or language-matched controls. Further, the time taken to detect an auditory signal, make a decision, or initiate a verbal response did not account for the differences between the groups. The findings are interpreted as evidence for language-appropriate processing skills acting upon imprecise or underspecified stored representations.

Sonification supports eyes-free respiratory monitoring and task time-sharing

Three experiments explored the effectiveness of continuous auditory displays, or sonifications, for conveying information about a simulated anesthetized patient's respiration. Experiment 1 established an effective respiratory sonification. Experiment 2 showed an effect of expertise in the use of respiratory sonification and revealed that some apparent differences in sonification effectiveness could be accounted for by response bias. Experiment 3 showed that sonification helps anesthesiologists to maintain high levels of awareness of the simulated patient's state while performing other tasks more effectively than when relying upon visual monitoring of the simulated patient state. Overall, sonification of patient physiology beyond traditional pulse oximetry appears to be a viable and useful adjunct to visual monitors. Actual and potential applications of this research include monitoring in a wide variety of busy critical care contexts.

Temporal relationship between the auditory brainstem response and focal responses of auditory nerve root and cochlear nucleus during development in the tammar wallaby (Macropus eugenii)

Thirty-two pouch-young tammar wallabies were used to discover the generators of the auditory brainstem response (ABR) during development by the use of simultaneous ABR and focal brainstem recordings. A click response from the auditory nerve root (ANR) in the wallaby was recorded from postnatal day (PND) 101, when no central auditory station was functional, and coincided with the ABR, a simple positive wave. The response of the cochlear nucleus (CN) was detected from PND 110, when the ABR had developed 1 positive and 1 negative peak. The dominant component of the focal ANR response, the N-1 wave, coincided with the first half of the ABR P wave, and that of the focal CN response, the N-1 wave, coincided with the later two thirds. In older animals, the ANR response coincided with the ABR's N-1, wave, while the CN response coincided with the ABR's P-2, N-2 and P-3 waves, with its contribution to the ABR P-2 dominant. The protracted development of the marsupial auditory system which facilitated these correlations makes the tammar wallaby a particularly suitable model. Copyright (C) 2001 S. Karger AG, Basel.

Functional development of the inferior colliculus (IQ and its relationship with the auditory brainstem response (ABR) in the tammar wallaby (Macropus eugenii)

To discover the developmental relationship between the auditory brainstem response (ABR) and the focal inferior colliculus (IC) response, 32 young tammar wallabies were used, by the application of simultaneous ABR and focal brainstem recordings, in response to acoustic clicks and tone bursts of seven frequencies. The ic or the tammar wallaby undergoes a rapid functional development from postnatal day (PND) 114 to 160. The earliest (PND 114) auditory evoked response was recorded from the rostral IC. With development, more caudal parts of the IC became functional until age about PND 127, when all parts of the IC were responsive to sound. Along a dorsoventral direction, the duration of the IC response decreased, the peak latency shortened, while the amplitude increased, reaching a maximum value at the central IC, then decreased. After PND 160, the best frequency (BF) of the ventral IC was the highest, with values between 12.5 and 16 kHz, the BF of the dorsal IC was the lowest, varying between 3.2 and 6.4 kHz, while the BF of the central IC was between 6.4 and 12.5 kHz. Between PND 114 and 125, the IC response did not have temporal correlation with the ABR. Between PND 140 and 160, only the early components of the responses from the ventral and central IC correlated with the P4 waves of the ABR. After PND 160, responses recorded from different depths of the IC had a temporal correlation with the ABR. (C) 2001 Published by Elsevier Science B.V.

Spontaneous and stimulus-evoked intrinsic optical signals in primary auditory cortex of the cat

Spontaneous and tone-evoked changes in light reflectance were recorded from primary auditory cortex (A1) of anesthetized cats (barbiturate induction, ketamine maintenance). Spontaneous 0.1-Hz oscillations of reflectance of 540- and 690-nm light were recorded in quiet. Stimulation with tone pips evoked localized reflectance decreases at 540 nm in 3/10 cats. The distribution of patches activated by tones of different frequencies reflected the known tonotopic organization of auditory cortex. Stimulus-evoked reflectance changes at 690 nm were observed in 9/10 cats but lacked stimulus-dependent topography. In two experiments, stimulus-evoked optical signals at 540 nm were compared with multiunit responses to the same stimuli recorded at multiple sites. A significant correlation (P < 0.05) between magnitude of reflectance decrease and multiunit response strength was evident in only one of five stimulus conditions in each experiment. There was no significant correlation when data were pooled across all stimulus conditions in either experiment. In one experiment, the spatial distribution of activated patches, evident in records of spontaneous activity at 540 nm, was similar to that of patches activated by tonal stimuli. These results suggest that local cerebral blood volume changes reflect the gross tonotopic organization of A1 but are not restricted to the sites of spiking neurons.

The association between auditory memory span and speech rate in children from kindergarten to sixth grade

This study reexamined the association between speech rate and memory span in children from kindergarten to sixth grade (N = 152) in order to potentially account for the inconsistencies within the published literature on this topic. Some of the inconsistencies in past research may reflect the different methods adopted in assessing speech rate. In particular, repeating word triples may itself involve memory demands, contaminating the correlation between speech rate and memory span in younger children. Analyses using composite speech rate and memory span measures showed that speech rate for word triples shared variance with memory span that was independent of speech rate for single words. Moreover, speech rate for word triples was largely redundant with age in explaining additional variation in memory span once the effects of speech rate for single words were controlled. (C) 2002 Elsevier Science.