Auditory Icon Alarms Are More Accurately and Quickly Identified than Current Standard Melodic Alarms in a Simulated Clinical Setting.

BACKGROUND: Current standard audible medical alarms are difficult to learn and distinguish from one another. Auditory icons represent a new type of alarm that has been shown to be easier to learn and identify in laboratory settings by lay subjects. In this study, we test the hypothesis that icon alarms are easier to learn and identify than standard alarms by anesthesia providers in a simulated clinical setting. METHODS: Twenty anesthesia providers were assigned to standard or icon groups. Experiments were conducted in a simulated intensive care unit. After a brief group-specific alarm orientation, subjects identified patient-associated alarm sounds during the simulation and logged responses via a tablet computer. Each subject participated in the simulation twice and was exposed to 32 alarm annunciations. Primary outcome measures were response accuracy and response times. Secondary outcomes included assessments of perceived fatigue and task load. RESULTS: Overall accuracy rate in the standard alarm group was 43% (mean) and in the icon group was 88% (mean). Subjects in the icon group were 26.1 (odds ratio [98.75% CI, 8.4 to 81.5; P < 0.001]) times more likely to correctly identify an alarm. Response times in the icon group were shorter than in the standard alarm group (12 vs. 15 s, difference 3 s [98.75% CI ,1 to 5; P < 0.001]). CONCLUSIONS: Under our simulated conditions, anesthesia providers more correctly and quickly identified icon alarms than standard alarms. Subjects were more likely to perceive higher fatigue and task load when using current standard alarms than icon alarms.

Factors Affecting Acoustics and Speech Intelligibility in the Operating Room: Size Matters.

INTRODUCTION: Noise in health care settings has increased since 1960 and represents a significant source of dissatisfaction among staff and patients and risk to patient safety. Operating rooms (ORs) in which effective communication is crucial are particularly noisy. Speech intelligibility is impacted by noise, room architecture, and acoustics. For example, sound reverberation time (RT60) increases with room size, which can negatively impact intelligibility, while room objects are hypothesized to have the opposite effect. We explored these relationships by investigating room construction and acoustics of the surgical suites at our institution. METHODS: We studied our ORs during times of nonuse. Room dimensions were measured to calculate room volumes (VR). Room content was assessed by estimating size and assigning items into 5 volume categories to arrive at an adjusted room content volume (VC) metric. Psychoacoustic analyses were performed by playing sweep tones from a speaker and recording the impulse responses (ie, resulting sound fields) from 3 locations in each room. The recordings were used to calculate 6 psychoacoustic indices of intelligibility. Multiple linear regression was performed using VR and VC as predictor variables and each intelligibility index as an outcome variable. RESULTS: A total of 40 ORs were studied. The surgical suites were characterized by a large degree of construction and surface finish heterogeneity and varied in size from 71.2 to 196.4 m (average VR = 131.1 [34.2] m). An insignificant correlation was observed between VR and VC (Pearson correlation = 0.223, P = .166). Multiple linear regression model fits and ß coefficients for VR were highly significant for each of the intelligibility indices and were best for RT60 (R = 0.666, F(2, 37) = 39.9, P < .0001). For Dmax (maximum distance where there is <15% loss of consonant articulation), both VR and VC ß coefficients were significant. For RT60 and Dmax, after controlling for VC, partial correlations were 0.825 (P < .0001) and 0.718 (P < .0001), respectively, while after controlling for VR, partial correlations were -0.322 (P = .169) and 0.381 (P < .05), respectively. CONCLUSIONS: Our results suggest that the size and contents of an OR can predict a range of psychoacoustic indices of speech intelligibility. Specifically, increasing OR size correlated with worse speech intelligibility, while increasing amounts of OR contents correlated with improved speech intelligibility. This study provides valuable descriptive data and a predictive method for identifying existing ORs that may benefit from acoustic modifiers (eg, sound absorption panels). Additionally, it suggests that room dimensions and projected clinical use should be considered during the design phase of OR suites to optimize acoustic performance.

Simultaneously extracted transient and steady-state evoked responses during general anesthesia: variability of different rates.

Unintended intraoperative awareness occurs in one to two individuals out of every one thousand treated with general anesthesia. Patients that experience intraoperative awareness have significant post-operative psychological sequelae. The ability to detect intraoperative awareness is currently suboptimal because the mechanism employed by anesthetic drugs to impair consciousness remains poorly understood. Studies have suggested that evoked potentials (EP) may be used to monitor the depth of anesthesia. Both transient and steady state responses can be simultaneously extracted using the Continuous Loop Averaging Deconvolution (CLAD) method with specially designed CLAD sequences. 20 Hz and 30 Hz jittered CLAD sequences in addition to 5 Hz isochronic and 40 Hz jittered CLAD sequences were applied in baseline awake and general anesthesia conditions. A qualitative method to assess the extracted EPs was developed in this study, termed Randomized Split Set Average (RSSA). The results showed that EPs extracted during general anesthesia require a greater number of sweeps to obtain a signal-to-noise ratio comparable to that observed in EPs extracted during the awake state. Therefore, the development of a real time or quasi real time EP monitoring system for anesthesia provides an increased challenge. The RSSA employed in this study is a useful method for assessing the signal quality of EP responses.