What is heart rate, anyway?

PT-SAFE: a software tool for development and annunciation of medical audible alarms

BACKGROUND

Recent reports by The Joint Commission as well as the Anesthesia Patient Safety Foundation have indicated that medical audible alarm effectiveness needs to be improved. Several recent studies have explored various approaches to improving the audible alarms, motivating the authors to develop real-time software capable of comparing such alarms. We sought to devise software that would allow for the development of a variety of audible alarm designs that could also integrate into existing operating room equipment configurations. The software is meant to be used as a tool for alarm researchers to quickly evaluate novel alarm designs.

METHODS

A software tool was developed for the purpose of creating and annunciating audible alarms. The alarms consisted of annunciators that were mapped to vital sign data received from a patient monitor. An object-oriented approach to software design was used to create a tool that is flexible and modular at run-time, can annunciate wave-files from disk, and can be programmed with MATLAB by the user to create custom alarm algorithms. The software was tested in a simulated operating room to measure technical performance and to validate the time-to-annunciation against existing equipment alarms.

RESULTS

The software tool showed efficacy in a simulated operating room environment by providing alarm annunciation in response to physiologic and ventilator signals generated by a human patient simulator, on average 6.2 seconds faster than existing equipment alarms. Performance analysis showed that the software was capable of supporting up to 15 audible alarms on a mid-grade laptop computer before audio dropouts occurred.

CONCLUSIONS

These results suggest that this software tool provides a foundation for rapidly staging multiple audible alarm sets from the laboratory to a simulation environment for the purpose of evaluating novel alarm designs, thus producing valuable findings for medical audible alarm standardization.

Comparison of four methods of automated recording of physiologic data at one minute intervals

INTRODUCTION

This study aims to evaluate possible differences between the maximum, minimum, and mean value over each epoch, or the instantaneous value at the end of the interval, when recording physiological data at 1-minute intervals.

METHODS

The mean arterial pressure (MAP), heart rate derived from the radial pulse (PULSE), end-tidal CO2 (etCO2), and the arterial O2 saturation by pulse oximeter (SpO2) were measured continuously in 10 patients during general anesthesia. Anesthesia was induced and maintained using the same technique for the first 10 minutes. At 1-minute intervals for each parameter, the maximum, minimum, and mean value (over the preceding minute), as well as the instantaneous value at the end of the recording epoch, were automatically downloaded to an electronic spreadsheet. The differences between the maximum and minimum, the maximum and mean, the mean and minimum, and the instantaneous and mean values were calculated for each patient.

RESULTS

We found differences between the maximum and minimum values recorded over each interval, between the maximum and mean values, between the mean and minimum values, and between the mean and instantaneous values recorded at the end of each minute interval for all physiological parameters examined.

CONCLUSIONS

From the data presented, we conclude that during the first 10 minutes of a general anesthetic, including anesthesia induction and endotracheal intubation, the values of physiologic parameters derived from different summary indices, namely the maximum, minimum, and mean values over the 1-minute interval or instantaneous at the end of the interval differ from each other. This source of error must be considered when designing systems for computerized recordkeeping of anesthesia charts and when interpreting the data stored in electronic databases.