Machine learning applied to multi-sensor information to reduce false alarm rate in the ICU

Abstract

Studies reveal that the false alarm rate (FAR) demonstrated by intensive care unit (ICU) vital signs monitors ranges from 0.72 to 0.99. We applied machine learning (ML) to ICU multi-sensor information to imitate a medical specialist in diagnosing patient condition. We hypothesized that applying this data-driven approach to medical monitors will help reduce the FAR even when data from sensors are missing. An expert-based rules algorithm identified and tagged in our dataset seven clinical alarm scenarios. We compared a random forest (RF) ML model trained using the tagged data, where parameters (e.g., heart rate or blood pressure) were (deliberately) removed, in detecting ICU signals with the full expert-based rules (FER), our ground truth, and partial expert-based rules (PER), missing these parameters. When all alarm scenarios were examined, RF and FER were almost identical. However, in the absence of one to three parameters, RF maintained its values of the Youden index (0.94–0.97) and positive predictive value (PPV) (0.98–0.99), whereas PER lost its value (0.54–0.8 and 0.76–0.88, respectively). While the FAR for PER with missing parameters was 0.17–0.39, it was only 0.01–0.02 for RF. When scenarios were examined separately, RF showed clear superiority in almost all combinations of scenarios and numbers of missing parameters. When sensor data are missing, specialist performance worsens with the number of missing parameters, whereas the RF model attains high accuracy and low FAR due to its ability to fuse information from available sensors, compensating for missing parameters.

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Fig. 1

Notes

  1. 1.

    In this paper, “missingness” of data is considered in two similar contexts. First is to describe parameter values that were missing in our TAMC ICU database. As mentioned above, we only used data without missing values. Second is to describe parameters that although have values in the dataset, are deliberately deleted by us in some of the experiments to check the RF ability to classify an alarm not relying on those missing parameters in order to imitate such a missingness situation at the ICU.

  2. 2.

    When the RF is trained without using a specific parameter, it is forced to find the best fit for the missing data in order to map the remaining parameters onto the alarm annotation/tag (“alarm” vs. “no alarm” or each of the seven clinical scenarios we identified) without using this parameter. That is, the remaining parameters provide a classification rule that dispenses with the missing parameter and thus, informally, we consider this behavior as “compensation” of the existing parameters to the missing parameter.

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Correspondence to Yuval Bitan.

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Appendices

Appendices

Appendix A: Full results for the first test

Unlike the RF model for which the output can be thresholded with different values, the FER/PER classification results are a single value (a binary output obtained by the model rules, e.g., ARTBPM < 50 mm Hg, CVP < 5 mm Hg, and CVP >  – 10 mm Hg indicate deterministically Hypovolemia). Thus, it is impossible to calculate the value of the area under the curve (AUC) for PER, and therefore these cells below are left empty. Green and orange cells indicate better and worse results, respectively, for each of the missing parameters in each clinical alarm scenario.

One missing parameter

figurea

Two missing parameters

figureb

Three missing parameters

figurec
figured

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Hever, G., Cohen, L., O’Connor, M.F. et al. Machine learning applied to multi-sensor information to reduce false alarm rate in the ICU. J Clin Monit Comput 34, 339–352 (2020). https://doi.org/10.1007/s10877-019-00307-x

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Keywords

  • False alarms
  • Intensive care unit
  • Machine learning
  • Missing data
  • Random forest