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. 2021 Apr 21;9(4):e25066. doi: 10.2196/25066

Table 8.

Sample Predicting Intensive Care Transfers and Other Unforeseen Events explanations.

Rank and feature namea Value Median (IQR)b Shapley score
Shapley values after PPV c threshold (t – 12.75 h)

1. Oxygen supplementation (rolling 24 h max) 7 L/min 2.0 (0.0-3.0) 1.06

2. SpO2d (rolling 24 h min) 85% 92.0 (90.0-94.0) 0.93

3. Respiratory rate 26 bpm 20.0 (18.0-20.0) 0.76

4. Temperature 39.1 ˚C 36.9 (36.8-37.2) 0.32

5. Protein level 5.7 6.0 (5.6-6.4) 0.13
Shapley values after sensitivity threshold (t – 11 h)

1. Oxygen supplementation (rolling 24 h max) 35 L/min 2.0 (0.0-3.0) 1.93

2. SpO2 (rolling 24 h min) 85% 92.0 (90.0-94.0) 1.09

3. Respiratory rate 24 bpm 20.0 (18.0-20.0) 0.73

4. Heart ratee 124 bpm 83.0 (74.0-92.0) 0.71

5. Temperature 39.1˚C 36.9 (36.8-37.2) 0.32

aThe top 5 features corresponding to Predicting Intensive Care Transfers and Other Unforeseen Events predictions as it crosses the PPV-aligned threshold and the sensitivity-aligned threshold as noted in Figure 6. These predictions represent two possible locations where a clinician could receive an alert that their patient is deteriorating. Such information could be shared alongside the prediction score to provide better clinical utility to health care providers. Note that oxygenation (supplemental oxygen, SpO2, and respiratory rate) and temperature play a dominant role in both cases.

bThe median and IQR are included for comparison, and are calculated using the COVID-19 data set.

cPPV: positive predictive value.

dSpO2: oxygen saturation as measured by pulse oximetry.

eHeart rate represented the primary difference between these two time points. When the Predicting Intensive Care Transfers and Other Unforeseen Events score first exceeded the PPV threshold 12.5 hours before the intensive care unit transfer, the heart rate remained at 65 bpm and was not among the top features as measured by Shapley. At 11 hours before the event, when the Predicting Intensive Care Transfers and Other Unforeseen Events score was at its highest, the heart rate had jumped to 124 bpm and was the fourth-most influential feature as measured by Shapley values.