From these 15 variables, first value, last value, highest value, lowest value and median value are calculated for nine variables and taken as features. Only first and last values are taken for four variables. For the dataset A, five outcome-related descriptors (SAPS Score, SOFA Score, length of stay, length of survival and in-hospital death) are available from which inhospital death (0 is represented as a survivor and 1 is represented as died in hospital) is taken as a target value.
1.3.2 Data Pre-Processing
Data pre-processing is one of the technique to filter and remove noisy data. 41 variables are given in the dataset. Among them 15 variables are selected out of which some of the variables are not carefully collected and having missing values. In this chapter, missing data are replaced by zeros.
1.3.3 Normalization
All the variables in the dataset are in different ranges and in different scales. The current values of data cannot be used for classification. If all the variables have the values in better ranges and scales, classifiers will work in a better way. A standard approach, z-score normalization method is used to normalize the variables.
Table 1.1 Time series variables with description and physical units recorded in the ICU [6].
| S. no. | Variables | Description | Physical units |
|---|---|---|---|
| 1. | Albumin | Albumin | g/dL |
| 2. | ALP | Alkaline Phosphate | IU/L |
| 3. | ALT | Alanine transaminase | IU/L |
| 4. | AST | Aspartate transaminase | IU/L |
| 5. | Bilirubin | Bilirubin | mg/dL |
| 6. | BUN | Blood urea nitrogen | mg/dL |
| 7. | Cholesterol | Cholesterol | mg/dL |
| 8. | Creatinine | Creatinine | mg/dL |
| 9. | DiasABP | Invasive diastolic arterial blood pressure | mmHg |
| 10. | FiO2 | Fractional inspired oxygen | [0–1] |
| 11. | GCS | Glasgow Coma Score | [3–15] |
| 12. | Glucose | Serum Glucose | mg/dL |
| 13. | HCO3 | Serum Bicarbonate | mmol/L |
| 14. | HCT | Hematocrit | % |
| 15. | HR | Heart Rate | bpm |
| 16. | K | Serum Potassium | mEq/L |
| 17. | Lactate | Lactate | mmol/L |
| 18. | Mg | Serum Magnesium | mmol/L |
| 19. | MAP | Invasive mean arterial blood pressure | mmHg |
| 20. | MechVent | Mechanical Respiration Ventilation | 0/1(true/false) |
| 21. | Na | Serum Sodium | mEq/L |
| 22. | NIDiasABP | Non-invasive diastolic arterial blood pressure | mmHg |
| 23. | NIMAP | Non-invasive mean arterial blood pressure | mmHg |
| 24. | NISysABP | Non-invasive systolic arterial blood pressure | mmHg |
| 25. | PaCO2 | Partial pressure of arterial carbon dioxide | mmHg |
| 26. | PaO2 | Partial pressure of arterial oxygen | mmHg |
| 27. | pH | Arterial pH | [0–14] |
| 28. | Platelets | Platelets | cells/nL |
| 29. | RespRate | Respiration Rate | bpm |
| 30. | SaO2 | O2 saturation in hemoglobin | % |
| 31. | SysABP | Invasive systolic arterial blood pressure | mmHg |
| 32. | Temp | Temperature | °C |