| Intervening variables | Levels | fo |
| Age | Neonate (0 - 30 days of age) | 1 |
|
| Infant (1 month - 2 years) | 33 |
|
| Preschool (2 - 6 years) | 5 |
|
| Child (6 - 12 years) | 6 |
|
| Adolescent (12 - 18 years) | 2 |
| Nutritional status | Low weight: BMI < 18.49 | 39 |
|
| Normal: 18.49 ≤ BMI ≤ 25.00 | 8 |
|
| Overweight: IMC > 25.00 | 0 |
| Puncture site | Internal jugular veins | 33 |
|
| Subclavian veins | 14 |
|
| Femoral veins | 0 |
| Professional expertise | Fellow under physician supervision | 46 |
|
| Physician supervisor | 1 |