| Co-Morbid Illnesses | ICU Therapies | Injuries | Ventilation |
| Cancer | CPR | Burns | Duration of mechanical ventilation |
| Chronic obstructive pulmonary disease (COPD) | Corticosteroid use | Coma | Intracuff pressure < 20 cm H2O |
| Chronic cardiac disease | Generale surgery | Head injury | Reintubation |
| Kidney failure | Neurosurgery | Multiple organ system failure (MOSF) | |
| Antacid | Acute respiratory distress sindrome (ARDS) | ||
| Paralytic agents | |||
| Prior antibiotic therapy | |||
| Tracheostomy | |||
| Use of nasogastric tube | |||
| Large volume gastric aspiration |