Autonomous control of inspired oxygen concentration during mechanical ventilation of the critically injured trauma patient

J Trauma. 2009 Feb;66(2):386-92. doi: 10.1097/TA.0b013e318197a4bb.


Background: Transport of mechanically ventilated patients in a combat zone presents challenges including conservation of resources. In the battlefield setting, the provision of adequate oxygen supplies remains a significant issue. Autonomous control of oxygen concentration may allow a reduction in mission load.

Methods: Trauma patients requiring ventilation and inspired oxygen concentration (FIO2) greater than 0.35 were evaluated for study. Patients were randomized to consecutive 4-hour periods of autonomous control or standard care. The system for autonomous control consisted of a ventilator, oximeter, and a portable computer. The portable computer housed the control algorithm and collected ventilator and oxygen saturation (SpO2) data every 5 seconds. The controller goal was to maintain SpO2 at 94% +/- 2% via discrete changes of 1% to 5%. Ventilator settings and SpO2 were recorded every 5 seconds for analysis.

Results: Fifteen patients were enrolled in this study. Oxygen saturation was maintained in the 92% to 96% saturation range 33% +/- 36% of the time during clinician control versus 83% +/- 21% during autonomous control. Oxygen usage was reduced by 44% during autonomous control. There was a slight difference in the total duration of SpO2 episodes less than 88% between groups (6.02 +/- 0.83 vs. 6.87 +/- 0.46 minutes, p < 0.05). There were no differences in the number of episodes of SpO2 <88%.

Conclusion: Autonomous control of FIO2 offers the opportunity for a reduction in oxygen usage, allowing a weight and resource reduction, without increasing risk of hypoxemia in ventilated trauma patients.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Algorithms
  • Blood Gas Analysis
  • Critical Illness*
  • Female
  • Glasgow Coma Scale
  • Humans
  • Injury Severity Score
  • Male
  • Microcomputers
  • Military Medicine
  • Oximetry / instrumentation*
  • Oxygen Inhalation Therapy / instrumentation*
  • Respiration, Artificial*
  • Transportation of Patients*