Closed-loop control of airway occlusion pressure at 0.1 second (P0.1) applied to pressure-support ventilation: Algorithm and application in intubated patients

Giorgio A. Iotti, Josef X. Brunner, Antonio Braschi, Thomas Laubscher, Maddalena C. Olivei, Alessandra Palo, Cinzia Galbusera, Andrea Comelli

Research output: Contribution to journalArticlepeer-review


Objective: Airway occlusion pressure at 0.1 sec (P0.1) is an index of respiratory center output. During pressure-support ventilation, P0.1 correlates with the mechanical output of the inspiratory muscles and has an inverse relationship with the amount of pressure-support ventilation. Based on these observations, we designed a closed-loop control which, by automatically adjusting pressure-support ventilation, stabilizes P0.1, and hence patient inspiratory activity, at a desired target. The purpose of the study was to demonstrate the feasibility of the method, rather than its efficacy or even its influence on patient outcome. Design: Prospective, randomized trial. Setting: A general intensive care unit of a university hospital in Italy. Patients: Eight stable patients intubated and ventilated with pressure-support ventilation for acute respiratory failure. Interventions: Patients were transiently connected to a computer-controlled ventilator on which the algorithm for closed-loop control was implemented. The closed-loop control was based on breath by breath measurement of P0.1 and on comparison with a target set by the user. When actual P0.1 proved to be higher than the target value, the P0.1 controller automatically increased pressure-support ventilation, and decreased it when P0.1 proved to be lower than the target value. For safety, a volume controller was also implemented. Four P0.1 targets (1.5, 2.5, 3.5, and 4.5 cm H2O) were applied at random for 15 mins each. Measurements and Main Results: The closed-loop algorithm was able to control P0.1, with a difference from the set targets of 0.59 ± 0.27 (SD) cm H2O. Conclusions: The study shows that P0.1 can be automatically controlled by pressure-support ventilation adjustments with a computer. Inspiratory activity can thus be stabilized at a level prescribed by the physician.

Original languageEnglish
Pages (from-to)771-779
Number of pages9
JournalCritical Care Medicine
Issue number5
Publication statusPublished - May 1996


  • Cough
  • Critical illness
  • Intubation
  • Lungs
  • Mechanical ventilation
  • Respiratory deadspace
  • Respiratory failure
  • Respiratory function tests
  • Ventilation, pressure-support
  • Ventilator weaning

ASJC Scopus subject areas

  • Critical Care and Intensive Care Medicine


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