PAV is a different approach to mechanical ventilation in which the ventilator guarantees the percentage of work which it does in the face of changes in respiratory system compliance and resistance. The pressure delivered varies from breath to breath. Usually this is set to overcome 80% of the work of breathing. Thus this mode is interactive, as the ventilator varies its output to maintain its proportion of the work load.
      The advantage of PAV is its ability to track changes in patient effort, which can occur rapidly in acute respiratory failure.