Pressure Support Ventilation (PSV)


Need for Spontaneous Mode of Mechanical Ventilation

  • Once Criteria are Met

Comparison Between Pressure Support Ventilation (PSV) and Proportional Assist Ventilation (PAV)

  • Definitions
    • Pressure Support (PSV): once triggered by patient effort, PS provides a pre-set fixed pressure until a cycling-off criterion is reached
      • As a result, the patient, by altering the pressure generated by respiratory muscles, may change the inspiratory flow and thus have partial control over the mechanical breath
      • This ability, however, is seriously compromised in the presence of abnormal respiratory system mechanics
      • Variability in tidal volume is generally low (assuming constant respiratory mechanics)
    • Proportional Assist Ventilation (PAV) (see Proportional Assist Ventilation, [[Proportional Assist Ventilation]]): ventilator pressure is proportional to instantaneous flow and volume and hence to pressure generated by the respiratory muscles
  • PAV Improves Patient-Ventilator Synchrony, as Compared to PSV [MEDLINE] (see Proportional Assist Ventilation, [[Proportional Assist Ventilation]])
    • PAV May Decrease Sleep Disruption, as Compared to PSV [MEDLINE]
  • PAV is Superior in Terms of Respiratory Muscle Unloading, as Compared to PSV (see Proportional Assist Ventilation, [[Proportional Assist Ventilation]])
    • PAV Increases the Probability of Remaining on Assisted/Unassisted Spontaneous Breathing Mode, as Compared to PSV [MEDLINE]
  • PAV Produces Higher Tidal Volume Variability, as Compared to PSV (see Proportional Assist Ventilation, [[Proportional Assist Ventilation]])
    • Decreased Tidal Volume Variability Has Been Associated with Impaired Lung Function and Higher Degree of Lung Damage in Experimental Acute Lung Injury Models [MEDLINE] [MEDLINE]
  • PAV Redistributes Ventilation from the Central to the Dorsal Lung Regions, as Compared to PSV (see Proportional Assist Ventilation, [[Proportional Assist Ventilation]])


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    • Noisy Pressure Support Ventilation: random variation of pressure support (noisy PSV) improves oxygenation and intrapulmonary shunt beyond what is observed with conventional PSV
  • Noisy pressure support ventilation: a pilot study on a new assisted ventilation mode in experimental lung injury. Crit Care Med 36: 818–827, 2008

  • Pressure support ventilation and biphasic positive airway pressure improve oxygenation by redistribution of pulmonary blood flow. Anesth Analg 109: 856–865, 2009


  • Respiratory function during pressure support ventilation. Chest 1986: 89:677–683 [MEDLINE]
  • Patient–ventilator interaction during acute hypercapnia: pressure-support vs. proportional-assist ventilation. J Appl Physiol 1996: 81:426–436 [MEDLINE]
  • Effects of chemical feedback on respiratory motor and ventilatory output during different modes of assisted mechanical ventilation. Eur Respir J 1999: 13:873–882 [MEDLINE]
  • Response of ventilator-dependent patients to different levels of pressure support and proportional assist. Am J Respir Crit Care Med 1999: 159:1716–1725 [MEDLINE]
  • Compensation for increase in respiratory workload during mechanical ventilation. Pressure-support versus proportional-assist ventilation. Am J Respir Crit Care Med 2000: 161:819–826 [MEDLINE]
  • Patient–ventilator interaction and sleep in mechanically ventilated patients: pressure support versus proportional assist ventilation. Crit Care Med 2007: 35:1048–1054 [MEDLINE]
  • Proportional assist ventilation with load-adjustable gain factors in critically ill patients: Comparison with pressure support.  Intensive Care Med  2008; 34:2026-2034 [MEDLINE]
  • Variable tidal volumes improve lung protective ventilation strategies in experimental lung injury.  Am J Respir Crit Care Med  2009; 179:684-693 [MEDLINE]
  • Distribution of regional lung aeration and perfusion during conventional and noisy pressure support ventilation in experimental lung injury.  J Appl Physiol  2011; 110:1083-1092 [MEDLINE]