Skip to main content


Volume 3 Supplement 1


Impact of The Assist Ventilation Mode On Work of Breathing (Wob): Neurally Adjusted Ventilatory Assist (Nava) Versus Pressure Support Ventilation (Psv) Versus Proportional Assist Ventilation Plus (Pav+)

Article metrics

  • 787 Accesses


During assisted mechanical ventilation, appropriate WOB prevents diaphragm atrophy and fastens weaning. During PSV the ventilator support is fixed, irrespective of the patient's effort. On the contrary, both the NAVA and PAV + algorithms are designed to amplify patient's spontaneous effort. [1], [2]


To test if the assist ventilation mode algorithm has an impact on patient's WOB.


In 12 patients NAVA, PSV and PAV+ were randomly applied in a crossover fashion, for 4 hours each. The electrical diaphragmatic activity (EAdi) was continuously recorded during all the modes. WOB per breath (WOBBREATH) was estimated by converting the EAdi pressure time product (PTP)/breath in muscular PTP/breath (PTPBREATH). The conversion factor was the ratio between EAdi peak and airway opening pressure negative peak during an end-expiratory occlusion.


See figure 1

Figure 1

PTP,breath vs time in the three ventilatory modes . Red lines: range of physiological PTP BREATH


PTPBREATH was in the physiological range during NAVA and PAV + whereas during PSV remained constantly below it. We speculate that, as compared to PSV, NAVA and PAV+ favored a correct matching between diaphragm contraction and ventilator assistance. Further studies are required to test if the WOB pattern during assisted ventilation has an impact on mechanical ventilation duration and other clinically meaningful outcome parameters.


  1. 1.

    Sinderby C, Navalesi P, Beck J, Skrobik Y, Comtois N, Friberg S, Gottfried SB, Lindström L: Neural control of mechanical ventilation in respiratory failure. Nat Med. 1999, 5 (12): 1433-6. 10.1038/71012. Dec

  2. 2.

    Younes M: Proportional assist ventilation, a new approach to ventilatory support. Theory Am Rev Respir Dis. 1992, 145 (1): 114-20. 10.1164/ajrccm/145.1.114. Jan

  3. 3.

    Bellani G, Mauri T, Coppadoro A, Grasselli G, Patroniti N, Spadaro S, Sala V, Foti G, Pesenti A: Estimation of patient´s inspiratory effort from the electrical activity of the diaphragm. Crit Care Med. 2013, 41 (6): 1483-91. 10.1097/CCM.0b013e31827caba0. Jun

Download references

Author information

Correspondence to R Di Mussi.

Rights and permissions

Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits use, duplication, adaptation, distribution, and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark


  • Pressure Support Ventilation
  • Ventilation Mode
  • Mode Algorithm
  • Airway Opening
  • Ventilation Duration