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Synchronized and proportional sub-diaphragmatic unloading in an animal model of respiratory distress



A sealed abdominal interface was positioned below the diaphragm (the “NeoVest”) to apply synchronized and proportional negative pressure ventilation (NPV) and was compared to positive pressure ventilation (PPV) using neurally adjusted ventilatory assist (NAVA). Both modes were controlled by the diaphragm electrical activity (Edi).


Eleven rabbits (mean weight 2.9 kg) were instrumented, tracheotomized, and ventilated with either NPV or PPV (sequentially) with different loads (resistive, dead space, acute lung injury). Assist with either PPV or NPV was titrated to reduce Edi by 50%.


In order to achieve a 50% reduction in Edi, NPV required slightly more negative pressure (−8 to −12 cm H2O) than observed in PPV (+6 to +10 cm H2O). The efficiency of pressure transmission from the NeoVest into gastric pressure was 69.6% (range 61.3–77.4%). Swings in esophageal pressure were more negative during NPV than PPV, for all conditions, due to transmission of negative pressure. Transpulmonary pressure was lower during NPV. Transdiaphragmatic pressure swings were reduced similarly for PPV and NPV, suggesting equivalent unloading of the diaphragm. NPV did not affect hemodynamics.


It is feasible to apply NPV sub-diaphragmatically in synchrony and in proportion to Edi in an animal model of respiratory distress.


  • Negative pressure ventilation (NPV), for example, the “Iron Lung,” may offer advantages over positive pressure ventilation.

  • In the present work, we describe the “NeoVest,” a system consisting of a sealed abdominal interface and a ventilator that applies NPV in synchrony and in proportion to the diaphragm electrical activity (Edi).

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Fig. 1: Schematic representation of experimental set-up and example of tracings.
Fig. 2: Diaphragm electrical activity (Edi) and esophageal pressure (Pes) swings during negative pressure ventilation (NPV) and positive pressure ventilation (PPV).
Fig. 3: Applied pressures and transpulmonary pressure during negative pressure ventilation (NPV) and positive pressure ventilation (PPV).
Fig. 4: Gastric pressure (Pga) swings during negative pressure ventilation (NPV) and positive pressure ventilation (PPV).
Fig. 5: Relationship between pressure in NeoVest (Pvest) compared to gastric pressure (Pga) during negative pressure ventilation (NPV).
Fig. 6: Transdiaphragmatic pressure (Pdi) during negative pressure ventilation (NPV) and positive pressure ventilation (PPV).

Data availability

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.


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The authors wish to thank M. Norman Comtois for his help with the analysis software and M. Greg Phillips for his work on the 3D printing of the NeoVest.


The study was supported by the St. Michael’s Hospital Foundation (Angels Den Award), The Global Health Innovation Award, and the RS McLaughlin Fund.

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Authors and Affiliations



J.B. and C.S. came up with the concept and designed the experimental protocol; J.B. analyzed the data, interpreted the data, and prepared the manuscript; H.-L.L. and C.L. carried out the experiments. C.S., D.M.C., H.L., and C.L. revised the manuscript. All authors approved the final version of the manuscript.

Corresponding author

Correspondence to Jennifer Beck.

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Competing interests

D.B. and C.S. have made inventions related to neural control of mechanical ventilation that are patented. The patents are assigned to the academic institution(s) where inventions were made. The license for these patents belongs to Maquet Critical Care. Future commercial uses of this technology may provide financial benefit to D.B. and C.S. through royalties. D.B. and C.S. each own 50% of Neurovent Research Inc. (NVR). NVR is a research and development company that builds the equipment and catheters for research studies. NVR has a consulting agreement with Maquet Critical Care. St. Michael’s Hospital has a research agreement with Maquet Critical Care AB (Solna, Sweden) and receives royalty and overhead from this agreement. The remaining authors have no competing interests to declare.

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Beck, J., Li, HL., Lu, C. et al. Synchronized and proportional sub-diaphragmatic unloading in an animal model of respiratory distress. Pediatr Res (2022).

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