The calculation of mechanical power is not suitable for intra-patient monitoring under pressure-controlled ventilation

  • Zhanqi Zhao
  • Inez Frerichs
  • Huaiwu He
  • Yun LongEmail author
  • Knut Möller
  • Ary Serpa Neto
  • Marcus J. Schultz

Original correspondence from Dr. Zhao et al.

Dear Editor,

We read with interest the paper by Serpa Neto et al. showing that mechanical power (MP) of ventilation is independently associated with in-hospital mortality and other outcomes in critically ill invasively ventilated patients [1]. Although MP might become a practical clinical outcome predictor, we would like to point out that MP calculation may not be suitable for intra-individual monitoring of ventilator-related causes of lung injury under pressure-controlled ventilation.

Serpa Neto et al. used a simplified equation for MP calculation [ 2], which is suitable in patients under volume-controlled ventilation. In pressure-controlled mode, R aw cannot be substituted by ( P peak –  P plat )/Flow and Flow by V T/ T insp. Further, an increase in V T is always negatively weighted in both original and simplified calculations, while the effect of recruitment is neglected. Considering the original calculation in [ 2]:
$$ {\text{MP}} = 0.098 \times...


Compliance with ethical standards

Conflicts of interest

The authors declared that they have no conflict of interest.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • Zhanqi Zhao
    • 1
    • 2
  • Inez Frerichs
    • 3
  • Huaiwu He
    • 4
  • Yun Long
    • 4
    Email author
  • Knut Möller
    • 2
  • Ary Serpa Neto
    • 5
    • 6
    • 7
  • Marcus J. Schultz
    • 5
    • 8
  1. 1.Department of Biomedical EngineeringFourth Military Medical UniversityXi’anChina
  2. 2.Institute of Technical MedicineFurtwangen UniversityVillingen-SchwenningenGermany
  3. 3.Department of Anesthesiology and Intensive Care MedicineUniversity Medical Center of Schleswig–Holstein Campus KielKielGermany
  4. 4.Department of Critical CareChinese Academy of Medical Sciences, Peking Union Medical College HospitalBeijingChina
  5. 5.Department of Intensive Care and Laboratory of Experimental Intensive Care and Anesthesiology (LEICA)Academic Medical CenterAmsterdamThe Netherlands
  6. 6.Department of Critical Care MedicineHospital Israelita Albert EinsteinSão PauloBrazil
  7. 7.Laboratory for Critical Care ResearchHospital Israelita Albert EinsteinSão PauloBrazil
  8. 8.Faculty of Tropical Medicine, Mahidol Oxford Tropical Medicine Research Unit (MORU)Mahidol UniversityBangkokThailand

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