Skip to main content

The Brody effect to detect hypovolemia in clinical practice

Introduction

The electrocardiogram (EKG) is a common monitoring method in intensive care medicine. Several studies suggest that changes in EKG morphology may reflect changes in volume status. The Brody effect, a theoretical analysis of left ventricular chamber size influence on QRS-wave amplitude, is the key element of this phenomenon. It is characterized by an increase in QRS-wave amplitude induced by an increase in ventricular preload [1]. This study investigated the influence of changes in intravascular volume status on respiratory variations of QRS-wave amplitude (EKG) compared with respiratory pulse pressure variations (PP).

Methods

In 17 pigs, EKG and arterial pressure were recorded. QRS-wave amplitude was measured from the Biopac recording ensuring that in all animals EKG electrodes were always at the same location. Maximal QRS amplitude (EKGmax) and minimal QRS amplitude (EKGmin) were determined over one respiratory cycle. EKG was calculated as 100 × ((EKGmax - EKGmin)/(EKGmax + EKGmin)/2). EKG and PP were simultaneously recorded. Measurements were performed during normovolaemic conditions, after haemorrhage and following retransfusion with constant tidal volume (10 ml/kg) and respiration rate (15/minute).

Results

At baseline, PP and EKG were both <12%. PP were significantly correlated with EKG (r2 = 0.89, P < 0.001). Volume loss induced by haemorrhage increased significantly PP and EKG. Moreover, during this state, PP were significantly correlated with EKG (r2 = 0.86, P < 0.001). Retransfusion significantly decreased both PP and EKG, and PP were significantly correlated with EKG (r2 = 0.90, P < 0.001).

Conclusion

Available correlations between PP and EKG at each time of the study were observed, meaning that EKG is a reliable parameter to estimate the changes in intravascular volume status and provide experimental confirmation of the Brody effect [2].

References

  1. 1.

    Cannesson M, Keller G, Desebbe O, Lehot JJ: Relations between respiratory changes in R-wave amplitude and arterial pulse pressure in mechanically ventilated patients. J Clin Monit Comput 2010, 24: 203-207. 10.1007/s10877-010-9235-3

    Article  PubMed  Google Scholar 

  2. 2.

    Brody DA: A theoretical analysis of intracavitary blood mass influence on the heart-lead relationship. Circ Res 1956, 4: 731-738.

    CAS  Article  PubMed  Google Scholar 

Download references

Author information

Affiliations

Authors

Corresponding author

Correspondence to R Giraud.

Rights and permissions

This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, 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 licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Reprints and Permissions

About this article

Cite this article

Giraud, R., Siegenthaler, N., Morel, D. et al. The Brody effect to detect hypovolemia in clinical practice. Crit Care 16, P232 (2012). https://doi.org/10.1186/cc10839

Download citation

Keywords

  • Pulse Pressure
  • Intensive Care Medicine
  • Pulse Pressure Variation
  • Respiratory Variation
  • Chamber Size