Cardiac power parameters during hypovolemia, induced by the lower body negative pressure technique, in healthy volunteers
Rimehaug, Audun Eskeland; Hoff, Ingrid E Taraldsrud; Høiseth, Lars Øivind; Hisdal, Jonny; Aadahl, Petter; Kirkeby-Garstad, Idar
Journal article, Peer reviewed
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http://hdl.handle.net/11250/2397748Utgivelsesdato
2016Metadata
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Background: Changes in cardiac power parameters incorporate changes in both aortic flow and blood pressure.
We hypothesized that dynamic and non-dynamic cardiac power parameters would track hypovolemia better than
equivalent flow- and pressure parameters, both during spontaneous breathing and non-invasive positive pressure
ventilation (NPPV).
Methods: Fourteen healthy volunteers underwent lower body negative pressure (LBNP) of 0, −20, −40, −60
and −80 mmHg to simulate hypovolemia, both during spontaneous breathing and during NPPV. We recorded
aortic flow using suprasternal ultrasound Doppler and blood pressure using Finometer, and calculated dynamic and
non-dynamic parameters of cardiac power, flow and blood pressure. These were assessed on their association with
LBNP-levels.
Results: Respiratory variation in peak aortic flow was the dynamic parameter most affected during spontaneous
breathing increasing 103 % (p < 0.001) from baseline to LBNP −80 mmHg. Respiratory variation in pulse pressure was
the most affected dynamic parameter during NPPV, increasing 119 % (p < 0.001) from baseline to LBNP −80 mmHg.
The cardiac power integral was the most affected non-dynamic parameter falling 59 % (p < 0.001) from baseline to
LBNP −80 mmHg during spontaneous breathing, and 68 % (p < 0.001) during NPPV.
Conclusions: Dynamic cardiac power parameters were not better than dynamic flow- and pressure parameters at
tracking hypovolemia, seemingly due to previously unknown variation in peripheral vascular resistance matching
respiratory changes in hemodynamics. Of non-dynamic parameters, the power parameters track hypovolemia slightly
better than equivalent flow parameters, and far better than equivalent pressure parameters.