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Non-invasive conductivity technique to detect changes in haematocrit: in vitro validation
C G Olthof1, P M Kouw, A J Donker
1Department of Anaesthesiology, Free University Hospital, Amsterdam, The Netherlands.
Medical & Biological Engineering & Computing
|September 1, 1994
Summary
A new multi-frequency conductivity device accurately measures on-line haematocrit (Ht) changes in extracorporeal circuits. This bloodless method shows significant correlation between Ht and intracellular conductivity, aiding clinical applications.
Area of Science:
- Biomedical Engineering
- Medical Devices
- Physiology
Background:
- Continuous on-line haematocrit (Ht) monitoring is lacking for extracorporeal circuits like dialysis or cardiac surgery.
- A novel multi-frequency conductivity system was developed for non-invasive, continuous Ht detection.
Purpose of the Study:
- To evaluate the accuracy of the developed device in measuring Ht alterations.
- To investigate the effects of mannitol on intracellular ion content, conductivity, and Ht.
Main Methods:
- Induced Ht alterations in human blood using pure and 20% mannitol solutions.
- Measured changes in intracellular ion content, intracellular conductivity, and Ht.
- Utilized a multi-frequency conductivity system for Ht detection.
Main Results:
- Both mannitol types reduced mean cellular volume and Ht, though with differing effects on intracellular ion content.
- A strong correlation (r = 0.90, p < 0.001) was observed between Ht and intracellular conductivity.
- The device accurately detected Ht and intracellular fluid volume changes.
Conclusions:
- The multi-frequency conductivity method provides accurate on-line Ht monitoring.
- This technology holds promise for clinical applications in extracorporeal circuits.
- Understanding mannitol's effects on cellular parameters is crucial for interpreting Ht measurements.