Noninvasive potassium measurements from ECG analysis during hemodialysis sessions

It is well known that blood potassium concentration [K⁺] has a strong influence on ECG signal and particularly on T-wave morphology. No quantitative relations between parameters derived from ECG analysis and potassium levels in the blood have been established for clinical use. We developed a new method to quantify [K⁺] from T-wave analysis in real-time and tested it on data from dialysis patients, in which [K⁺] varies significantly during the session. The agreement between ECG-based potassium estimator and the reference potassium measurements was good (absolute error: 0.49±0.16 mM) for most of the sessions (30/39) except for 9 (absolute error: 1.17±0.36 mM) in which the presence of a systematic error all along the session did not allow reliable estimates. Bland-Altman analysis showed that the overall systematic error was almost null (-0.03 mM) whereas the standard deviation was 0.83 mM. The manual correction of the bias over each dialysis session resulted in excellent results for all patients. Preliminary results are promising although further investigation is required to understand the reason for session-dependent bias in some patients.