Title :
Accuracy limitations of chronaxie values
Author :
Geddes, Leslie A.
Author_Institution :
Dept. of Biomed. Eng., Purdue Univ., West Lafayette, IN, USA
Abstract :
The strength-duration curve is a plot of the threshold current (I) versus pulse duration (d) required to stimulate excitable tissue. On this curve are two points: 1) rheobase (b) and 2) chronaxie (c). Rheobase is the threshold current for an infinitely long-duration stimulus. Chronaxie, the excitability constant, is the duration of a pulse of current of twice rheobasic strength. The mathematical expression for the strength-duration curve is I=b(1+c/d). Although there are many published values for chronaxie for various excitable tissues, the range of variability for a given tissue type is quite large. This paper identifies five factors that can affect the accuracy of chronaxie measurement and shows that the most reliable values can be obtained with a rectangular pulse delivered from a constant-current source.
Keywords :
bioelectric potentials; neuromuscular stimulation; accuracy limitations; chronaxie values; constant-current source; excitability constant; excitable tissue stimulation; infinitely long-duration stimulus; pulse duration; rectangular pulse; rheobase; strength-duration curve; threshold current; Biological materials; Biomedical electrodes; Biomedical engineering; Biomedical materials; Circuits; Impedance; Pulse measurements; Shape; Temperature distribution; Threshold current; Action Potentials; Cell Membrane; Chronaxy; Differential Threshold; Electric Impedance; Electric Stimulation; Electrodes; Energy Transfer; Membrane Potentials; Reproducibility of Results; Sensitivity and Specificity;
Journal_Title :
Biomedical Engineering, IEEE Transactions on
DOI :
10.1109/TBME.2003.820340
