Pitfalls in kinetic studies of multiexponential decay processes with special emphasis on desaturation curves of arterial Na.

The purpose of this study was to detect and solve apparently trivial methodological flaws in experiments of the decay type which can invalidate any fitting procedure or compartmental analysis. The problems dealt with consisted in maintaining the steady state conditions defining the "true" starting time of the efflux and its optimal duration, determining the number of exponential terms and finding how many data points are necessary to identify them. The solutions proposed include avoidance of tissue blotting prior to the efflux, running a separate non effluxed sample, stopping the washout when the log plot of remaining and effluent counts becomes parallel, use of the optimization if the correlation coefficient for curve fitting and adequate the frequency of counting to the decay rate. Errors resulting from the failure to comply with these requirements are illustrated with samples.