No abstract

An algorithm is presented for the processing of smooth biological signals with an important implicit data reduction. It is a solid basis for an automatic analysis of these signals. The algorithm is based on the approximation of the signals with a linear combination of cubic B-splines. Depending on the parameters, a data reduction of between 8:1 and 12:1 can be achieved. The most important differences from conventional biological signal processing methods are the representation of the signal by the coefficients of the linear combination instead of a series of samples and the analysis by calculations of the time of the appearance of patterns instead of iterative searching. The approximation and analysis of long-lasting multichannel signals can be performed online with a modern microprocessor. Approximating the signal with a linear combination of cubic B-splines with equally spaced knots, according to the linear least-squares criterion gives the desired data reduction and an elegant way to perform an automatic analysis. A window calculation scheme makes it possible to handle very long signals online.

A new method for automatic analysis of resting lower esophageal sphincter pressure and postdeglutitive motor activity of esophageal body and lower esophageal sphincter (LES) is validated by comparing the results obtained with automatic and manual analysis of 11,700 esophageal body pressure peaks, 390 resting LES pressure measurements, and 3900 LES relaxations. The automatic analysis is based on the on‐line transformation of pressure recordings into a mathematical formula using B‐spline functions, which allows one to use the same parameters as those generally applied in manual analysis of esophageal manometric recordings. Statistical evaluation of the results indicates that this method provides a faithful analysis of the pressure tracings. The difference between manual and automatic analysis (mean ± SD) was only + 1.49 ± 4.26 mm Hg for wave amplitude, ‐0.15 ± 0.61 seconds for wave duration, +0.37 ± 1.05 cm/second for progression velocity, +0.95 ± 1.38 mm Hg for resting LES pressure, and ‐2.0 ± 1.67 mm Hg for residual LES pressure after deglutition. Wave form was correctly recognized in 95.3% of the waves. Pressure recordings were obtained from a study on the effect of the PGE1 analogue rioprostil (600 and 300 μg), administered orally on esophageal motor function in 10 normal volunteers. The drug increased both the resting LES pressure and the amplitude of esophageal body contractions and decreased the completeness of LES relaxation after swallowing.