A new method for steep apnea classification using wavelets and feedforward neural networks

Objectives: This paper presents a novel approach for steep apnea classification. The goal is to classify each apnea in one of three basic types: obstructive, central and mixed. Materials and methods: Three different supervised Learning methods using a neural network were tested. The inputs of the neural network are the first level-5-detail coefficients obtained from a discrete wavelet transformation of the samples (previously detected as apnea) in the thoracic effort signal. In order to train and test the systems, 120 events from six different patients were used. The true error rate was estimated using a 10-fold cross validation. The results presented in this work were averaged over 100 different simulations and a multiple comparison procedure was used for model selection. Results: The method finally selected is based on a feedforward neural network trained using the Bayesian framework and a cross-entropy error function. The mean classification accuracy, obtained over the test set was 83.78 +/- 1.90%. Conclusion: The proposed classifier surpasses, up to the author's knowledge, other previous results. Finally, a scheme to maintain and improve this system during its clinical use is also proposed. (c) 2004 Elsevier B.V. All rights reserved.