Schematic representation of the method used to identify pre-inspiratory potentials from the raw EEG signal and the ventilatory flow signal.

<p>(Adapted from Raux et al., <i>Anesthesiology</i>—<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0084534#pone.0084534-Raux3" target="_blank">[19]</a>—with permission from the authors and the publisher.) Artwork Robin Jacqueline. The EEG signal is segmented in epochs defined according to the ventilatory flow signal (1). These epochs are ensemble averaged (2). The resulting signal is inspected visually for a putative pre-inspiratory potential (3) of which the presence is ascertained through the calculation of a linear regression over the region of interest and comparison of the slope of this regression with 0. See “<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0084534#s2" target="_blank">Methods</a>” for details. Pre-inspiratory potentials and the related motor potentials are normally absent during quiet breathing.</p

Average pre-inspiratory EEG tracings in one of the congenital central hypoventilation syndrome patient.

<p>In each of the panels, the top trace depicts the Cz-EEG signal, and the bottom trace depicts ventilatory flow. The vertical line indicates the onset of inspiration. In the “inspiratory threshold loading” panel, inspiration is preceded by a shift upward of the EEG trace (horizontal double arrowed red line) that is characteristic of a pre-inspiratory potential. This observation is similar to that made in normal individuals <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0084534#pone.0084534-Raux1" target="_blank">[12]</a>. In contrast to normal individuals however, a pre-inspiratory potential can also be seen, abnormally, in the three “control condition” panels (control 1: resting ventilation with minimal constraint, namely a respiratory inductance plethysmography vest only; control 2: resting ventilation while breathing through a pneumoatchograph; control 3: as control 2, but during the washout period following inspiratory loading) and in the “CO₂ stimulated breathing” panel.</p

Average pre-inspiratory EEG tracings in one of the control subjects.

<p>In each of the panels, the top trace depicts the Cz-EEG signal, and the bottom trace depicts ventilatory flow. The vertical line indicates the onset of inspiration. In the three “control condition” panels (control 1: resting ventilation with minimal constraint, namely a respiratory inductance plethysmography vest only; control 2: resting ventilation while breathing through a pneumoatchograph; control 3: as control 2, but during the washout period following inspiratory loading), inspiration is not preceded by any change in the EEG signal (absence of pre-inspiratory potentials). In the “CO₂ stimulated breathing” panel, inspiration is also not preceded by any change in the EEG signal (absence of pre-inspiratory potentials). In contrast, in the “inspiratory threshold loading” panel, inspiration is preceded by a shift upward of the EEG trace (horizontal double arrowed red line) that is characteristic of a pre-inspiratory potential. This pattern exactly corresponds to what is expected in normal individuals <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0084534#pone.0084534-Raux1" target="_blank">[12]</a>.</p