Figure 1: Inspiratory flow limitation. Example of a recording of “inspiratory flow limitation” as indicated by the monitoring of nasal airflow through the “nasal cannula-pressure transducer.” No apnea or hypopnea is present in the segment, but the sleep EEGs (4 channels-1-4 from top) indicate the presence of cyclic alternating pattern phase A2, indicative of NREM sleep disturbances. The recording of the nasal cannula measuring airflow exchange is presented on channel 14 from top The figure shows the presence of flow limitation with the presence of an abnormal wave contour: instead of a smooth round wave contour, there is a truncation of the wave contour during inspiration (per convention; up part of the wave), there is no mouth breathing (oral thermistor - channel 15 from top), and chest and abdomen inductive plethysmography bands are indicating breathing efforts. The figure shows a worsening of the flow limitation from left to right with decrease in amplitude of the wave. This worsening is associated with the occurrence of snoring (channel 13 from top). However, with onset of snoring, there is another event occurring: nasal cannula-pressure transducer is an unreliable way to measure expiratory flow, and if an expiratory flow limitation occurs a different variable must be monitored. Normally expiration is mostly “passive” with the absence of involvement of expiratory muscles (monitored on channel 19 from top-bottom channel) as can be seen there is the appearance of “active” contraction of expiratory muscles as seen on the right of the figure. There are simultaneous changes in the inspiratory wave contour with reduction of its amplitude and appearance of expiratory efforts. The oxygen saturation (channel 11 from top) changes somewhat with SaO2going from 94% to 93%, but this 1% change is not a change monitored in any international atlas. Channel 12 monitors the finger photoplethysmography, i.e., the finger vaso-constriction, per convention the curve is presented such as an increase in vasoconstriction indicative of sympathetic activation is associated with a downward displacement of the curve. As can be seen in association with occurrence of snoring and other flow changes, there is a change of the photoplethysmography curve indicative of repetitive stimulation of the sympathetic nerve with snoring, and with swings of the photoplethysmography more pronounced at the right of the figure indicative of a larger stimulation of the sympathetic tone associated with worsening of inspiratory and expiratory flow limitation. None of these changes are taken into consideration in the international scoring manuals looking at abnormal breathing during sleep, despite the fact that many disruptions occur and worsen with snoring.