Figure 2.

Endograms of placebo versus pimavanserin nights (subgroup of seven patients that had increased arousal threshold on pimavanserin) illustrate breath-by-breath values of ventilation at different degrees of ventilatory drive (per diaphragm electromyography). Solid lines show the group median values for each degree of ventilatory drive: color varies to illustrate the increased likelihood of a respiratory event at lower ventilation and ventilatory drive (see color bar). Shading denotes the interquartile range on placebo (blue) and pimavanserin (red). The solid purple dots illustrate ventilation near eupneic drive (i.e., V_PASSIVE, higher values reflect reduced collapsibility). The solid red dots represent ventilation at degrees of drive preceding arousal (i.e., V_ACTIVE). V_MIN is ventilation at the lowest deciles of the drive. Note that on pimavanserin, V_MIN corresponds to V_PASSIVE (i.e., pimavanserin prevented dips in the ventilatory drive). Ventilation and drive data are expressed as a percentage of eupneic ventilation during non-rapid eye movement sleep (VEUPNEA; original units: L/min). V_EUPNEA = baseline ventilation obtained from periods of resting wakefulness.