Fig. 6From: Respiratory drive: a journey from health to diseaseBrain curve (red line), unsupported (dashed black line) and supported with PS (green line) ventilation curves, relatively late in the course of critical illness of the patient of Fig. 5. A High PS, stable breathing. B Unstable breathing with increasing PS. Point 1: PaCO2 during unsupported spontaneous breathing; Point 2: RCO/min corresponding to desired V’E with unsupported spontaneous breathing; Point 3: actual PaCO2 with PS during stable breathing (stable ventilation); Point 4: RCO/min corresponding to desired V’E with PS ventilation (stable ventilation); closed circles: apneic threshold; Point 5: Actual V’E that results in apnea; Notice that with PS ventilation curve is shifted to the left of brain curve. See text for further explanation. PS: pressure support; RCO/min: respiratory centers output per min; V’E: minute ventilationBack to article page