Fig. 5From: Respiratory drive: a journey from health to diseaseBrain curve (red line), unsupported (dashed black line) and supported with PS (green line) ventilation curves early in the course of critical illness of the patient of Fig. 4. Point 1: desired PaCO2 by respiratory centers; Point 2: theoretical PaCO2 during unsupported spontaneous breathing; Point 3: actual PaCO2 with PS during stable breathing (steady state); Point 4: RCO/min corresponding to desired V’E with unsupported spontaneous breathing; Point 5: RCO/min corresponding to desired V’E with PS ventilation; Notice the unmet demands without (difference in ventilation between points 2 and 4), and with PS (difference in ventilation between points 3 and 5). PS: pressure support; RCO/min: respiratory centers output per min; V’E: minute ventilationBack to article page