One approach to circulation and blood flow in the critical care unit

Figure 1 Renal autoregulation. Total renal blood flow over a range of perfusion pressure. Adapted from[61].

Figure 2 Cerebral autoregulation. Blood flow over a range of perfusion pressures. Reproduced from[4] with permission of the Society of Photo Optical Instrumentation Engineers (SPIE)

Figure 3 Relationship between oxygen delivery and venous oxygenation/oxygen consumption. VO₂: Oxygen consumption; QO₂: Oxygen flow delivery; ER: Extraction ratio; ERc: Critical point of extraction; QO₂c: Critical point of delivery.

Figure 4 Protocol for early goal-directed therapy. Adapted from[9].

Figure 5 Guyton’s model of venous return and cardiac output in relation to the right atrial pressure. Adapted from[62].

Figure 6 Frank-Starling curves representing normal contractility, diastolic dysfunction, and contractile dysfunction. Pcwp: Pulmonary capillary wedge pressure. Adapted from[63].

Figure 7 Modified cardiac function curve representing the central venous pressure measured in the clinical setting by superimposing Guyton’s model of venous return and Frank-Starling contractility curve. CO: Cardiac output; CVP: Central venous pressure; PRA: Right atrial pressure; VR: Venous return; PMS: Mean systemic filling pressure. Adapted from[62].

Figure 8 Description of the systolic pressure variation and pulse pressure variation during mechanical ventilation. SPV: Systolic pressure variation; PPV: Pulse pressure variation; artP: Arterial pressure; awP: Airway pressure; SBP: Systolic pressure. PP = 100 x (PPmax – PPmin) / [(PPmax + PPmin)/2].