Closed-Loop Pharmacologic Control of Blood Pressure: A Review of Existing Systems

Figures

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  Figure 1. Autonomic Nervous System and Arterial Baroreceptor Reflexes. Both sympathetic and parasympathetic nerves innervate the sinoatrial (SA) and atrioventricular (AV) nodes. The myocardium is innervated by sympathetic nerves. Arterial and venous vessels throughout most of the body are innervated by sympathetic nerves, whereas the parasympathetic nervous system innervates vessels in the genital organs and gastrointestinal tract. Autonomic efferent activity is regulated by the baroreceptor reflex, in response to changes in arterial pressure detected at the carotid sinus and aortic arch baroreceptors. The response to a change in posture is illustrated. ACh, acetylcholine; AV, atrioventricular; CNS, central nervous system; E, epinephrine; MAP, mean arterial pressure; NE, norepinephrine; SA, sinoatrial. Reproduced with permission from reference [1]. Copyright 2013, Elsevier

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  Figure 2. A Basic Controlled-Loop System to Maintain Blood Pressure. A single measured variable (MAP) acts as feedback followed by two system changes: a change in vasopressor and a change in vasodilator that together act to maintain MAP in a normal range. MAP, mean arterial pressure

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  Figure 3. Closed-Loop System Reaching Equilibrium. Depending on the speed of detection and response, the system can reach an equilibrium state with MAP maintained at or very close to a normal range. MAP, mean arterial pressure Reproduced with permission from reference [2]. Copyright 2018, Springer.

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  Figure 4. Closed-Loop System. The system used by R.V. Jackson and colleagues for controlling BP with sodium nitroprusside and a microprocessor. Reproduced with permission from reference [5]. Copyright 1977, Wiley.

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  Figure 5. Closed-Loop Drug Infusion System for Automated Hemodynamic Resuscitation in Septic Shock. a). Block diagram of the system for simultaneous control of mean arterial pressure (AP) and cardiac output (CO) in septic shock. AP* and CO* represent target AP and target CO, respectively. From these target variables, target values of systemic arterial resistance (R*) and stressed blood volume (V*) are determined (red rectangle). Subject’s R, V, and Frank-Starling slope of the left ventricle (S) are calculated from AP, CO, central venous pressure (CVP) and pulmonary wedge pressure (PWP) (blue rectangle). The proportional-integral controller adjusts infusion rate of noradrenaline (NA) to minimize the difference between R and R* (green rectangle). A non-linear controller adjusts infusion of Ringer’s acetate (RiA) to minimize the difference between V and V* (orange rectangle). b). Block diagram of the proportional-integral controller. Ki and Kp represent the integral and proportional gain constants, respectively. s is a Laplace operator. Reproduced with permission from reference [23]. Copyright 2017, Springer Nature.

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  Figure 6. Closed-Loop Vasopressor System. The system with its different components used by Joosten and his colleagues in Erasme Hospital, Brussels, Belgium, during a cardiac case. Reproduced with permission from reference [28]. Copyright 2019, Elsevier.