Elsevier

Journal of Critical Care

Volume 30, Issue 3, June 2015, Pages 652.e1-652.e7
Journal of Critical Care

Electronic Articles
Engineering control into medicine

https://doi.org/10.1016/j.jcrc.2015.01.019Get rights and content

Abstract

The human body is a tightly controlled engineering miracle. However, medical training generally does not cover “control” (in the engineering sense) in physiology, pathophysiology, and therapeutics. A better understanding of how evolved controls maintain normal homeostasis is critical for understanding the failure mode of controlled systems, that is, disease. We believe that teaching and research must incorporate an understanding of the control systems in physiology and take advantage of the quantitative tools used by engineering to understand complex systems.

Control systems are ubiquitous in physiology, although often unrecognized. Here we provide selected examples of the role of control in physiology (heart rate variability, immunity), pathophysiology (inflammation in sepsis), and therapeutic devices (diabetes and the artificial pancreas). We also present a high-level background to the concept of robustly controlled systems and examples of clinical insights using the controls framework.

Section snippets

Systems and control loops

The term system is often loosely applied. Using an engineering perspective, we define a system as a functional entity of interacting components that accepts and analyzes inputs, and produces outputs. The systems of interest in medicine are generally dynamic, that is, systems with changing inputs and outputs (often widely varying) over time. Control systems are all around us, but largely invisible when they work well: engineered controls maintain the output of our technologies within tolerable

Heart rate control

Heart rate (HR) is an example of an output of a physiologically controlled system that we have studied in the control context [3]. The system requirement in this case is to maintain (control) acceptably small errors in the critical provision of nutrient and oxygen delivery to vital organs, including muscle oxygen delivery in response to both external and internal (eg, inspiratory and expiratory intrathoracic pressure changes) workload disturbances (Fig. 2). Control is accomplished via autonomic

Control systems and disease

Physiologic systems control is dominated by control loops (glucose regulation, circadian rhythms, menstrual cycles, osmoregulation). Degradation in function of a controlled system may occur on the basis of failure of any of the system components, but loss of the controller invariably leads to systems failure (overt disease). As such, many disorders can be considered “loopopathies,” reflecting the importance of the controller (rather than its elements) in pathophysiology (Table 2). Diseases may

Conclusion

Control engineers are experts at designing and analyzing complex systems but have traditionally had little contact with clinicians. Clinicians generally do not consider the control strategies that fail in pathologies they face daily. We maintain that collaboration between engineers and clinicians is now required for the achievement of selected significant advances in medicine. For example, the collaboration of data engineers and clinicians will be required for the design and production of

Acknowledgment

The authors would like to thank Professor John C. Doyle of Caltech for his insightful comments and discussion, and Yuan Lai for his assistance with the figures. Leo Anthony Celi is funded through Grant R01 EB017205-01A1 from the National Institutes of Health.

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    Conflict of interest: The authors report no potential conflict of interest that exists with any companies/organizations whose products or services may be discussed in this manuscript.

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