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Automation of anaesthesia: a review on multivariable control.
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Measuring the predictive performance of computer-controlled infusion pumps. J Pharmacokinet Biopharm ; 63— Propofol anesthesia and rational opioid selection: determination of optimal ECEC95 propofol-opioid concentrations that assure adequate anesthesia and a rapid return of consciousness. Export Citation.
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User Account Log in Register Help. Search Close Advanced Search Help. My Content 1 Recently viewed 1 Design and implementat Show Summary Details. More options …. See all formats and pricing. You must be logged in to access this feature. IN this issue of Anesthesiology, Struys et al. Can automated closed-loop anesthesia improve patient outcomes? Anesthesiologists often compare themselves to pilots because they have similar work environments and work functions. Automated flight control is standard in professional aviation industry because it reduces workload during busy times and reduces certain types of pilot error.
We in anesthesia have been slow or even reluctant to adopt such technology, although the first demonstration of closed-loop anesthesia was described by Bickford in A generic closed-loop system is shown in figure 1. What constitutes anesthesia is still hotly debated, with no sensor able to measure changes in depth of anesthesia. What has been established is that alteration in consciousness is at least a required component of anesthesia.
Although consciousness itself may be difficult to define, recent work has demonstrated that derivatives of the electroencephalogram, i. Thus, sensors now exist to measure at least one component of the anesthetic, making it amenable to closed-loop control. This has been a major step for developing clinically acceptable closed-loop anesthesia. However, improvements in sensor technology and artifact detection and elimination remain challenges for their routine use in closed-loop anesthesia.
The components of a typical automated drug delivery system. The next objective is to take the step from a drug dose the control signal for unconsciousness to the desired set point e. The algorithm is not as simple as delivering x mg for a given change in Bispectral Index units. The ability to obtain the set point for unconsciousness is dependent on achieving in the brain biophase a concentration of the drug that will produce this set point.
In turn, the concentration of the drug in the biophase is determined both by the dose administered and by its pharmacokinetics. Innovations in pharmacokinetic modeling have enabled the development of target-controlled delivery systems. These developments have been crucial in providing closed-loop anesthesia.
Unfortunately, biologic systems have significant variance within a population, and the pharmacokinetic parameters used within the models are likely to result in inaccuracies for any given individual. In addition, there may be up to fold differences in the relation between concentration and effect pharmacodynamics among individuals. Pharmacodynamics may also vary over time and during surgery according to the intensity of the applied noxious stimulus.
This adds further complexities to the algorithm. Variability may be caused by pharmacokinetics or pharmacodynamics. One may assume that pharmacodynamics between individuals do not vary and thus any difference in the measured effect is caused by the pharmacokinetic parameters.
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Alternatively, one may assume that the pharmacokinetic parameters are always correct but that pharmacodynamics vary among individuals. Struys et al. During induction, propofol was administered using an open-loop mode i. This relation between concentration and effect was used to construct a Hill curve for each individual.
In this early stage of development, we need to establish the optimal approach for closed-loop systems used to provide anesthesia. Figure 3. Broad framework of closed-loop Propofol delivery system. A closed-loop system senses the level of output, feedbacks this information, compares it to a set point that defines the desired output level and uses the difference to push the output towards the set point. Because of more frequent sampling of the control variable and more frequent changes to the rate of drug delivery than with manually delivered anaesthesia, the stability of the control variable may be greater.
At the same time, the dose delivered is customized to meet the exact requirements of each patient, thereby overcoming the problems of inter-individual differences and differing levels of surgical stimulation. Ngai Liu, M. Glass, M. Rampil, M. Figure 2 explaining the BIS index was very necessary and came at the correct time in the article.
I appreciated the informational graphic as it made it easier to understand the complex idea. The evidence from the study helped to substantiate the importance of the application. I was not aware of the problems occurring within the anesthetic world, but I can agree that anything that helps with being knocked out during a difficult procedure is a very important topic to look into. Reducing the cost to the clinic and workload of the anesthesiologist is important as it could also lower the cost of the procedure if it reduces the complexity in the long run which is also important to the medical field.
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It is important that the controlled and manipulated variables are stated clearly for this process as it is a bit more difficult of an idea to work with and allows the reader to ground exactly what is happening in the system with these specifications. The potential disturbance variables include sudden jumps in readings.
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As we recently went some different controller schemes, it might be interesting to propose which type of controller scheme would aid in reducing the effects of the different disturbance variables on the output of the system. Figure 3 was useful in understanding the general outline of the control loop proposed. At the end of the article, the authors return to the reason why their product is important and how it will better the current procedure, which is important in reminding the reader why everything that was said so far mattered. I think this article has great technical content, but is not super reader friendly.
This reads a bit more like a research article than a blog post. A bit more relaxed language would help with the readability. Another suggestion would be breaking up the article more into smaller almost question and answer sections so that the reader can follow exactly what is being explained as the post goes along.
This is a higher level application that requires a bit more scientific and specific language, and could be helped further explanation as to what certain things are and why they are important on a lower level. This blog post was written very well and has all of the correct content. It is also very intriguing and definitely has a current market.
I think the proposed control scheme makes sense and the disturbance variables are clearly listed. While they were addressed by saying that an anesthesiologist would still need to be present, it would be interesting if there were any other potential ideas for controlling these disturbance variables or reacting to them.
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I enjoyed reading this article and feel like I learned something new and very important. I hope I have one of these machines helping my anesthesiologist if I get surgery! This entire article was incredibly interesting to read! I was shocked by how close it seems we may be to offering robotic, physician care. Personally, I cannot help but be a little nervous to let a machine administer a drug to patients that has fatal side effects when taken in too large of a dose.
Nevertheless, if the system is proven to be more precise in its administration than current techniques, then I can see this being implemented into health care in the near future. This being said, I think a little more depth into how exactly the system would work in a health care environment would be useful. For example, are human anthologists still needed to operate the machinery or can the set point just be determined by some computer algorithm and then any individual in the hospital can set the machine to that set-point and hook it up to the patient?
If the use of a trained human is still required then I think it would be interesting to ponder the usefulness of this system, economically. Right now, anesthesiologists are paid large salaries to complete their job, in part because of the many years of training it takes to master this skill. That being said, if they are still needed as more of a back-up measure if the system were to fail, would they still be paid the same or would their salary decrease.
On another note, all parts of the proposed scheme were extremely well explained. At no point did I find myself questioning any of the medical terminology used throughout the article. I also thought that all of the figures used were extremely helpful in discussing your topics and helping the reader to visualize the processes you were speaking of.
This especially holds true for the BIS index in figure 2, since that is an obscure topic when you first hear about it. Again, this article was extremely well thought out and kept my attention the whole time! I am interested to see where this may take the world of medicine in the years to come! Nice job!
First of all, I think you guys did a really good job! I believe this technology will definitely benefit patients in surgeries. The structure of this paper is well organized. It first introduces the background information of this technique and then states how it works.
The proposed control scheme is well explained and reasonable. I really like figures you provided in the paper since it did help me understand those subtle and unfamiliar terms such as the BIS index. As you guys said in the paper, the controlled variables include the measurement of the heart rate, blood pressure, respiration and oxygen level in the blood. Because of these variables varied significantly for people with different age, gender and other factors, EEG and BIS are chosen as the alternatives.
In this system, the amount of propofol injected is the manipulated variable.