Deep sleep in safe hands as anaesthetic automated
20 October 2009
LabVIEW Software was used in developing a closed-loop control method for an automated anaesthesia system as Dr. Thomas M. Hemmerling reports
The challenge was to automate the control of general anaesthesia delivery and monitoring of the patient during surgical procedures so anaesthesiologists can focus more on other patients during surgery.
NI LabVIEW graphical programming software was used, as part of a closed-loop control system, to automatically monitor a patient’s depth of consciousness, level of pain, and muscle relaxation to calculate and then administer appropriate doses of anaesthetic drugs.
When conducting a surgical procedure, doctors typically administer anaesthetics to block all sensation for the patient including the feeling of pain or distress. Based on the type of procedure, patients can receive a local, spinal or general anaesthetic. When using local or spinal techniques, only the surgical site is anaesthetised and the patient remains partly conscious, while general anaesthetics render the patient unconscious and in a state of paralysis during the surgery.
General anaesthesia consists of drugs that produce three reactions: hypnosis to remove the patients’ consciousness and put them in a deep sleep, analgesia to block the conscious sense of pain, and relaxation to prevent unwanted muscle movement. Before surgeons begin their procedures, anaesthesiologists choose the appropriate doses of the medications to achieve all three of these reactions. Throughout the surgery, anaesthesiologists must manage the levels of medications they administer, which can consume more than 20 percent of their time.
Bringing LabVIEW into the operating room with McSleepy
To reduce the time anaesthesiologists spend administering anaesthetic doses and permit more time for them to manage other aspects of the surgery, our team of anaesthesiologists and biomedical engineers at McGill University developed a prototype for an automated anaesthesia system. Known as “McSleepy,” after doctors McDreamy and McSteamy on the popular television show “Grey’s Anatomy,” the goal of this system is to assist anaesthesiologists, not replace them. Also, McSleepy is not intended to perform better than an anaesthesiologist, but it has the ability to do so on any given day.
McSleepy is a closed-loop control system that monitors a patient’s depth of consciousness, level of pain and muscle movements throughout surgery and intravenously administers appropriate doses of the respective medications based on the acquired data. To use McSleepy, anaesthesiologists insert an IV and apply the sensors that measure muscle movement to the patient. They must then input patient information including age, height, weight and sex; the type of surgery being performed; and any preferences the anaesthesiologist has regarding the drug doses for the patient.
After the system begins to administer the drugs, McSleepy monitors and controls the drug doses every minute through a mathematical algorithm we developed using LabVIEW graphical programming software. The patient’s data is then displayed on a GUI, which we also developed using LabVIEW, so that the anaesthesiologist can see how the patient responds to the anaesthetics administered by McSleepy. By using LabVIEW to develop the GUI, we integrated familiar graphical elements such as dials that look like speedometers and thermometers and colour coding to track the patient’s level of consciousness using a bispectral index. We also used our novel “Analgoscore” to track the patient’s level of pain.
Designing McSleepy to be a safe, smart system
To avoid giving the patient too much or too little medication in the event that McSleepy does not function properly, we built multiple safety features into the closed-loop control system. First, anaesthesiologists can manually override any aspect of the system. For example, if the computer stops receiving signals from one of the sensors, the machine automatically enters basic manual mode. Throughout the procedure, the machine calculates the average amount of anaesthetics given to the patient during each 15-minute period. In the event that the system does not work properly, it can then administer the average amount of anaesthetics to keep the patient asleep and pain-free until either the problem is resolved or the anaesthesiologist begins to manually control the anaesthesia.
Additionally, if anaesthesiologists operate the system in semiautomatic mode so that they can manually input doses of medications, and they input something that does not seem right, such as accidentally entering too much of a certain drug, the machine warns the anaesthesiologists that the dose is too high.
Another important feature of McSleepy is that we built the program with artificial intelligence. The machine can learn things such as the surgeon’s preferences and the length of the various procedures performed. After use on approximately 20 of the same surgeries with the same surgeon, McSleepy begins to recognise patterns. Additionally, at the end of each surgery, McSleepy stores trend data. Overall, because the machine is a closed-loop control system that uses a combination of artificial intelligence and human input, McSleepy may actually be safer than having only an anaesthesiologist administer the medications.
The benefits of developing a closed-loop control system using LabVIEW
When engineers and scientists want to incorporate a new idea into clinical testing as quickly as possible, they need an easy-to-use programming language that gives them the best results in the least amount of time. LabVIEW is well-suited for this purpose because programming with this graphical environment is far easier than programming with more difficult languages such as C+ or Java.
Also, by developing a GUI with LabVIEW, we can address the common problem with most closed-loop control systems, which is that they lack a user interface so the user cannot see what is happening. Human interaction is very important to anaesthesiologists, who like our system because it is not a black box. They can easily monitor the amount of anaesthetics being administered and make changes if needed. In fact, at the Society for Technology in Anaesthesia annual meeting in January 2009, fellow anaesthesiologists awarded the McSleepy design team with the Excellence in Technology Innovation Award.
We initially used LabVIEW because we wanted to create a screen that looked nice and made sense. With a user interface that is so simplistic, both the anaesthesiologists and surgeons in the operating room can look at McSleepy and understand the data. Overall, the beauty of LabVIEW is that it is easy to use and it creates a nice graphical interface.
The future of McSleepy
As one of the recipients of the 2009 National Instruments Medical Device Grant, we upgraded to the LabVIEW 8.6 platform, which helps us deploy the McSleepy interface to personal digital assistants (PDAs). In doing so, anaesthesiologists can perform distant control, monitoring and recording of their patients. This is critical because many countries lack specialists such as anaesthesiologists, and, in the future, anaesthesiologists may need to take care of several patients at one time.
We currently have a fully functional prototype of the McSleepy system with off-the-shelf hardware and our proprietary algorithm that we developed using LabVIEW. Using our current prototype, we are developing a method to enter the market within five years. This plan includes securing funding to conduct more research to further enhance and commercialise our system, as well as seeking approval from both Health Canada and the U.S. Food and Drug Administration.
To see a video about this application please go to: http://sine.ni.com/cs/app/doc/p/id/cs-11762
Dr. Thomas M. Hemmerling works at the Department of Anaesthesiology, McGill University in Montreal.
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