Rahul Panesar, MD, and Sean Cavanaugh, BS and Christopher Gallagher, MD describe their efforts to build an inexpensive, wireless partial seizure mechanism for pediatric status epilepticus simulation scenarios.
The most common neurologic disorder in children is seizures, with up to 6% of all children having at least one episode by the age of 16. Seizures can be non-convulsive (i.e., absence, complex-partial) or convulsive (partial or generalized), presenting in a wide array of settings, including infection, fever, electrolyte abnormalities, stroke, trauma, intoxication, tumor formation or neurocutaneous syndromes. Convulsive seizures lasting for longer than 30 minutes or two or more discrete seizures without a return to baseline mental status are defined as convulsive status epilepticus (CSE). The annual incidence of CSE is reported to be 10 to 73 episodes/100,000 children and the mortality reported to be between 2.7% and 8% with an overall morbidity between 10 and 20%. Therefore, early recognition of CSE is paramount to timely intervention and subsequent resuscitation and treatment. The need for rapid administration of medications, securing the airway and assessing the cardiac, respiratory and neurologic function of the patient requires a coordinated effort of the resuscitating team, which is amenable to high-fidelity simulation.
Currently, several high-fidelity pediatric mannequin models are available commercially that provide multiple functionalities including breathing, palpable pulsation, heart sounds, phonation and pupillary responses. At our institution, we have employed the pediatric Laerdal SimJunior® mannequin, which has an additional feature of head movement to simulate seizure activity. However, if bag mask ventilation techniques are applied, movement of the head can be subdued, resulting in lack of recognition of CSE. Therefore, we explored new techniques to provide a more explicit indication that seizure activity was present. Current devices simulating seizure activity include inflating/deflating bags to replicate generalized seizures and those that move the head as well as a recently-described mechanical device that can simulate partial seizures in an infant mannequin. However, a cost-effective, wireless mechanism simulating a partial seizure for a child-sized mannequin has not been described.
Our goal was to build an inexpensive, wireless partial seizure mechanism for our pediatric status epilepticus simulation scenario to move either a leg or arm of the SimJunior® mannequin. We set out to construct a simple vibratory, remote-controlled circuit using off-the shelf technology that could be readily reproduced with toy parts available at most retail stores.
We searched local retail stores to find vibratory children’s toys that housed motorized devices powerful enough to feasibly move the mannequin limb. Additionally, we searched for remote-controlled devices that could provide the transmitter and receiver components of the circuit to turn the motor on and off. During this process, we were determined to design and build the entire device as simply and inexpensively as possible to allow easy reproducibility and replacement of parts, while providing the optimal amount of movement to simulate seizure-like movements. After construction of a prototype, we would implement it in a high-fidelity simulation of pediatric status epilepticus.
The motorized device we found to be adequate to our need was in an infant toy musical bouncing ball (Fisher Price® Bounce and Giggle Pig ™), though a variety of other vibratory and bouncing toys are available for approximately $(US) 30. After testing toy functionality, we removed the batteries (3 AA batteries), opened the casing and disconnected the motor from the wiring to the circuit and the speaker, and detached the battery casing (Figure 1).The motor drives an eccentric gear transmission causing a vibration effect. Now isolated, the motor was ready for connection to the receiver circuit.
Circuit: Transmitter and Receiver
The transmitter and receiver components of the circuit were found in a remote-controlled toy car (New Bright© RC, New Bright Industrial Co., Ltd, model #4310) that operated at the 49 MHz frequency signal for approximately $10. The transmitter unit was powered by 2 AA batteries supplying 3.0 volts DC to a circuit of several surface mounted capacitors, load resistors and a packages 48.3877 MHz can-crystal radio frequency (RF) transmitter, with a 22 gauge 8-inch copper wire for an antenna. The movement of either the thumb knob controller switch caused an RF transmission frequency which activated two different channels (forward/backward, right/left) on the receiver circuit. Each knob allowed a slightly different carrier frequency to allow distinct signaling of the receiver channels.
The receiver (Figure 2) embedded in the car was powered by 2 AAA batteries, supplying 3.0 volts DC. The antenna is a 22 gauge 8-inch copper wire. The receiver power supply had a 2-pole on/off switch. With the receiver power switch in the “on” position, and either of the transmitter thumb knobs moved, the receiver activated several field effect transistors to saturate, causing the closing of the 3.0 volt power circuit connected to the DC motor, thereby activating the motor and causing the vibratory effect.
After testing functionality of the remote and car, the car was stripped down to the receiver component which sat on the battery casing. The wiring from the car’s circuit connected two wires to the front motor to move the front wheels to the left and right. Two additional wires connected to the rear motor to move the rear wheels forward, thereby propelling the car. These wires were cut and the front wires were soldered to the motor end plates to turn it on or off (Figure 3). The motor was activated with the 3.0 volts from the receiver circuit when the transmitter knobs were pushed, giving the vibratory motion desired. The receiver circuit was then secured to the motor with adhesive glue and electrical tape (Figure 4).
To avoid altering the mannequin, a small 4 x 2 inch compartment was cut 2 inches into the foam cushion of the gurney where the mannequin calf and heel region would normally rest (Figure 5). The seizure gadget was placed inside with the extension of the motor compartment right side up.
A solid piece of plastic was placed on the bottom to avoid dampening of the vibration and foam was placed around the gadget to dampen any noise emanating from the motor. The leg was placed on top of the motor and secured with Velcro® straps to the gurney to avoid displacement by simulation participants. The leg was draped with a hospital sheet which accentuated the movement of the limb, allowing participants to more easily recognize the simulated partial seizures.
This device was incorporated into the Pediatric Simulation Program at our institution for the status epilepticus scenario in an 8-year old boy with severe pneumonia, hypoxia and hyponatremia. During the simulation scenario, the facilitator in the simulation suite would observe the session and, while wirelessly communicating with the control room behind a two-way mirror, was able to activate the movement of the mannequin limb at his or her discretion by moving the back/forward switch on the remote controller. Thus, the facilitator could discretely control the duration and frequency of movement from up to 15 feet away, depending on the interventions by the participants and the progression of the scenario. After the simulation, the seizure gadget would be removed from the compartment, batteries removed and all components stored safely in the control room, all without the mannequin having been altered.
To date, we have used the seizure gadget in two simulations in the high-fidelity suite as well as one in-situ simulation in the general pediatric ward. In each session, the gadget was able to achieve the intended effect of simulating seizure activity and the participants acknowledged the movement as such. The facilitator was able to covertly control the seizure activity at his or her discretion, depending on the actions of the participants. The device did not affect the mannequin, was easily placed into position, did not interfere with other wireless devices and was safely stored afterwards with battery removal. The small amount of noise produced by the motor was eclipsed by the commotion of the room and ambient noises of the code.
The literature shows high simulator validity is crucial to enhance the realism of a simulation session and subsequently education for participants, improving their skills and responses to critical events, and ultimately, will lead to greater patient safety. High-fidelity mannequins and a variety of tools and techniques to improve the realistic features of simulation are being investigated in academic and commercial sectors to address this aspect of simulation-based education. We have demonstrated that a simple wireless seizure gadget can be readily constructed from commercially available toy parts and effectively incorporated into a simulation scenario depicting partial complex seizures in a pediatric mannequin. To the best of our knowledge, this the first wireless pediatric partial seizure device reported in the literature.
Implications from this work include using other cost-effective remote controlled gadgets to improve the fidelity and realism of simulation, such as building remote-controlled LEDs to change skin color or motors to initiate bleeding. Additionally, we have begun to build circuits with more than one motor per wireless controller; as in our case, so as to allow multiple limbs to vibrate independently or in unison. Lastly, this portable seizure gadget can be adapted to various-sized mannequins, including infants, in a variety of environments and scenarios, for similar effects.
Limitations to this device include obstruction to the radio frequency in the simulation lab. We discovered that the technician in the control room could not use the remote control since the glass and wall separating the simulation suite and control room obstructed the signal. Therefore, the facilitator in the simulation suite handled the controller. However, this was not a hindrance to fidelity; rather, the facilitator had acute control over how long and often the partial seizure would manifest. Additionally, interference from other electronic devices in the simulation suite that would alter the signal from the remote controller was not observed. Finally, the device is not completely concealed; though it was embedded into the gurney, participants could see it under the leg if the removed the hospital sheet. However, the Velcro strap hid most of the gadget and this did not seem to affect their overall response from participants.
A wireless, inexpensive, easily reproducible and compact seizure gadget can be built from commercial toy circuits to enhance the fidelity of medical simulations involving partial complex seizures in a pediatric mannequin.
Editor’s Notes: Rahul Panesar, MD, is an Assistant Clinical Professor in the Division of Pediatric Critical Care Medicine, Department of Pediatrics at Stony Brook Long Island Children’s Hospital, Stony Brook New York. Co-author Sean Cavanaugh, BS, is Senior Simulation Technician at the Clinical Skills Center, Stony Brook University Medical Center and co-author Christopher Gallagher, MD, is Professor in the Department of Anesthesia at Stony Brook University Hospital. Dr. Panesar acknowledges the contributions of Bill Giangarra, Senior Biomedical Engineering Technician in Biomedical Engineering at Stony Brook University Hospital.