Last year, less than half of all Americans got their flu shots—and only one in three healthy adults did. One of the reasons people skip this inoculation is a fear of needles, but some doctors believe this can be easily helped.
Indeed, an estimated 10 percent of the population has needle phobia, and some studies put the number as high as 22 percent. So developing a pain-free way to administer vaccines, draw blood and start IV lines has become a primary concern of doctors, especially those who specialize in anesthesia and treating pain.
Recently, at the annual meeting of the American Society of Anesthesiologists, William McKay, a professor of anesthesiology and pain management at the University of Saskatchewan, presented a needle that allegedly makes injections painless by using vibration, pressure and temperature to trick the brain.
The cobbled-together system is comprised of a force transducer, vibrator and temperature-control module, pieces of equipment regularly used in pain clinics. The elements are controlled by a computer and connect to a Von Frey’s needle, which can buckle but withstand force, via a copper plate. Over the course of 1,650 pricks, McKay and his teammates were able to determine that if they apply 100-hertz vibrations with up to 400 torr of pressure (the equivalent of about half the Earth’s atmospheric pressure) at about 100 degrees Fahrenheit for 20 seconds prior to injection, then the subjects’ pain level wouldn’t break a 3 on the 0-10 pain scale. (The data indicated that applying cold actually produced better results than heat, but subjects complained that the chill was uncomfortable.)
What might sound like simple misdirection is actually anchored in neurology. The device plays off of the gate control theory of pain, which was developed by a team of doctors at McGill University in the 1960s. Gate theory has shown that nerve sensations—be they pain, temperature or tickles—pass through the same conduits en route to the brain for processing. The feeling of a finger prick, for instance, travels through the nerve to the dorsal part of the spine, where a synapse connects with the next neuron, allowing the signal to travel on to the thalamus and into the brain. Gate theory posits that only so much sensory information can travel that pathway at once.
“If all the synapses are quiet,” explains McKay, “and you stick your finger, the synapse is widely open and up [the pain] goes. If there are other things going on, the synapse isn’t as open for as long or as widely, so not as much pain sensation can traffic through.”
The technique, McKay freely admits, is nothing new. The Atlanta-based company MMJ Labs, for example, currently markets Buzzy, a palm-sized device that uses cold and vibration to decrease injection and other pain in children. But he hopes that his work will help make other devices more precise. “What we’ve done is quantify these [factors] and try to find the optimal levels of vibration on the skin and what’s the best temperature,” he says. “Some company will make use of that data.”
Needles that use gate-control might be able to one-up other pain-free offerings, which focus primarily on drug delivery. The Fluzone system, for instance, reduces pain by only puncturing the skin instead of both skin and muscle. Other devices, such as the PharmaJet and BioJect, remove needles entirely, using a tiny pressurized jet to deliver drugs, such as insulin. McKay says his system could be easily modified to work with standard needles for drawing blood, starting IVs and for pediatric use. “You just have to make [the needle] a little different shape,” he says, becuase blood draws and IV starts enter the skin at a different angle than injections.
For the time being, McKay will remain focused on shots, so his next step is to initiate a clinical trial, perhaps at a flu vaccination clinic. McKay, who's in his 70s and nearing the end of his career, has no immediate plans to bring a device to market. "I don't even know if it's patentable," he adds. Rather he hopes that his findings will help inform companies, doctors and nurses out to deliver painless pricks.