How Air-Powered Computers Can Prevent Blood Clots

A new air-powered computer sounds alarms when certain medical devices fail, providing a more reliable and less expensive way to prevent blood clots and strokes — all without electronic sensors.

Described in a journal article DeviceThe computer not only runs on air, but it also uses air to issue warnings. It immediately sounds a whistle when it detects a problem with the vital compression machine it is designed to monitor.

Intermittent pneumatic compression or IPC devices are leg sleeves that periodically fill with air and compress a person’s legs to increase blood flow. This helps prevent blood clots that can lead to blocked blood vessels, strokes, or death. These machines are typically powered and monitored by electronic devices.

“IPC devices can save lives, but all the electronics inside them make them expensive. So we wanted to develop a pneumatic device that eliminates some of the electronics, to make these devices cheaper and safer,” said William Grover, associate professor of bioengineering at UC Riverside and author of the corresponding paper.

Pneumatic systems move compressed air from one place to another. Freight train emergency brakes work this way, as do bicycle pumps, tire pressure gauges, respirators, and IPC devices. It made sense to Grover and his colleagues to use one pneumatic logic device to control another and make it safer.

This type of device works similarly to electronic circuits, performing bit parity calculations. “Say I want to send a message that’s ones and zeros, like 1-0-1, three bits,” Grover explains. “Decades ago, people realized they could send those three bits with an extra piece of information to make sure the recipient gets the right message.”

This extra information is called a parity bit. The bit is a number: 1 if the message contains an odd number of ones, and 0 if it contains an even number of ones. If the number 1 appears at the end of a message containing an even number of bits, it is clear that the message is in error. Many electronic computers send messages in this way.

A computer running on compressed air uses the pressure differences of the air flowing through 21 tiny valves to count the number of ones and zeros. If no counting errors have occurred, the whistle does not sound.

If the device explodes, it is a sign that the machine needs repair. In a video demonstration of the air computer, Grover and his students are shown damaging an IPC device with a knife, rendering it unusable. A few seconds later, the whistle sounds.

“This device is about the size of a matchbox. It replaces a handful of sensors and a computer,” Grover said. “So we can reduce costs while still detecting problems in a device. It could also be used in high-humidity or high-temperature environments that aren’t ideal for electronics.”

Monitoring IPC devices is just one application of aerial computing. For his next project, Grover would like to design a device that could eliminate the need for a task that kills people every year: moving grain to the top of large silos.

Large buildings filled with corn or wheat grain silos are common in the Midwest. Often, a human must enter them with a shovel to break up the grain and level the piles inside.

“A lot of deaths happen because the grain moves and the person gets stuck. A robot could do that job instead of a person. However, these silos are explosive and a single electrical spark could blow up a silo, so an electronic robot may not be the best choice,” Grover said. “I want to create an air-powered robot that could operate in this explosive environment, not generate sparks and keep humans out of harm’s way.”

Pneumatic computing is an idea that has been around for at least a century. In the past, pneumatic pianos that could play music were made from perforated rolls of paper. After the advent of modern computing, engineers lost interest in pneumatic circuits.

“Once a new technology becomes dominant, we lose sight of other possible solutions to problems,” Grover said. “What I like about this research is that it can show the world that there are situations today where ideas that are more than 100 years old can still be useful.”