Another Kind of Circulatory System

In the depths of the hospital, through doors that often go unnoticed by most employees, is a transportation system that plays a huge role in modern health care. The passengers are not people, although some are samples of people – blood samples, that is, secured in a “carrier” and on their way to the hospital lab. The carriers – cylindrical cartridges with a secure latch on each end — race all over the hospital through pneumatic tubes hidden deep behind the walls. Unit nurses can send samples to the lab for testing, or receive blood products and medications to administer to their patients.

Pneumatic tube systems have been used in communications, banking, health care and industry since the mid-1800s to move small things from one place to another much faster than a human could travel — even faster than a car. Digital communication has taken over the conveyance of messages, but when it comes to transporting an actual object across a hospital campus, the pneumatic tube still reigns supreme.

The pneumatic tube system at University of Maryland Medical Center (UMMC) is one of the most complex in existence, according to Pevco, the company that designed and installed it some 20 years ago at UMMC’s University Campus, and has updated and expanded it through the years  The last big upgrade was 2011, when UMMC added two additional miles of pipe, interchange rooms, 25 new pieces of equipment and 10 additional zones.

Before this system was installed, the hospital staff included couriers hired specifically to “run” blood products, lab samples, and pharmaceuticals. They were fast, but no match for the tube system once it was installed. It takes 15 minutes to walk from the two furthest points in the hospital, but only five minutes for a carrier in the tube system.

A pneumatic delivery system transports containers through tube networks using air pressure. The nerve center of the system is a computer that takes up so little space it only requires a small closet. When a nurse or lab technician enters a destination into one of the 99 stations throughout the hospital, the computer selects the quickest available route, waits until the route is clear, then uses vacuum to pull the carrier out of the station into the pipes.

The “whoosh” sound a carrier makes heading down a clear passageway is music to the ear of Richie Stever, CHFM, LEED AP, director of operations and maintenance at UMMC.

“The system is designed like a roadway system,” Stever said. “When the pipe  — think of it as a highway —  is clear, the carrier is lifted from the station with a motor that creates suction, and then it travels through the pipe until it reaches a diverter – like a highway interchange — switches roads, and then is moved with pressure via a motor until it reaches its final destination.”

There are 5.5 miles of pipe throughout the complex, with the average time for deliveries being less than five minutes. To create that kind of power, the tube system is backed by 22 blower motors that push and pull air through the pipes.  There are 22 zones the items can travel through, and 103 diverters. Diverters are used to make bridges from station to station. The diverter is placed at an intersecting point and changes the carrier’s path to a different tube. There are three interchange rooms in the system where the diverters are used to change the direction of the carriers.

The carriers are numbered cylindrical cartridges equipped with two latches on each end as well as foam padding to protect the contents during their trip – sometimes miles at a time.  There are 99 carrier stations throughout the hospital building, with seven in the Central Pharmacy, eight in the North Core Laboratory, seven in the South Core Laboratory, three in the Blood Bank and one at each nurses’ station.

When a carrier comes through to the station, a tone will sound to let those nearby know that a specimen or blood product has just come in. Those 99 stations generate more than 5,000 transactions per day at a speed of around 500 feet per second.

As with any complex machine, things can go wrong, but built-in features kick in to fix them. If a blower is off-line because of mechanical or electrical failure, another blower within the system can do the job. If a cartridge opens up en route and spills the contents, technicians use measurements to figure out where the spill or clog is  before deploying a special “squeegee” — more like a large sponge — that is as big as the inside of the tubes. The squeegee is sent through the tubes multiple times to clean up the spill.

“Twenty years ago, when we installed the first part of the tube system, we never imagined we would be able to send a thousand carriers in a day,” said Scott Kruelle, system operator for the tube system. “Now, we send more than 5,000 carriers a day.”