For as long as oxygen has been administered to hospital patients, there's been no continuous, non-invasive, real-time method for determining how well the patient is absorbing it.
Dip Molded: The flexible nasal cannula
employs a chamber-inside-a-chamber
Now, a new medical product known as the Smart Capnoline Cannula is said to be the first patient interface that provides a true, continuous absorption waveform for anesthesiologists drawing breathing samples while delivering oxygen. The flexible plastic cannula can also serve as a valuable asset for patients receiving oxygen in hospital beds or at home.
"The amount of oxygen being absorbed is a key indicator that allows emergencies to be addressed immediately," notes Sam LaBanco, director of mechanical engineering for Herbst Lazar Bell Inc., which worked with Oridion Medical 1987 Ltd. (Jerusalem, Israel) on the design of the new cannula. The level of oxygen being absorbed can also provide medical personnel with an early indicator of life-threatening events.
The Smart Capnoline Cannula provides all those capabilities because it delivers oxygen to patients while it simultaneously measures their CO2 output. By doing so, it plows new ground in the patient care arena.
The new device is able to do both because it incorporates two separate chambers, rather than the usual one. An internal chamber collects CO2 breathed out by the patient, and an external chamber is used for delivery of oxygen.
Unlike conventional cannula, which deliver oxygen through two hoses in the nostrils, the new device provides oxygen through a series of tiny holes, each measuring 0.08 inch, pierced into the external chamber. Oxygen is essentially "sprayed" under the nose, where the patient can inhale it.
The hoses located at the nostrils, now capture outgoing CO2 exhaled by the patient. Air passes through the double-pronged hose, enters the internal chamber, then travels through a dedicated hose on the left side of the patient's face, to a machine called a capnograph, which analyzes the breath chemistry.
Although the cannula sounds simple, engineers struggled to develop a manufacturing technique for the chamber-inside-a-chamber configuration. Their solution was to design the cannula as four distinct components, which are made with a four-piece mandrel consisting of stainless steel investment castings. A dip-molding process forms the part. The mandrel is dipped in liquid PVC, allowed to cure, and then disassembled in a way that produces a flexible, single-piece part.
"We brainstormed other methods to form the part, but in the end we were afraid the others wouldn't have been economically viable for our client," says Julie Willis, a mechanical engineer who worked on the project. "Also, we didn't want to be too operator-dependent, to ensure high quality."
LaBanco and Willis say they worked with a team of engineers and designers from Herbst Lazar Bell, Inc., including fellow team members Steve Remy, Len Czuba, and Jason Billig. They also had constant input from engineers at Oridion Medical, as well.
Engineering team members said they expect the cannula to serve in a variety of applications, ranging from surgical monitoring of anesthesized patients to everyday bedside monitoring at home. The device, they say, not only helps doctors determine how well oxygen is being absorbed; it also aids in knowing if medical treatments are effective.
"The object was to find a way to accurately measure CO2, while still supplying oxygen to the patient," LaBanco says. "This accomplishes that, and does so non-invasively."
Contact Sam LaBanco, Herbst Lazar Bell Inc., 355 North Canal St., Chicago, IL 60606; Tel: (312)454-1116; or Enter 547; www.hlb.com.