Making Needles Obsolete
New Technology Painlessly Measures Blood, Tissue Chemistry

Being poked and prodded may become a thing of the past, thanks to refinements being made to a device known as a “current-near-infrared spectroscope.” When perfected, the spectroscope will measure patients’ blood and tissue chemistry – without using needles.

“Once complete, this device will allow chemical analysis and diagnosis without removing samples from the patient. It will be useful for monitoring surgery patients, assessing severity of traumatic injury, and evaluating injuries in space,” said Babs Soller, M.D., a researcher on the National Space Biomedical Research Institute’s smart medical systems team.

The institute is a NASA-funded consortium of 12 medical institutions, including Baylor College of Medicine, that are studying the health risks related to long-duration space flight, then transferring the knowledge learned to benefit patients on Earth.

Today, patients commonly encounter near-infrared spectroscopy at the doctor’s office. The pulse oximeter, used for measuring oxygen saturation, is one example. This device employs a small clip placed on the finger or ear to measure the amount of oxygen carried by the blood, along with pulse rate.

“The technology works by emitting wavelengths from near-infrared light that pass through skin and to some extent bone, allowing physicians to get chemical information about tissues and blood,” said Soller, a research associate professor of surgery at the University of Massachusetts Medical School.

To refine the technology for more varied measurements, Soller and colleagues are gathering data from patients. Study participants include cancer, cardiac surgery and trauma patients.

“We’re measuring hematocrit, tissue pH and tissue oxygenation using our device and standard techniques,” she said. “These data will give us the information needed to derive equations to calibrate the new near-infrared instrument.”

The blood and tissue measurements will provide key information, such as whether a patient is anemic and whether there are adequate levels of oxygen and blood flow to muscle tissue cells.

To make the device accurate regardless of skin color or body-fat content, Soller’s group is gathering data from 100 subjects representing five ethnic groups – African-American, Asian, Caucasian, Hispanic and Mediterranean.

“Near-infrared light is absorbed by pigment in darker skin, so we are collecting data and developing equations that remove the influence of skin color and fat content on measurements,” Soller said. “Once we adjust for these variables, we can take measurements on the arm or leg or even sew sensors into clothes.”

The final step will be to develop clinical guidelines for the measurements, so physicians understand the significance of the readings.

“Tissue pH and oxygenation are new medical parameters, so we have to determine specific values that, based on the readings, allow us to identify when a person is in shock or in need of treatment,” Soller said.

Since the technology is being designed to meet the lightweight, low-power and portable requirements of the space program, it will also be useful in ambulances, helicopters and emergency rooms.

“The beauty of the noninvasive technique is that it allows physicians to take measurements continuously, once a second if you want,” she said. “We think these measurements may help prevent serious complications from traumatic injuries by providing early indications of low – oxygen availability.”

Soller feels the device will be particularly useful for treating patients with shock caused by excessive bleeding or heart attack, patients with internal bleeding, and pediatric patients, where it can be difficult to take multiple blood samples.

The technology also has potential use in exercise and endurance training.

“Tissue pH can measure how hard a person’s muscles are working. The device could be used to determine when the muscles are exhausted, so you could use it to develop a personal training program,” she said.

The prototype device currently uses two optical fibers, one shining the light into the patient and the other carrying the reflected light back to a device that analyzes the data. However, it still needs to be smaller for space use.

“We’re actively looking for a commercial partner to build a miniature version of the device,” she said.

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©2006 Texas Medical Center

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