January 29, 1999

Study of infant transportation lands students national award

Study of infant transportation lands students national award

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Vanderbilt medical students Gargi Gajendragadkar (left) and Julie Boyd developed a way to test the vibrations experienced by critically ill newborns during transport. (Photo by Donna Jones Bailey)

Transporting critically sick infants to Vanderbilt University Medical Center from community hospitals is a feat made possible by the Newborn Emergency Transport Program¹s state-of-the-art vehicles.

But little was known about whether continuous vibrations inside the "Angel" and "Cherub" transport ambulances affect the tiny, delicate cargo inside.

Two second-year Vanderbilt University School of Medicine students looked into the issue last year in their Introduction to Biomedical Research class. The students, Gargi Gajendragadkar and Julie Boyd, received a Young Investigator Award in November from the National Perinatal Association for their work.

They hope to soon have their work published as other investigators continue the research that the budding investigators began last year.

The study compared the abilities of a standard foam mattress and a gel mattress in different combinations to lessen the vibration during routine transport conditions. The research expanded on prior work that showed the infants were exposed to prolonged, low-frequency, high-amplitude vibration during transport.

It is not known how this continuous vibration affects infants, but studies done with adults have shown possibly harmful swings in temperature and heart rate.

The research compared four combinations of mattresses in the incubator: no mattress, foam, gel and a foam/gel combination. The results of the study were surprising.

"The idea of the mattress is to make the infant more comfortable," said Dr. Jayant P. Shenai, professor of Pediatrics and medical director of the Newborn Emergency Transport Program. "Previously it was thought that the gel mattress reduced the vibrations more. What was most surprising for us to find was that none of the mattresses dampened any of the vibrations. They actually accentuated the vibrations," Shenai said.

Of all the combinations, however, the gel mattress and the gel/foam combination accentuated the vibrations the least.

The research was performed in the Angel ambulance with a mannequin inside the transport incubator. Each mattress combination was tested on both a city and a highway route. An instrument called an accelerometer, similar to a tiny electrode, was used to measure both the amplitude and frequency of the vibration. One was placed on the forehead of the mannequin and one was placed on the base of the incubator so the investigators could measure whether the vibration experienced at the bottom of the incubator was dampened or accentuated by the time it reached the forehead of the infant-sized mannequin.

"It¹s a simple study with clinical applications," Shenai said.

The students also found that the performance of the mattress was dependent upon the weight of the mannequin and that the vibration was at its worst on the city routes.

"The students tried the same experiment using a 300 gram mannequin as opposed to a 2,000 gram mannequin. Everything was accentuated if the mannequin was smaller," Shenai said. "The present combination of mattresses we are using is totally ineffective against vibration for very small babies. That finding has particular relevance because we often transport babies as small as 500 grams. It is the babies of that size that need the most protection against vibration because they¹re most vulnerable."

Boyd said the students are pleased with the study.

"We were trying to approximate life conditions by using the mannequin in the ambulance," Boyd said. "Our study did not investigate the physiological effects of vibration on neonates, but this is an area that we¹ve suggested for future study."

Shenai said the logical next step is for the incubator to be modified so that the patient compartment is motionless.

The students said their research would not have been possible without the interdisciplinary cooperation of Shenai, Guillermo D. Hahn, Ph.D., associate professor of Civil and Environmental Engineering; Beverly G. Mellen, Ph.D., assistant professor of Preventive Medicine; Darek Potter, a Vanderbilt engineering student; Cheryl Major, R.N., neonatal outreach coordinator; and James Altick, a long-time driver of the Angel ambulance.

This is the second study under Shenai¹s supervision that has won the National Perinatal Association Young Investigator Award. Last year, Patricia Chu and Christine Wang, now third-year students, won the award for their study on how to measure the caloric and nutrition content of human milk. The study also came from the Introduction to Biomedical Research class.

The class has produced some outstanding researchers, Shenai said.

"It introduces every medical student here to some kind of research project. So we end up having about 100 students per class who are potentially good investigators of the future."