Two University of Virginia neurobiologists have invented a monitor to help parents determine whether their infant suffers from symptoms that indicate the need for further medical care.

The device consists of an alarm, a visual monitor and a crib-sized pad that senses an infant's motion. If the monitor indicates that the infant has stopped breathing for more than 30 seconds while asleep, an alarm sounds. The alarm might awaken the infant, or prompt a parent or other adult to rush over to shake the infant awake. Either action will cause the infant to resume breathing.

"Our vision really from the first was to have a device that was universal" and that was inexpensive and easy enough to operate for home use, said W. Otto Friesen, co-inventor with Gene D. Block. The monitor probably will be sold for about $275 when direct-mail marketing begins later this month, according to Lifescale Technologies of Meriden, Conn., which has licensed the patent rights from the university's Alumni Patents Foundation.

Most other monitors are used for infants who are believed to have a higher-than-normal chance of succumbing to the mysterious "sudden infant death syndrome." These monitors must be attached to the infant and cost up to $200 a month to rent, according to Penny Williamson, executive director of the National Sudden Infant Death Syndrome Foundation, which is based in Landover.

Friesen and Block stressed that if an infant stops breathing and is awakened by the monitor alarm or by shaking, parents should go to a pediatrician, who may prescribe additional medical care and use of one of the more sophisticated monitors. The inventors see their monitor as merely a screening device.

Most infants thought to be susceptible to sudden infant death syndrome are taken off monitors when they are about six months old, and parents using the new monitor are expected to do the same. "What I see happening is that the monitor will be passed around" for use by other infants just as clothing and car seats are, said Christopher G. L. Jones, president of Lifescale Technologies.

Some concern over this kind of monitor was voiced by the chairman of the National Sudden Infant Death Syndrome Foundation's research board, Dr. Allen Merritt, associate professor of pediatrics at the University of California at San Diego.

Merritt noted that apnea, the sudden cessation of breathing, "is a symptom, like a fever" and could be the sign of an ailment other than sudden infant death syndrome. Just getting the infant breathing again might give parents such a sense of relief that they might not seek medical aid, he said.

"The question remains whether or not such a monitor will give the family or the pediatrician the information that he or she needs in order to perform more sophisticated investigations on the infant," Merritt said. "Only . . . clinical studies . . . can resolve this question. Hopefully, these studies will be performed before the marketing of this item with potential for misinformation to parents."

Block said the unpredictability of the syndrome means that every infant is at some risk. He compared his device to a smoke detector, which is installed even though "none of us expect a fire."

Following its usual course of action, the university will give Block and Friessen 15 percent of the royalties from the monitor and additional research money. Since the Alumni Patents Foundation was established in 1977, the Charlottesville-based school has earned an average of $250,000 a year from licensing faculty inventions.

Its most successful invention was a device for testing multiple blood samples simultaneously and automatically, according to Ralph D. Pinto, the foundation's executive director. The inventor, Dr. Gary Brooker, a pharmacologist, is now at George Washington University. Pinto cited the University of Virginia's medical, chemistry, engineering, physics and biology staffs as the source of many patentable inventions.

This is such a big business nationwide that there is, inevitably, a Society of University Patent Administrators. It has 360 members, some of whom represent more than one institution, according to the current president, Spencer Blaylock of Iowa State University. Blaylock said that at least 300 universities probably have some invention-related research activities.