Aug. 7, 1998 By Victoria White
GAINESVILLE, Fla.---Some people find inhaling helium fun at a party, where the squeaky, high-pitched voices it creates can be comical. But for deep-water divers, who breathe a helium-oxygen mix, such speech distortions can prove dangerous and costly.
In cooperation with the U.S. Navy, University of Florida researchers are trying to improve communication by analyzing the body's "workload" of breathing and speaking under the pressure of a simulated dive. As divers descend deeper and deeper, increasing water pressure transforms the ordinary task of inhaling and exhaling--and therefore speaking--into a tiring athletic event.
Researchers are trying to determine if divers can be trained to breathe and speak differently to make their words more understandable. Such training may include exercising the breathing muscles-pumping iron for the respiratory system.
"Having good communication between divers is an important safety issue," said Jerry Pelton, a former diver who is the Navy's equipment specialist for diver communication systems. "If they can't talk to each other and be understood, they could get in harm's way in a hurry and not be able to perform the tasks we put them down there to do."
"'Bottom time' is expensive," said Capt. Marie Knafelc, a physician who is medical director for the Navy Experimental Diving Unit in Panama City, Fla. "The more time you waste not understanding the other person, the longer it will take to do the job."
Professional divers perform such underwater tasks as laying pipelines, repairing holes in ships that have run aground and changing propellers on aircraft carriers or submarines. When working deep-generally below 190 feet -- they breathe helium and oxygen. The helium is used to replace nitrogen, a normal component of air that becomes intoxicating and too thick to breathe comfortably under pressure.
"Helium speech" is a problem for divers when they're in the water and when they're living in the dry, pressurized chamber of a ship's deck; in such chambers, divers can spend months at a time, breathing the oxygen-helium mix while resting from their work in the water and planning for their next dive. The dry, pressurized chamber exists to save valuable personnel time: Divers do not have to decompress repeatedly after working underwater.
Currently, divers try to communicate the best they can with their helium-altered voices and hand signals. Sometimes, they use headsets or handsets to transmit their voices to surface level, where an electronic helium speech unscrambler makes the words more intelligible and feeds them back into their earphones and those of other divers.
That system is not a perfect solution, Pelton said. Even "unscrambled" voices can be difficult to understand. While the Navy tries to improve the unscrambler, it also has contracted with UF to try to improve the speakers.
The Navy Experimental Diving Unit offers researchers the ability to test their ideas without anyone getting wet. At the Florida Panhandle facility this summer, lead UF investigator Christine Sapienza, associate professor of communication sciences and disorders in the College of Liberal Arts and Sciences, and Paul Davenport, professor of physiology in the College of Veterinary Medicine, conducted breathing and speaking tests on nine Navy divers who spent 22 days in a sophisticated dry chamber that simulates the atmospheric conditions of 500 and 1,000 feet below sea level.
Sapienza and Davenport are investigating the body's physical adjustments to breathe and speak while under pressure. In particular, they are examining the work of the respiratory muscles and associated changes in the larynx (the upper part of the trachea that contains the vocal cords). They also are determining what happens when a diver speaks more loudly or slowly than normal -- two strategies to improve speech intelligibility that collaborating researchers from the University of Mississippi, Johns Hopkins Applied Physics Lab and the Naval Submarine Medical Research Lab are evaluating.
While final results will not be ready for several months, Davenport said it appears loud helium speech is more understandable. But, he noted, "Speaking more loudly takes a lot more effort. So it may increase the clarity of speech, but cause respiratory failure. The diver's ability to work may then go down because he can't breathe as much as he needs."
To resolve that tradeoff, UF researchers, led by Daniel Martin, associate professor of physical therapy in the College of Health Professions, hope to test a training program to strengthen respiratory muscles.
"This is truly a collaborative effort," Sapienza said. "Solving the communication problem ultimately will involve understanding how the underwater environment affects the load on the respiratory system, the load on the larynx and the articulation of speech."
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