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Environmental Factor, June 2012

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Predicting breathing rates with personal exposure monitors

By Nancy Lamontagne

RTI’s compact MicroPEM device

RTI’s compact MicroPEM device measures particulate matter and incorporates accelerometer technology that allows the prediction of breathing rates. (Photo courtesy of RTI International)

Charles Rodes, Ph.D.

Rodes said that the grant award allowed the researchers to greatly extend the value of their work in a timely manner. (Photo courtesy of RTI International)

New personal monitoring technology, developed by NIEHS grantees, measures exposure levels and predicts breathing rates based on movement. Since a person running or even walking breathes much faster than someone sitting on a bench, this technology could provide a more accurate assessment of how much pollution a person inhales, and help to strengthen associations between environmental exposures and disease.

A pilot study, published in the journal Atmospheric Environment, showed that the new technology accurately predicted breathing rates for most of the 22 adult participants wearing personal exposure monitors during a variety of activities.

“The exposure estimates used in past studies may not have represented the amount of pollution that actually entered the body,” said Charles Rodes, Ph.D., senior fellow at RTI International in Research Triangle Park, N.C., and senior author for the study. “The new technology could be useful for understanding how environmental exposures affect asthma and other diseases.”

Multi-institute collaboration

Researchers from RTI, the Massachusetts Institute of Technology (MIT) in Cambridge, Mass., Columbia University in New York, and Stanford University in California, all contributed to the new technology, through a collaboration funded by a Genes, Environment, and Health Initiative (GEI) Exposure Biology Program grant award. The Exposure Biology Program, a component of GEI, supports researchers developing technologies to measure environmental exposures that contribute to the development of disease.

Rodes explained that RTI and Columbia had incorporated accelerometers that sense movement in three directions into their prototype personal exposure devices to monitor compliance. Meanwhile, researchers led by William Haskell, Ph.D., professor emeritus at Stanford, and Stephen Intille, Ph.D., formerly a professor at MIT and now at Northeastern University, were using a wireless accelerometer and a mobile phone to collect 24-hour activity and sleep information. The researchers from the various institutions met at a GEI meeting and began brainstorming about how to better use accelerometer data.

Linking breathing and moving

The MIT group developed an algorithm to translate the accelerometer motion information into a sensitive variable to predict breathing rates, and the groups worked together to develop protocols to test the algorithm using the personal exposure devices developed by the RTI and Columbia researchers. The algorithm worked well and showed a linear relationship between the accelerometer data and breathing rate for a variety of activities, such as sitting, standing, and walking, when participants wore the monitors on the hip, ankle, upper arm, thigh, or in the pocket. It did not work as well when the monitor was worn on the arm, the activity was bicycling, or the adults were more than 70 years old.

Steven Chillrud, Ph.D., a researcher at Columbia and co-author of the study, said that the researchers who collaborated on this work have also collected data on 20 boys and girls, ages 11 to 15, to see if the monitors work equally well in children. Although more studies are needed, the personal monitor could be particularly useful for children, because it is comfortable to wear.

“Next, we have to show that the technology really improves the accuracy of exposure measurements,” Rodes said. NIEHS epidemiologist Matthew Longnecker, M.D., Sc.D., proposed that the team help validate the accuracy of the new technology by using the RTI device to measure 48-hour exposure to indoor air pollution from cookstoves in South Africa.

Citation: Rodes CE, Chillrud SN, Haskell WL, Intille SS, Albinali F, Rosenberger M. 2012. Predicting adult pulmonary ventilation volume and wearing compliance by on-board accelerometry during personal level exposure assessments. Atmospheric Environment; doi:10.1016/j.atmosenv.2012.03.057 [Online 6 April 2012].

(Nancy Lamontagne is a science writer with MDB, Inc., a contractor for the NIEHS Division of Extramural Research and Training, Superfund Research Program, and Worker Education and Training Program.)

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