Measurement of neural respiratory drive via parasternal intercostal electromyography in healthy adult subjects
Victoria MacBean, Cara Hughes, Gavin Nicol, Charles C. Reilly, Gerrard F. Rafferty
Published in the journal Physiological Measurement, October 2016
Parasternal intercostal electromyography (EMGpara) is a method used to measure breathing function by monitoring signals sent from the brain, to the parasternal intercostal muscles (muscles between the ribs). These muscles, together with the diaphragm (a thin muscle under the lungs) and some others, move together to control your breathing. EMGpara can be used to measure a person’s neural respiratory drive (NRD), which is an indication of the strength of the respiratory (breathing) muscles under a certain amount of strain (how hard the muscles may have to work when they are coping with different diseases or environments). This method is an alternative to other more traditional practices that, for example, may involve the use of needles. Therefore, EMGpara is less invasive and ideal for monitoring the breathing muscles in many groups of people.
In the case of this study EMGpara was measured in healthy adults in order to discover what factors determine normal EMGpara readings. The participants were over the age of 18, and were of different body types and sexes.
In preparation for the EMGpara tests, each participant’s body size, shape and composition was measured – this included taking note of their height, weight, hip and waist size, body fat percentage and body mass index – as well as tests to confirm that each person had normally functioning lungs.
Electrode stickers were placed on the chest to measure the EMGpara signals as the subjects breathed normally and effortfully. The tests were repeated at a later date to make sure the results could be reproduced, thereby checking that the EMGpara technique is consistent.
The study suggests that sex is the most important factor in determining EMGpara; a higher value for EMGpara was observed in the women who took part. This may be because in general, woman have smaller lungs and narrower airways compared to men and their respiratory muscles are usually not as strong.
Age did not seem to have a significant effect on the readings; however this could have been because the average age of those involved was only 31, and those who were older were quite athletic, meaning their respiratory health was very good.
The results of this study can be used as a reference for what a normal EMGpara reading is, and therefore they can be used when assessing patients in the future. The study included many people from different backgrounds, so it is quite representative of the population. The study was also important in working out which methods and techniques are best for measuring EMGpara, as well as for highlighting possible areas of further research for future studies.
This summary was produced by Djenné Oseitwum-Parris, Year 12 student from Burntwood School, Wandsworth, as part of our departmental educational outreach programme.