Objectives: The present study was performed to investigate the best way of using surface electromyography (sEMG) in evaluation of muscle involvement in nasal valve function. The function of the nasal muscles in nasal valve movements has not been investigated sufficiently and in the present study we tried to improve the way of testing these muscles introducing the intranasal placement of surface EMG electrodes.
Methods: Skin surface electromyography (EMG) and intranasal electrode EMG investigation of nasal muscles was performed in two groups (n = 30 for each Group) of healthy subjects: (1) subjects with extremely effective coordination of nasal muscles and (2) those with extremely poor coordination of nasal muscles. Functions of the nasal muscles were assessed by EMG in response to breathing and voluntary nasal movements.
Results: In both Groups, during normal breathing all the tested muscles were not active. During forced nasal inspiration in Group 1 the transverse nasalis, anomalous nasi, alar nasalis and dilator naris anterior were active. In Group 2 during forced nasal inspiration these muscles remained inactive. During rhythmic widening of the nostril, the tested nasal muscles were active in subjects of Group 1 and significantly less active in Group 2 (p = 0.0024). In both Groups the amplitude of muscle activity, recorded from intranasal electrodes was significantly higher that the amplitude recorded from the skin electrodes (p < 0.05). During the tests with two intranasal electrodes, the insignificant difference was detected in amplitude between left and right nostrils in majority of subjects (Group 1 p = 0.15; Group 2 p = 0.1).
Conclusion: We conclude that in human population the ability to operate nasal muscles is varying from person to person, i.e. the nasal muscles can be either inactive ("relatively rudimentary") or active. This fact should be taken into account before any surgical intervention is planned. The subjects with active nasal muscles can control the function of their nasal valve. The intranasal surface EMG is a more direct and precise EMG method for nasal valve evaluation in comparison to skin surface EMG testing.