Quantitative motor unit potential analysis in the diaphragm: a normative study

Although quantitative motor unit potential (MUP) analysis has an established role in other skeletal muscles, it has not been performed in the diaphragm. The aim of the present study was to test whether such studies are possible and to establish normative data. Twenty-nine healthy volunteers (15 men), aged 21-65 years (median, 33 years), were studied using standard concentric needle electrodes, and equipment with the facility for template-operated multi-MUP analysis. Needle electrodes were inserted into the right medial recess of the seventh to ninth intercostal spaces. During MUP sampling, subjects were asked to hold their breath in partial inspiration for 5 s. At least 20 MUPs were obtained in 28 subjects. Diaphragmatic MUPs were confirmed to be much smaller than those of limb muscles. We found diaphragmatic quantitative MUP analysis to be possible in healthy volunteers. However, further studies in patient groups are needed to establish the feasibility and clinical value of such studies.