Safety factor in single human motor end-plates studied in vivo with single fibre electromyography.

In a single fibre EMG investigation on healthy subjects the relationship between the neuromuscular jitter and the safety factor of the motor end-plate relative to curare was studied. A positive correlation was found between the jitter increase after a standard dose of D-tubocurarine and the initial jitter. The conclusion was drawn that the neuromuscular jitter can be used as an indicator of the safety factor. There are a number of nerve-muscle disorders in which the jitter is increased, probably indicating a reduced safety factor which may be of clinical importance when these patients are subjected to diseases or drugs which would otherwise not produce neuromuscular symptomatology.