SIMULATION OF COUGH IN MAN BY MAGNETIC STIMULATION OF THE THORACIC NERVE ROOTS

Normal cough requires abdominal muscle contraction. We have previously reported contraction of the abdominal muscles elicited by a single pe rcutaneous magnetic stimulation of the thoracic nerve roots. We hypoth esized that paired magnetic twitches could generate sufficient tension in the abdominal muscles to simulate cough. Therefore, six normal sub jects were stimulated at the T10 intervertebral level in the seated po sition. We measured the gastric pressure elicited by paired magnetic s timuli (pTw Pga) with interstimulus intervals in the range of 10 ms (1 00 Hz) to 999 ms (1 Hz). In the second part of the study we evaluated paired stimuli (at the frequency found to produce the greatest respons e) using a valve to simulate the function of the glottis; the valve wa s arranged such that it opened once mouth pressure exceeded a predeter mined threshold. Mean pTw Pga during stimulation for the 6 subjects wa s 74 cm H2O (range, 30-109), and mean peak flow was 209 L/min (range, 128-345 L/min). These values were increased if the subject took a prio r inspiration or had previously made a vigorous expiratory effort. Com parable values for a maximal natural cough were 212 cm H2O and 649 L/m in. We conclude that paired magnetic thoracic nerve root stimulation p roduces gastric pressure and expiratory flow of an order of magnitude comparable to a natural cough.