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Phrenic Nerve Stimulation

Magnetic stimulation can be used for bilateral or unilateral phrenic nerve stimulation. Its advantages over electrical stimulation are ease of positioning, repeatability and much improved patient tolerance. It is used reliably to assess the function of respiratory muscles by measuring the diaphragmatic response and strength. The ease of application and patient comfort makes it possible to also carry out longitudinal monitoring studies. Magnetic stimulation can be used to obtain responses even when the phrenic nerve cannot be located using conventional electrical stimulation.

Mills et al (1995) looked at the ability of four different magnetic coils to produce unilateral phrenic stimulation in five normal subjects, assessed from twitch transdiaphragmatic pressure (TwPDI) measurements and diaphragmatic electromyogram (EMG) recordings. They found that unilateral magnetic phrenic nerve stimulation is easy to apply and is a reproducible technique in the assessment of hemidiaphragm contractility. It is well tolerated and allows hemidiaphragm contractility to be rapidly and reliably assessed because precise positioning of the coils is not necessary. This may be particularly useful in patients. In addition, the anterolateral positioning of the coil allows the use of the magnet in the supine patient such as in the operating theatre or intensive care unit (Mills et al. 1995).

Twitch Pdi measurement may be used to confirm or refute the diagnosis of bilateral or unilateral diaphragm weakness. In patients with neuromuscular disease Twitch Pdi may permit accurate clinical assessment of disease progress. Ongoing developments include the adaptation of magnetic stimulation for use with neonates or children. Additionally, by measuring pressure changes in the mouth (Twitch Pmo) it is now possible to obtain a non-volitional measure of diaphragm strength.

References

  • Mills et al., Thorax, 1995.

Products

  • Magstim 200²
    A single pulse, monophasic stimulator used for cortical and peripheral stimulation.
  • Magstim BiStim² & Upgrade
    The BiStim² is an extension of the 200². Two of the single pulse systems are combined through a connecting module, so that paired pulses can be delivered through one coil.
  • Magstim Rapid², Super Rapid², & the Super Rapid² Plus¹
    The Magstim Rapid² is a single pulse and repetitive stimulator with high frequency capabilities. It is ideal for therapeutic applications as well as a wide variety of research fields.
  • Articulated Coil Stand
    The Magstim Articulated Coil Stand arm is an elegant multi-movement mechanism capable of holding a stimulating coil over an exceptionally wide range of movement.
  • Interface Module
    The Magstim Stimulator Interface Module provides additional interface functionality for all of the 2nd generation Magstim Stimulators (200², BiStim² and Rapid²).
  • Double Small 25mm Coil
    The Double Small 25mm Coil has been designed for enhanced positional accuracy in peripheral stimulation.

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