Diaphragmatic pacing: an alternative to long-term mechanical ventilation.

Electrical percutaneous stimulation of the phrenic nerves was first employed in 1948 by Sarnoff to provide temporary artificial ventilation in patients with respiratory failure. However, the technique was limited by development of infection around the electrode. Short-term radiofrequency stimulation of the phrenic nerves was first utilised by Glenn in 1964 and adapted to long-term use in patients with central hypoventilation in 1968 and with traumatic quadriplegia in 1972. The technique employed alternate pacing of each hemidiaphragm with high frequency stimulation (25-30 Hz) with a respiratory rate of 12 to 17 per minute which, in a series of 17 quadriplegic adults, although initially successful, was self-limiting because of eventual damage to the nerves and diaphragms. More recently, continuous bilateral simultaneous low frequency (up to 8 Hz) stimulation with a respiratory rate of 5 to 9 per minute has not induced myopathic changes. This phenomenon has been attributed to: 1. the conversion of the mixture of slow and fast twitch fibres in the diaphragm to a uniform population of fatigue resistant fibres induced by low frequency stimulation, and 2. the reduction in the total current necessary to achieve adequate gas exchange when both diaphragms contract simultaneously with the less frequent stimulation at lower energy. Diaphragmatic pacing has been applied to infants and children with emphasis on the selection of patients and optimum setting of stimulus parameters. This communication presents a case report of diaphragmatic pacing in a child with a review of the principles of application. The advantages and disadvantages compared to mechanical ventilation are also discussed.