Spinal cord stimulation: a new method to produce an effective cough in patients with spinal cord injury

Abstract

Patients with spinal cord injury have an increased risk of developing respiratory tract infections as the result of expiratory muscle paralysis and consequent inability to cough. We have developed a method by which the expiratory muscles can be activated via lower thoracic and upper lumbar spinal cord stimulation to produce an effective cough mechanism. In a tetraplegic patient who required frequent (8.57+/-2.3 times per week [mean+/-SEM]) caregiver assistance to facilitate airway clearance and expectoration of secretions, three epidural electrodes were applied in the T9, T11, and L1 spinal cord regions. During stimulation at the T9 and L1 levels, airway pressures were 90 and 82 cm H2O, respectively. Peak expiratory flow rates were 6.4 L/s and 5.0 L/s; respectively. During combined (T9+L1) stimulation, airway pressure and expiratory flow rate increased to 132 cm H2O and 7.4 L/s, respectively. Addition of the third lead did not result in further increases in pressure generation. These values are characteristic of those observed with a normal subject. Because the patient is able to trigger the device independently, he no longer requires caregiver support for airway management. If confirmed in additional patients, spinal cord stimulation may be a useful method to restore an effective cough mechanism in patients with spinal cord injury.

Figures

Figure 1.

Representative tracings of expiratory flow and airway pressure during stimulation at T9 (40 V, 53 Hz, 150 μs), L1 (40 V, 53 Hz, 200 μs), and combined stimulation (T9+L1) at TLC.

Figure 2.

Mean changes ± SEM in airway pressure generation during stimulation at T9, T11 (40 V, 53 Hz, 200 μs), L1 and combined stimulation (T9+T11+L1) at FRC and TLC (stimulus parameters same as Figure 1).

Figure 3.

Relationship between stimulus frequency and mean airway pressure generation ± SEM during stimulation at T9, L1, and combined stimulation (T9+L1) at FRC (stimulus parameters same as Figure 1).