Am. J. Respir. Crit. Care Med.,
Volume 156, Number 1, July 1997, 122-126
Efficacy of Combined Inspiratory Intercostal
and Expiratory Muscle Pacing to Maintain
Artificial Ventilation
ANTHONY F.
DIMARCO,
JAROSLAW R.
ROMANIUK,
KRZYSZTOF E.
KOWALSKI,
and
GERALD S.
SUPINSKI
Pulmonary Division, Department of Medicine, Case Western Reserve University, MetroHealth Medical Center, Cleveland, Ohio
Many patients with ventilator-dependent quadriplegia have coincident phrenic nerve injury and
therefore cannot be offered phrenic nerve pacing. The purpose of this study was to assess the utility
of combined inspiratory intercostal and expiratory muscle pacing to provide complete ventilatory
support. Studies were performed in 15 anesthetized dogs. An electrode was positioned on the epidural surface of the upper thoracic spinal cord to activate the inspiratory intercostal muscles; a separate
electrode was positioned on the epidural surface of the lower thoracic spinal cord to activate the expiratory muscles. In an attempt to replicate the effects of inspiratory intercostal pacing alone in humans, stimulus parameters during upper thoracic spinal cord stimulation were adjusted to provide
suboptimal levels of ventilation (end-tidal PCO2 of 55 to 60 mm Hg). Expiratory muscle activation was
triggered electrically by the inspiratory signal with a 4.2-s delay resulting in alternate inspiratory and
expiratory muscle pacing at a combined rate of 14 breaths/min. Combined pacing was maintained
for an arbitrary period of 3 h. Initial intercostal muscle pacing alone resulted in an end-tidal PCO2 of
57.1 ± 1.1 mm Hg. After the addition of expiratory muscle pacing, end-tidal PCO2 fell to 36.3 ± 1.2 mm Hg. Tidal volume during both inspiratory and expiratory muscle pacing and end-tidal PCO2 remained stable throughout the study period. Our results suggest that combined alternate inspiratory and expiratory muscle pacing may be a viable alternative method of artificial ventilation in ventilator-dependent quadriplegic patients. DiMarco AF, Romaniuk JR, Kowalski KE, Supinski GS. Efficacy of combined inspiratory intercostal and expiratory muscle pacing to maintain artificial ventilation.
