Cough following low thoracic hemisection in the cat

Abstract

A function of the abdominal expiratory muscles is the generation of cough, a critical respiratory defense mechanism that is often disrupted following spinal cord injury. We assessed the effects of a lateral T9/10 hemisection on cough production at 4, 13 and 21 weeks post-injury in cats receiving extensive locomotor training. The magnitudes of esophageal pressure as well as of bilateral rectus abdominis electromyogram activity during cough were not significantly different from pre-injury values at all time points evaluated. The results show that despite considerable interruption of the descending pre-motor drive from the brainstem to the expiratory motoneuron pools, the cough motor system shows a significant function by 4 weeks following incomplete thoracic injury.

Figure 1

Cross-section lesion extents. The smallest lesions were incomplete hemisections with ipsilateral ventro-medial white matter sparing (A, B). The complete-hemisections had ipsilateral gray and white matter damage and contralateral gray and white matter sparing (C). The largest lesions were over-hemisections with variable contralateral gray and white matter damage dorsally and ventrally (D, E, F). White indicates areas of remaining tissue; Black indicates areas of tissue loss/damage and scar tissue.

Figure 2

Cough characteristics. Representative un-filtered and moving average integrated electromyograms of the right rectus abdominis and left rectus abdominis with corresponding esophageal pressures (cmH₂0) during cough in a cat 13 weeks post-hemisection (A). The single cough, as well as the subsequent bout of coughing, show robust esophageal pressures and EMG activities bilaterally which are similar to those seen in normal cats. Representative unfiltered RA EMGs show the pre-expulsive behavior seen during some coughs at all post-SCI timepoints during the inspiratory phase (B). The duration of pre-expulsive EMG activity was similar to previously reported studies. (C). A prolonged Pes rise time was seen in some coughs at 13wphx compared to other time points. When this prolonged rise time occurred, it was not accompanied by an increase in Pes.