Mechanism of Active Expiration in Tetraplegic Subjects

Abstract

Traumatic tetraplegia produces paralysis of all the well-recognized muscles of expiration. Yet, tetraplegic subjects usually have a small expiratory reserve volume on spirographic examination. To understand the mechanism that enables these patients to empty their lungs actively, we studied the pattern of chest-wall motion during voluntary expiration. We found negligible changes in abdominal dimension, but all subjects had a marked and reproducible decrease in the dimension of the upper rib cage. Electrical measurements established that the subjects had active use of the clavicular portion of the pectoralis major, and changing the orientation of these muscle fibers by maintaining the shoulders in abduction reduced their expiratory reserve volume by about 60 percent (P less than 0.001). We therefore conclude that the clavicular portion of the pectoralis major plays a crucial part in the mechanism of active expiration in tetraplegic subjects. Training of this muscle bundle could, by increasing its strength and endurance, improve the effectiveness of coughing in such subjects and perhaps diminish the prevalence of bronchopulmonary infections.

Electromyographic signal-activated functional electrical stimulation of abdominal muscles: the effect on pulmonary function in patients with tetraplegia

“…The pectoralis major muscle, which is active in patients with tetraplegia during cough 3,4 and has been shown to be active during both the inspiratory and the expiratory phases of cough in cats, 16 was the first muscle chosen in this study as a source of triggering signals. Signals obtained from other muscles, however, such as the deltoid, which also contracted in our patients during inspiration or the inspiratory phase of cough, produced a stronger expiration.…”

“…Diaphragmatic power can be adequate in these patients, and they may have satisfactory breathing in the supine position, or when a constant passive pressure is applied to their abdomen by spastic abdominal muscles or an elastic band, because chest elastic recoil and the applied pressure return the diaphragm to a sufficiently high position after expiration. 3,4 Breathing can be further assisted by postural drainage with head-down tilt that helps remove respiratory tract secretions. 5,6 Nevertheless, constantly applied pressure and positioning cannot produce forced expiration or coughing, which is necessary for efficient removal of secretions and solid particles from the respiratory tracts.…”

Maximal static mouth respiratory pressure in spinal cord injured patients: correlation with motor level

“…23 Patients with lesions above T6, may generate expiratory pressure by the action of the clavicular portion of the major pectoral muscle. 24,25 For practical reasons, we attributed an arbitrary unit value for each level of lesion in the correlative analysis. This number may not fully reflect actual difference from one level to another.…”

Benefit of triple-strap abdominal binder on voluntary cough in patients with spinal cord injury

“…[1][2][3] Even though this group is unable to actively contract their abdominal muscles, previous studies have shown that production of cough in this population can still be an active process, with the contraction of clavicular portion of the pectoralis major and latissimus dorsi. [4][5][6] A few studies that focus on improving cough ability among persons with SCI have been conducted. These include studies on therapeutic manoeuvres, 7 use of abdominal binders, [8][9][10][11][12][13] the use of electrical stimulator 14,15 and functional magnetic stimulator.…”