Intercostal muscle motor behavior during tracheal occlusion conditioning in conscious rats

Abstract

A respiratory load compensation response is characterized by increases in activation of primary respiratory muscles and/or recruitment of accessory respiratory muscles. The contribution of the external intercostal (EI) muscles, which are a primary respiratory muscle group, during normal and loaded breathing remains poorly understood in conscious animals. Consciousness has a significant role on modulation of respiratory activity, as it is required for the integration of behavioral respiratory responses and voluntary control of breathing. Studies of respiratory load compensation have been predominantly focused in anesthetized animals, which make their comparison to conscious load compensation responses challenging. Using our established model of intrinsic transient tracheal occlusions (ITTO), our aim was to evaluate the motor behavior of EI muscles during normal and loaded breathing in conscious rats. We hypothesized that 1) conscious rats exposed to ITTO will recruit the EI muscles with an increased electromyogram (EMG) activation and 2) repeated ITTO for 10 days would potentiate the baseline EMG activity of this muscle in conscious rats. Our results demonstrate that conscious rats exposed to ITTO respond by recruiting the EI muscle with a significantly increased EMG activation. This response to occlusion remained consistent over the 10-day experimental period with little or no effect of repeated ITTO exposure on the baseline ∫EI EMG amplitude activity. The pattern of activation of the EI muscle in response to an ITTO is discussed in detail. The results from the present study demonstrate the importance of EI muscles during unloaded breathing and respiratory load compensation in conscious rats.

Usefulness of Parasternal Intercostal Muscle Ultrasound during Weaning from Mechanical Ventilation

“…The relationship between diaphragm function and the recruitment of extradiaphragmatic inspiratory muscles has been described in animal models and in humans, although few data are available in ICU patients. 8,[31][32][33][34] The diaphragm is the main inspiratory muscle and diaphragm dysfunction elicits a series of adaptive mechanisms that enable ventilation and pulmonary gas exchange to be maintained within reasonable limits. Patients with chronic diaphragm dysfunction exhibit an increase in extradiaphragmatic inspiratory muscles contraction that is associated with respiratory discomfort.…”

Coordination of airway protective behaviors and swallow: effects of afferent feedback and sex.

“…The primary function of the intercostal muscles is to mechanically maintain proper rib placement (De Troyer, Kirkwood, & Wilson, 2005;Feldman, 1986) and stability during movement. Their activity is highly modulated by feedback from their muscle spindles, Golgi tendon organs, and other joint receptors (D'Angelo, 1982;De Troyer, 1997;Jaiswal & Davenport, 2016). Compared to caudal, rostral ribs contain a higher density of mechanoreceptors and increased movement-related activation during breathing (D'Angelo, 1982).…”

“…For example, an increase in muscle tension during tracheal occlusion results in an increase in firing rate of golgi tendon organs (Shannon, Shear, Mercak, Bolser, & Lindsey, 1985). Primary function of the intercostal muscle is to maintain proper rib placement in coordination with diaphragm contraction (Jaiswal & Davenport, 2016) and stability during movement (De Troyer, Kirkwood, & Wilson, 2005;Feldman, 1986). Due to higher density of muscle spindles in the rostral rather than caudal intercostal muscles, there is a greater contribution to tidal volume from rostral ribcage in times of high inspiratory drive (D'Angelo, 1982).…”

“…Intercostal muscles are strongly susceptible to proprioceptive feedback from their muscle spindles, golgi tendon organs and costovertebral joint receptors (D'Angelo, 1982;Jaiswal & Davenport, 2016). Intercostal muscles are modulated on a breath by breath basis (Jaiswal & Davenport, 2016) and feedback to medullary respiratory centers (Shannon, Shear, Mercak, Bolser, & Lindsey, 1985).…”

“…Intercostal muscles are strongly susceptible to proprioceptive feedback from their muscle spindles, golgi tendon organs and costovertebral joint receptors (D'Angelo, 1982;Jaiswal & Davenport, 2016). Intercostal muscles are modulated on a breath by breath basis (Jaiswal & Davenport, 2016) and feedback to medullary respiratory centers (Shannon, Shear, Mercak, Bolser, & Lindsey, 1985). It is widely accepted that golgi tendon organs, not muscle spindles, have an inhibitory effect on medullary inspiratory neurons (Bolser, Lindsey, & Shannon, 1983, 1984 which lead to a decrease in diaphragm, intercostal and laryngeal muscle activity .…”