Effects of unilateral airway occlusion on rib motion and inspiratory intercostal activity in dogs. Issue 7 (10th April 2017)

• Record Type: Journal Article
• Authors: Leduc, Dimitri; Marechal, Sarah; Taton, Olivier; Blairon, Bernard; Legrand, Alexandre
• Is Part Of: Physiological reports. Volume 5:Issue 7(2017)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2017-04-10
• Subjects: Intercostal muscles -- mechanics of breathing -- pleural pressure transmission -- respiratory muscles -- rib cage motion; Physiology -- Periodicals; 571
• DOI: 10.14814/phy2.13242
• Languages: English
• ISSNs: 2051-817X

Abstract

Abstract: Unilateral bronchial occlusion, a complication of many lung diseases, causes dyspnea but the mechanism of this symptom is uncertain. In this study, electromyographic (EMG) activity in the parasternal and external intercostal muscles in the third intercostal space and inspiratory motion of the third rib on both sides of the thorax were assessed during occlusion of a main bronchus for a single breath in anesthetized dogs. Occlusion produced a 65% increase in external intercostal EMG activity in both hemithoraces without altering parasternal EMG activity. Concomitantly, the inspiratory cranial rib motion showed a 50% decrease on both sides of the thorax. These changes were unaffected by bilateral vagotomy. However, when an external, caudally oriented force was applied to the third rib on the right or left side so that its inspiratory cranial displacement was abolished, activity in the adjacent external intercostals showed a twofold increase, but rib motion and external activity in the contralateral hemithorax remained unchanged. It is concluded that during occlusion of a main bronchus, the increase in external intercostal activity is induced by the decrease in inspiratory cranial rib displacement in both hemithoraces, and that this decrease is determined by the increase in pleural pressure swings on both sides of the mediastinum. This mechanism, combined with the decrease in PaO2, induces similar alterations when unilateral bronchial occlusion is maintained for a series of consecutive breaths. Abstract : Unilateral occlusion of a main bronchus for a single breath in anesthetized dogs leads to a bilateral decrease in the inspiratory cranial rib motion and to a bilateral increase in electromyographic (EMG) activity in external intercostal muscles without altering parasternal EMG activity. This effect is determinated by the increase in pleural pressure swings on both sides of the mediastinum during unilateral occlusion of a main bronchus. This mechanism, combined with the decrease in PaO2, induces similar alterations when unilateral bronchial occlusion is maintained for a series of consecutive breaths.