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Effects of unilateral airway occlusion on rib motion and inspiratory intercostal activity in dogs

View Article: PubMed Central - PubMed

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.

No MeSH data available.


Related in: MedlinePlus

Parasternal intercostal and external intercostal inspiratory EMG activity on both sides of the thorax during unilateral bronchial occlusion for a single breath. EMG/Ti activities are expressed as percentages of activity recorded during control. Note the marked increase in external intercostal activity on both sides of the thorax during occlusion. Values are means ± SE from the eight animals.
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phy213242-fig-0002: Parasternal intercostal and external intercostal inspiratory EMG activity on both sides of the thorax during unilateral bronchial occlusion for a single breath. EMG/Ti activities are expressed as percentages of activity recorded during control. Note the marked increase in external intercostal activity on both sides of the thorax during occlusion. Values are means ± SE from the eight animals.

Mentions: The records of external intercostal and parasternal intercostal EMG activity in the third interspace and of the inspiratory motion of the third rib on both sides of the rib cage obtained in a representative animal during control breathing and during unilateral bronchial occlusion are shown in Figure 1. The mean ± SE values of EMG obtained in the eight animals are displayed in Figure 2. ΔPao developed in the occluded bronchus was −10.2 ± 2.5 cm H2O.


Effects of unilateral airway occlusion on rib motion and inspiratory intercostal activity in dogs
Parasternal intercostal and external intercostal inspiratory EMG activity on both sides of the thorax during unilateral bronchial occlusion for a single breath. EMG/Ti activities are expressed as percentages of activity recorded during control. Note the marked increase in external intercostal activity on both sides of the thorax during occlusion. Values are means ± SE from the eight animals.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5392528&req=5

phy213242-fig-0002: Parasternal intercostal and external intercostal inspiratory EMG activity on both sides of the thorax during unilateral bronchial occlusion for a single breath. EMG/Ti activities are expressed as percentages of activity recorded during control. Note the marked increase in external intercostal activity on both sides of the thorax during occlusion. Values are means ± SE from the eight animals.
Mentions: The records of external intercostal and parasternal intercostal EMG activity in the third interspace and of the inspiratory motion of the third rib on both sides of the rib cage obtained in a representative animal during control breathing and during unilateral bronchial occlusion are shown in Figure 1. The mean ± SE values of EMG obtained in the eight animals are displayed in Figure 2. ΔPao developed in the occluded bronchus was −10.2 ± 2.5 cm H2O.

View Article: PubMed Central - PubMed

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.

No MeSH data available.


Related in: MedlinePlus