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Published on: July 10, 2018
Effect of the respiratory-related bronchial rhythmic constriction on alveolar ventilation in the dog
Tetsuri Kondo1, Ichiro Kobayashi, Naoki Hayama
1Department of Medicine, Tokai University School of Medicine, 21-1 Gakkyo, Oiso, Kanagawa, 259-0198, Japan. tetsuri@oiso.u-tokai.ac.jp
Abstract:
The middle-sized bronchus constricts during mid-inspiration through early-expiration. The purpose of this study was to elucidate the physiological role of this respiratory-related bronchial rhythmic constriction (RRBRC). The following parameters were measured in 12 decerebrated and paralyzed dogs: pressure from a balloon-tipped catheter in the fifth-generation bronchus (to reveal RRBRC), efferent neurogram from C(5) phrenic, and ventilatory flow and volume. We found a small but significant reduction of peak expiratory flow of mechanical ventilation during RRBRC. During bilateral vagal cold block, RRBRC was simulated by intermittent electric stimulation of vagal fibers distal to the cold block. This stimulus evoked a decrease in peak expiratory flow and in Pa(CO2) (approximately 1.5 mmHg). After vagal warming, mechanical ventilation was terminated, and blood gases were maintained normal by extracorporeal oxygenation. During each RRBRC ventilatory volume decreased by approximately 3 ml. The changes in gas volume and RRBRC disappeared after bilateral vagotomy. These findings support the concept that the physiological role of RRBRC is to facilitate alveolar gas exchange by reducing expiratory flow, anatomical dead space, or both.
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