[Physiological role of respiratory-related bronchial constriction].
The respiration-related rhythmic constriction of the fifth-generation bronchi was analyzed in 11 tracheostomized dogs. During spontaneous breathing, the bronchial pressure (Pbr) estimated with a balloon-tipped catheter increased almost in parallel with the pleural pressure (Ppl) in the early inspiratory phase, but decreased in the late inspiratory phase. The parallel duration/inspiratory duration was 0.72 +/- 0.19 (mean +/- SD). This finding was more prominent in hypercapnia, but statistical significance was not obtained. When the efferent phrenic nerve fibers were electrically stimulated (pulse train, 0.1 ms, 30 Hz, 5 V, 2 s), Pbr changed almost in parallel with Ppl during the inspiratory phase, and expiration was completed significantly earlier than during spontaneous breathing (time constant 0.17 +/- 0.06 s vs 0.26 +/- 0.07 s). Bronchial constriction in early expiration may increase airway pressure and keep patency of the peripheral bronchi.
Tazaki
G
G
Department of Medicine, Tokai University School of Medicine, Isehara, Kanagawa 259-1193 Japan.
Kondo
T
T
Kobayashi
I
I
Hayama
N
N
Ohta
Y
Y
D000403:Airway Resistance / Q000502:physiology; D000818:Animals; D001980:Bronchi / Q000502:physiology*; D016084:Bronchoconstriction / Q000502:physiology*; D004285:Dogs; D006935:Hypercapnia / Q000503:physiopathology; D012119:Respiration; D012125:Respiratory Center / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology