Pisarri T E, Giesbrecht G G
Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska 68178, USA.
J Appl Physiol (1985). 1997 May;82(5):1566-72. doi: 10.1152/jappl.1997.82.5.1566.
Cooling intrathoracic airways by filling the pulmonary circulation with cold blood alters pulmonary mechanoreceptor discharge. To determine whether this initiates reflex changes that could contribute to airway obstruction, we measured changes in tracheal smooth muscle tension and bronchial arterial flow evoked by cooling. In nine chloralose-anesthetized open-chest dogs, the right pulmonary artery was cannulated and perfused; the left lung, ventilated separately, provided gas exchange. With the right lung phasically ventilated, filling the right pulmonary circulation with 5 degrees C blood increased smooth muscle tension in an innervated upper tracheal segment by 23 +/- 6 (SE) g from a baseline of 75 g. Contraction began within 10 s of injection and was maximal at approximately 30s. The response was abolished by cervical vagotomy. Bronchial arterial flow increased from 8 +/- 1 to 13 +/- 2 ml/min, with little effect on arterial blood pressure. The time course was similar to that of the tracheal response. This response was greatly attenuated after cervical vagotomy. Blood at 20 degrees C also increased tracheal smooth muscle tension and bronchial flow, whereas 37 degrees C blood had little effect. The results suggested that alteration of airway mechanoreceptor discharge by cooling can initiate reflexes that contribute to airway obstruction.
通过用冷血充盈肺循环来冷却胸内气道会改变肺机械感受器的放电。为了确定这是否会引发可能导致气道阻塞的反射性变化，我们测量了冷却引起的气管平滑肌张力和支气管动脉血流的变化。在9只氯醛糖麻醉的开胸犬中，将右肺动脉插管并灌注；单独通气的左肺提供气体交换。在右肺进行阶段性通气时，用5℃的血液充盈右肺循环，使受神经支配的气管上段平滑肌张力从基线75g增加23±6（SE）g。收缩在注射后10秒内开始，约30秒时达到最大。切断颈迷走神经后反应消失。支气管动脉血流从8±1ml/min增加到13±2ml/min，对动脉血压影响很小。时间进程与气管反应相似。切断颈迷走神经后，这种反应大大减弱。20℃的血液也会增加气管平滑肌张力和支气管血流，而37℃的血液影响很小。结果表明，冷却引起的气道机械感受器放电改变可引发导致气道阻塞的反射。
