Sorkness R L, Vidruk E H
Respir Physiol. 1986 Oct;66(1):41-52. doi: 10.1016/0034-5687(86)90137-4.
Three awake dogs with chronic tracheostomies were used to study the effects of hypoxia (12% O2) on tracheal smooth muscle tone. Pressure changes within a water-filled cuff in an isolated portion of the cervical trachea reflected changes in tracheal tone. During spontaneous ventilation, hypoxia produced hyperventilation, but no significant change in tracheal tone. If hypocapnia was prevented with inspired CO2 during hypoxia, one of three dogs increased tracheal tone, and all dogs increased ventilation beyond that measured with hypoxia alone. When the awake dogs were ventilated mechanically to prevent changes in ventilation, hypoxia always increased tracheal tone. We made independent changes in ventilation and CO2 similar to the spontaneous responses to hypoxia to test these effects on tracheal tone. When the dogs were ventilated mechanically first with 2% CO2, and then with no CO2, the resulting drop in end-tidal CO2 always decreased tone. When the tidal volume on the ventilator was increased under hyperoxic, isocapnic conditions, tracheal tone always decreased. We conclude that the normal ventilatory response to hypoxia opposes the bronchoconstrictor effect of hypoxia, resulting in no net change in tracheal smooth muscle tone.
选用三只做过慢性气管切开术的清醒犬，研究低氧（12%氧气）对气管平滑肌张力的影响。颈段气管分离部分内充满水的袖带内的压力变化反映气管张力的变化。在自主通气期间，低氧导致通气过度，但气管张力无显著变化。如果在低氧期间通过吸入二氧化碳来防止低碳酸血症，三只犬中有一只气管张力增加，并且所有犬的通气量增加幅度超过仅低氧时测得的通气量。当对清醒犬进行机械通气以防止通气变化时，低氧总是会增加气管张力。我们独立改变通气和二氧化碳水平，类似于对低氧的自主反应，以测试这些因素对气管张力的影响。当犬首先用2%二氧化碳进行机械通气，然后不再通气时，呼出末二氧化碳的下降总是会降低张力。当在高氧、等碳酸血症条件下增加呼吸机的潮气量时，气管张力总是会降低。我们得出结论，对低氧的正常通气反应会对抗低氧的支气管收缩作用，导致气管平滑肌张力无净变化。
