Effect of chemoreceptor denervation on the pulmonary vascular response to atelectasis

Six dogs anesthetized with 30 mg/kg pentobarbital were ventilated after differential cannulation of the main stem bronchi. Following sternotomy, blood flow was monitored by electromagnetic flow probes on the left pulmonary artery (QL) and on the pulmonary trunk or aorta (QT). Following 10 min of bilateral 100% O2, QL was 37.4 +/- 5.8% of QT. When left lung atelectasis was induced while the right lung remained on 100% O2, PaO2 remained above 75 mm Hg and QL fell to 26.1 +/- 5.0% of QT. However, when the right lung was ventilated with room air while the left lung remained atelectatic, PaO2 fell to 50.0 +/- 2.6 mm Hg and QL rose to 36.7 +/- 6.2% of QT. Six dogs which had undergone peripheral chemoreceptor denervation prior to these experiments showed a similar decrease in perfusion of the atelectatic left lung when the right lung was ventilated with 100% O2, but did not increase blood flow to the atelectatic lung during systemic hypoxemia. Thus, the increased blood flow to the atelectatic lung which occurs during systemic hypoxemia appears to be mediated by the arterial chemoreceptors.