Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.
J Exp Biol. 2013 Oct 1;216(Pt 19):3611-9. doi: 10.1242/jeb.087197. Epub 2013 Jun 20.
Unidirectional, continuous airflow through the avian lung is achieved through an elaborate air sac system with a sequential, posterior to anterior ventilation pattern. This classical model was established through various approaches spanning passively ventilated systems to mass spectrometry analysis of tracer gas flow into various air sacs during spontaneous breathing in restrained ducks. Information on flow patterns in other bird taxa is missing, and these techniques do not permit direct tests of whether the basic flow pattern can change during different behaviors. Here we use thermistors implanted into various locations of the respiratory system to detect small pulses of tracer gas (helium) to reconstruct airflow patterns in quietly breathing and behaving (calling, wing flapping) songbirds (zebra finch and yellow-headed blackbird). The results illustrate that the basic pattern of airflow in these two species is largely consistent with the model. However, two notable differences emerged. First, some tracer gas arrived in the anterior set of air sacs during the inspiration during which it was inhaled, suggesting a more rapid throughput through the lung than previously assumed. Second, differences in ventilation between the two anterior air sacs emerged during calling and wing flapping, indicating that adjustments in the flow pattern occur during dynamic behaviors. It is unclear whether this modulation in ventilation pattern is passive or active. This technique for studying ventilation patterns during dynamic behaviors proves useful for establishing detailed timing of airflow and modulation of ventilation in the avian respiratory system.
鸟类肺部的单向、连续气流是通过一个精心设计的气囊系统实现的，该系统具有从后到前的顺序通气模式。这个经典模型是通过各种方法建立的，包括被动通气系统和对受限制的鸭子在自主呼吸时示踪气体流入各个气囊的质谱分析。其他鸟类类群的气流模式信息缺失，而且这些技术也不允许直接测试在不同行为期间基本气流模式是否会发生变化。在这里，我们使用植入呼吸系统不同位置的热敏电阻来检测示踪气体（氦气）的小脉冲，以重建安静呼吸和行为（鸣叫、振翅）鸣禽（斑马雀和黄头黑鹂）的气流模式。结果表明，这两个物种的基本气流模式与模型基本一致。然而，出现了两个值得注意的差异。首先，一些示踪气体在吸入期间到达前一组气囊中，这表明气体通过肺部的速度比以前假设的要快。其次，在鸣叫和振翅期间，两个前气囊之间的通气差异出现，表明在动态行为期间气流模式发生了调整。尚不清楚这种通气模式的调节是被动的还是主动的。这项用于研究动态行为期间通气模式的技术对于确定鸟类呼吸系统中气流的详细时间和通气的调节非常有用。
