Brown R, Slutsky A S
J Appl Physiol Respir Environ Exerc Physiol. 1984 Dec;57(6):1865-71. doi: 10.1152/jappl.1984.57.6.1865.
With airways obstruction, panting frequency affects plethysmographically determined thoracic gas volume (Vtg) because the extrathoracic airway acts as a shunt capacitor. Stanescu et al. (19) suggested that in the calculation of Vtg, use of esophageal (delta Pes) rather than mouth pressure (delta Pm) swings might eliminate the problem. We measured total lung capacity (TLC) plethysmographically in 10 subjects with chronic airways obstruction (CAO) and in four normal subjects. TLC (using delta Pm) was derived from Vtg obtained from slow-(approximately 1 Hz) and fast- (approximately 4 Hz) panting frequencies. In the normal subjects and four subjects with CAO, TLC was also obtained using delta Pes. In these subjects abdominal gas compression and decompression did not contribute significantly to the frequency dependence of TLC. In CAO, TLC was frequency dependent in direct proportion to the severity of obstruction. Although the frequency dependence was greater using delta Pm to calculate Vtg, it also occurred using delta Pes. Thus it could not be explained entirely by the shunt capacitor effect of the extrathoracic airways. The residual and significant overestimations of TLC (reflected by frequency dependency of TLC derived from Vtg calculated from delta Pes) may be explained by interregional nonhomogeneities during the panting maneuver.
气道阻塞时，呼吸频率会影响体积描记法测定的胸腔气体容积（Vtg），因为胸外气道起到分流电容的作用。斯特内斯库等人（19）提出，在计算Vtg时，使用食管压力变化（delta Pes）而非口腔压力变化（delta Pm）波动可能会消除该问题。我们用体积描记法测量了10例慢性气道阻塞（CAO）患者和4例正常受试者的肺总量（TLC）。TLC（使用delta Pm）由慢呼吸频率（约1Hz）和快呼吸频率（约4Hz）下获得的Vtg推导得出。在正常受试者和4例CAO患者中，也使用delta Pes获得了TLC。在这些受试者中，腹部气体压缩和减压对TLC的频率依赖性贡献不大。在CAO患者中，TLC与阻塞严重程度成正比，具有频率依赖性。尽管使用delta Pm计算Vtg时频率依赖性更大，但使用delta Pes时也会出现频率依赖性。因此，这不能完全由胸外气道的分流电容效应来解释。TLC的残留且显著的高估（由根据delta Pes计算的Vtg得出的TLC的频率依赖性反映）可能由呼吸动作期间的区域间不均匀性来解释。
