Ballam G O, Clanton T L, Kunz A L
J Appl Physiol Respir Environ Exerc Physiol. 1982 Dec;53(6):1378-85. doi: 10.1152/jappl.1982.53.6.1378.
Awake upright White Leghorn roosters (Gallus domesticus) were unidirectionally ventilated. Electromyographic activity from inspiratory and expiratory muscles was recorded to demarcate inspiration and expiration. During inspiration, the rate of inflation of the air sac system was varied while the CO2 concentration of the gas passing through the lungs was maintained constant. Inspiratory duration was inversely related to the rate of inflation, producing an inspiratory volume-time threshold (VT) curve with a negative slope. When the CO2 concentration was increased in the lungs, the inspiratory VT curve shifted to the right with a concurrent increase in slope. If the rate of deflation was varied during expiration, it was found that expiratory duration was inversely related to the rate of deflation, producing an expiratory VT curve with a positive slope. Increasing the CO2 concentration shifted the curve to the left with an increased slope. These results indicate that inspiratory and expiratory phase durations are a function of both mechanical and chemical feedback.
清醒直立的白来航公鸡（家鸡）进行单向通气。记录吸气和呼气肌肉的肌电图活动以划分吸气和呼气。在吸气过程中，气囊系统的充气速率变化，同时通过肺部的气体二氧化碳浓度保持恒定。吸气持续时间与充气速率呈负相关，产生一条斜率为负的吸气容积-时间阈值（VT）曲线。当肺部二氧化碳浓度增加时，吸气VT曲线向右移动，斜率同时增加。如果在呼气过程中放气速率变化，发现呼气持续时间与放气速率呈负相关，产生一条斜率为正的呼气VT曲线。增加二氧化碳浓度使曲线向左移动且斜率增加。这些结果表明吸气和呼气阶段持续时间是机械和化学反馈两者的函数。
