Brice A G, Forster H V, Pan L G, Lowry T F, Murphy C L, Mead J
Department of Physiology, Medical College of Wisconsin, Milwaukee 53226.
J Appl Physiol (1985). 1991 Feb;70(2):715-25. doi: 10.1152/jappl.1991.70.2.715.
We studied the changes in breathing and respiratory muscle electromyograms (EMG) during passively induced increases in end-expiratory lung volume (EELV) in awake normal (N), hilar nerve-denervated (HND), carotid body-denervated (CBD), and HND + CBD ponies. EELV was increased by applying continuous negative pressure (-10 and -20 cmH2O) around the torso of the standing pony. In all groups, negative pressure produced sustained increases in EELV that were linearly related to the degree of negative pressure. Elevated EELV decreased breathing frequency (f) in N and CBD ponies but increased f in HND and HND + CBD ponies. When EELV was increased, tidal volume was unchanged or above control in N ponies but was below or near control in the other groups. In all groups during elevated EELV, arterial PCO2 initially decreased but then increased relative to control with isocapnia achieved after approximately 1.5 min. In all groups, the elevated EELV was accompanied by increased stimulation of the diaphragm as indicated by increased rate of rise of the integrated EMG (P less than 0.05). During elevated EELV, the duration of diaphragm EMG was reduced, but only in HND ponies was this reduction significant (P less than 0.05). In N ponies, the major effect of elevated EELV on the expiratory transversus abdominis (TA) muscle was an increase (P less than 0.05) in duration of activity and therefore total activity. The work of breathing was thus presumably shifted more to this muscle during elevated EELV. These changes in TA timing were not observed in HND and HND + CBD ponies during elevated EELV. We conclude that elevation of EELV, which presumably places the diaphragm on a less favorable portion of its length-tension relationship, results in compensatory increased stimulation of the diaphragm that is not critically dependent on hilar and carotid chemoreceptor afferents. However, hilar afferents do contribute to the changes in diaphragm and TA duration of activity during elevated EELV.
我们研究了清醒的正常（N）、肺门神经去神经支配（HND）、颈动脉体去神经支配（CBD）以及HND + CBD小马在被动诱导呼气末肺容积（EELV）增加期间呼吸和呼吸肌肌电图（EMG）的变化。通过在站立的小马躯干周围施加持续负压（-10和-20 cmH₂O）来增加EELV。在所有组中，负压使EELV持续增加，且与负压程度呈线性相关。EELV升高使N和CBD小马的呼吸频率（f）降低，但使HND和HND + CBD小马的f增加。当EELV增加时，N小马的潮气量不变或高于对照，但在其他组中潮气量低于或接近对照。在所有组中，EELV升高期间，动脉PCO₂最初下降，但随后相对于对照升高，约1.5分钟后达到等碳酸血症。在所有组中，EELV升高伴随着膈肌刺激增加，表现为积分EMG上升速率增加（P < 0.05）。在EELV升高期间，膈肌EMG的持续时间缩短，但仅在HND小马中这种缩短具有统计学意义（P < 0.05）。在N小马中，EELV升高对呼气时腹横肌（TA）的主要影响是活动持续时间增加（P < 0.05），因此总活动量增加。因此，在EELV升高期间，呼吸功可能更多地转移到了这块肌肉上。在EELV升高期间，HND和HND + CBD小马未观察到TA时间的这些变化。我们得出结论，EELV升高可能使膈肌处于其长度 - 张力关系中较不利的部分，导致膈肌的代偿性刺激增加，而这种增加并不严重依赖于肺门和颈动脉化学感受器传入神经。然而，肺门传入神经确实对EELV升高期间膈肌和TA活动持续时间的变化有影响。
