Banchero N, Gimenez M, Rostami A, Eby S H
Respir Physiol. 1976 Sep;27(3):305-21. doi: 10.1016/0034-5687(76)90060-8.
The effects of exposure to simulated altitude on skeletal muscle and on the cardiocirculatory system rhave been studied on awake, conscious, dogs (16-39 kg) at rest and during moderate treadmill exercise at 15% incline. Measurements were obtained in Denver at a PB of 635 mm Hg and after 3 weeks of continuous exposure to a PB of 435 mm Hg using a hypobaric chamber. At both levels of PB the dogs showed marked panting, associated with pulmonary hyperventilation and low PaCO2's (28 mm Hg at 635 and 17 mm Hg at 435 mm Hg). Resting VO2's were high (12.4 and 11.4 ml/min-kg) reflecting the high respiratory outputs. [Hb] and Hct increased significantly after 3 weeks at 435 mm Hg with a 4 mm Hg decrease in P50. Q, HR, SV and systemic blood pressures were normal in both normoxic and hypoxic animals, at rest as well as during exercise. Arterial and mixed venous PO2's decreased in the hypoxic dogs (82 to 56 and 42 to 36 mm Hg, respectively) but arterial O2 content, arterial-venous O2 content difference and systemic O2 transport remained unchanged. Capillary density in the sternothyroid muscle doubled (617 to 1245 cap/mm2) after 3 weeks at a PB of 435, whereas the average muscle fiber diameter decreased about 30%. Calculations indicate that the PO2 in the 'lethal corner' of the muscle fiber is relatively higher in the hypoxic animal because of the decrease in fiber size and intercapillary distances.
在清醒、有意识的16 - 39千克犬处于休息状态以及在坡度为15%的跑步机上进行适度运动期间，研究了暴露于模拟海拔对骨骼肌和心血管系统的影响。测量是在丹佛（气压为635毫米汞柱）以及使用低压舱连续暴露于435毫米汞柱3周后进行的。在两个气压水平下，犬均表现出明显的喘息，伴有肺通气过度和低动脉血二氧化碳分压（635毫米汞柱时为28毫米汞柱，435毫米汞柱时为17毫米汞柱）。静息时的耗氧量较高（分别为12.4和11.4毫升/分钟·千克），反映出高呼吸输出量。在435毫米汞柱环境下3周后，血红蛋白浓度和血细胞比容显著增加，而P50降低了4毫米汞柱。在常氧和低氧动物中，无论是休息时还是运动时，心输出量、心率、每搏输出量和全身血压均正常。低氧犬的动脉血氧分压和混合静脉血氧分压降低（分别从82降至56毫米汞柱和从42降至36毫米汞柱），但动脉血氧含量、动静脉血氧含量差和全身氧运输保持不变。在435毫米汞柱气压下3周后，胸骨甲状肌的毛细血管密度增加了一倍（从617增至1245根/平方毫米），而平均肌纤维直径减小了约30%。计算表明，由于纤维尺寸和毛细血管间距减小，低氧动物肌纤维“致死角”处的氧分压相对较高。
