1. To study the lymph flow dynamics in the intact thoracic duct, we applied an ultrasound transit-time flow probe in seven anaesthetized and four unanaesthetized adult sheep (approximately 60 kg). In unanaesthetized non-fasting animals we found that lymph flow in the thoracic duct was always regular pulsatile (pulsation frequency, 5.2 +/- 0.8 min-1) with no relation to heart or respiratory activity. At baseline the peak level of the thoracic duct pulse flow was 11.6-20.7 ml min-1 with a nadir of 0-3.6 ml min-1. Mean lymph flow was 5.4 +/- 3.1 ml min-1. The flow pattern of lymph in the thoracic duct was essentially the same in the anaesthetized animals. 2. In both the anaesthetized and unanaesthetized animals, the lymph flow response to a stepwise increase in the outflow venous pressure showed interindividual variation. Some were sensitive to any increase in outflow venous pressure, but others were resistant in that lymph flow did not decrease until outflow venous pressure was increased to higher levels. This resistance was also observed in the high lymph flow condition produced by fluid infusion in the anaesthetized animal and mechanical constriction of the caudal vena cava in the unaesthetized animals. Pulsation frequency of the thoracic duct flow initially increased and then decreased with a stepwise increase in the outflow venous pressure. This initial increase might be a compensatory response to maintain lymph flow against elevated outflow venous pressure. 3. To test the effect of long-term outflow venous pressure elevation in unanaesthetized sheep, outflow venous pressure was increased by inflation of a cuff around the cranial vena cava for 1, 5 or 25 h. The cuff was inflated to a level where lymph flow was reduced. Lymph flow remained low or decreased further during the entire cuff-inflation period. We calculated the lymph debt caused by the outflow venous pressure elevation and the amount 'repaid' when venous pressure returned to normal. Lymph debt for 25 h was 6400 ml but only 200 ml was repaid. Since we observed no visible oedema formation in the lower body of the sheep, the non-colloidal components of the lymph must have been reabsorbed into the bloodstream, most likely in the lymph nodes.
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机译：1.为了研究完整胸导管中的淋巴流动动力学，我们在七只麻醉过的和四只未经麻醉的成年绵羊（约60公斤）中应用了超声渡越时间流量探头。在未麻醉的非禁食动物中，我们发现胸导管中的淋巴流始终是规律的搏动性（搏动频率为5.2 +/- 0.8 min-1），与心脏或呼吸活动无关。在基线时，胸导管脉冲血流的峰值水平为11.6-20.7 ml min-1，最低点为0-3.6 ml min-1。平均淋巴流量为5.4 +/- 3.1 ml min-1。在麻醉的动物中，胸导管中淋巴的流动模式基本相同。 2.在麻醉和未麻醉的动物中，对流出静脉压力逐步增加的淋巴流量反应均存在个体差异。有些对流出静脉压力的增加敏感，但另一些则有抵抗力，因为直到流出静脉压力增加到更高水平，淋巴流量才减少。在麻醉动物的液体输注和未麻醉动物的尾腔机械收缩产生的高淋巴流量条件下，也观察到了这种抵抗。胸导管流量的脉动频率最初随着流出静脉压力的逐步增加而先增加然后降低。最初的增加可能是对维持淋巴流量抵抗升高的流出静脉压的补偿性反应。 3.为了测试未麻醉羊的长期流出静脉压升高的效果，通过在颅腔静脉周围套囊充气1、5或25 h来增加流出静脉压。将袖带充气至减少淋巴流量的水平。在整个袖带充气期间，淋巴流量保持较低水平或进一步下降。我们计算了由流出静脉压升高引起的淋巴结债务，以及当静脉压恢复正常时“偿还”的金额。 25小时的淋巴负债为6400毫升，但仅偿还了200毫升。由于我们观察到绵羊下半身没有可见的水肿形成，因此淋巴液的非胶体成分必须已经被重吸收到血液中，最有可能在淋巴结中。
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