THE EFFECTS OF HEIGHTENED NEGATIVE PRESSURE IN THE CHEST, TOGETHER WITH FURTHER EXPERIMENTS UPON ANOXIA IN INCREASING THE FLOW OF LUNG LYMPH

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Abstract
The anatomy of the lung lymph drainage in the dog is described, and it is made clear that lung and heart lymph enter the blood through the right lymphatic duct. It is held that cardiac activity, measured through output. remaining steady, fluctuations in lymph flow from the right duct reflect changes in the production and flow of lung lymph. Expts. are described which show that when an animal breathes against resistance so as to increase intrathoracic negative pressure, the flow of lymph from the lungs increases; and if the resistance to inspiration is very high, there may be not only a gain in the flow of lung lymph but the fluid may actually become bloody. These facts indicate the influence of the extravascular negative pressure in producing transudation of fluid from the lung capillaries into the lung parenchyma. Further expts. are described in which, under absolutely uniform artificial respiration, expiration being without suction. dogs have been subjected to progressive severe anoxia. When the O2 in the mixture used for artificial respiration was 13.5%, no increase in the flow of lung lymph was noted. On reducing the O2 to 10%, a sudden increase in the flow of lung lymph occurred, which ceased promptly on returning to ventilation with air. The changes in the production and flow of lung lymph during anoxia cannot be attributed to increased cardiac output or extension of the filtering bed of the lung capillaries, since the output of the heart fell markedly during anoxia. Consequently it must be concluded that when sufficient O2 is not available the lung capillaries promptly become abnormally permeable, but if this condition is not allowed to go too far they readily return to normal by ventilation with adequate O2.

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