The significance of respiration for thoracic duct flow in relation to other driving forces of lymph flow

Experiments were performed to study the effect of respiratory intrathoracic pressure changes upon thoracic duct lymph propulsion as compared to other forces driving lymph flow in anaesthetized and artificially ventilated dogs. The effect of an open bilateral pneumothorax upon thoracic duct flow and protein composition was determined at rest, with passive limb movement and during saline infusion. The effect of hyperventilation was also tested.Thoracic duct flow was 30 l/min/kg, 45 l/min/kg and 60 l/min/kg at rest, with passive limb movement and saline infusion, respectively. These flows were decreased by opening the pneumothorax by 11 l/min/kg, 12 l/min/kg and 8 l/min/kg, respectively, and returned to the control level after the thorax was closed. The lymph protein concentration and lymph albumin to globulin ratio were not changed significantly. During hyperventilation, lymph flow was increased and showed a retarded decrease after hyperventilation had ceased. Lymph protein composition was not changed significantly by hyperventilation.The data confirm that lymph is propelled in anaesthetized dogs by respiratory intrathoracic pressure changes. The significance of this respiratory pump decreases, when lymph flow is increased by activation of the tissue pump or vis a tergo. Consequently, the respiratory pump may be assumed to play a secondary role in lymph propulsion in the conscious state when the other forces driving lymph flow are more predominant.Presented in part at the 48th meeting of the Deutsche Physiologische Gesellschaft 18]Supported by the Deutsche Forschungsgemeinschaft