Lymphatics and lymph in acute lung injury

Lymph flow will be discussed as part of the drainage and fluid balance of lung tissue and abdomen as well as a qualitative analysis of inflammatory processes.

Measurement of lung lymph is still a technical challenge. Mechanical ventilation and positive end-expiratory pressure impede lung lymph flow by increased intrathoracic pressure and increased central venous pressure. Positive end-expiratory pressure may thus enhance edema formation of the lung. Inflammatory spread from abdomen to the lung via the lymphatic system has been shown in a number of experimental studies. Ligation or diversion of the thoracic duct has been proposed to blunt the effects of noxious stimuli mediated by lymphatics to the lungs. Lymphatics have a major role on abdominal fluid balance while draining extravascular fluid accumulation and edema, especially during sepsis. Mechanical ventilation with high airway pressure increases abdominal edema (ascites) and spontaneous breathing protects from edema formation.

Lymph flow measurements are still a difficult task to perform; however, new results show an important function in the fluid balance of the lung and abdomen. Inflammatory spread may occur from the lung to the periphery by the blood stream and from the abdomen to the lung by lymph flow.