Background: Spontaneous breathing creates a negative pressure in the thoracic cavity. This drives the respiratory punmp and increases venous return to the heart. During mechanical ventilation, intrathoracic and central venous pressure increase, which impedes venous return. The thoracic duct runs through the pleural cavity, possibly also benefiting from negative pressure during spontaneous breathing, before emptying into the venous system. Lymphatic congestion would distend the lymphatic vessels, and in-vitro studies have shown that distension follows patterns similar to the length-tension relationship of myocytes. We plan to examine if the use of mechanical ventilation affects lymphatic activity.  

Methods: This is an analytical, experimental study of 20 cardiopulmonary healthy individuals, 18-30 years of age, undergoing surgery for malformations in the jaw in general anesthesia. Near-infrared Fluorescent Imaging of lymphatic vessels in the lower limb is recorded and contraction frequency and velocity are measured for 30 minutes at normal ventilation pressure followed by 30 minutes at elevated ventilation pressures (10 mmH2O raise in PIP and PEEP). Finally, a short period of breath-hold and subsequent completion of the surgical procedure at standard ventilation pressures. A baseline sequence during spontaneous breathing is recorded on the pre-op evaluation  one week before the surgery.   

Results: Results are pending.

Conclusion: This study will contribute with knowledge on the basic physiologic function of the lymphatic system, and how mechanical ventilation might affect this. Altered lymphatic activity would emphasize the importance of individual mechanical ventilation protocols to reduce the risk of post-operative edema and other lymphatic related complications following mechanical ventilation.