Increased sheep lung vascular permeability caused by pseudomonas bacteremia

Area of Science:

• Pulmonary Physiology
• Microbiology
• Pathophysiology

Background:

• Elevated pulmonary vascular pressures can increase lung lymph flow.
• The effects of bacterial infections on lung fluid dynamics and lymphatic function are complex.

Purpose of the Study:

• To compare the effects of increased pulmonary vascular pressure versus Pseudomonas aeruginosa infusion on lung lymph dynamics.
• To investigate the role of lung lymphatics in managing fluid overload during infection.
• To assess changes in lung vascular permeability.

Main Methods:

• Awake sheep preparation with left atrial balloon inflation to control pulmonary vascular pressure.
• Intravenous infusion of Pseudomonas aeruginosa.
• Measurement of lung lymph flow, lymph and plasma protein concentrations.
• Indicator dilution lung water studies.
• Postmortem lung water analysis.

Main Results:

• Increased pulmonary vascular pressure elevated lymph flow but decreased lymph-plasma protein concentration ratios.
• Pseudomonas aeruginosa caused transient systemic effects and a delayed, sustained increase in lung lymph flow (3-10x baseline).
• During Pseudomonas-induced lymph flow increase, lymph-plasma protein ratios were near baseline, and lymph protein flow was elevated, with normal lung water in most sheep.

Conclusions:

• Pseudomonas aeruginosa induces a prolonged increase in lung vascular protein permeability.
• Lung lymphatics serve as a high-capacity mechanism for removing excess filtered fluid, preventing pulmonary edema.
• Changes observed suggest alterations in the structure of lung vessel walls.