High-frequency ventilation: lymph flow, lymph protein flux, and lung water

The effects of high-frequency oscillatory (HFV) ventilation on lung fluid balance and microvascular permeability to macromolecules were measured in open-chest dog lungs. Prenodal lung lymph flow, concentration of total plasma proteins in lymph and plasma, pulmonary arterial and left atrial pressure, cardiac output, and blood-free lung wet-to-dry weight ratios were measured for conventional mechanical ventilation (CMV, 12/min, 200-300 ml tidal volume) and HFV of 15 Hz and a stroke volume of 40-50 ml for normal and elevated left atrial pressures. HFV increased both lymph flow and lung water (68 and 20%, respectively), and lymph-to-plasma ratios of total plasma proteins remained unchanged. When left atrial pressure was increased, an analysis of lymph protein flux indicates that the lung microvascular permeability was not altered by HFV. The increase in lymph flow and lung water associated with HFV may reflect an increased microvascular exchange surface area or a change in interstitial fluid pressure.