Effect of lymphatic outflow pressure on lymphatic albumin transport in humans

The effects of posture on the lymphatic outflow pressure and lymphatic retu rn of albumin were examined in 10 volunteers. Lymph flow was stimulated wit h a bolus infusion of isotonic saline (0.9%, 12.6 ml/kg body wt) under four separate conditions: upright rest (Up), upright rest with lower body posit ive pressure (LBPP), supine rest (Sup), and supine rest with lower body neg ative pressure (LBNP). The increase in plasma albumin content (Delta Alb) d uring the 2 h after bolus saline infusion was greater in Up than in LBPP: 8 2.9 +/- 18.5 vs. -28.4 mg/kg body wt. DAlb was greater in LBNP than in Sup: 92.6 vs. -22.5 +/- 18.9 mg/kg body wt (P< 0.05). The greater <Delta>Alb in Up and Sup with LBNP were associated with a lower estimated lymphatic outf low pressure on the basis of the difference in central venous pressure (Del ta CVP). During LBPP, CVP was increased compared with Up: 3.8 +/- 1.4 vs. - 1.2 +/- 1.2 mmHg. During LBNP, CVP was reduced compared with Sup: -3.0 +/- 2.2 vs. 1.7 +/- 1.0 mmHg. The translocation of protein into the vascular sp ace after bolus saline infusion reflects lymph return of protein and is hig her in Up than in Sup. Modulation of CVP with LBPP or LBNP in Up and Sup, r espectively, reversed the impact of posture on lymphatic outflow pressure. Thus posture-dependent changes in lymphatic protein transport are modulated by changes in CVP through its mechanical impact on lymphatic outflow press ure.