Lymph flow transients following elevation of venous pressure in the dog hindpaw

Lymph flow transients were studied in a dog paw preparation when venous pressure was elevated by 15 and 25 mmHg. The lymph flow transients showed a very rapid initial increase which then declined to a steady-state value that was one-half the peak lymph flow response for both pressure changes. Lymph flow increased in the initial 5.3 minutes following venous pressure elevation to 10.4 +/- 2.0 and 18.1 +/- 4.5 times the normal lymph flow (mean +/- standard deviation) for the 15 and 25 mmHg increases in venous pressure, respectively. However, approximately 9 minutes after attaining the maximal flow rate, the lymph flow declined to only 5.5 +/- 0.7 and 9.8 +/- 1.8 times the control values. These data demonstrate another condition in which lymph flow is not maintained at the maximal capability. Possible mechanisms causing the observed biphasic lymph flow response to capillary pressure elevation are: 1) changes in Starling forces oppose an increase in capillary pressure; 2) the rate of change in tissue fluid pressure affects lymph flow to a greater extent than does the absolute change in tissue fluid pressure; or, 3) the lymphatics empty upon elevation and refill as the capillaries filter.