Lymph Flow In Instrumented Dogs Varies With Exercise Intensity

Abstract

ObjectiveTo determine the relationship between exercise intensity and thoracic duct lymph flow.MethodsFive dogs were surgically instrumented with an ultrasonic flow transducer on the thoracic lymph duct and a catheter in the descending thoracic aorta. After recovery from surgery, data were collected at rest and as the dogs ran on a treadmill at speeds from 0 to 10 mph for 1 min at each speed with 15 min rest intervals.ResultsHeart rate increased significantly during exercise, whereas mean aortic pressure did not change. Resting lymph flow was 1.7 ± 0.2 ml/min. Exercise at 1.5 mph significantly raised lymph flow to 3.9 ± 0.6 ml/min (P < 0.01), 121% higher than resting flow. Lymph flow was further elevated at higher treadmill speeds, reaching 9.0 ± 1.6 ml/min (P < 0.01) at 10 mph, 419% higher than resting flow. Regression analysis demonstrated a linear relationship between treadmill speed and the percent increase in lymph flow (see Figure). After exercise, lymph flow returned rapidly to the resting value, but at higher speeds, lymph flow remained significantly greater than resting flow for 1 min (P < 0.01).ConclusionExercise increases lymph flow, and this increase is positively correlated with exercise intensity. (Support: NIH grant U19 AT002023 and Osteopathic Research Center.)