Lymphatic pump

Abstract: The contractile properties of the mesenteric collecting lymphatics of the rat were analyzed under control conditions and during periods of enhanced lymph formation using in vivo microscopic techniques. Pressure and diameter were simultaneously monitored in microscopic collecting lymphatics, and lymphatic pump function was analyzed in accordance with basic principles of cardiac mechanics. The lymphatic contractile cycle was divided into two phases of systole and four phases of diastole. Under control conditions, lymphatics contracted with a frequency of 6.4 +/- 0.61 beats/min and ejected approximately 67% of their end-diastolic volume. Ten minutes after the rate of lymph formation was elevated by plasma dilution, end-diastolic diameter, contraction frequency, ejection fraction, and stroke volume increased. Pressure in the lymphatic network became less pulsatile in high lymph flow states. Contractility, an index of inotropic changes in lymphatic pump, was unaltered when lymph flow was increased by plasma dilution. Furthermore, the maximal shortening velocity of lymphatic smooth muscle did not change during periods of enhanced lymph flow. Thus it appears that passive increases in the rate of lymph formation exert few, if any, inotropic effects on the lymphatic pump. The augmented stroke volume and contraction frequency appear to result mainly from intrinsic stretch-dependent mechanisms set in motion by elevated preload. These data represent the first comprehensive characterization of both the flow-generating and muscle characteristics of intact collecting lymphatics and provide a basis for future studies on the physiological regulation of lymphatic contraction.

Abstract: Axillary surgery for breast cancer may be followed, months to years later, by chronic arm lymphedema. A simple ‘stopcock’ mechanism (reduced lymph drainage from the entire limb through surviving lymphatics) does not explain many clinical aspects, including the delayed onset and selective sparing of some regions, e.g., hand. Quantitative lymphoscintigraphy reveals that lymph drainage is slowed in the subcutis, where most of the edema lies, and in the subfascial muscle compartment, which normally has much higher lymph flows than the subcutis. Although the muscle does not swell significantly, the impaired muscle drainage correlates with the severity of arm swelling, indicating a likely key role for muscle lymphatic function. A new method, lymphatic congestion lymphoscintigraphy, showed that the edema is associated with a reduced contractility of the arm lymphatics; the weaker the active lymphatic pump, the greater the swelling. Delayed lymphatic pump failure may result from chronic raised afterload,...

Abstract: Axillary surgery for breast cancer partially obstructs lymph outflow from the arm, chronically raising the lymphatic smooth muscle afterload. This may lead to pump failure, as in hypertensive cardiac failure, and could explain features of breast cancer treatment-related lymphoedema (BCRL) such as its delayed onset. A new method was developed to measure human lymphatic contractility non-invasively and test the hypothesis of contractile impairment. 99mTc-human IgG (Tc-HIG), injected into the hand dermis, drained into the arm lymphatic system which was imaged using a gamma-camera. Lymph transit time from hand to axilla, ttransit, was 9.6 ± 7.2 min (mean ±s.d.) (velocity 8.9 cm min−1) in seven normal subjects. To assess lymphatic contractility, a sphygmomanometer cuff around the upper arm was inflated to 60 mmHg (Pcuff) before 99mTc-HIG injection and maintained for >> ttransit. When Pcuff exceeded the maximum pressure generated by the lymphatic pump (Ppump), radiolabelled lymph was held up at the distal cuff border. Pcuff was then lowered in 10 mmHg steps until 99mTc-HIG began to flow under the cuff to the axilla, indicating Ppump≥Pcuff. In 16 normal subjects Ppump was 39 ± 14 mmHg. Ppump was 38% lower in 16 women with BCRL, namely 24 ± 19 mmHg (P= 0.014, Student's unpaired t test), and correlated negatively with the degree of swelling (12–56%). Blood radiolabel accumulation proved an unreliable measure of lymphatic pump function. Lymphatic congestion lymphoscintigraphy thus provided a quantitative measure of human lymphatic contractility without surgical cut-down, and the results supported the hypothesis of lymphatic pump failure in BCRL.

Abstract: The thoracic pump and the abdominal pump are osteopathic manipulative (OM) lymphatic pump techniques frequently used by osteopathic physicians to treat patients with infections (eg, pneumonia, otitis media). Although there is a widely accepted belief among the osteopathic medical profession that increasing lymphatic flow is beneficial, no measurements of lymph flow during osteopathic manipulative treatment have been reported. The authors surgically instrumented five mongrel dogs to record lymphatic flow in the thoracic duct (TDF) and cardiac variables during three intervention protocols. After recovery from surgery, canine subjects were placed in a standing-support sling, and TDF, cardiac output, mean aortic blood pressure, and heart rate were recorded during two randomized 30-second sessions of manipulative intervention using the osteopathic thoracic pump and abdominal pump techniques on two successive days. Lymph flow in the thoracic duct increased from 1.57+/-0.20 mL x min(-1) to a peak TDF of 4.80+/-1.73 mL x min(-1) during abdominal pump, and from 1.20+/-0.41 mL x min(-1) to 3.45+/-1.61 mL x min(-1) during thoracic pump. Lymph flow in the thoracic duct and cardiac variables were also recorded for canine subjects during physical activity (ie, treadmill exercise at 3 miles per hour at 0% incline). During physical activity, TDF increased from 1.47+/-0.33 mL x min(-1) to 5.81+/-1.30 mL x min(-1). Although cardiac variables did not change significantly during manipulative intervention with lymphatic pump techniques, cardiac output and heart rate did increase during physical activity. The authors conclude that physical activity and manipulative intervention using thoracic pump and abdominal pump techniques produced net increases in TDF (P<.05).