Measurement of lymph flow velocity in non-edematous extremities using Transonic Transit Time Ultrasound Microvascular Flowprobe (AureFlo®), a pilot study

Research on lymph vessels has been done for years, however, only few studies
described lymphatic flow or flow velocity. Lymph flow is generated by lymph
production and lymph propulsion. It is known that collecting lymph vessels have
a smooth musculature and move lymph fluid actively through pulsation. These
muscles are stretch-sensitive and respond according to Starling*s law of the
heart, by increasing frequency and stroke volume of pulsation as a result of
increased ultrafiltration. One-way valves in the vessels also contribute to
lymph propulsion and prevent retrograde flow.

Fischer et al. described measurement of flow velocity in single lymphatic
capillaries of humans using fluorescence microlymphography in 1996. After
injection of fluorescein isothiocyanate-dextran, direct observation of the dye
advancement in the microvessels was used to measure flow velocity. Directly
after dye injection, velocities of 5,5 mm/s were reached. However, the median
velocity during initial network filling was 0.51 mm/s and the median resting
lymphatic capillary velocity was 9.7 µm/s.
Modi et al. (2007) tested whether there is lymphatic pump failure in breast
cancer treatment-related lymphedema due to chronically raised lymphatic smooth
muscle afterload. They measured a mean hand-axilla velocity of 8.9±5.8 cm/min
(1.48±0.97 mm/s) in uncuffed normal subjects, no significant difference in
cuffed normal arms (60mmHg) and a significant decrease of velocity in cuffed
swollen arms (3.2±8.9 cm/min; 0.53±1.48 mm/s). Lymphedema was associated with a
38% decrease in pump force.

Until now, the lymph flow could only be measured indirectly by calculating an
average speed over a certain distance
(foot-inguinal or hand-axilla). With the invention of the Flowprobe for
microsurgical anastomoses, flow can be measured quantitatively and directly.
Early results from Chen et al. (2015) were promising, although only lymphedema
patients were included in the study. Direct, local flow in healthy patients has
not been described yet.

The aim of this study is to measure the lymphflow in the superficial
lymphvessels in the dorsal forearm in patients with no history of lymphedema.
In order to further study lymphedema and to improve the technique of
lymphaticovenous anastomoses, it is important to know the healthy situation.
This healthy situation will be described, based on the measurements that will
be performed in this study.
The primary research question is: What is the lymph flow velocity (ml/min) in
the superficial lymphvessels of the dorsal forearm in patients without a
history of lymphedema?

This observational study will not be randomized and will not be blinded.
Patients undergoing a free radial forearm flap reconstruction will be included
by the plastic surgeon during the preoperative consultation.
Via the incision made for the flap harvesting, a superficial lymph vessel will
be chosen, using a microscope. The plastic surgeon will measure the lymph flow
according to the protocol, using the Transonic Transit Time Ultrasound
Microvascular Flowprobe (AureFlo®). Results will be noted anonymously in
standardized tables.

The subjects will only be included if a operation of the forearm is indicated.
Therefore, no extra incisions or other invasive procedures will be performed
for the study. During the measurement, the patient is under general anesthesia.
Furthermore, no postoperative consequences can be expected from the
measurement. Therefore, te extent of the burden is very limited and there are
no risks associated with participation.