High-sensitivity optical lymph flow-meter

An optical flow-meter is described which allows precise and continuous registration of the flow of lymph from cannulated human lymph vessels. The cannula from the lymph vessel is connected to the measurement tubing of the instrument where the flow is measured by automatically monitoring the movement of an air bubble introduced into the flow at the beginning of the measurement. The limit of sensitivity of the instrument is about 0.1 microliter, allowing reliable registration of stroke volumes of about 1 microliter which typically occur in human leg lymphatics. The size and capacity of the instrument were chosen to be suitable for clinical use. A technical description of the instrument is given. Application of the instrument is illustrated with recording of lymph flow and lateral intralymphatic pressure in a prenodal lymph vessel of the human leg.