Hydrostatic float valve and intravenous system supplied therewith

A system for supplying a controlled flow of fluid to a patient comprising:

• a main bag useful as a fluid supply source,
• a drip chamber supported below said main bag and having an upper end portion communicating with said main bag and a flexible lower end portion, said drip chamber constructed and arranged to receive fluid by gravity from said main bag,
• primary tubing communicating with said lower end portion of said drip chamber,
• manual valve means constructed and arranged along the length of said primary tubing below said drip chamber to open and close a fluid path through said primary tubing,
• said drip chamber including an apertured valve seat fixed thereto having a given thickness and an aperture of given size extending through said thickness,
• said fluid path including a closed portion below said valve seat and above said manual valve means capable of developing a back pressure against gravity in an upward direction when said flexible lower end portion is pinched while said manual valve means is closed,
• a valve having a vertical stem narrower than and extending through said aperture and longer than said given thickness, an enlarged upper head wider than said aperture extending from the upper portion of said stem and lower fingers extending from the lower portion of said stem beyond the width of said aperture, said valve having a specific gravity slightly more than that of said fluid but less than the total force due to the combination of said back pressure and the buoyancy of said fluid so that when the fluid level rises to a predetermined level above said valve seat and said back pressure is increased sufficiently by pinching the flexible lower end portion of said drip chamber while said manual valve means is closed, said valve rises by a combined force resulting from said increased back pressure and buoyancy to a level where said fingers engage said valve seat before said enlarged valve head rises to said predetermiend fluid level to provide a restrictded passage for fluid between said enlarged head and said valve seat and through said valve seat and said lower portion of said drip chamber and through said primary tubing when said manual valve means is open to cause said back pressure to reduce sufficiently until the combination of said buoyancy and said reduced back pressure is too small to prevent said enlarged valve head from lowering to engage said valve seat and close said valve aperture to completely stop said flow of fluid into said primary tubing immediately when said combination becomes too small.

A method of supplying intravenous fluid to a patient comprising:

• flowing intravenous fluid drop by drop by gravity into a patient via a drip chamber, primary tubing having a closed portion, manual control valve means for closing said closed portion and a catheter,
• maintaining an apertured valve seat of given thickness fixed within said drip chamber at a level above said closed portion and below a fluid supply level within said drip chamber to divide said drip chamber into an upper portion and a flexible lower portion,
• said closed portion being capable of increasing back pressure therewithin when the rate of fluid inflow into said closed portion exceeds the rate of fluid outflow therefrom and decreases when the rate of fluid outflow from said closed portion exceeds the rate of fluid inflow thereinto,
• maintaining a vertically movable float valve having an enlarged upper head, a valve stem longer than said given thickness and at least a pair of lower fingers extending radially from said valve stem, said float valve having a specific gravity slightly greater than that of said fluid, in axially movable relation to said fixed apertured valve seat,
• flowing said intravenous fluid into said upper portion of said drip chamber whereby said enlarged valve head rests on said valve seat aperture until said upper portion is filled with said fluid to a predetermined fluid level,
• closing said manual control valve means,
• compressing said flexible lower portion of said drip chamber to provide a back pressure sufficient to cooperate with the buoyancy of said fluid to lift said enlarged valve head from said apertured valve seat to permit flow of said fluid by gravity from said upper portion of said drip chamber into said flexible lower portion,
• opening said manual control valve to flow said fluid through said tubing and said catheter,
• controlling the upward movement of said enlarged valve head relative to said apertured valve seat so that said enlarged valve head is located in spaced relation above said apertured valve seat,
• inspecting the fluid that flows out of said catheter to determine the absence of entrapped air bubbles, and when said outward flow of fluid is free of bubbles,
• closing said manual control valve means to stop said outward flow of said fluid,
• inserting said catheter into said patient,
• opening said manual control valve to cause said fluid to flow into said patient,
• sufficiently reducing the back pressure on said enlarged valve head whenever said fluid flows from said closed portion of said primary tubing at a faster rate than it enters said closed portion of said primary tubing to permit said enlarged valve head to reengage said valve seat aperture to prevent further flow of said fluid into said flexible lower portion.