Device for filtering arterial blood

The invention relates to a device for filtering arterial blood.

It is known to provide extracorporeal blood circulation circuits, with arterial blood filtering devices which have the function of retaining microaggregates and microemboli, i.e. minute air bubbles occurring in blood, to prevent them from reaching the patient.

A very common type of these devices comprises a filter composed of three layers of net folded longitudinally and sunk, at the ends, in a supporting filler element, such as polyurethane resin, known as potting, this filter is arranged into a space inside a containment structure provided with connections for the inflow of the blood to be filtered and the outflow of the filtered blood, and with a connection for evacuating the air bubbles. Examples of these devices are shown in US-A-4 411 783 and in GB-A-1 501 665.

A disadvantageous characteristic of the known devices resides in the fact that the potting at the upper end of the filter, being in the form of a compact body, retains the air bubbles below which, blocked by the filter, return upwards in the spaces comprised between the folds of the net, thus preventing their evacuation.

The aim of the present invention is to provide a device for filtering arterial blood wherein any stagnation of air bubbles is completely prevented.

Within the scope of this aim, an object of the invention is to design a device inside which blood can circulate without being subject to dangers of haemolysis.

The aim proposed, as well as the object mentioned, are achieved by a device for filtering arterial blood, according to the invention, as defined in the characterizing part of claim 1.

Further advantages will become apparent from the description of a preferred, but not exclusive, embodiment of the invention, illustrated only by way of non-limitative example in the accompanying drawing, wherein: <ul id="ul0001" list-style="none"><li>Fig. 1 is a cross section view of the invention along a plane passing through its axis;</li><li>Fig. 2 is a plan view of the invention with a partial cross section at the line II-II of figure 1.</li></ul>

With reference to the above described figures, the reference numeral 1 designates the filter composed, in a known manner, of three layers of net, two outer supporting layers and one intermediate filtering layer. The net is folded and lies in a portion of space having the shape of a hollow body of revolution inside a containment structure generally indicated by the reference numeral 2. The containment structure is provided with a blood inflow connection 2a, a blood outflow connection 2b, and with a connection 2c for the evacuation of the air bubbles contained in the blood.

The main peculiarity of the invention resides in the fact that, while the lower end of the filter 1 is sunk, in a known manner, in the compact annular block of supporting filler material 3 known as potting, consisting for example of polyurethane resin, the upper potting generally indicated by 4 comprises a plurality of tabs 5 deriving monolithically from a continuous inner band 6 and connecting the individual folds of the net.

The cover 7 with a central hole 7a covers the portion of space comprising the filter 1, which the elements 8 which derives from the bottom of the structure 2 acts as a support for said filter and as partial filler for the cavity 11 comprised therein, so as to reduce the amount of blood contained in the device.

The functional characteristics achieved with the device according to the invention are evident: blood enters through the tangential connection 2a and forms an eddy in the portion of space above the cover 7, which performs the double function of preventing the contact of the blood in this vorticose motion with the potting 4 which, due to its jagged shape, may create a harmful haemolysis effect, and of defining a region of blood at rest, lying thereunder after it has passed through the hole 7a, and therefore in a condition favourable for accepting the micro-bubbles trapped by the filter, as will be described hereinafter.

As an effect of the abovementioned vorticose motion, most of the air present separates from the blood in the form of bubbles 9, said bubbles being immediately evacuated through the connection 2c. The blood then descends, by following the path indicated by the arrows, in contact with the filter 1, then pass through the filter entering the portion of space adjacent to the element 8 and eventually flows out through the connection 2b; the air bubbles 10 still present in the blood are trapped by the filter 1 and go back up, without any obstacle, towards the underlying region of blood at rest below the cover 7, by virtue of the particular shape of the potting 4, from there they pass through the hole 7a into the upper region and then leave through the connection 2c.

Thus the described configuration of the potting at the upper end of the net is such as to completely prevent the stagnation of air bubbles inside the device, and it is important to observe that it has the maximum effectivness not only in devices of the type described, with the inflow of blood above and the outflow below, but in any type of devices regardless of their general structure, in particular it is effective also in devices having both the inflow and the outflow of the blood at the lower region.

The invention thus described is susceptible to numerous modifications and variations, all of which are within the scope of the claims.