Surgery – Means for introducing or removing material from body for... – Treating material applied to or removed from external...
Reexamination Certificate
1998-06-09
2001-07-03
Nguyen, Anhtuan T. (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material applied to or removed from external...
C604S115000
Reexamination Certificate
active
06254580
ABSTRACT:
This invention relates to apparatus for use in sampling fluids from the human or animal body using a suction blistering technique and to a method of sampling using such apparatus.
It is a known laboratory technique to form a suction blister on an area of skin by applying a suction cup to the skin within which a partial vacuum is sustained for a period of about two to three hours, the resulting suction blister resulting from the accumulation of a clear liquid plasma filtrate beneath an area of epidermis which becomes detached during this period from the underlying dermis of the skin. This detached area of epidermis forms a blister roof which can be painlessly opened or removed to gain access to the plasma filtrate and the plasma filtrate may then be sampled for analysis. Removal of this area of epidermis creates a standardised skin erosion. Plasma filtrate will continue to be generated at the exposed dermis (so long as dehydration and crust formation is prevented) so that by collecting and sampling this plasma filtrate, repeated or continuous analysis may continue over a period of time before the dermis becomes covered with a fresh epidermal layer as a result of the natural healing process.
Sampling and analysing such plasma filtrate has been shown to be an effective and minimally invasive alternative to other forms of sampling body fluids such as the use of implanted perforate tubes or intravenous cannulas.
This technique is particularly suited to analytic methods requiring only small quantities of sample fluids.
According to the present invention there is disclosed apparatus for use in a suction blister technique of sampling fluid from the human or animal body, the apparatus comprising a cup defining a chamber and having a rim portion defining an aperture communicating with the chamber, an annular flange extending outwardly from the rim portion whereby in use the flange is sealingly attachable to the body such that an area of skin closes the aperture, and a ducted portion connected to the cup and defining a duct communicating with the chamber, the cup further comprising a roof merging with the rim portion and formed of resiliently deformable material having a shape memory urging the roof into an expanded configuration in which the roof is held clear of the aperture and wherein the roof is deformable into a collapsed configuration in which the roof is proximal to the aperture.
An advantage of such apparatus is that the cup may remain in place during both the formation of a suction blister, the opening of the suction blister and subsequent sampling of plasma filtrate, thereby simplifying overall the procedure of obtaining a sample. The deformation of the roof of the cup between the expanded configuration and the collapsed configuration may be utilised to displace plasma filtrate from the chamber for the purpose of sampling, the plasma filtrate being expelled through the duct.
A further important advantage is that the size and shape of the chamber is selectively adaptable firstly to allow sufficient room for the growth of a suction blister while the roof is in the expanded configuration and secondly to restrict to a minimum the dead space volume during subsequent extraction of plasma filtrate when the roof is in the collapsed configuration. It is therefore not necessary to replace the suction cup used for formation of the suction blister with a separate apparatus with minimal chamber volume for use in sampling plasma filtrate.
The advantage of enabling the chamber volume to be minimised during sampling plasma filtrate arises from the relatively slow rate at which plasma filtrate continues to be generated at the skin erosion formed by removal of the epidermis from the underlying dermis, it being desirable to minimise the dead space volume within any collecting chamber, particularly when continuing to take samples for analysis over a period of time, either by allowing the plasma filtrate to progressively flow from the duct unaided or when the rate of production of plasma filtrate is enhanced by the application of suction.
The duct preferably communicates with the chamber via an access port which may conveniently be defined in the rim portion and the ducted portion may project outwardly from the rim portion and be formed integrally with the flange.
Locating the access port in the rim portion ensures that the access port through which plasma filtrate may be extracted from the chamber is in the immediate vicinity to the exposed dermis from which the plasma filtrate forms. This location is also advantageous in that collapsed configuration of the roof since it ensures that the access port continue to communicate with the reduced volume of the chamber.
Preferably the flange is provided with an adhesive layer operable in use to sealingly secure the flange to the body.
Other means may alternatively be used to sealingly secure the flange, such as for example use of straps binding the flange in intimate contact with the skin, preferably including annular grooves on the underside of the flange to enhance sealing action.
The apparatus may comprise a hollow needle which is longitudinally and slidably received in the duct so as to be movable longitudinally between a retracted position in which an innermost end of the needle is retracted from the chamber and an advanced position in which the innermost end projects into the chamber.
The hollow needle may thereby be used to disrupt the detached epidermis constituting the roof of a suction blister simply by moving the needle into the advanced position to rupture the detached epidermis and then retracting the needle. Plasma filtrate released by disrupting the detached epidermis may then be extracted via the hollow needle.
Conveniently the needle comprises a connector mounted at an outer end of the needle for coupling a co-operating connector in fluid communication with the chamber via the hollow needle.
The use of such a connector thereby enables a suction device initially to be coupled to the hollow needle to apply suction to the chamber during the formation of a suction blister and subsequently for the connector to be used to couple an analysing apparatus to the needle for receiving plasma filtrate.
The apparatus may comprise locking means operable between the needle and the ducted portion for locking the needle in the retracted position.
Such locking means has the advantage of ensuring that the needle does not become accidentally moved into its advanced position before completion of the formation of a suction blister.
A seal may advantageously be located in the duct so as to be penetrated by the needle. This is particularly important during the maintenance of suction within the chamber via the hollow needle.
Alternatively, the hollow needle may be a sliding fit within the duct of sufficient tightness to ensure an airtight seal.
As an alternative to the use of a hollow needle, the apparatus may comprise a connector formed integrally with the ducted portion and operable to couple a co-operating connector in fluid communication with the chamber via the duct.
The connector may therefore be connected initially to a source of suction in order to apply a partial vacuum within the chamber during the suction blister forming period and may subsequently be replaced by connection of an plasma filtrate collecting or analysing device.
Disruption of the suction blister may conveniently be achieved by incorporating in the cup a side port communicating with the chamber and closed by a septum which is penetrable in use by a needle and which is self healing on withdrawal of the needle.
Alternatively, the roof may be provided with blister disrupting formations projecting into the chamber.
This removes the need to provide any needle to disrupt the detached epidermis of the suction blister.
Conveniently the blister disrupting formations comprise first and second teeth having respective first and second pointed ends located adjacent one another when the roof of the cup is in the expanded configuration and which progressively move apart when the roof is being deformed
Flehr Hohbach Test Albritton & Herbert LLP
Nguyen Anhtuan T.
Thissell Jeremy
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