the micro - volume blood transfer device , a mvbtd 20 , is depicted in fig1 . mvbtd 20 is disposed with a capillary - size transfer tube between 18 - 24 gauge , but which is preferably a 20 gauge micro bore transfer tube 21 between 30 - 40 mm in length with a blunt tip , 0 . 9 mm in outer diameter and 0 . 584 mm in inner diameter in a preferred embodiment . the micro bore transfer tube 21 is bonded to a y - connector 22 , 24 mm in total length with 10 mm that serve as the male component to the hub holding the micro bore transfer tube 21 . the y - connector 22 is attached to micro bore extension tubes 23 , which have a 1 . 9 mm outer diameter and a 0 . 9 mm inner diameter , and are 42 mm in length , in a preferred embodiment , but could range between 20 - 65 mm in alternative embodiments . the length of the micro bore extension tubes 23 along with the blunt transfer tube 21 is calibrated to allow exactly the volume required to clear three times the dead space required to obtain clean blood , approximately 0 . 5 ml . the micro bore extension tubes 23 are disposed with a mini pinch clamp for the clearance side 24 and a mini pinch clamp for the sample side 34 are distinctly colored and labeled to enable the user to selectively fill either side of the device . one side is designated for collection of the clearance blood while the other is designated for the collection of the blood sample . both micro bore extension tubes 23 are further disposed with female lures 25 , which are a total of 22 mm in length in a preferred embodiment , but the micro bore extension tubes 23 could range in length from 5 - 70 mm in length in alternative embodiments . finally each female lure 25 is capped with a porous plug 26 containing a 0 . 22 um filter in a preferred embodiment , but the porosity of the plug 26 could range from 0 . 22 - 3 . 0 um . the mvbtd 20 is designed to be inserted through a split - septum t - connector 27 into the base of an arterial catheter hub 28 , where the micro bore transfer tube 21 comes to rest 1 - 2 mm from the catheter opening 29 . this allows for blood to flow into the micro bore transfer tube 21 directly from the indwelling arterial catheter 29 , and does not allow fluid from the fluid filled catheter hub 28 or t - connector 27 to flow into the micro bore transfer tube 21 . this by - passing of the catheter hub 28 significantly reduces the clearance volume required . the amount of clearance blood is precisely measured to be less than 0 . 5 ml , which is an acceptable clearance volume for an arterial line blood draw . the device can be used for a peripheral arterial line ( pal ) catheter blood draw . with both micro bore extension tubes 23 clamped shut , the device is inserted into a t - connector 27 attached to the catheter hub 28 coming to rest 1 - 2 mm from the catheter opening 29 . in this embodiment the micro bore extension tube 23 on the clearance line side has a self - venting plug 26 attached which allows patient blood pressure to push blood into the clearance line , without utilizing any aspirating pressure . in other embodiments a self venting syringe or an aspirating syringe is attached to the clearance side of the device and the clearance side clamp 24 is released allowing blood from the catheter 29 to enter the micro bore transfer tube 21 and travel up the clearance side until it reaches the attached clearance collector 25 . the amount of clearance blood required to clear all the dead space in the device is approximately 0 . 2 ml . in the preferred embodiment where the plug 26 remains in place the mini pinch clamp for the clearance side 24 does not have to be reapplied prior to a self - venting syringe being attached to the blood sample side , the mini pinch clamp for the sample side 34 is released allowing clean blood to flow up the micro bore collection tube 21 and into the syringe , filling it to the desired pre - set volume of blood . the mini pinch clamp for the sample side 34 is then re - applied . multiple syringes and sample amounts could be taken if desired , i . e . blood gas , glucose , lab tests , which may require multiple syringes . when conducting a uac draw , the mini pinch clamp for the clearance side 24 is released and the clearance volume of 0 . 5 ml is slowly returned to the patient . this is not required for pal draws . the device is removed from the t - connector 27 and deposited within an appropriate waste container . flushing the device is not required for a pal draw and is a low 0 . 3 ml up to 0 . 5 ml for the uac draw . if the device is going to be flushed after use , a flushing syringe can be attached to the valve port 31 in the blood pressure monitoring line 30 . the current method has no interference with waveform obtained from the monitored line as there are no parts of the micro volume blood transfer device that are required to be in line with the hemodynamic monitoring setup . the device can also be utilized to draw clean blood from a uac . with both micro bore extensions tubes 23 clamped shut , the device is inserted into a t - connector 27 attached to the catheter hub 28 coming to rest 1 - 2 mm from the catheter opening 29 . a self venting syringe is attached to the clearance side of the device , and the mini pinch clamp for the clearance side 24 is released allowing blood from the catheter to enter the micro bore transfer tube 21 and travel up the clearance side until it reaches the attached self venting syringe , pre - set to the desired clearance volume , approximately 0 . 5 ml of blood . this clearance volume clears all the umbilical catheter dead space and represents at least three times the catheter lumen fluid volume . the mini pinch clamp for the clearance side 24 is then reapplied , a second self venting syringe is attached to the blood sample side and the mini pinch clamp for the sample side 34 is released . when the mini pinch clamp for the sample side 34 is opened clean blood flows up the micro bore transfer tube 21 and into the syringe , filling to the desired pre - set volume of blood . the mini pinch clamp for the sample side 34 is then re - applied . after the sample is collected , mini pinch clamp for the clearance side 24 is released and the held clearance volume of 0 . 5 ml is slowly returned to the patient . the mini pinch clamp for the clearance side 24 is re - applied . the sample syringe with sample blood is then removed for testing . the device mvbtd 20 is removed from the t - connector 27 and deposited within an appropriate waste container . a 10 ml flush syringe may be attached to the valve port 31 at the end of the t - extension set . only 0 . 5 ml is needed to flush the catheter after use so the 10 ml flush syringe only needs replacement after 15 - 20 blood draws , or once per day if a 10 ml flush syringe were used . this reduces multiple line accesses for flushing because there is no need to replace the flush syringe every time there is a blood draw , which in turn reduces the possibility of infection and contamination to the patient and caregiver . the current method has no interference with waveform obtained from the monitored line as there are no parts of the micro volume blood transfer device that are required to be in line with the hemodynamic monitoring setup . it will be understood that various modifications can be made to the various embodiments of the present invention herein disclosed without departing from the spirit and scope thereof . for example , various devices are contemplated as well as various types of construction materials . also , various modifications may be made in the configuration of the parts and their interaction . therefore , the above description should not be construed as limiting the invention , but merely as an exemplification of preferred embodiments thereof . those of skill in the art will envision other modifications within the scope and spirit of the present invention as defined by the claims appended hereto .
a micro - volume blood transfer device to facilitate the collection of small volumes of clean arterial blood from patients who may be volume restricted for blood loss such as low - birth weight infants .