The Big Little Things, Part I: Bevel Alignment
Posted on September 10, 2014
By Mitch Valdmanis, M.Eng.
When a person sees RIVA operating for the first time, they see the robot dancing around the cell, shuttling items to-and-fro between subsystems; they watch as fluid is transferred between containers at one of the syringe manipulators; and they notice how the inventory carousels rotate around to present the correct inventory items to the robot. However, they are unlikely to notice all of the small, precise operations taking place to make sure all of this happens smoothly. In a short series of posts, I would like to illustrate a few of these processes and how they contribute to the overall effectiveness of RIVA.
Close-up of a needle bevel front and side.
The first such process that I would like to highlight is what we call “bevel alignment”. This is the patented1 process of aligning the bevels at the tips of the syringe needles so that each time a new needle is inserted into a vial’s stopper it goes through the same hole in the stopper. For example, here is a series of pictures showing three different vial stoppers. Each of the three vials underwent a slightly different process.
Vial stopper surfaces after being punctured once (left), 10 times with aligned needle bevels (middle), and 10 times with unaligned needle bevels (right).
The first stopper, on the left, was punctured only once by a single needle. Notice the ‘C‘ shaped arc of the cut formed by the needle – the middle of the arc is where the tip of the needle went through the stopper.
The second stopper, in the middle, has been punctured 10 times by 10 different needles, with RIVA aligning the bevels of each needle prior to engaging the vial. Notice how similar the cut looks to that in the first stopper, only more defined, almost as if it had only been punctured once.
Finally, the third stopper has also been punctured 10 times by 10 different needles, however this time the needle bevels were manually misaligned with each other after RIVA had aligned them, as if they had never been aligned in the first place. Notice that there are many overlapping ‘C’ cuts into the stopper.
Going through the same hole with each needle is important for two reasons. First, overlapping cuts in a stopper can lead to fluid leaks. If there are two or more overlapping incisions in a vial stopper and a needle is inserted through one of them, then the other incisions would be pried open slightly, forming gaps in the stopper through which fluid could leak, as illustrated below. Depending on the orientation of the vial, liquid drug could leak out of the vial in to the RIVA cell, or air could leak into or out of the vial. Air leaking through the stopper would affect the air pressure in the vial and could ultimately lead to liquid leaks from the vial as well. This is particularly relevant for chemo drugs where controlling drug contamination is critical. (RIVA’s management of the air pressure inside of vials is the topic for another post.)
Inside view of vial stoppers with needles inserted after 10 punctures. On the left, all 10 needles were aligned by RIVA. On the right, the 10 needles were not aligned. Notice the gap in the rubber around the needle on the right as compared to the tight grip of rubber around the needle on the left.
The second risk with overlapping punctures is coring of the vial stopper, where small bits of the stopper break off. The bits that break off could be pushed into the liquid in the vial and potentially drawn into the syringe and ultimately administered to a patient. Overlapping punctures greatly increase the risk of stopper coring. In an extreme case a series of punctures could even cut a large circular piece of material out of a stopper.
RIVA mitigates these risks by ensuring that the needle of each syringe is aligned the same way so that the vial stopper is not cut any more than necessary. Bevel alignment is just one of the techniques employed by RIVA to ensure smooth operation and safe output products. In the coming weeks I will discuss several more.
Note: The resiliency of different vial stoppers to repeated needle punctures varies for each type of stopper based on its material and shape. All vials must be tested to determine their individual puncture limit.
1 – Control of fluid transfer operations US 8267129 B2
Mitch Valdmanis is a software developer at Intelligent Hospital Systems, developer and manufacturer of RIVA – a fully automated IV compounding system
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