How Much Vacuum is Enough? Is More Better?

by Jon Batzdorff on Tuesday, June 29, 2010 5:56 AM

Yes, in most cases, more vacuum is better.

Some prosthetists have reported that too much vacuum in an elevated vacuum socket causes discomfort and "pulling" and too little fails to provide linkage between the socket and the residual limb. The argument goes that there is a "sweet spot" at around 10"Hg. One set of pump instructions even recommends "only enough to suspend the socket".  This is not a good reference since actually the the socket can be suspended with no vaccum at all using just the sealing sleeve. The goal is to achieve the best possible linkage, which is achieved with maximum possible vacuum.

Experience suggests that, just as in traditional suction sockets, discomfort and pulling occurs when there is lack of total contact or a lack of even socket pressures. If the fit of the socket is correct, the vacuum can be much higher and the linkage much better. I suggest that, if there is pulling and discomfort, check the socket fit distally BEFORE simply having the patient use less vacuum. The exceptions would be with invaginated and severe scarring and adhesions where vacuum may intially have to be reduced.

Troubleshooting the Elevated Vacuum Socket

by Jon Batzdorff on Thursday, January 21, 2010 12:11 PM

There are two saying that I keep in mind when looking for leaks in an elevated vacuum prosthesis.

Alan Watts, the Eastern philosopher, once advised, “Don’t just do something…..Stand there!!!”
The second saying is anonymous: “Remember that you always find your lost keys in the last place you look.”
A colleague of mine was trying to please a patient who complained that the Harmony system took too long to pump up. She wanted to try something else.  He changed her over to the Limb Logic. The patient said the Limb Logic never gave her enough vacuum. they went back to Harmony.  The prosthetist even tried three different suspension sleeve models in an attampt to get better vacuum.  Since it continued to leak with each sleeve, he decided that it was not a sleeve problem and went back to the original sleeve. He then asked for my help.  We took Alan Watts' advice and we “stood there” and looked at it along time. Then we tested the socket off of the patient. We were using the Otto Bock flexible plastic socket attachment elbow to attach the vacuum tube to the socket as per instructions.  For testing purposes, we attached a hose to the plastic elbow and put a gauge on the hose and a hand pump. Then we sealed the top of the socket with the gel end pad that comes with the OWW troubleshooting kit.  We pumped up the socket and found that we could not pump it up above 20" Hg.  And then it quickly lost vacuum. We then exchanged the plastic elbow for the older metal type that threads into the socket. It sealed perfectly and we tested it again. This time the valve and tube were sealed perfectly. We continued to test the rest of the system and found that the sleeve also was leaking. It had appeared perfect, but indeed it had some pinholes.   We replaced the sleeve with a new sleeve and continued to test. Finally the system was sealed and we gave it back to the patient. She then quite liked the Harmony system. 
The lesson: Don’t assume anything; don’t rush to blame components or patient preference. If it leaks it leaks. Make no conclusions about components or socket design until the system is holding a vacuum without leaking.