Thanks Bill, and thank you for the paper MAK. All of three measurements were low. No inflow volume flow in this particular study. It occurs to me that most people can drink faster than .06 L/min, depending on how good the bartender is. This is why I'm fishing for a technical explanation rather than a clinical one.


On Wed, Mar 7, 2018 at 4:01 PM, Bill Schroedter <[log in to unmask]> wrote:

I would (of course) agree with Ann Marie and also would ask about a volume flow calculation from the inflow artery. I have come to believe those are more reproducible.  How many measurements were obtained and were they all that low?  In my experience with this, a single measurement is always suspect and therefore would want to know if there were there numerous calculations in the ball park or was this an outlier!  

B

 

 

William B Schroedter, BS, RVT, RPhS, FSVU

4120 Woodmere Park Blvd

Suite 8B

Venice, Florida  34293

www.qualityvascular.com

www.virtualveincenter.com

 

 

 

From: UVM Flownet <[log in to unmask]> On Behalf Of Ann Marie Kupinski
Sent: Wednesday, March 7, 2018 2:29 PM
To: [log in to unmask]
Subject: Re: Volume Flow Artifacts

 

Hi Steve,

 

I do a lot of these and usually at about 6 weeks post op.  Yes upper arm AVF flow rates are higher than the those at the wrist level and of course, the vessel diameter is greater.  A diameter of 2.2 mm is very small.  It this is at 6 weeks, I’d say the low flow rates are at least in part due to the vessel not dilating.  Per the big fistula maturation study AVF flow at 1 day post-op is more than 50% of the 6-week flow rate in majority of patients.  You probably have the article but I attached it here. 

 

You said the waveforms looked normal in shape – this makes me think it is a maturation issue.  I have seen plenty of venous outflow issues but most with impact the waveform/pulsatility.  Was there any calcification present in the native arterial wall?  Did you measure flow in the inflow artery?  If the spectral trace done by the instrument stays within the middle of the waveform and doesn’t drop to zero then I would guess the calculation of the mean velocity is correct and there is no issue with the technique.

 

Ann Marie

 

From: UVM Flownet [mailto:[log in to unmask]edu] On Behalf Of Steve Knight
Sent: Wednesday, March 7, 2018 10:07 AM
To: [log in to unmask]
Subject: Volume Flow Artifacts

 

I reviewed a case of an AVF exam that had very low Volume Flow Velocities reported (less than 0.06 L/min). The waveforms  were obtained approx 5 cm distal to the arterial anastomosis in a straight uniform vein section one month post-op and looked normal in shape. Velocities were not impressively low. Diameter was about 2.2cm. 4 cardiac cycles were included in the calculation. The autotrace of peak velocity and mean velocity tracked the spectral profile without noticeable deviation. The series of beats measured did include a PVC with a low EDV. Also, the degree of fistula maturity may be a factor. I would like to hear others who do a lot of Vol Flow measurements of early dialysis fistulas weigh in here.

Thanks,

Steve K

 

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