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Kidney Week

Abstract: TH-PO334

Proving the Value of the BluedopTM Device in the Renal Unit

Session Information

  • Vascular Access - I
    November 07, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
    Abstract Time: 10:00 AM - 12:00 PM

Category: Dialysis

  • 704 Dialysis: Vascular Access


  • King, David H., Mid Essex Hospitals, Chelmsford, United Kingdom
  • Ali, Abdelgalil Abdelrahman, Broomfield Hospital, Chelmsford, United Kingdom

Static Pressure Ratio SPR, showed early promise as a monitoring device in prediction of Arteriovenous Fistula Failure. ‘Arterial’ needle pressure is monitored with dialysis pump switched off. Blood pressure on the venous outflow will rise towards central arterial level in the presence of a ‘blood flow limiting’ venous stenosis. The method is not widely used, possibly due to difficulties in compensating for hydrostatic height difference between needle and mean blood pressure MAP measured on the contralateral arm. We suggest a simpler alternative using identical principles solves many of the practical problems associated with the earlier technique.


The BluedopTM device is intended to measure mean blood pressure non-invasively, without the use of needles, is unaffected by pump speed and can be applied at any suitable part of the AVF without any requirement for hydrostatic height correction. We have named our parameter ‘Non Invasive Static Pressure Ratio’ SPRn. A Doppler Ultrasound probe is used to sample blood flow waveforms from the distal brachial artery. A patented function based on blood velocity waveform shape calculates non-invasive intra AVF mean perfusion pressure MPP 2.This is comparable to the needle pressure measured directly in the AVF. SPRn is calculated as SPRn = MPP/MAP. The complete measurement takes approximately 5 minutes. and can be carried out by regular Renal Unit Staff without significantly interfering with their normal duties.


The range of SPRn values in normally functioning AVF was established in 479 dialysis patients. Following this 340 prospective measurements were made on 73 patients over a 10 week period. SPRn in 27 AVF rose above the +2SD normal limit. Of these 23 had 60% or greater focal stenosis shown on Duplex scanning, 2 were maturing AVF and 2 had no significant stenosis. A review of clinically identified ‘failing’ AVF in the same unit showed that 48% were found to be ‘false alarms’ in Duplex studies. BluedopTM reduced the number of false alarms to 18%.


BluedopTM offers a practical solution to the perennial problem of unheralded AVF failure. It also has the desirable property of indicating AVF status during the maturing phase

1 A Besarab et al, Vol.47,no.5, pp 1364-1373, 1995
2 D H King et al, , J Vasc Access,2015, 16 (3):211-217, DOI: 10.5301/jva.5000324