What You Should Know About Using NIV Studies

By Dana Giacalone, DPM, and Khurram Khan, DPM

The cuffs should be the same width or 25 percent larger than the width of the part they encircle. If the cuff is too narrow, the pressure will be falsely elevated. Using a Doppler probe, you would inflate the cuff so pedal sounds are no longer audible. Then slowly deflate the cuff and record the pressure in the cuff when you first hear the sound. This represents the pressure of the artery where the cuff is located.5
According to Bowker and Pfeifer, the pressure changes correlate directly with flow.5 So an index of 0.5 represents only 50 percent of the expected blood flow. A gradient of 40mmHg or greater between the ipsilateral or contralateral levels suggests an occlusion or highly stenotic segment. There is discrepancy with this value as Hoffman suggests 30mmHg and Pellerito suggests 20mmHg.2,4 These values can be misleading if collateral flow is so extensive that a 20-30 mmHg drop does not occur or in a situation in which there are non-compressible vessels due to calcification.1,4,5

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