Spectrum analysis of large toe plethysmographic waveshape.

To assess plethysmographic waveform diagnostic utility in peripheral vascular disease, a spectrum analyzer was attached to the output of a conventional mercury strain gauge sensor. The resulting quantified waveforms were compared with geometrically determined waveform characteristics and resting ankle pressure ratios for a group of 16 men who ranged from healthy to severely occluded (lower extremities). Of the various harmonics contained within the waveform, second harmonic magnitude best correlated with those geometric waveform characteristics believed to possess diagnostic value. Second harmonic magnitude was positively related (0.9 correlation coefficient) to the 1.33 power of resting ankle pressure ratio. Because it does not require exercise or pressure cuffs, spectrum analyzer waveform based diagnosis may be suited for mass screening purposes.