Noninvasive Measurement of the Human Peripheral Circulation: Relationship Between Laser Doppler Flowmeter and Photoplethysmograph Signals from the Finger

Abstract

Under certain conditions laser Doppler flowmeter (LDF) signals obtained from the finger pulp may appear very similar to those obtained by use of a direct current (dc) photoplethysmograph (PPG). A combined LDF/PPG system was used in conjunction with a circumference strain gauge as an index of vol ume change to identify the conditions in which the correlation between these signals was good.

Simultaneous LDF and dc PPG measurements were made on 10 normal vol unteers by using arterial occlusion and on 7 normal subjects by using the Val salva maneuver at different elevations of the forearm and hand with respect to the midsternum. By altering the elevation of the upper limb the influence of venous filling on each of the signals during these maneuvers was observed.

Since the dc PPG signal always appeared similar to the volume change indi cated by the circumference strain gauge, it is concluded that the dc PPG signal is related to blood volume change if allowance is made for the effects of blood oxygenation. In circumstances of low venous filling, however, blood volume changes correlate well with blood flow changes, producing the correlation be tween the dc PPG and LDF traces.

The dc PPG signal may be used as a means of monitoring changes in blood flow in the finger only when venous filling is low and the return remains unre stricted. Thus, in investigations using this method, the relative position of the limb with respect to the heart should always be indicated. The LDF method appears to be a reliable indicator of blood flow changes in the microcirculation irrespective of the degree of venous filling.

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References

Hertzmann AB , Spealman CR : Observations on the finger volume pulse recorded photoelectrically. Am J Phys 119:334-335, 1937.

Cooke ED , Bowcock SA , Smith AT : Photoplethysmography of the distal pulp in the assessment of the vasospastic hand. Angiology 36:33-40, 1985.

Roald OK , Seem E. : Treatment of Raynaud's phenomenon with Ketanserin in patients with connective tissue disorders. Br Med J 289:577-579, 1984.

Challoner Avj : Noninvasive Physiological Measurements, Volume 1, ed. by Rolfe P. London : Academic Press, 1985, pp 125-151.

Lafferty K. , De Trafford JC , Potter C. , et al: Reflex vascular responses to contralateral thermal stimuli during the normal menstrual cycle: A hormonal basis to Raynaud's phenomenon. Clin Sci 68:639-645, 1985.

De Trafford JC , Lafferty K. : What does photoplethysmography measure? Med Biol Eng Comp 22:479-480, 1984.

Stem MD : In-vivo evaluation of microcirculation by coherent light scattering. Nature 254:56-58, 1975.

Bonner R. , Nossal R. : Model for laser Doppler measurement of blood flow in tissue. Appl Opt 20:2097-2107, 1981.

Fairs Sle , De Trafford JC , Roberts VC : Practical Aspects of Skin Blood Flow Measurement. Proceedings of the Biological Engineering Society, (BES) Dundee, March, 1985, Vol. 1. ed. by Spence VA, Sheldon CD. London: BES, 1985, pp 11-17.

10.

Boggett D. , Blond J. , Rolfe P. : Laswer Doppler measurement of blood flow in skin tissue. J Biomed Eng 7:225-232, 1985.

11.

Almond NE , Jones DP , Bowcock SA , et al: Technology in Health Care. Proceedings of the Biological Engineering Society (BES) 25th Anniversary Conference, Cambridge, September, 1985, ed. by Byford GH. London: BES, 1985, pp 133-134.

12.

Nilsson GE , Tenland T. , Oberg PA : A new instrument for continuous measurement of tissue blood flow by light beating spectroscopy. IEEE Trans Biomed Eng 27:12-19, 1980.