Alrick B. Hertzman

Photoelectric Plethysmography of the Fingers and Toes in Man

Summary Photoelectric plethysmographs for the fingers and toes are described which use electrocardiographs for the recording and which have definite advantages in routine clinical observations on the circulation. The validity of the technique is established (1) by comparison of the photoelectric records with simultaneous records obtained with transmission plethysmographs, (2) by comparison of the photoelectric records in instances of circulatory disturbances with independent directional confirmation by other methods in the literature.

Functional Analysis of the Vasomotor Innervation of the Dog's Hind Footpad

Vascular responses in the large central pad of the dogs foot were recorded during stimulation of the lumbosacral sympathetic trunk and correlated with the site of stimulation and the subsequent histologic analysis of the excised trunk. The resulting description of the preganglionic inflow and postganglionic outflow from the trunk demonstrated marked variations in the anatomic patterns of the vasomotor innervation of the footpad in various animals. Complete preganglionic denervation of this vascular bed required extirpation of the entire lumbar trunk caudalward as far as L-7 in addition to the interruption of those preganglionic pathways through the spinal nerves which do not pass through the sympathetic trunk.

Comparative Estimation of Blood Supply of Skin Areas from Photoelectrically Recorded Volume Pulse

The principle of the photoelectric plethysmograph 1 has been applied to the comparison of the richness of the blood supply in several skin areas. Vertical illumination of the skin is provided by an ophthalmoscope bulb. Enough light is scattered through the subcutaneum to provide a sufficiently satisfactory transillumination to permit the detection of changes in the circulation in the skin by a photoelectric cell placed over the transilluminated area. The variations in the photoelectric current with changes in the blood content of the skin are recorded on the electrocardiograph after amplification. The volume pulse of the skin so recorded probably is an index of the arterial inflow with each heart beat and so can be used as an index of the blood supply of that skin area. (Special hemodynamic conditions will, of course, limit the specific application of the statement). Arterial constriction in the skin decreases the volume pulse; vasodilatation increases it. The amplitude and form of the recorded wave will also vary with the size and number of arterial vessels in the transilluminated area. Quantitation of the recorded wave in terms of arbitrary units is effected by comparing the size of the wave with the deflection obtained from inserting a glass filter (a thin glass sheet) between the photoelectric cell and the transilluminated skin area. Although the question as to what is the actual blood equivalent of the filter in terms of cc of blood per 100 cc of skin tissue is an involved one, 1 a tentative approach to the problem is provided in the data of Turner, et al. 2 Their average volume pulse in the finger tip at heart level is 2.8 mm3 or .06% of the soft tissue volume.

CUTANEOUS VASCULAR AND CARDIAC RESPONSES TO HEAT

During exposures of the nude resting subject to various levels and increases in ambient temperature (climatic chamber) cutaneous arterial vasodilatation (as recorded by photoelectric Plethysmographs) may differ in onset and amount in the digits forearm, calf, cheek and ear. Similar regional differences in sweating have been reported previously. There was no systematic relation of the cutaneous vasodilatation in a given region to sweating in the same area. Local skin temperature seems to be closely related to the local vascular events. Increases in the stroke volume and rate of the heart accompanied the cutaneous vasodilatation but the possibility that the latter entirely accounted for the increased cardiac load was considered unproven.

Responses of dog's pad vessels to epinephrine following sympathectomy or denervation.

Augmented reactivity of the skin vessels of the hind limbs of dogs to doses of l-epinephrine in the physiologic range could not be detected following conventional sympathectomy. Larger doses of epinephrine resulted in exaggerated reactions. Augmented reactivity of these vessels to physiologic doses of epinephrine was detectable if total cholinergic as well as adrenergic denervation of the limb was accomplished.