Noninvasive methods for evaluation of extracranial cerebrovascular disease. A comparison

Sixty-five patients with clinical evidence of carotid occlusive disease were evaluated by the Doppler ophthalamic test, ophthalmodynamography, and oculopneumoplethysmography prior to angiography. Clinical assessment was accurate 68% of the time, with 32% of patients having no arteriographic evidence of significant disease. The sensitivity of the noninvasive tests was dependent on the extent of the carotid stenosis. When the extent was greater than 60% of the cross-sectional diameter, the Doppler ophthalmic test was accurate 54% of the time; the ophthalmodynamography test, 61% of the time; and the oculopneumoplethysmographic test, 97% of the time. In lesions encompassing 50% to 60% of the vessel diameter, the Doppler ophthalmic test was accurate 15% of the time; the ophthalmodynamography test, 17% of the time; and the oculopneumoplethysmographic test, 10% of the time. With less than 50% stenosis, none of the noninvasive tests detected atherosclerotic lesions. Although many diseased vessels were missed, the low incidence of false-positive tests enhanced the usefulness of these methods in augmenting the accuracy of clinical evaluation.

Doppler ultrasound and supraorbital photoplethysmography for noninvasive screening of carotid occlusive disease

Doppler ultrasound and supraorbital photoplethysmography were 95 per cent accurate in identifying or excluding significant carotid obstruction in 156 vessels of seventy-six consecutive patients undergoing arteriography. Plethysmography was more sensitive but less specific than Doppler ultrasound. These technics provide simple, rapid, and accurate detection of significant carotid occlusive disease.

Noninvasive measurements of digital arterial pressure and compliance in man

A noninvasive method was developed for measuring the digital arterial pressure and the compliance by using a fingertip pneumoplethysmograph and a pneumatic cuff. The compliance (C) of the digital artery was obtained from the peak amplitude of the volume pulse wave (deltaVp-a) under the effect of the cuff pressure (Po-a) by the equation: C = deltavp-a/(Ps - P-o-a) during the dicrotic phase defined in this study. The normal mean value was 11.37 +/- 0.59 X 10(-5) cm3/mmHg. On lowering of the cuff pressure, the moment when the deltaVp value becomes positive is regarded as the systolic pressure (Ps). At the end of the dicrotic phase, the mean amplitude (deltaVss') of the pulse wave during one pulse cycle (SS') and the ratios (deltaVss'/deltaVsd), where deltaVsd is the mean amplitude of the wave during the systolic period (SD), of successive waves after a particular wave fail to increase at the same rate when the cuff pressure decreased below the diastolic pressure. The cuff pressure corresponding to this particular wave is regarded as the diastolic pressure (Pd). The mean value of the mean digital pressure of normotensive subjects was 80.6 +/- 1.2 mmHg.

Automatic quantitation of venous hemodynamics with an electrically calibrated strain gauge plethysmograph

Strain gauge plethysmography has permitted noninvasive quantitation of altered venous hemodynamics in the legs of patients with venous disease. A new plethysmograph has been developed which avoids previous problems of mechanical calibration of gauges and the necessity for a recorder for calculating blood flows. This instrument permits accurate electrical calibration of mercury-in-Silastic gauges which are effectively at the corners of the Wheatstone bridge and are supplied by constant current for linear output. A timer and follow-and-hold circuit allow automatic calculation of rates of change in limb circumference and, thus, blood flow, from a panel meter. The accuracy of the automatic versus the graphic methods of quantitating venous outflow and reflux flow was determined in 20 normal subjects. Venous outflows were 15.1 +/- 0.5 (mean +/- 1 S.E.M.) and 15.9 +/- 0.4 cc/min/100 cc by automatic and graphic methods, respectively (r = 0.96, p less than 0.01). Reflux flows were 2.1 +/- 0.2 and 2.3 +/- 0.2 cc/min/100 cc by the automatic and graphic methods, respectively (r = 0.93, p less than 0.01). This plethysmograph may prove to be a simple, rapid, and accurate device for evaluating altered hemodynamics in venous disease.

[Problems in the methods and equipment of dielectrography]

An equivalent diagram representing the study sector of the body with non-contact electrodes placed upon it is considered. The relationship between the equivalent parallel circuit capacitance value and changes in the electric conductivity and capacitance of the study tissues is analyzed. Dielectrography enables it to register changes occurring in the active conduction of the body section lying between electrodes, i.e. to watch over the volume of blood filling various tissues and organs. Circuitry variants for registration dielectrograms are proposed. Recordings taken from different body areas are submitted.

Vascular responses in the human periodontal ligament and alveolar bone detected by photoelectric plethysmography: the effect of force application to the tooth

A modification of the technique of photoelectric plethysmography has been developed to monitor changes in the microcirculation of the human periodontal ligament and adjacent alveolar bone, whereby detection is made of light reflected from or transmitted through a tissue during alterations in blood volume, flow or distribution. Light is conducted to and from the periodontal tissues via miniature fiberoptics placed within the root canals of endodontically treated teeth, or illuminated through the external surface of the gingiva towards the root. Circulatory activity was monitored both with the teeth at rest and under forces up to 480 gm. Horizontal and axial forces were found to produce a decrease in blood volume in the area of the periodontal tissue under compression. In an area under tension, an initial increase in blood volume was followed by a decrease as the magnitude of force rose above the critical 90 to 180 gm level. The pulse volume, however, was increased during both phases. Analysis of the biphasic and pulse volume changes suggests that autoregulation of blood vessel tone occurs in the periodontal tissues as a result of alteration in extravascular tissue pressure when the root is moved relative to the alveolus. It is proposed that this autoregulatory mechanism may play a role in alveolar bone metabolism by producing alteration in local tissue oxygen tension.

Measurement of pulmonary capillary blood flow in infants by plethysmography

An accurate method for measuring effective pulmonary capillary blood flow (Qc eff) in infants has been developed with an adaptation of the plethysmographic technique. Measurements were made on 19 preterm. 14 small-for-dates, and 7 fullterm normal infants with a constant volume whole body plethysmograph in which the infant rebreathed nitrous oxide. There was a highly significant correlation between Qc eff and body weight, and this relationship was unaffected by premature delivery or intrauterine growth retardation. Mean Qc eff in preterm, small-for dates, and fullterm infants was 203, 208 and 197 ml min-1 kg-1, respectively, with no significant differences between the groups. A significant negative correlation existed between Qc eff and haematocrit in the preterm infants. There was no relationship between weight standardized Qc eff and postnatal age in any of the groups. With this technique, it was possible to readily recognise the presence of rapid recirculation (indicative of shunting) in several of the infants, suggesting that rebreathing methods for the assessment of Qc eff should not be applied indiscriminately during the neonatal period. By taking care to overcome the potential sources of technical error, it was possible to obtain highly reproducible results of Qc eff in infants over a wider age range than has been previously reported.

Elastic properties of blood vessels determined by photoelectric plethysmography

The dynamic elastic properties and vascular reactions of human blood vessels in vivo are studied by means of the photoplethysmographic method. The measurement of the mechanical properties of the blood vessel walls is based on measurement of blood volume changes resulting from changes in external pressure. The blood volume changes are mon itored by measuring the opacity changes in vascular bed, in this case, the distal phalanx of the finger. The elastic properties thus measured reflect some average property of a whole vascular bed. The technique is simple, noninvasive, and does not cause any damage or discomfort to the subject.

In healthy young subjects, blood vessel elasticity was found to be constant in the range between the systolic and diastolic pressure. However the volume-pressure curves showed a hysteresis loop, i.e., the curves obtained during the increase of intravascular pressure differed from those obtained when pressure was decreased.

The elasticity of the vascular walls of patients suffering from peripheral vascular diseases was found to be significantly different; their volume- pressure curves were nonlinear and had a much wider hysteresis loop (indicating a lower critical opening pressure), and their vascular reactions to changes in pressure were different.

Possible uses of the method for diagnosing and evaluating arterio sclerotic and other vascular diseases and for studying vascular changes and reactions under conditions such as shock, heart failure, external abnormal pressures, and various drugs, are discussed.

The use of digital rheoplethysmography for the study of psychogenic and neurogenic factors in man

The use of the RPG in the qualitative and quantitative study of the state of the intact digital vasculature of intact man is illustrated and emphasized. Rheoplethysmography is the only method for quantitatively recording continuously and simultaneously the volumes and rates of inflow, outflow and the differences between inflow and outflow and the rate of basal blood flow in the digits of intact man or in any organ or tissue that can be isolated in a plethysmographic cup. The effects of psychogenic and neurogenic factors on the peripheral circulation of man were studied with the RPG, and the results demonstrate how useful this method is for such studies of the fingertip.

Oculoplethysmography: an adjunct to arteriography in the diagnosis of extracranial carotid occlusive disease

A four and a half year study documents that oculoplethysmography, in conjunction with carotid phonoangiography, fulfills the criteria of an effective noninvasive adjunct to arteriography in the diagnosis of extracranial carotid occlusive disease. The risk and expense of unnecessary arteriographic studies can be reduced and accuracy of arteriographic technics and interpretations can be enhanced by routine application of oculoplethysmography.

Blood pressure measurement of all five fingers by strain gauge plethysmography

The aim of the present paper was to study the methodological problems involved in measuring systolic blood pressure in all five fingers by the strain gauge technique. In 24 normal subjects, blood pressure at the proximal phalanx of finger I and both at the proximal and the intermediate phalanx of the other fingers was measured using a 24-mm-wide cuff. Blood pressure at the proximal phalanx was higher than that at the intermediate phalanx in all fingers except finger V. The difference of blood pressure values corresponded well with circumference of the finger. In 15 normal subjects, blood pressure at the proximal phalanx was compared in fingers I, III, IV, and V, using 16, 20, 24 and 24 mm wide cuffs. Finger blood pressure was closest to arm systolic blood pressure when a 24-mm or 27-mm-wide cuff was used in fingers I, III, and IV, and with a 20-mm-wide cuff in finger V. As the standard deviation of the mean values was larter with the 27-mm-wide cuff than with the 24-mm-wide cuff, the 24-mm-wide cuff was considered to be most suitable for clinical use in fingers I, II, III, and IV. By using the 20-mm-wide cuff in finger V and the 24-mm-wide cuff in the other fingers, normal value of finger blood pressure was determined for both proximal and intermediate phalanxes.

[Pneumooxyhemographic method for the comprehensive study of circulation and respiration]

Over 3000 pneumoxyhaemogrammes were recorded in 1840 persons. Periods, types and criteria of pathology were differentiated in the structure of the pneumoxyhaemogramme. The method permits to reveal early forms of cardiovascular pathology. It is applicable for the examination of both normals and patients for early diagnosis of cardiovascular pathology, for the control of the therapeutic effect, and for a dynamic observation in the course of a dispensary screening.

A simple plethysmographic method for differentiating primary from secondary varicose veins

Characteristics of venous flow were studied in 81 normal legs and in 98 legs with varicose vein disorders. The change in the volume in the calf after calf muscle contractions was studied using the strain gauge technique with the patients in the erect position. During contractions of the calf muscle, the volume in the calf decreases, chiefly because of reduction of blood volume in the veins. After cessation of the contractions, there is a gradual return of volume to precontraction values. This was measured in seconds and called venous return time and in milliliters times 100 milliliters of tissue-1 times minutes-1 and called venous reflux flow. In normal persons, the venous return time was 21.9+/-6.7 (S.D.) seconds, and in patients with venous disorders, the corresponding time was 6.9+/-2.9 (S.D.) seconds. Venous reflux flow which was inversely correlated with the venous return time was 11.4+/-4.9 and 22.3+/-7.3 (S.D.), respectively. A good correlation was found between venous return time and venous pressure measurements. No age or sex differences were seen. In patients with superficial venous insufficiency, the venous return time and venous reflux time became normal when the diseased portion of the vein was compressed. In patients with insufficient perforating veins or damaged deep vein valves, external compression did not change venous flow characteristics. This indicates that the method can be used preoperatively to differentiate between primary and secondary varicose veins and, thus, influence the type of operation to be performed. The method can easily be applied for clinical purposes.