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A novel and noninvasive method of estimation of oxygen saturation in arterial blood (SpO 2 ), employing the popular photoelectric plethysmographic (PPG) principle, is presented here. Based on a refined model for the attenuation of light in a PPG sensor, a simple method of computation of SpO 2 that is not influenced by interfering parameters of a patient such as skin colour and quantum of intervening tissue between the source and the detector in a PPG sensor as well as sensor dependent parameters such as source intensity and detector sensitivity is identified. Preliminary results obtained on a prototype pulse oximeter, built and tested, demonstrate the practicality of the proposed method.

Extraction of extra-cardiac information from photoplethysmography (PPG) signal is a challenging research problem with significant clinical applications. In this study, radial basis function neural network (RBFNN) is used to reconstruct the gastric myoelectric activity (GMA) slow wave from finger PPG signal. Finger PPG and GMA (measured using Electrogastrogram, EGG) signals were acquired simultaneously at the sampling rate of 100 Hz from ten healthy subjects. Discrete wavelet transform (DWT) was used to extract slow wave (0-0.1953 Hz) component from the finger PPG signal; this slow wave PPG was used to reconstruct EGG. A RBFNN is trained on signals obtained from six subjects in both fasting and postprandial conditions. The trained network is tested on data obtained from the remaining four subjects. In the earlier study, we have shown the presence of GMA information in finger PPG signal using DWT and cross-correlation method. In this study, we explicitly reconstruct gastric slow wave from finger PPG signal by the proposed RBFNN-based method. It was found that the network-reconstructed slow wave provided significantly higher (P < 0.0001) correlation (?0.9) with the subject's EGG slow wave than the correlation obtained (?0.7) between the PPG slow wave from DWT and the EEG slow wave. Our results showed that a simple finger PPG signal can be used to reconstruct gastric slow wave using RBFNN method. � 2011 International Federation for Medical and Biological Engineering.

This article investigates the possibility of extracting gastric motility (GM) information from finger photoplethysmographic (PPG) signals non-invasively. Now-a-days measuring GM is a challenging task because of invasive and complicated clinical procedures involved. It is well-known that the PPG signal acquired from finger consists of information related to heart rate and respiratory rate. This thread is taken further and effort has been put here to find whether it is possible to extract GM information from finger PPG in an easier way and without discomfort to the patients. Finger PPG and GM (measured using Electrogastrogram, EGG) signals were acquired simultaneously at the rate of 100 Hz from eight healthy subjects for 30 min duration in fasting and postprandial states. In this study, we process the finger PPG signal and extract a slow wave that is analogous to actual EGG signal. To this end, we chose two advanced signal processing approaches: first, we perform discrete wavelet transform (DWT) to separate the different components, since PPG and EGG signals are non-stationary in nature. Second, in the frequency domain, we perform cross-spectral and coherence analysis using autoregressive (AR) spectral estimation method in order to compare the spectral details of recorded PPG and EGG signals. In DWT, a lower frequency oscillation (?0.05 Hz) called slow wave was extracted from PPG signal which looks similar to the slow wave of GM in both shape and frequency in the range (0-0.1953) Hz. Comparison of these two slow wave signals was done by normalized cross-correlation technique. Cross-correlation values are found to be high (range 0.68-0.82, SD 0.12, R = 1.0 indicates exact agreement, p

A comprehensive model, which has the advantages of both lumped parameter and distributed parameter, has been developed with the objective of investigating the respiratory influences in radial artery pressure pulse as in photoplethysmography (PPG). It integrates lumped parameter cardiopulmonary (CP) model and transmission line arterial tree model from aorta to radial artery. The cardio-pulmonary interaction is realized by incorporating respiratory-induced variations in intrapleural pressure (Ppl) in circulatory system. The PPG signal of the model is considered as the radial artery pulse. To investigate the interaction Valsalva Maneuver (VM) condition has been simulated for different Ppl magnitude (10, 20, 30, and 40 mmHg) and for different time duration (5, 10, 15, and 20 s), and validated with PPG signal recorded in 10 normal subjects performing VM. The effects of test duration and VM pressure are studied in both the simulation and the experiments with specific focus on the maximal (%?) changes in Heart Rate (HR), and Mean Arterial Pressure (MAP) during phases II and IV of VM. The correlation coefficients derived from model result have good agreement with experimental results. As radial artery pulse plays important role in both allopathy and alternate medicine systems, this model can serve to study its clinical importance in detecting cardiac and respiratory pathologies. � 2010 Biomedical Engineering Society.

Peripheral arterial elastic properties are greatly affected by cardiovascular as well as other pathologies, and their assessment can provide useful diagnostic indicators. The photoplethysmographic technique can provide finger blood volume and pressure waveforms non-invasively, which can then be processed statically or beat-to-beat to characterize parameters of the vessel wall mechanics. We employ an occlusion-deflation protocol in 48 healthy volunteers to study peripheral artery compliance-related indices over positive and negative transmural pressure values as well as under the influence of a valid vasoconstrictor (cigarette smoking). We calculate beat-to-beat indices (compliance index CI, distensibility index DI, three viscoelastic model parameters (compliance C, viscosity R and inertia L), pressure-volume loop areas A and damping factor DF as well as symmetrical (C(max)) and asymmetrical (C(A)(max)) static compliance estimates, and their distributions over transmural pressure. All distributions are bell-shaped and centred on negative transmural pressure values. Distribution heights were significantly lower in the smoking group (w.r.t. the non-smoking group) for C, CI, DI and significantly higher in R and DF. The estimated volume signal time lag was also significantly lower in the smoking group. Left and right distribution widths were significantly different in all parameters/groups but DI (both groups), C(A)(max), A (smoking group) and L (non-smoking group), and positions of maxima/minima were significantly altered in C(A)(max), R and DF. C, DF and CI are seen to be most sensitive under this protocol, while C(max) and C(A)(max) are seen to be insensitive. These quantities provide complementary, time- and transmural pressure-dependent information about arterial wall mechanics, and the choice of index should depend on the physiological conditions at hand as well as relevant time resolution and transmural pressure range.

Spinal cord injury results in loss of supraspinal control of sympathetic outflow, yet preservation of spinal reflexes. Given the importance of reflex activation of sympathetic vasoconstrictor neurones to the generation of autonomic dysreflexia, we assessed the input–output relationship of the spinal somatosympathetic reflex induced by electrical activation of cutaneous afferents over the lower abdominal wall. In 13 spinal cord-injured subjects (C4-T10) we tested the hypothesis that the magnitude and duration of the vasoconstriction is directly related to the magnitude and duration of the stimulus train. Cutaneous vasoconstriction was measured with photoelectric plethysmography over a finger and toe; continuous blood pressure was recorded by radial artery tonometry, heart rate by ECG chest electrodes and sweat release by skin conductance. Four sets of trains of cutaneous electrical stimuli (20 Hz 1 s, 20 Hz 20 s, 20 Hz 1 s alternating on-and-off for 20 s and 1 Hz 20 s) were applied to the abdominal wall (10 mA) at 2-min intervals. Nine subjects showed vasoconstrictor responses to the stimulus trains. On average, both the magnitude and duration of the responses were similar irrespective of the type of stimulus train. We conclude that there is a non-linear relationship between somatic inputs and sympathetic vasoconstrictor outputs, and argue that a sustained vasoconstriction need not imply continuous sensory input to the spinal cord.

Measurement of sympathetic effector organ responses to selective activation of muscle and skin nociceptors below lesion in spinal cord-injured (SCI) subjects.To test whether selective noxious stimulation below lesion causes exaggerated sympathetic responses in human SCI.Prince of Wales Medical Research Institute, Australia.Twelve subjects (C5-T10, ASIA A-C), none of whom had sensation below the lesion, were included in the study. Selective stimulation of muscle or cutaneous nociceptors was produced by bolus injection of hypertonic (5%) saline into the tibialis anterior muscle or overlying skin and compared with non-noxious electrical stimulation of the abdominal wall. Cutaneous vasoconstrictor (photoelectric plethysmography) and sudomotor (skin conductance) responses, in addition to respiration, heart rate and continuous arterial pressure were monitored.Electrical stimulation of the abdominal wall caused a significant increase in arterial pressure (31.8+/-6.1%). Conversely, intramuscular or subcutaneous injection of hypertonic saline caused no significant changes in blood pressure (-3.0+/-2.4%; -1.4+/-3.4%) heart rate, skin blood flow or sweat release.While hypertonic saline injected into muscle or skin induces strong pain, cutaneous vasoconstriction and sweat release in able-bodied subjects, we saw no evidence of exaggerated sympathoexcitation when these same noxious stimuli were delivered below lesion in subjects with SCI. This suggests that certain types of somatic noxious input may not trigger autonomic dysreflexia, and questions the concept that any painful stimuli originating below lesion can reliably trigger dysreflexia.

A variety of optical techniques have been developed over the years for experimental use in vascular disease, mainly for the assessment of lower limb peripheral arterial disease (PAD). Optical techniques have several advantages over more traditional experimental approaches. Photoplethysmograph (PPG) was one of the earliest methods used for this purpose; PPG satisfies many of the conditions for a non-invasive technique to estimate skin blood flow using infrared light, not only for research but also in clinical practice. PPG is a promising, safe and easy-to-use tool for diagnosis and early screening of various atherosclerotic pathologies and could be useful for regular GP-assessment or even self-monitoring of PAD at home or during individual physical exercises. This review discusses the application of PPG in the assessment of PAD.

The authors use photoelectric plethysmography to determine the external occlusion pressure for blood vessels in human tissue in vivo. Three wavelengths are employed; 950 nm (infra-red), 640 nm (red) and 583 nm (yellow). Each probe is applied in turn to one finger of each subject. Pressure is applied, using a neonatal blood pressure cuff, to the finger via the probe. This pressure is increased linearly to 20 kPa (150 mmHg) over 15 s and then decreased linearly to zero over 15 s. The pressure at which perfusion returns is obtained for four repeat measurements at each wavelength. The mean (+/-standard deviation) occlusion pressures for all 13 subjects investigated are 7.1 (+/-1.9) kPa for infra-red, 6.3 (+/-1.7) kPa for red and 5.8 (+/-1.8) kPa for yellow. The pressure is 0.79 (+/-0.83) kPa lower for red compared with infra-red (P < 0.01), 0.54 (+/-0.60) kPa lower for yellow compared with red (P < 0.002) and 1.3 (+/-1.0) kPa lower for yellow compared with infra-red (P < 0.005). The reduced penetration of shorter optical wavelengths can be used to detect the lower occlusion pressures of the smaller blood vessels nearer the skin surface.

This review summarizes research dealing with the validity of commonly used methods for measuring systemic blood pressure during exercise. Arterial blood pressures measured from within peripheral arteries exaggerate systolic blood pressures because of wave form reflection but provide representative mean and diastolic pressures of the central arterial circulation. Manual and automated sphygmomanometry are the best noninvasive indirect methods of blood pressure measurement to estimate ascending aorta systolic pressures; however, both methods significantly underestimate diastolic pressures at rest and during exercise. The error in diastolic pressure measurement increases with increasing exercise intensity. The accuracy of many indirect noninvasive devices for blood pressure measurement at rest and during exercise can be questioned because of the use of unsuitable criterion methods. Ascending aorta pressures should ideally be used as a gold standard or criterion method for blood pressure measurement during exercise and instrument/method validation. However, given the constraints of varied criterion standards and current recommendations for blood pressure measurement, the following units were found to be acceptable devices for measuring systolic blood pressure during exercise: Accutracker II, A&D TM 2421, Colin 630 (auscultation), Critikon 1165, and possibly the Paramed 9350.

An artificial neural network (ANN) was trained to classify photoelectric plethysmographic (PPG) pulse waveforms for the diagnosis of lower limb peripheral vascular disease (PVD). PPG pulses from the lower limbs, and pre- and post-exercise Doppler ultrasound ankle to brachial systolic blood pressure ratio measurements were obtained from patients referred to a vascular investigation laboratory. A single PPG pulse from the big toe of each leg was processed and normalized, and used as input data to the ANN. The ANN outputs represented the diagnostic classifications (normal, significant PVD and major PVD) and the ANN was trained with the ankle to brachial pressure indices (ABPI). The ANN structure consisted of an input layer (50 neuron units from the PPG pulse input), a single hidden layer (15 neurons) and an output layer (3 neurons for the PVD diagnoses). The back-propagation learning algorithm was used to train the ANN for 500 epochs with a PPG training set of pulses from 100 legs. Test data for network assessment comprised pulses from a further 50 legs (20 normal and 30 PVD, of which 15 were categorized as having major disease). A network sensitivity of 93% and specificity of 85% was achieved with respect to the Doppler ABPI standard, giving a diagnostic accuracy of 90%. The results of this study indicate that a neural network can be trained to distinguish between PPG pulses from normal and diseased lower limb arteries. The simplicity of PPG measurement and neural network classification holds promise for the screening of lower limb arterial PVD.

Knowledge of the mechanical properties of the small arteries is important for understanding physiological and pathophysiological conditions in the human peripheral circulation. We have recently developed a new method for the noninvasive measurement of arterial elastic properties in human fingers using photoelectric plethysmography. In this study, the pressure-volume relationship. an index for expressing arterial elasticity, was measured by this method in the finger arteries of 91 healthy subjects and 102 patients with coronary artery disease. Aging effects on the elastic properties of finger arteries were examined in healthy subjects classified into three groups: under 30. 31-49, and over 50 years of age. The pressure-volume curve shifted downward with increase in age, indicating that the elasticity of finger arteries decreased with age. Patients with 75% or greater coronary stenosis, as compared with age-matched healthy subjects, showed distinctly lower elasticity of finger arteries. As the number of diseased coronary arteries increased, the elasticity of finger arteries tended to decrease steadily. The elasticity of finger arteries decreased in coronary disease patients with hypertension much more than in those without hypertension. These results suggest that age-related changes in arterial elasticity can occur in peripheral small arteries, and that peripheral arteries in patients with coronary atherosclerosis are less elastic than those in healthy subjects.

Photoelectric plethysmography is not new, but is a simple noninvasive technique to determine erythrocyte volume and oxygen saturation. The data are immediately available, accurate, repeatable, and recordable. Methods currently used for estimating microcirculation and oxygen saturation include clinical tests such as observation of skin color, temperature changes, capillary refill, and bleeding; chemical tests such as fluorscein injection; radioactive isotopes (24Na, 131I, 99mTc, and 133Xe); and instrumental methods (both invasive and noninvasive) such as temperature and infrared thermometry, thermocouples, oxygen probes, and/or the plethysmometer. None of these methods is entirely satisfactory.

SUMMARY The transepidermal water loss (TWL), photoelectric plethysmography and reflex photometry were parallelly registered on the involved hands and forearms of psoriatics. The TWL values showed a fairly good correlation with the clinical course of the disease: they increased during the active phase and decreased after return to normal. The vascular tests did not show a strict parallelism with the clinical state. On the basis of the findings, the temporal relations between epidermal and vascular factors during the different phases of the psoriatic process are discussed. The TWL can be used to predict a relapse occurring on the area investigated but not on a distant area.

Photoelectric plethysmography was employed to record amplitude changes in pulsatile blood flow from each of the supraorbital fields during carotid compression in 75 patients scheduled for carotid angiography. Tests were performed with patients in the supine position. Transducers were held in place with interposed translucent transfer tape. Circuitry was arranged to provide an upstroke during systole with sensitivity to record pulse waves between 10 and 20 mm in height. The common carotid arteries were compressed alternately for a duration of 4 to 6 pulses. Ratios of mean pulse wave amplitudes both before and during compression on the ipsilateral (I) and contralateral (C) sides were computed. Discriminatory analysis was employed to develop a test criterion with proper weights to ratios involving I and C. Employing this test criterion 67 percent (27 of 40) patients with radiologically significant carotid obstruction and 91 percent (32 of 35) without it were correctly identified. Tests on 11 additional patients correctly identified 4 of 5 with internal carotid obstruction and 6 of 6 without it. The results suggest that alteration of supraorbital opacity pulse amplitudes during carotid compression provides a rapid non-invasive test for unilateral carotid stenosis or occlusion.

A noninvasive method for estimating the mean capillary pressure Pcap and the pre-and postcapillary resistance ratio Rv/Ra in human fingers is described. Volume change in a finger segment was detected with a transmittance-type infra-red photoelectric plethysmograph during a gradual and linear increase in occluding cuff pressure. There was an inflection point in the volume curve which would be produced by the difference in the compliance between the arterial and venous vascular bed in the segment. This transitional point was assumed to represent the complete compression of the venous vascular bed at the cuff pressure level. Thus Pcap was defined as the cuff pressure corresponding to the inflection point. Rv/Ra was calculated from the Pcap, the venous pressure Pv and the mean arterial pressure Pam. The latter two pressures, Pv and Pam, were also indirectly and simultaneously measured by the compression pressure of another cuff and by our new type of volume oscillation method, respectively. The values of Pcap and Rv/Ra were in good agreement with those reported by other investigators.

Using a photoelectric probe placed under a cuff, skin blood pressure was measured at the arm in 104 normotensive subjects and in 62 hypertensive subjects aged 20–60 years simultaneously with auscultatory measurement of arm blood pressure. The cuff was inflated to suprasystolic pressure level so that skin ischaemia was present, as evidenced by blanching. On gradual cuff release skin blood pressure was defined as the external counter pressure at which the skin began to redden, probably due to filling of capillaries and venules. A significant correlation was found between skin blood pressure and systolic respectively diastolic arm blood pressure. The skin blood pressure was found significantly higher in the hypertensive subjects than in normals (118 mm Hg, S.D. 21 compared to 86 mm Hg, S.D. 13, p < 0.01). These findings suggest that a high central blood pressure is transmitted far out in the arterial vascular system. Increasing central blood pressure gives an increasing gradient between central and periphera...

Systemic involvement and spectrum of autoantibodies were evaluated in 91 patients presenting with Raynaud's phenomenon. Decreased pulmonary diffusing capacity was observed in 23 percent, esophageal hypomotility in 14 percent and renal involvement in 5 percent of the patients, all without clinical symptoms. Arthralgia or a history of arthritis was present in 27 percent and skin abnormalities in 30 percent. Extent of systemic involvement was correlated with the severity of Raynaud's phenomenon, as measured by photoelectric plethysmography (r = 0.38; p < 0.01). In addition, both the variety of different autoantibodies in the serum of individual patients and the titer of antinuclear antibodies were positively correlated with the number of affected organ systems (r = 0.63; p < 0.01 and r = 0.65; p < 0.01, respectively). Raynaud's phenomenon is an important clinical sign of asymptomatic systemic disease. Measurements of its severity and serologic parameters are helpful in predicting the extent of systemic involvement.

Photoelectric Plethysmography (PPG) Was Used to investigate blood flow changes closeto superficial subcutaneous injection sites. As a validation procedure, the PPG response to subcutaneous injection of a known hyperemic agent, prostaglandin E, (10−5 M), was shown to correlate strongly with subcutaneous blood flow changes estimated by the established technique of133Xe washout. Changes in blood flow over the subcutaneous injection sites of insulin (Actrapid) and insulin diluent were measured by photoelectric plethysmography in six nondiabetics and in six stable and seven brittle insulin-dependent diabetics. In all subject groups, an acute increase in local blood flow was seen within 2 min of both insulin and diluent injections, probably caused by injection trauma. At diluent injection sites, this acute hyperemia faded rapidly, blood flow returning to preinjection levels within 15–20 min, and there was no further increase in blood flow in any of the subjects. Insulin injected into the nondiabetics and stable diabetics caused a pronounced increase in local blood flow, sustained for at least 60 min after injection. In the brittle diabetics, however, there was no prolonged local hyperemia, the response being significantly less than that seen in both the nondiabetics and the stable diabetics. Insulin-related hyperemia close to injection (or infusion) sites may be important in subcutaneous insulin absorption. Its near-absence in brittle diabetics may contribute to the impaired response to subcutaneous insulin characteristic of these patients.

The goal of this investigation is to develop a noninvasive technique to assess the patency of the internal carotid artery. A noncontact photoelectric plethysmograph was designed to measure intraocular blood volume pulsations. This technique is appropriate for an evaluation of carotid stenosis since the ophthalmic artery is a branch of the internal carotid. With this noncontact instrument a beam of light is passed from a photoelectric system through the pupil. Light is reflected from the retinal and choroidal vasculature and is detected by a photodetector. This instrument has been used successfully in a series of experiments with pigmented and albino rabbits. The results demonstrate that the instrument measures the light reflected from the intraocular vasculature by the following observations: 1) an occlusion of the ca-rotid artery causes a disappearance of the ocular pulse; and 2) the amplitude of the ocular pulse is smaller in the pigmented rabbit when compared with the albino rabbit. Ocular movement artifacts and low reflected signal amplitude (due to light absorption by the retinal pigment) may necessitate the use of signal analysis techniques in patient studies.

In an observer-blind, randomised cross-over trial, in 12 patients, the effects on the peripheral circulation of antihypertensive doses of atenolol, labetalol and propranolol and placebo were compared. After a placebo period of at least 4 weeks, patients were allocated at random to one of the three active drug treatments. After active treatment for at least 6 weeks and a fall in diastolic pressure (DP) to less than 90 mmHg subjects were switched to the next medication. At the end of each period, photo-electric plethysmography (PHELP) was done on all fingers of one hand cooled over 4 min in water in steps of 3 degrees C from 33 degrees to 12 degrees C, and subsequently warmed in room air (20 degrees C) for a period of 10 min. Blood flow changes during cooling were expressed as a percentage of the initial PHELP value (% PHELP). Areas under the curves, representing the % PHELP/cooling period and % PHELP/warming-up period, showed that within the temperature range normally encountered in daily life, labetalol preserved finger blood flow significantly better than propranolol and marginally better than placebo. With atenolol, finger blood flow was not significantly different from that during the three other regimens, but there were significantly fewer other side-effects. It is concluded that labetalol may be the drug of choice for hypertensive patients treated with beta-blocking agents whose peripheral arterial circulation seems inadequate at low temperatures.

In photoelectric plethysmography a distinction is made between the reflection methods. Uncertainties still exist, especially regarding the origin of the reflected signal: some investigators attach quantitative value to the amplitude of the plethysmogram. The various findings are reconsidered. Various fluids are pulsatingly pumped through an in vitro circuit. Flow, pressure and volume pulsations are measured, as is the total light intensity detected by a photoelectric plethysmograph with the small variations caused in it by the pulsations in flow. Both phase and amplitude of the resulting plethysmogram are studied and the results compared with those found in vivo at the fingers and auricles. In vitro, the variations in light reflection are in phase with the volume pulsations: this can only be ascribed to reflection by orienting erythrocytes. In vivo, however, the light reflection, like the light transmission, is in anti-phase with the volume excursions, thus eliminating the determinative effect of light reflection by orienting erythrocytes--the strong reflection from surrounding tissues completely dominates reflection from erythrocytes. Since erythrocytes also have absorptive properties, and the light reflection is in anti-phase with the volume excursions, it is concluded that this absorptivity can manifest itself over the strong reflection from surrounding tissue. In vivo, therefore, the reflection plethysmogram is, in principle, an absorption measurement. The relationship between intensity of detected light and resultant voltage may not be linear: this nonlinearity may not be neglected when amplitude changes are compared. Amplitude changes of different plethysmograms may only be compared quantitatively if there is no difference in their light-voltage relationship.

With a new oscillometric method equipped with a transmittance infrared photoelectric plethysmograph, indirect systolic, and mean arterial pressures were measured in 12 normotensive and hypertensive subjects with systolic and mean arterial pressures ranging from 55 to 163 mmHg and from 95 to 200 mmHg, respectively. The pressure values obtained by this method were compared with direct measurements of the brachial intra-arterial pressure recorded simultaneously. A fairly good correlation between the pairs of simultaneous data from these two methods were obtained.

Collateral circulation of the hand and digits was evaluated in 20 healthy male volunteers using a modified Allen's test and photoelectric plethysmography. A borderline (7-14 sec) Allen's test was present in 12.5% and 2.5% required more than 15 seconds for thenar flush. Photoplethysmography was then used to compare the relative contributions of ulnar artery flow to total arterial flow into the hand. This ratio, (ulnar/total) was termed the flow index (FI). Average FI for the first digit (thumb) was 0.59, and for the second digit (index) was 0.64. The FI difference between the first digit and that of the third, fourth and fifth digits was statistically significant (p less than 0.01). The FI difference between the second digit and the third, fourth and fifth digits was also statistically significant (p less than 0.05). These results imply that Allen's test may be misleading, indicating adequate collateral circulation when in fact collateral blood flow to the digits may be poor or nonexistent.

In 80 hands with arterial occlusive disease, systolic blood pressure at the wrist and in all fingers was measured by photoelectric plethysmography. The correlation of such pressures with angiographic evidence of organic obstruction or the development of digital ischemic signs was studied. Digital blood pressure was normal in all 184 fingers in which there was at least one obstruction-free arterial path to and through the finger. Ischemic signs developed in only one. Of 203 fingers with occlusion in vessels in or leading to both sides of the finger, a decreased pressure was seen in 173 and a normal pressure in 30. Ischemic signs were observed in 132 of 173 fingers with a decreased pressure, and in two of 30 with a normal pressure. The clinical significance of measurement of digital blood pressure in arterial occlusive disease is discussed.

Thurfyl nicotinate and methacholine reactions on the uninvolved and involved skin of patients with atopic dermatitis were investigated by reflectometry and photoelectric plethysmography. Temporal variations in response and multiple patterns were found and the significance of these findings is discussed.

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.

N-octylamine was applied to the surface of the volar forearm of 20 volunteers at environmental temperatures, of 35°, 65°, 95°, and 115° F. The amine was dissolved in ethylene glycol to make solutions of 10, 25, and 50%. These solutions were applied in droplets of 30µg, and the vasodilatory effect as the end-point of skin penetration was measured by photoelectric plethysmography. The rate of penetration increased with temperature and concentration. N-octylamine induced wheal formation and erythema, and the increase in cutaneous blood flow was found to be mainly in area of the wheal. It was proposed that the effect of temperature on penetration involved epidermal factors.

A new technique, photoelectric plethysmography, was used to measure heart rate of the chick embryos with a minimum of environmental disturbances. Progressive increase in the daily average heart rate (218 to 276 beats per minute) was observed from the third to the fifteenth day of incubation. By 18 days of age the heart rate decreased to 263. The embryonic movement was detected on the fourth day of incubation and increased throughout the incubation period. Embryonic movement disappeared after phenobarbital injection. Injection of epinephrine to 16-day old embryos raised the heart rate from 264 to 420 beats per minute. Vasopressin depressed embryonic heart rate.

SummaryPhotoelectric plethysmographs for the fingers and toes are described which use electrocardiographs for the recording and which have definite advantages in routine clinical observations on th...

Zur photoelektrischen Registrierung von Hautvolumpulsen an den Gliedmasen bietet die Verwendung reflektierten Lichtes nachHertzman Vorteile gegenuber der bekannteren Hautdurchleuchtung. Sie beruhen hauptsachlich auf der besseren Lichtausnutzung durch das Reflexverfahren und auf der Moglichkeit, plane Hautstellen zu untersuchen. Es wird ein zur diagnostischen Untersuchung von Hautvolumpulsen bei arteriellen Durchblutungsstorungen entwickeltes und erprobtes Gerat beschrieben. Seine Empfindlichkeit kann gepruft und auf einen Standardwert eingestellt werden. So bleiben die registrierten Pulsamplituden unabhangig von Empfindlichkeitsanderungen des Gerats. Prufung und Anwendung werden unter Angabe von Storungsquellen mit Kurvenbeispielen erlautert.

VARIATIONS in the blood content of the female breast are of special interest be-cause the vascularity of this part may be influenced physiologically (by pu- V berty, the menstrual or ovulatory cycle, pregnancy, lactation, menopause) either by or with relation to the sex hormones. Breast pathology (engorgement, mastitis, tumors) also produces distinct circulatory changes. Several investigators have reported the use of photoelectric cells for the detection of changes in the blood content of tissues. Hertzjman (1) reported “the development of photoelectric plethysmographs which lend themselves to clinical use in dynamic anal-ysis of the peripheral circulation and which may be 'plugged in in place of the patient's leads on the electrocardiograph.” The photoelectric plethysmograph used by us (fig. 1, 2) was adapted from various arrangements described by Hertziman (2). The breast is illuminated by a 2.5 volt 500 milliampere (radio panel) bulb, powered, by 4 dry cells (6 volts).

The clinical application of photoelectric plethysmography is described. Its use in following vascular reactions, such as the spastic phenomena of Raynaud's disease, or in evaluating the completeness of sympathetic denervation of the skin, is indicated by selected examples. Its use in estimating the arterial blood supply of the skin of various areas is illustrated on a normal subject, on a patient after sympathectomy, and after treatment with intermittent venous occlusion and iontophoresis in a case of intermittent claudication.

Background: Changes describing digital and forearm circulation after radial artery harvest have been reported infrequently. Methods: This prospective study examined digital perfusion and forearm collateral circulation preoperatively and postoperatively in patients who underwent coronary artery bypass grafting with radial artery free grafts. Noninvasive evaluation was conducted with digital photoelectric plethysmography and color flow and pulsed Doppler studies. Results: Thumb perfusion index decreased from 1.25 to 0.84 (30%, P

More information regarding the nature of the damage caused by radiation to the vascular bed of the skin in humans would obviously be desirable. The task is made very difficult by ethical considerations so atraumatic, non-invasive methods which might yield useful data should be investigated. Only very few procedures are currently available which can be used repeatedly without discomfort to the patients. Apart from visual observation of the severity of the skin reaction most non-invasive methods are based on reflectance photometry—either in the d.c. or a.c. modes—and measure changes in skin blood volume (Challoner and Ramsay, 1974). Changes in skin blood volume pulse (BVP) following irradiation have not, to my knowledge, been reported. Photoelectric plethysmography has been used successfully to investigate vascular abnormalities such as those found in Raynaud's disorders (Chucker et al., 1973), changes in skin blood pressure before and after treatment of hypertensive subjects (Gyntelberg et al., 1974), and ...

Prior to cannulation of the dorsalis pedis artery the collateral circulation through the plantar arch should be examined to evaluate the consequence of an occlusion of this artery. We selected the photoelectric plethysmography

Advantage has been taken of the fact that the opacity of tissues to light varies with the blood content, to record photoelectrically the changes in the blood content of the nasal septum.The arrangement used (shown schematically in Fig. 1) is essentially an adaptation of the photoelectric plethysmograph for the finger, previously reported.1 Illumination of the septum is provided by a small ophthalmoscope bulb inserted in one nares. Local heating is largely prevented by a heavy metal cap which, placed over the bulb, conducts the heat away to the lamp carrier. Local heating may be practically eliminated by using a mirror arrangement which permits the light source to be placed some distance from the nares. The latter method of providing illumination has the additional advantage of offering opportunity to control amplification, independent of septal luminosity, through predetermined decrements in light intensity by means of suitable filters. The light transmitted by the septum is reflected out the other nares ...

Diastolic pressure Pd was indirectly measured by vibrating a finger artery with a 10 Hz sinusoidal pressure variation during a gradual increase (or decrease) in occlusive cuff pressure Pc. Pulsatile arterial volume changes on which sinusoidal variations are superimposed were detected by a transmitted infra-red photoelectric plethysmograph (TIPP). It is known that volume change in an artery shows a maximum amplitude at the transmural pressure Pt level equal to 0 mm Hg due to the nonlinear viscoelastic properties of the arterial wall. For the same reason, the amplitude of the sinusoidal volume variation reached its maximum at the end-diastolic phase, when Pc was controlled to be exactly equal to Pd. The indirect Pd values determined from Pc were compared with those simultaneously measured by a direct method in rabbit forelegs and by the volume-compensation method in human fingers. Using the principle of the volume oscillometric method systolic and mean pressures were also determined by this system.

Two new types of non-invasive method for measuring arterial blood pressure recently developed by us are reviewed. Both of the methods are based on the characteristics of the pressure-volume relationship in the artery. One is the volume-oscillometric method; and the other is the volume-compensation method, based on the vascular unloading principle. Both methods employ photoelectric plethysmography for detection of arterial volume changes in the biological segment. The volume-oscillometric method can measure systolic and mean arterial pressure, and is applicable to long-term ambulatory monitoring. The volume-compensation method allows the beat-by-beat measurement of systolic and diastolic pressure and the recording of the pressure waveform continously and non-invasively. This paper discusses the measurement principle and evaluates the accuracy of each method as compared with direct measurements. Preliminary descriptions of newly designed instruments based on these two methods, and a few examples of the indirect pressure recordings, are also described. The results obtained show that the non-invasive methods for measuring arterial pressure presented here appear promising for use not only in physiological studies, but also in clinical practice and research laboratories.

Systolic blood pressure at various levels of the leg was measured in 80 normal subjects by photoelectric plethysmography with a blood pressure cuff. Due to the higher pressure value at the thigh, calf, ankle, and foot and lower pressure value at the toe, the pressure gradient between each proximal site and the toe was significantly higher in the older (50-82) than in the younger age group (17-49). Therefore, normal values were determined separately in these two groups. In 64 limbs of 42 patients with arterial occlusive disease, a comparison between segmental blood pressure and arteriographic findings was made. Segmental blood pressure may be a rough indicator of the severity of arterial occlusion present and may refrect the status of the major conduits of the leg. An abnormal ankle-toe pressure gradient was found in only 52 per cent of limbs, although all 64 limbs had undergone an occlusive process distal to the ankle. In limbs with significantly low ankle blood pressure due to proximal lesions, less frequency and severity of an abnormal ankle-toe pressure gradient were seen than in limbs with normal ankle blood pressure. When pressure gradients between two different levels are used in clinical work, the blood pressure at the more proximal level should be always considered.

Photoelectric plethysmography has already been used for a very long time to monitor the circulation during anaesthesia, because it is a non-invasive method which can be applied easily and rapidly. Because of the accessibility during anaesthesia it is almost exclusively applied to the skin of the fingers, toes or ears. During the past few years much more knowledge has been acquired about the background of the method and in this paper we intend to present a review of our research with this method in approximately 500 patients. In particular the difference between the plethysmograms recorded from finger and earshell will be discussed. The review is preceded by an explanation of the basic principles.

During a period of 11 months 45 amputations, 31 below-knee and 14 above-knee, were performed in 42 patients with gangrene of the lower extremity. A newly introduced standardized photoelectric technique for measurement of local skin perfusion pressure (SPP) was used preoperatively and the result used in selection of the proper amputation level. An overall healing rate of 89 per cent was found. 69 per cent of the amputations were performed below-knee. The healing rates for individual SPP-levels were identical to those obtained with the cumbersome isotope washout technique. The standardized photoelectric technique is simple, rapid and causes the patient only negligible discomfort, allowing repeated measurements on different levels of the leg.