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At least 883 records · Page 49Linked to original sources
PubMed1992

ECG gated radionuclide plethysmography--a method for the assessment of pulmonary systolic blood volume increase.

During cardiac systole the stroke volume of blood which is ejected from the right ventricle increases the pulmonary blood volume. This systolic pulmonary blood volume increase is measured by using ECG gated chest scintigrams obtained with 99Tcm-labelled red blood cells. The total radiation counts in a region of interest that includes either the right or the left lung increases during systole. On the average, the increase of the total pulmonary systolic radiation was found to be 62% of the systolic radiation decrease in the left ventricle region of interest. The discrepancy between the value of the systolic pulmonary blood volume increase and that of stroke volume is attributed to blood flow from the lungs into the left atrium during the cardiac systole period.

Adult↗
PubMed1988

Repeatability of peripheral pulse measurements on ears, fingers and toes using photoelectric plethysmography.

Peripheral pulses have been recorded and analysed to determine the accuracy with which pulse transit times (PTTs) can be measured. Measurements of PTT between the ECG Q-wave and various peripheral sites were made in 10 normal subjects on 10 separate days. Mean values were determined for the ears (174 ms), fingers (245 ms), and toes (361 ms). The technique was sufficiently accurate to detect small changes in PTT due to changes in posture; sitting to lying, 5.2 ms. When comparing simultaneous measurements on bilateral sites only small differences in PTT were discovered, and these were not significant in the study group as a whole. However, these differences were significant in some individuals. When the subjects raised a single arm or leg, significant differences (38 ms and 49 ms respectively) were recorded between sides. The day-to-day repeatability sigma (expressed as the square root of the within-subject mean square variance) of individual PTT measurements on a subject (supine) was for ears, fingers and toes respectively 9.4, 9.2 and 12 ms. For right-left differences the repeatability was 7.2, 5.9 and 14 ms. Hence changes in PTTs, or differences between right and left sides, can be detected from single measurements with 95% confidence if they exceed approximately 20 ms in ears or fingers and 30 ms in toes.

Adult↗
PubMed1993

Development of a neural network screening aid for diagnosing lower limb peripheral vascular disease from photoelectric plethysmography pulse waveforms.

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.

Humans↗
PubMed2007

Body-composition assessment in infancy: air-displacement plethysmography compared with a reference 4-compartment model.

BACKGROUND: A better understanding of the associations of early infant nutrition and growth with adult health requires accurate assessment of body composition in infancy. OBJECTIVE: This study evaluated the performance of an infant-sized air-displacement plethysmograph (PEA POD Infant Body Composition System) for the measurement of body composition in infants. DESIGN: Healthy infants (n = 49; age: 1.7-23.0 wk; weight: 2.7-7.1 kg) were examined with the PEA POD system. Reference values for percentage body fat (%BF) were obtained from a 4-compartment (4-C) body-composition model, which was based on measurements of total body water, bone mineral content, and total body potassium. RESULTS: Mean (+/- SD) reproducibility of %BF values obtained with the PEA POD system was 0.4 +/- 1.3%. Mean %BF obtained with the PEA POD system (16.9 +/- 6.5%) did not differ significantly from that obtained with the 4-C model (16.3 +/- 7.2%), and the regression between %BF for the 4-C model and that for the PEA POD system (R2 = 0.73, SEE = 3.7%BF) did not deviate significantly from the line of identity (y = x). CONCLUSIONS: The PEA POD system provided a reliable, accurate, and immediate assessment of %BF in infants. Because of its ease of use, good precision, minimum safety concerns, and bedside accessibility, the PEA POD system is highly suitable for monitoring changes in body composition during infant growth in both the research and clinical settings.

Absorptiometry, Photon↗
PubMed2002

Evaluating the relationship between arterial blood pressure changes and indices of pulse oximetric plethysmography.

UNLABELLED: The finger plethysmographic waveform of pulse oximeters is a qualitative indicator of fingertip perfusion. This waveform has been used to assess the depth of anesthesia. Its cyclical changes associated with mechanical ventilation have also been used to detect changes in blood volume under normotensive conditions and has revealed that minimal normotensive hypovolemia can cause a significant increase in the delta-down component of this waveform. Hypovolemia may be associated with hypotension; the latter may be due to causes other than hypovolemia. Because the effects of the hypotension on plethysmographic waveform have not been evaluated, it may be difficult to detect hypovolemia in these conditions by inspecting a plethysmogram. Therefore, we performed this study to evaluate the effect of normovolemic hypotension on characteristics of plethysmographic waveform in 33 adult patients undergoing general anesthesia with controlled hypotension. The delta-down and ventilatory systolic variation components were increased significantly with decreases in systolic blood pressure. The result of this study shows that the effect of pharmacologic hypotension on the plethysmographic waveform of pulse oximeter is similar to that of minimal hypovolemia. Therefore, blood volume may be inaccurately assessed by the inspection of ventilatory-induced cyclical changes of pulse oximetric waveform in the presence of hypotension. IMPLICATIONS: The cyclical respiratory-induced changes in the amplitude of the pulse oximeter waveform can be used to detect normotensive hypovolemia. This study shows that hypotension produces the same effect. Therefore, in hypotensive conditions, we cannot determine the presence of hypovolemia.

Adult↗
PubMed1990

Breathing patterns in lambs after oleic acid lung injury utilizing respiratory inductive plethysmography.

We measured breathing patterns utilizing a respiratory inductive plethysmograph (RIP) in seven healthy nonsedated lambs after an iv infusion of oleic acid (50 mg/kg) to induce acute pulmonary edema. Our single position graphic (SPG) calibration technique was employed for gain factor calculation. Accuracy was validated by the simultaneous volume measurement of RIP and integrated pneumotachography (PNT). Of a total 840 validation breaths, 467 (56%) were within 5% of PNT, 734 (87%) were within 10%, and 834 (99.9%) were within 20%. In each study baseline physiologic and breathing pattern data were collected and also at 15, 30, 60, 90, 150, and 210 min postoleic acid infusion. Validation of RIP accuracy before each data collection revealed 29% required new gain factor calculation. Recalibration was done within 5 min. Excluding respiratory frequency, which remained at 30% above baseline, variables were not significantly different than baseline measurements at the 210-min interval. Results suggest that calibration of RIP using our SPG technique is a time-efficient method and that RIP can accurately measure breathing patterns, providing an additional tool for assessment of experimental lung injury in lambs.

Animals↗
PubMedDate not supplied

Comparative trial of indapamide and hydrochlorothiazide in essential hypertension, with forearm plethysmography.

Seventeen patients (11 males) 34-66 years in age with uncomplicated essential hypertension completed a randomized, placebo-controlled, double-blind cross-over study comparing indapamide (IND) 2.5 mg q am with hydrochlorothiazide (HCT) 50 mg q am. The lead-in placebo period of 2 months was followed by two active drug phases of 3 months' duration separated by a 2-month placebo-washout period. The mean standing systolic/diastolic pressures (+/- SD) during placebo were 150 +/- 18/98 +/- 6 mm Hg. The pressures were 137 +/- 16/90 +/- 7 IND and 137 +/- 17/91 +/- 7 mm Hg on HCT. Thus the drugs produced similar systolic, diastolic, and mean arterial pressures. Orthostatic changes in mean pressure and heart rate were similar with the two drugs. Both drugs decreased serum potassium (-14.3% with IND and -13.7% with HCT), and increased serum uric acid (+26.7% with IND and +25.7% with HCT), and cholesterol (+11.7% with IND and +11.1% with HCT) equally. Forearm blood flow (FBF) and venous compliance (FVC) were measured by a plethysmographic technique in six of the patients. FBF during placebo of 3.53 +/- 0.58 ml/min/100 ml forearm volume was increased to 4.01 +/- 0.74 ml/min during IND and decreased to 3.40 +/- 1.16 ml/min on HCT, but our sample size did not permit detection of significant differences. FVC was not altered from baseline by the drugs. No side effects attributable to either of the two drugs were elicited. We conclude that IND did not differ from HCT in its effect on blood pressure, heart rate, venous compliance, or biochemistry. A possible peripheral arteriolar vasodilator effect on IND should be investigated further.

Adult↗
PubMed1978

Doppler ultrasound and digital plethysmography to determine the need for sympathetic blockade after frostbite.

Thirty patients seen following frostbite injury during a 2-week period were treated with rapid rewarming in a saline bath. Vascular laboratory evaluations including digital plethysmograms and Doppler ultrasound mapping of digital vessels and distal palmar and pedal arches revealed three general degrees of vascular response to cold injury after rewarming. The most common, the hyperdynamic response, implying patent digital vessels, was often clinically apparent, with warm, red digits. Regional sympathectomy may be troublesome in these patients. Patients without a hyperdynamic response, including those whose Doppler and plethysmographic examinations were within normal limits for noncold exposed individuals, had evidence of vascular compromise at the digital level and benefited from regional sympathectomy with intra-arterial reserpine.

Doppler Effect↗