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PubMed1987

[Validity of plethysmography and the digital temperature recovery test in the diagnosis of primary and occupational Raynaud's phenomenon].

Of 405 patients with Raynaud's phenomenon seen for clinical investigation, including 210 with vibration-induced white fingers, 365 were evaluated with sequential determination of digital temperature recovery time after cold exposure, and plethysmography after cold provocation. The results of this objective testing were compared with the results of the clinical evaluation in an attempt to check the former's usefulness as a tool to prove the diagnosis of the vasospastic condition and to assess its degree of impairment. The sensitivity of digital recovery time and plethysmography was, respectively, 56.5% and 80.5% in the primary Raynaud's phenomenon, 48.7% and 67.8% in the secondary Raynaud's phenomenon, and 49.1% and 69.7% in the vibration syndromes. The specificity of these tests was 79.6% and 67.7% for the secondary Raynaud's phenomenon, and 71.4% and 36.8% for the vibration syndrome. When digital recovery time and plethysmography are used together, the sensitivity is increased to 78.8% for the vibration-induced white fingers and 85.5% for the primary Raynaud's phenomenon. Objective evidence of Raynaud's phenomenon can be obtained by provocative digital recovery time and plethysmography, especially if the two tests are considered together, but their response was too unpredictable to assess accurately the degree of severity and the degree of impairment caused by the vasospastic disease. Nevertheless, they remain a useful and necessary adjunct to the clinical evaluation, particularly when dealing with occupational Raynaud's phenomenon.

Adult↗
PubMed1986

Calibration of respiratory inductive plethysmography in spontaneously breathing lambs and piglets.

Respiratory inductive plethysmography is a method of assessing breathing pattern without an airway connection. We employ a single position graphic calibration technique for gain factor calculation. Nineteen studies were completed in piglets and 20 studies were completed in lambs. The single position graphic technique utilizes selection of two breaths from a 20 s run of breaths with different ribcage/pneumotachograph and abdomen/pneumotachograph ratios for gain calculation. Validation of gains was performed by comparing volumes obtained simultaneously by respiratory inductive plethysmography and pneumotachography. Total study time ranged between 15 and 30 min. Results suggest that the single position graphic calibration technique provides time-efficient and accurate calibration of respiratory inductive plethysmography in the spontaneously breathing, sedated lamb and piglet, allowing respiratory inductive plethysmography to become an additional tool for ventilatory parameter measurement.

Animals↗
PubMedDate not supplied

A new interpretive method for impedance plethysmography.

Clinical experience revealed that Wheeler's interpretative method for impedance plethysmography studies resulted in a large number of false negative and borderline interpretations, so a new interpretative method was created using additional impedance plethysmography parameters. This study was performed to compare this new method with Wheeler's method in 21 patients with suspected deep venous thrombosis. The accuracy of each method was determined by comparing the impedance plethysmography interpretations with venography. The patients were divided into groups according to venogram results of no thrombosis, and tibial (calf) venous thrombosis. Nine of the 21 patients had no thrombosis on venogram. Wheeler's method and the new method both resulted in 56% true-negative interpretations. Twelve of the 21 patients had proximal deep venous thrombosis and/or tibial venous thrombosis on venogram. Wheeler's method resulted in 8% true-positive interpretations and 17% false-negative interpretations. Of the patients in the study, 62% had borderline interpretations. The new method resulted in 75% true-positive interpretations and no false-negatives. The new method decreased the borderline interpretations to 33%. By calculating a basal impedance difference between the patient's two legs, the new method did provide guidelines that could identify patients with borderline interpretations who would require additional testing. The new impedance plethysmography interpretative method did lower the number of borderline and false-negative interpretations, and it provided guidelines to identify patients with borderline interpretations who need further testing.

Algorithms↗
PubMedDate not supplied

[Comparative study of plethysmography and spirometry in asthmatic children].

The aim of the study was to evaluate the results of plethysmography in comparison to spirometry. A retrospective study of pulmonary function tests was performed in 50 asthmatic children, 6 to 15 years old, free of acute symptoms. Mild airway obstruction was found in 8 spirometries, while the other 42 were found within normal limits. In the plethysmography, obstruction was found in 27 cases, 23 without abnormalities in resistance or specific conductance. Eleven cases suggested pulmonary air trapping and/or hyperinflation. Airway obstruction was evident in 54% of plethysmographies. The difference between both studies was significant, also as well as the airway obstruction and intensity of the clinical disease. We therefore conclude that the plethysmography shows more alteration in their parameters than spirometry for the detection or suggestion of airway obstruction in asthmatic children during asymptomatic periods.

Adolescent↗
PubMed1988

Failure of impedance plethysmography to follow exercise-induced changes in limb blood flow.

1. The blood flow in the forearm and the calf of six healthy volunteers was measured at rest and after exercise by impedance plethysmography using pulsatile (QZp) and venous occlusion (QZocc) methods, and by venous occlusion strain gauge plethysmography (Qsg). 2. At rest, the impedance QZp method gave values slightly higher than those of Qsg. In the forearm, the ratio QZp to Qsg was 1.26 in the supine position and 1.97 in the upright sitting position. For the calf muscle, the ratios were 1.08 in the supine position and 1.23 in the upright position. 3. Immediately after exercise, Qsg increased from resting values of approximately 2-4 ml min-1 100 ml-1 to mean values of 16-25 ml min-1 100 ml-1 in upright and supine arm or leg exercise. In contrast, the QZp values after exercise increased to only 3.1-4.6 ml min-1 100 ml-1. QZocc likewise failed to show increases in flow except in the supine leg exercise, where flow increased to 8.7 ml min-1 100 ml-1. 4. In an additional subject, it was shown that electrode position had no significant effect on the QZp blood flow measurement after exercise. 5. The failure of QZp to accurately follow the change in Qsg with exercise was probably due in part to pulsatile venous outflow. In addition, changes in microvessel packed cell volume and shear rate may influence the observed QZp. It is concluded that impedance plethysmography is not valid for estimation of limb blood flow during reactive hyperaemia after exercise.

Adult↗
PubMed1988

Measurement of tidal volume during high frequency ventilation by impedance plethysmography.

Electrical impedance plethysmography was evaluated in lambs as a method of measuring tidal volume (VT). Over tidal volumes ranging from 15 to 414% of estimated dead space, and frequencies of 300 to 1000 breaths/min, correlation between VT measured by the impedance technique and VT measured by whole-body plethysmography was 0.98. Above 600 breaths/min, the correlation between the two methods was 0.94. Independent calibration of the impedance technique using a pneumotachograph at conventional rates of ventilation yielded absolute values of VT which closely corresponded to values obtained with the whole-body plethysmograph (slope = 1.05, intercept = 1.4 ml, r = 0.99). These results support the potential utility of impedance plethysmography in clinical applications of high frequency ventilation.

Animals↗
PubMed1992

Plethysmography. A treatise on its evolution, differential methodology and clinical utilization. 1973.

Plethysmography is the observation and use of volume changes in physiologic entities. The most influential short-term effect is caused by the pulsatile flow of blood. Attempts to convert these pulsatile volume changes into minimum required blood flow per unit of time have been successful clinically. Plethysmography can be accomplished by encapsulating digits, limbs and entire bodies. Volume changes in the member cause volume changes in the fixed chamber which then influences an observational medium. Plethysmography can also be accomplished with a strain gauge, direct application of electricity to flesh, changing opacity effects on tissue, ultrasound (the Doppler effect) or the piezoelectric method. The piezoelectric plethysmograph was successfully tested on 55 patients.

Blood Circulation↗
PubMed2001

Determination of skeletal muscle perfusion using arterial spin labeling NMRI: validation by comparison with venous occlusion plethysmography.

T(1)-based determination of perfusion was performed with the high temporal and spatial resolution that monitoring of exercise physiology requires. As no data were available on the validation of this approach in human muscles, T(1)-based NMRI of perfusion was compared to standard strain-gauge venous occlusion plethysmography performed simultaneously within a 4 T magnet. Two different situations were investigated in 21 healthy young volunteers: 1) a 5-min ischemia of the leg, or 2) a 2-3 min ischemic exercise consisting of a plantar flexion on an amagnetic ergometer. Leg perfusion was monitored over 5-15 min of the recovery phase, after the air-cuff arterial occlusion had been released. The interesting features of the sequence were the use of a saturation-recovery module for the introduction of a T(1) modulation and of single-shot spin echo for imaging. Spatial resolution was 1.7 x 2.0 mm and temporal resolution was 2 s. For data analysis, ROIs were traced on different muscles and perfusion was calculated from the differences in muscle signal intensity in successive images. To allow comparison with the global measurement of perfusion by plethysmography, the T(1)-based NMR measurements in exercising muscles were rescaled to the leg cross-section. The perfusion measurements obtained by plethysmography and NMRI were in close agreement with a correlation coefficient between 0.87 and 0.92. This indicates that pulsed arterial techniques provide determination of muscle perfusion not only with superior spatial and temporal resolution but also with exactitude.

Adult↗
PubMed1984

Impedance plethysmography in the diagnosis of arterial and venous disease.

The objective of this paper is to review the theoretical basis and clinical application of electrical impedance plethysmography in the noninvasive evaluation of peripheral arterial and venous disease. Theoretical, experimental and clinical studies have now demonstrated a direct relationship between electrical impedance changes and limb volume changes. Potential sources of error have also been identified. This has led to the development of clinical tests based on impedance plethysmography for the detection of peripheral arterial disease, venous insufficiency and venous outflow obstruction. Impedance plethysmography, using the method of venous occlusion, is presently the most commonly employed noninvasive method for the detection of deep venous thrombosis.

Blood Volume↗
PubMed1999

Assessment of endothelium-mediated vasodilation of the peripheral circulation by transcutaneous ultrasonography and venous occlusion plethysmography.

Transcutaneous ultrasonography is a non-invasive technique with the ability to measure the volumetric blood flow of the peripheral circulation. Peripheral blood flow can be determined by high-resolution imaging of vessel diameter coupled with Doppler assessment of flow velocity. This method, however, has not been validated in vivo. Accordingly, brachial artery flow in response to intraarterial infusion of vasodilators was assessed by ultrasonography in 16 healthy subjects and compared to values obtained simultaneously by venous occlusion plethysmography. Blood flow calculated from ultrasound-derived vessel diameter and flow velocity was found to highly correlate with plethysmographic flow, with r values ranging from 0.83 to 0.99. Using this ultrasound technique combined with plethysmography, the response of conduit and resistance vessels to endothelium-mediated vasodilation was characterized. Doppler velocity rose dramatically with endothelium-dependent acetylcholine (970%), but only modestly with endothelium-independent vasodilators, nitroglycerin (292%) and nitroprusside (340%). Despite eliciting the greatest overall forearm flow response, acetylcholine resulted in a smaller increase in conduit diameter (15.4%) than nitroglycerin (21.8%), and only a comparable change than nitroprusside (14.6%). Taken together, these results suggest that acetylcholine acts predominantly on resistance vessels, whereas nitrovasodilators affect mainly conduit vessels. In summary, transcutaneous ultrasonography can be used reliably to assess flow changes in the peripheral circulation. Combined with plethysmography, this technique is useful for determining the relative contribution of conduit and resistance vessels to peripheral flow, particularly in the assessment of endothelium-mediated vasodilation.

Adult↗
PubMed1985

Limitation of impedance plethysmography in assessing efficacy of dihydroergotamine-heparin prophylaxis of deep vein thrombosis.

The sensitivity of impedance plethysmography (IPG) for diagnosing deep vein thrombosis was evaluated in the presence of dihydroergotamine, an agent with significant venoconstrictor activity. In a prospective, randomized, controlled clinical trial, 105 patients undergoing total hip replacement surgery were investigated to evaluate the thromboprophylactic efficacy of DHE-Heparin using IPG and 125I-Fibrinogen Leg Scanning to monitor the incidence of DVT. Retrospective analysis of the IPG data indicated that DHE-Heparin impaired the sensitivity of impedance plethysmography by decreasing venous capacitance and venous outflow. Although the patient sample size was relatively small, the results showed trends which suggested that the utility of impedance plethysmography for diagnosing DVT was limited in the presence of a vasoactive agent. Alternate noninvasive diagnostic methods may need to be considered in select patients receiving concomitant medications possessing venoconstrictor activity.

Blood Circulation↗
PubMed1993

Strain gauge plethysmography for the detection of deep venous thrombosis.

Deep venous thrombosis is a widely recognized medical problem which results in significant morbidity and mortality. Venography is the current 'gold standard' diagnostic test for deep venous thrombosis; however it is costly, invasive and is unnecessarily performed in 50% of cases. This paper describes a self-contained, non-invasive system for automatic venous occlusion plethysmographic measurement and analysis. An examination of 274 symptomatic limbs was conducted using strain gauge plethysmography and a subsequent venographic examination was then performed. The plethysmographic results were then compared with venography so as to develop a means of discrimination for thrombotic and non-thrombotic limbs. Strain gauge plethysmography using the Belfast DVT Screener yielded a sensitivity of 100% and a sensitivity of 66.3% for proximal segment DVT. The efficacy of the discriminatory algorithm was then tested for the diagnosis of DVT in a further 101 symptomatic patients. A sensitivity of 94.7% and a specificity of 81.7% were observed for strain gauge plethysmography for proximal segment thrombosis in this patient group. The Belfast DVT Screener is highly sensitive for deep venous thrombosis and may be used to reduce the need for venography, which is of benefit to both the patient and clinician.

Adult↗
PubMed2001

Comparison of endothelial function evaluated by strain gauge plethysmography and brachial artery ultrasound.

Strain gauge plethysmography and brachial artery ultrasound are widely used to study endothelial function. No data on correlation between these two procedures are reported. The present study compared these two methods and investigated the correlation between vasodilation and brachial wall shear stress. In six healthy subjects and ten patients with hypertension or obesity, strain gauge plethysmography was performed in resting conditions and after infusion of 7.5,15 and 30 microg/min of acetylcholine, and brachial artery ultrasound in resting conditions and after 5 min hand ischemia. Wall shear stress was calculated as: blood viscosity x blood velocity/internal diameter. Forearm blood flow following acetylcholine infusion increased more in healthy subjects than in patients with hypertension or obesity. In addition, brachial artery dilated more in the former group. Change in brachial artery diameter correlated with change in forearm blood flow, calculated as area under the curve of acetylcholine infusion (r=0.739, P<0.001). Wall shear stress was higher in healthy subjects (67.8+/-20.0 dynes/cm(2)) than in patients with either hypertension or obesity (39.2+/-16.7, P<0.001), and correlated with variations of diameter (r=0.796, P<0.0002), and marginally of blood flow (r=0.516, P<0.05). The present findings demonstrate that there is a high correlation between endothelial function evaluated by strain gauge plethysmography and brachial artery ultrasound. Wall shear stress correlates with brachial artery diameter change following hand ischemia, and marginally with blood flow change following acetylcholine infusion.

Acetylcholine↗
PubMed1998

The signal in total-body plethysmography: errors due to adiabatic-isothermic difference.

Total-body plethysmography is a technique often employed in comparative physiology studies because it avoids excessive handling of the animals. The pressure signal obtained is generated by an increase in internal energy of the gas phase of the system. Currently, this increase in internal energy is ascribed to heating (and water vapour saturation) of the inspired gas. The standard equation for computing tidal-volume implies that only temperature and saturation differences can be responsible for generating the ventilation signal. In this study, we were able to demonstrate that the difference between the external process of the thoracic expansion, which is adiabatic, and the internal process of it, which is isothermic, is an important factor of internal energy change in the total-body plethysmography method. In other words, organic tissues transfer heat to the entering gas but also to the present gas, in a way that keeps internal expansion an isothermic process. This extra amount of energy was never taken into account before. Therefore, experiments using such a technique to measure tidal-volume should be done using isothermic chambers. Moreover, due to uncertainties of the complementary measurements (ambient and lung temperatures, ambient water vapour saturation) needed to compute tidal-volume using total-body plethysmography, a minimal temperature difference about 15 degrees C between body and ambient should exist to keep uncertainties in tidal-volume values below 5%. However, this limit is not absolute, because it varies as a function of humidity and degree of uncertainty of the complementary measurements.

Algorithms↗
PubMed1982

[Transthoracic electrical impedance plethysmography and thermodilution: comparative evaluation of two methods for cardiac output measurement in man].

The measurement of cardiac output by electrical impedance plethysmography (non invasive technic) seems to be attractive but is still the subject of a certain number of critics. The authors have tried to compare it with a method which validity is well documented, the thermodilution. By these two methods, 87 measures of cardiac output have been performed in 14 hospitalized patients in intensive care, attained of various affections but exempts of cardiac or pulmonary lesions and in stable hemodynamic state. The stroke volume measured by electrical impedance plethysmography is calculated using Kubicek's formula: SV = Q (L2/Zo2) (dz/dt min) t. Results were as follows: absence of significative difference between the coefficients of variation of each series of measures (coefficient of mean variation, 5,6 +/- 3,4 p. cent for impedance and 3,8 +/- 3,2 p. cent for thermodilution); absence of significative difference between the mean values of cardiac output (7,59 +/- 2,69 l . min-1 for impedance and 7,72 +/- 1,99 l . min-1 for thermodilution); highly significant correlation between values for cardiac output obtained for each of these two methods )r = 0,804; n = 87; p less than 0,001). The authors conclude that in patients in intensive care whose pulmonary or cardiovascular system is not in critical situation, the electrical impedance plethysmography appear as a secure method for cardiac output measurement. However its generalisation still require other works.

Adolescent↗
PubMed2003

Simultaneous measurement of instantaneous heart rate and chest wall plethysmography in short-term, metronome guided heart rate variability studies: suitability for assessment of autonomic dysfunction.

Instantaneous heart rate and chest wall motion were measured using a 3-lead ECG and an air pressure chest wall plethysmography system. Chest wall plethysmography traces were found to accurately represent the breathing pattern as measured by spirometry (average correlation coefficient 0.944); though no attempt was made to calibrate plethysmography voltage output to tidal volume. Simultaneous measurements of heart rate and chest wall motion were made for short periods under metronome guided breathing at 6 breaths per minute. The average peak to trough heart rate change per breath cycle (AVEMAX) and maximum correlation between heart rate and breathing cycle (HRBRCORR) were measured. Studies of 44 normal volunteers indicated clear inverse correlation of heart rate variability parameters with age (AVEMAX R = -0.502, P < 0.001) but no significant change in HRBRCORR with age (R = -0.115). Comparison of normal volunteers with diabetics with no history of symptoms associated with autonomic failure indicated significant lower heart rate variability in diabetics (P = 0.005 for AVEMAX) and significantly worse correlation between heart rate and breathing (P < 0.001 for HRBRCORR). Simultaneous measurement of heart rate and breathing offers the possibility of more sensitive diagnosis of autonomic failure in a simple bedside test and gives further insight into the nature of cardio-ventilatory coupling.

Adult↗
PubMed1993

Skeletal muscle blood flow in heart failure measured by ultrafast computed tomography: validation by comparison with plethysmography.

OBJECTIVES: Abnormalities of skeletal muscle perfusion and metabolism may be important in the symptomatic limitation of patients with chronic heart failure. A method for assessing both skeletal muscle blood flow and mass would be useful in clinical practice and research. Ultrafast computed tomography has the potential to make these measurements. The aim was to determine the accuracy with which skeletal muscle blood flow could be measured by ultrafast computed tomography in patients with chronic heart failure. METHODS: Leg blood flow measured by venous occlusion plethysmography was compared with skeletal muscle blood flow by ultrafast computed tomography. Fourteen patients with chronic heart failure (aged 51 to 76 years) were investigated. Plethysmography and ultrafast computed tomography measurements were performed at rest and during hyperaemic flow induced by symptom limited bicycle exercise followed by five minutes of leg ischaemia. The ultrafast computed tomography measurements were made by analysing the opacification of the blood pool and of the muscle after an intravenous bolus of non-ionic radio-opaque contrast. RESULTS: Flows assessed by plethysmography ranged from 1.5 to 38.1 ml x 100 ml-1 x min-1. The slope of the line relating the two methods was 1.1 (95% confidence interval 0.91 to 1.31), and the mean (95% limits of agreement) of the differences between the two methods was 2.5(10.6) ml x 100 ml-1 x min-1. CONCLUSIONS: Ultrafast computed tomography is a useful tool in the measurement of both skeletal muscle mass and perfusion in humans.

Aged↗
PubMed1999

Partitioning of respiratory mechanical impedance by absolute and differential body plethysmography.

We have recently demonstrated the feasibility of partitioning total respiratory impedance (Zrs) into its airway (Zaw) and tissular (Zti) components by measuring alveolar gas compression (Vpl) plethysmographically during pressure oscillations at the airway opening (Peslin et al.). The aim of this study was to comparatively evaluate an alternative approach: the measurement of Zrs and of the transfer function (FTF) between airway flow and body surface flow obtained by absolute body plethysmography. The two approaches are theoretically equivalent, provided thermal and other artifacts are properly eliminated. Zrs and Vpl (method 1) and Zrs and FTF (method 2) were measured in 11 healthy subjects from 4 to 29 Hz, using a pressure-type and a flow-type plethysmograph, respectively. Inspired gas was conditioned to body temperature and pressure, saturated with water vapor in both instances to minimize thermal factors. Zaw and Zti spectra computed from both sets of data were quite similar in shape. Neither airway resistance nor tissue compliance differed significantly; tissue resistance, however, was about 14% lower with method 1, which may be due to imperfect gas conditioning. The reproducibility of the data was similar with the two approaches. We conclude that absolute body plethysmography is as reliable as differential body plethysmography to partition Zrs.

Adult↗