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PubMed2005

Air-displacement plethysmography: here to stay.

PURPOSE OF REVIEW: Air-displacement plethysmography holds promise as an alternative to more traditional body composition techniques, although our understanding of air-displacement plethysmography is less than complete. Specifically, factors that influence its validity and application in certain populations, for example children, the obese, and athletes, must be better understood. This review will summarize recent findings on the validity and precision of air-displacement plethysmography and will focus primarily on papers published since 2004, with particular attention on its use in infants. RECENT FINDINGS: The most significant recent findings in the air-displacement plethysmography literature are mechanistic in nature specifically dealing with measurement issues such as heat, moisture, clothing, and recently, inter-device variability. SUMMARY: It is important to recognize that air-displacement plethysmography can be a practical instrument in the evaluation of body composition in a wide range of populations. Therefore, based on the body of literature that has emerged, air-displacement plethysmography appears to be a suitable and reliable instrument in the assessment of body composition. Of particular interest is its use in pediatric and obese individuals, areas requiring further study. Research is also needed to help us better understand sources of measurement error.

Adipose Tissue↗

PubMed1995

Pressure sensor plethysmography: a method for assessment of respiratory motion in children.

Noncalibrated respiratory inductance plethysmography has been used to measure respiratory function by calculation of the phase angle and, more recently, by determination of the ratio of each time to reach peak tidal expiratory flow to total expiratory time (TPEF/TE). Since TPEF/TE is known to be decreased in airway obstruction when derived from flow signals obtained by a pneumotachograph, we wanted to develop an alternative method to measure rib cage and abdominal respiratory movements. For this purpose, we used two pressure sensors attached to the skin above the umbilicus and in the right medioclavicular line at the fourth intercostal space: "pressure sensor plethysmography". We tested the ability of this method to assess thoracoabdominal asynchrony and TPEF/TE by comparison with respiratory inductance plethysmographic and pneumotachographic measurements in 30 children, aged 1-12 yrs, with airway obstruction. The mean difference (95% confidence interval (95% CI)) between phase angles obtained by respiratory inductance plethysmography and pressure sensor plethysmography was only -5.8 degrees (range -18.0 to +6.4 degrees). Similarly, all methods used to measure TPEF/TE agreed well: mean differences (95% CI) between pneumotachographic and respiratory inductance plethysmographic, pneumotachographic and pressure sensor plethysmographic, and respiratory inductance plethysmographic and pressure sensor plethysmographic measurements of TPEF/TE were +0.01 (range -0.05 to +0.06), -0.03 (-0.09 to +0.03) and -0.03 (-0.10 to +0.04), respectively. We conclude that pressure sensor plethysmography is a simple and noninvasive method, and suitable to measure thoracoabdominal asynchrony and TPEF/TE ratios as well as respiratory inductance plethysmography and pneumotachography.

Abdomen↗

PubMed1985

Diagnostic efficacy of impedance plethysmography for clinically suspected deep-vein thrombosis. A randomized trial.

Impedance plethysmography is an accurate noninvasive method to test for proximal vein thrombosis, but it is insensitive to calf-vein thrombi. We randomly assigned patients on referral with clinically suspected deep-vein thrombosis and normal impedance plethysmographic findings to either serial impedance plethysmography alone or combined impedance plethysmography and leg scanning (which has been shown to be essentially as sensitive as venography) and compared the long-term outcomes. During the initial surveillance, deep-vein thrombosis was detected in 6 of 311 patients (1.9%) tested by serial impedance plethysmography alone and in 30 of 323 patients (9.3%) (most with calf-vein thrombi) tested by the combined approach (p less than 0.001). During long-term follow-up, no patient died from pulmonary embolism; but 6 patients (1.9%; 95% confidence limits, 0.7% to 4.2%) tested by serial impedance plethysmography developed deep-vein thrombosis compared with 7 patients (2.2%; 95% confidence limits, 0.9% to 4.4%) tested by the combined approach. Serial impedance plethysmography used alone is an effective strategy to evaluate such symptomatic patients.

Adult↗

PubMed1989

Calibration of respiratory inductive plethysmography during quiet and active sleep in lambs.

Respiratory inductive plethysmography provides a noninvasive method of measuring breathing patterns. Calibration of respiratory inductive plethysmography requires calculation of gain factors for ribcage and abdomen transducers utilizing 2 breathing patterns with different ribcage and abdomen contributions and tidal volume measured by either spirometry or integrated pneumotachography. The purpose of this study was to determine if respiratory inductive plethysmography can be calibrated to provide accurate measurements during quiet and active sleep in lambs. We used a least squares linear regression calibration technique with breaths selected from quiet sleep and active sleep to calculate gain factors in 6 tracheostomized lambs. Validation of gain factors was performed by comparing tidal volumes obtained simultaneously by respiratory inductive plethysmography and pneumotachography during quiet sleep and active sleep. Tidal volume differences between respiratory inductive plethysmography and pneumotachography on validation runs of 15 consecutive breaths each revealed 90% of validation breaths within +/- 20% during quiet sleep and 82% of validation breaths within +/- 20% during active sleep. These data provide evidence that respiratory inductive plethysmography can be calibrated to allow breathing pattern measurement during sleep.

Animals↗

PubMed1998

How reproducible is bilateral forearm plethysmography?

AIMS: In studies using strain-gauge forearm plethysmography to measure changes in forearm blood flow (FBF) during intra-arterial infusions of vasoactive substances, measurements are often made in both arms simultaneously and the change in ratio of the infused and control arms used to express responses. However, the reproducibility of bilateral plethysmography in this setting has not been addressed in published studies. The unilateral technique remains in use, and forearm vascular resistance (FVR), an alternative method of expressing responses, is used by some investigators. We have assessed: (a) the intra-subject variability of bilateral FBF measurements (FBF ratios) at rest, after unilateral forearm exercise, and during intra-arterial infusions of vasoconstrictor substances; (b) whether bilateral plethysmography is more reproducible than unilateral plethysmography; and (c) the reproducibility of FVR (unilateral and bilateral). METHODS: Study 1 Nine healthy subjects attended 3 study days, 1 week apart. FBF was measured at rest and after 2 min of standardized unilateral forearm exercise; between-day intra-subject variability was expressed as coefficients of variation (CV) calculated using two-way analysis of variance (ANOVA). Study 2 Five healthy subjects attended 2 study days when FBF was measured during incremental infusions of noradrenaline (15, 30, 150, 300 pmol min[-1]) and angiotensin II (1, 5, 10, 50 pmol min[-1]); for each individual subject at each dose intra-subject variability was assessed using the difference between responses (percentage change from baseline) on days 1 and 2. RESULTS: Study 1 At rest, intra-subject variability (CV) of baseline FBF ratios was 19% compared with 31% (left) and 39% (right) for unilateral FBF measurements. After ipsilateral exercise, unilateral FBF measurements were more reproducible (32 vs 17%) than FBF ratios; by 20 min after exercise, the previous pattern had been re-established (19 vs 27%). Intra-subject variability (CV) of baseline FVR ratio and post-exercise FVR was 14%. Study 2 Inter-quartile ranges of the differences between responses on days 1 and 2 (FBF ratios vs FBF) were: angiotensin II 14 vs 18%; noradrenaline 16 vs 27%. CONCLUSIONS: FBF ratios are more reproducible than unilateral FBF measurements at rest (CV 19% vs 39%) and for measuring responses to intra-arterial infusions of vasoconstrictor substances. FVR may have a small reproducibility advantage. Non-experimental stimuli can cause significant and misleading changes in measured responses if unilateral measurements are used; it is therefore recommended that responses to intra-arterial infusions should be measured using bilateral forearm plethysmography with the results expressed as FBF ratios.

Angiotensin II↗

PubMed2000

Computerized strain-gauge plethysmography - An alternative method for the detection of lower limb deep venous thrombosis?

AIM: To test the ability of computerized strain-gauge plethysmography to act as a screening test for lower limb deep venous thrombosis (DVT). MATERIALS AND METHODS: Over an 8-month period, all patients referred to our Medical Assessment Unit with suspected lower limb DVT were considered for inclusion in the study. Each patient underwent both plethysmography and ascending venography within 24 h, and the presence or absence of thrombus in the popliteal, superficial femoral or iliac veins was noted. The results of the two tests were then used to determine the accuracy of computerized strain-gauge plethysmography in detecting above knee DVT. RESULTS: The screening tests and venograms of 239 patients referred with clinically suspected lower limb DVT were compared. The false negative rate of plethysmography was 15.4%, which is significantly different from the 4.8% claimed by the manufacturers of this device (P = 0.00003). CONCLUSIONS: In a population of acute admissions with suspected lower limb DVT, computerized strain-gauge plethysmography is not suitable for use as a screening test due to an unacceptably high proportion of false negative screens.

Diagnosis, Computer-Assisted↗

PubMed1993

A comparison of real-time compression ultrasonography with impedance plethysmography for the diagnosis of deep-vein thrombosis in symptomatic outpatients.

BACKGROUND: Impedance plethysmography performed serially over a one-week period has been shown to be an effective diagnostic strategy for patients with clinically suspected acute deep-vein thrombosis. Compression ultrasonography has a high sensitivity and specificity for the detection of proximal-vein thrombosis. The clinical value of repeated ultrasonography in the management of symptomatic deep-vein thrombosis is unknown. METHODS: We conducted a randomized trial in 985 consecutive outpatients with clinically suspected deep-vein thrombosis to compare the diagnostic value of serial impedance plethysmography (494 patients) and serial compression ultrasonography (491 patients). We compared the positive predictive values of both tests for the diagnosis of venous thrombosis, using contrast venography as a reference. The frequencies of venous thromboembolism during a six-month follow-up period were also compared in patients with repeatedly normal results in order to evaluate the safety of withholding anticoagulant therapy from such patients. RESULTS: The positive predictive value of an abnormal ultrasonogram was 94 percent (95 percent confidence interval, 87 to 98 percent), whereas the predictive value of impedance plethysmography was 83 percent (95 percent confidence interval, 75 to 90 percent) (P = 0.02). In patients with repeatedly normal results, the incidence of venous thromboembolism during the six-month follow-up period was 1.5 percent (95 percent confidence interval, 0.5 to 3.3 percent) for serial compression ultrasonography, as compared with 2.5 percent (95 percent confidence interval, 1.2 to 4.6 percent) for serial impedance plethysmography. CONCLUSIONS: In making the diagnosis of deep-vein thrombosis in symptomatic outpatients, serial compression ultrasonography is preferable to impedance plethysmography, in view of its superior performance in detecting venous thrombosis.

Adolescent↗

PubMed2000

Whole body air displacement plethysmography compared with hydrodensitometry for body composition analysis.

AIMS: To assess the acceptability and feasibility of whole body air displacement plethysmography in children and to determine its precision and agreement with hydrodensitometry, an appropriate reference method. METHODS: Age specific two component model equations were used to predict fat mass from body density in 22 children aged 8-12 years and in 10 adults for comparison of methods. Precision for each method was established from duplicate measurements. RESULTS: Plethysmography was accepted more readily than hydrodensitometry (100% v 69% provided duplicate measurements). Precision for fat mass in children was 0.38 kg by plethysmography and 0.68 kg by hydrodensitometry, and results were similar in adults. The mean (SD) fat mass in children was 6.9 kg (4.0) and 6.7 kg (4. 2) by plethysmography and hydrodensitometry, respectively, but 95% limits of agreement between methods were large (-4.1 kg to 3.5 kg fat). CONCLUSION: Plethysmography was more readily accepted and had better precision than hydrodensitometry. It also provided similar body composition results for the group but not for all individual children.

Adipose Tissue↗

PubMed1988

Lower-extremity venous thrombosis: comparison of venography, impedance plethysmography, and intravenous manometry.

This study was undertaken to compare impedance plethysmography with lower-extremity venography and venous manometry in the diagnosis of acute deep venous thrombosis (DVT) of the lower extremity. Ninety-six extremities were studied. In this population, in which the prevalence of acute DVT was 43.8%, plethysmography had a sensitivity of 86.8% and a specificity of 72.0%. The predictive value of abnormal findings at plethysmography was 70.2%, and the predictive value of normal findings at plethysmography was 87.8%. Venous manometry was performed successfully in 89 extremities. A statistically significant difference was shown in the mean intravenous pressure between patients with and without acute DVT. However, there was considerable overlap between the two populations, limiting the predictive value of impedance plethysmography in any given patient.

Adult↗

PubMed2001

From Belfast to Mayo and beyond: the use and future of plethysmography to study blood flow in human limbs.

Venous occlusion plethysmography is a simple but elegant technique that has contributed to almost every major area of vascular biology in humans. The general principles of plethysmography were appreciated by the late 1800s, and the application of these principles to measure limb blood flow occurred in the early 1900s. Plethysmography has been instrumental in studying the role of the autonomic nervous system in regulating limb blood flow in humans and important in studying the vasodilator responses to exercise, reactive hyperemia, body heating, and mental stress. It has also been the technique of choice to study how human blood vessels respond to a variety of exogenously administered vasodilators and vasoconstrictors, especially those that act on various autonomic and adrenergic receptors. In recent years, plethysmography has been exploited to study the role of the vascular endothelium in health and disease. Venous occlusion plethysmography is likely to continue to play an important role as investigators seek to understand the physiological significance of newly identified vasoactive factors and how genetic polymorphisms affect the cardiovascular system in humans.

Cardiovascular Diseases↗

PubMed2000

Optoelectronic plethysmography in intensive care patients.

We used optoelectronic plethysmography to study 11 normal subjects during quiet and deep breathing, six sedated and paralyzed patients with acute lung injury and acute respiratory distress syndrome (ALI/ARDS) receiving continuous positive pressure ventilation (CPPV) (positive end-expiratory pressure [PEEP] = 10 cm H(2)O, tidal volume [VT] = 300, 600, 900 ml), and seven ALI/ARDS patients receiving pressure support ventilation (PSV) (PEEP 10 cm H(2)O, pressure support = 5, 10, 15, 25 cm H(2)O). The volumes measured using optoelectronic plethysmography were compared with measurements taken using spirometry and pneumotachography. The three methods were highly correlated. The discrepancies found were 1.7 +/- 5.9%, -1.6 +/- 5.4%, and 4.9 +/- 6.4% when comparing optoelectronic plethysmography with spirometry, optoelectronic plethysmography with pneumotachography, and spirometry with pneumotachography, respectively. Accuracy of the compartmentalization procedure (upper thorax, lower thorax, and abdomen) was assessed by calculating compartmental volume changes during isovolume maneuvers. The discrepancy from the ideal zero line was -2.1 +/- 48.3 ml. Abdominal contribution to inspired volume was greater for normal subjects than for PSV patients (63 +/- 11% versus 43 +/- 14%, p < 0.001). It decreased with VT for normal subjects (48.5 +/- 15%, p < 0.05), whereas it increased for CPPV patients (61 +/- 10%, p < 0.05). No significant distribution differences were found between 5 and 25 cm H(2)O PSV. We conclude that optoelectronic plethysmography is a feasible technique able to provide unique data on the distribution of chest wall volume changes in intensive care patients.

Adult↗

PubMed1988

Diagnosis of femoropopliteal venous thrombosis: comparison of duplex sonography and plethysmography.

Duplex sonography and impedance plethysmography were correlated with contrast venography to compare the sensitivity, specificity, and accuracy of the two noninvasive techniques for the diagnosis of femoropopliteal venous thrombosis. Sensitivity, specificity, and accuracy of duplex sonography were 90%, 100%, and 97%, respectively, when compared with venography in 32 patients. Sensitivity, specificity, and accuracy of plethysmography were 100%, 63%, and 72%, respectively, when compared with venography in 25 patients. In 21 patients, plethysmography was either nondiagnostic or could not be done because of clinical difficulties. Eighteen of these patients had diagnostic duplex examinations. Duplex sonography exhibits similar sensitivity but higher specificity than plethysmography. Duplex sonography also permits diagnostic examinations in patients in whom diagnostic plethysmography cannot be performed.

Adult↗

PubMed2006

Diaphragm ultrasonography as an alternative to whole-body plethysmography in pulmonary function testing.

OBJECTIVE: Whole-body plethysmography is a common method of measuring pulmonary function. Although this technique provides a sensitive measure of pulmonary function, it can be problematic and unsuitable in some patients. The development of more accessible techniques would be beneficial. METHODS: A prospective study was performed to validate diaphragm ultrasonography as an alternative to whole-body plethysmography in patients referred for pulmonary function testing. Diaphragm movement and position were assessed by ultrasonography after standard pulmonary function testing using whole-body plethysmography. RESULTS: A wide range of lung function was observed. Standard lung volumes were as follows: total lung capacity, 5.57 +/- 1.31 L, residual volume, 2.27 +/- 0.56 L; and vital capacity, 3.30 +/- 0.98 L (mean +/- SD). The ratio of forced expiratory volume in 1 second to forced vital capacity was calculated as 0.69 +/- 0.08. Ultrasonography showed that mean diaphragm excursion values were 11.1 +/- 3.8 mm (2-dimensional), 14.7 +/- 4.1 mm during quiet breathing (M-mode), and 14.8 +/- 3.9 mm during a maximal sniff (M-mode). The velocity of diaphragm movement rose sharply during the sniff maneuver from 15.2 +/- 5.8 mm/s during quiet breathing to 104.0 +/- 33.4 mm/s. Static 2-dimensional measures of diaphragm position at the end of quiet inspiration or expiration correlated with standard measures of lung volume on plethysmography (eg, a correlation coefficient of 0.83 was obtained with end inspiration and vital capacity). All measures of diaphragm movement (whether by 2-dimensional or M-mode techniques) were poorly correlated with any lung volumes measured. CONCLUSIONS: These data suggest that dynamic measurements using diaphragm ultrasonography provide a relatively poor measure of pulmonary function in relation to whole-body plethysmography.

Adrenergic beta-Agonists↗

PubMed1988

Utility of impedance plethysmography in the diagnosis of recurrent deep-vein thrombosis.

Serial impedance plethysmography has been shown to be a safe and effective alternative to venography in the management of patients with clinically suspected acute venous thrombosis. The rate of normalization of an initial abnormal impedance plethysmogram and, consequently, the usefulness of impedance plethysmography in the management of patients with recurrent symptoms is, however, unknown. In a prospective cohort follow-up study, 161 consecutive patients with proved venous thrombosis and abnormal impedance plethysmograms were studied for one year. After 3, 6, 9, and 12 months, the impedance plethysmograms had normalized in 67%, 85%, 92%, and 95% of the patients, respectively. Thirty-five patients (22%) returned with clinically suspected recurrent thrombosis, of whom 31 had normal impedance plethysmograms prior to their return. In 18 of these patients, repeated tests were normal; these patients did not undergo anticoagulant therapy, and follow-up disclosed no subsequent adverse consequences. In the other 13 patients, the test again became abnormal; 11 patients were shown by venograms to have recurrent deep-vein thrombosis. Consequently, 29 (83%) of the 35 patients in whom the suspicion of recurrent thrombosis arose could have been managed with impedance plethysmography alone without the necessity for venography or anticoagulant therapy. It is concluded that normalization of impedance plethysmography tests occurs in almost all patients within nine months, and that serial impedance plethysmography is useful for patient management in nearly 90% of patients presenting with recurrent symptoms.

Acute Disease↗

PubMed1986

Comparison of Doppler and strain-gauge plethysmography to detect vasculogenic impotence.

Doppler penile-pressure determinations to diagnose vasculogenic impotence require an experienced technician, can be time-consuming, yield inconsistent results and require much penile manipulation. Therefore the authors assessed and compared strain-gauge plethysmography as an alternative noninvasive procedure. Sixty-one patients with erectile failure had penile blood pressure determined by Doppler and indium-gallium alloy in Silastic strain-gauge plethysmography. Penile brachial indices were calculated. Strain-gauge results agreed with the Doppler measurements in all but three patients whose indices were found to be normal by Doppler and borderline by strain-gauge plethysmography. The sensitivity, accuracy and specificity of strain-gauge plethysmography were 93%, 95% and 100% respectively. Doppler determinations required an average of 20 minutes to perform, strain-gauge measurements only 4. The authors conclude from this study that strain-gauge plethysmography is a rapid, reliable, accurate method of determining penile blood pressures.

Blood Pressure↗

PubMed1987

[Variations in venous physiology in the healthy subject. Postural and venous occlusion plethysmography studies].

The principal characteristic of the venous network is its distensibility, the reason for its role as blood reservoir and cardiovascular adaptation system. This distensibility varies continuously as a function of venous tone, of neurocardiovascular adaptation and of the method used for its determination. The importance of variability of venous physiology was investigated by postural and venous occlusion plethysmography. Two series of tests were performed in 3 healthy volunteers, each being treated over one month: one series involved 19 determinations during May 1985, the other 14 determinations in December 1985. Two plethysmographic methods were employed: conventional venous occlusion plethysmography in decubitus with compression of 50 mm Hg and postural plethysmography with venous occlusion only, using gravity force during variations in position of subjects. Venous filling, a function of venous distensibility, varied between 16.7 and 17.8% during venous occlusion and 23.9 and 31.7% during postural plethysmography. Emptying half-life was from 20.7 to 40.7%. Emptying rate was, by the 6th second, 17.3 to 21.6% for venous occlusion and 27.3 to 32.3% for postural plethysmography. A relation was not found between results for the two methods, suggesting that they explore different phenomena. Variability of venous physiology parameters is marked, modulations being due to general or local factors, the former acting on both legs simultaneously: exterior temperature, neurocardiovascular physiology, digestion, stress, relaxation. Factors can have their effects reduced by differential study of the two limbs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗

PubMed1982

Diagnosis of deep vein thrombosis by combination of Doppler ultrasound flow examination and strain gauge plethysmography. An alternative to venography only in particular conditions despite improved accuracy of the Doppler method.

Doppler ultrasound flow examination, strain gauge plethysmography and contrast venography were performed in 160 lower limbs of 80 in-patients. Deep vein thrombosis (DVT) was suspected in 87 limbs. Using measurement of venous stop-flow pressure, the Doppler method hae an overall sensitivity of 83%. By combined use of Doppler and Plethysmography, sensitivity was increased to 96%. Specificity was 62% and 51%, respectively. With a positive and a negative predictive value of 80% and 73%, respectively, the combination of both non-invasive method cannot reliably replace venography in the diagnosis of DTV, although all (40/40) thromboses proximal to or involving the popliteal segment were detected by either Doppler and Plethysmography or both. After exclusion of 14 patients (18%) suffering from conditions known to alter the results of these non-invasive methods, the positive predictive value of abnormal findings in both Doppler and Plethysmography was increased to 94% for suspected limbs, whilst negative predictive value of both negative Doppler and Plethysmography was 90%, allowing the avoidance of venography in these patients.

Adolescent↗

PubMed1993

Venous assessment using air plethysmography: a comparison with clinical examination, ambulatory venous pressure measurement and duplex scanning.

Air plethysmography was compared with clinical assessment, ambulatory venous pressure measurement and duplex ultrasonography in 103 unselected limbs with venous disease and ten normal control limbs without such disease. Measurements of venous function obtained by air plethysmography showed considerable overlap between groups of limbs classified on the basis of clinical condition or by the presence of popliteal incompetence detected by duplex scanning. The measurement of venous refilling time using air plethysmography correlated poorly with that obtained by venous cannulation (rs = 0.58). The residual volume fraction did not correlate with ambulatory venous pressure measurement (rs = 0.04). Air plethysmography was not found to be as useful as previously reported. The residual volume fraction should not be accepted as a substitute for ambulatory venous pressure measurement, which remains the 'gold standard' test of venous function.

Blood Pressure Determination↗