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PubMed1997

Relationship between venous pressure and tissue volume during venous congestion plethysmography in man.

1. Venous congestion strain-gauge plethysmography enables the non-invasive assessment of arterial blood flow, fluid filtration capacity (Kf), venous pressure (Pv) and isovolumetric venous pressure (Pvi) in man. One of the major assumptions of this technique, that cuff pressure (Pcuff) applied to the limb equals Pv at the level of the strain gauge, was tested in this study. 2. In nine healthy male volunteers (mean age, 29.3 +/- 1.2 years) the saphenous vein was cannulated with an 18-gauge catheter proximal to the medial malleolus. The subjects were supine and Pv was continuously measured during the application of small step (8-10 mmHg) increases in congestion Pcuff (up to 70 mmHg). Pcuff, changes in limb circumference and Pv were recorded by computer for off-line analysis. Since the determination of Kf is influenced by the changes in plasma oncotic pressure, venous blood samples were obtained at the start of the study, when Pcuff was raised to 30 mmHg and again to 65 mmHg and 4 min after deflation of the cuff. 3. The relationship between Pv and Pcuff was linear over the range of 10-70 mmHg (n = 9, 69 measurements, slope 0.91, r = 0.97, P << 0.001). The non-invasively measured calf Pv, based on the intercept of the relationship between the vascular compliance component (Va) and Pcuff, was 8.0 +/- 0.4 mmHg, which was not significantly different from the corrected invasively measured Pv value of 8.8 +/- 0.3 mmHg (P = 0.08). 4. Venous blood lactate and haemoglobin concentrations, as well as colloid osmotic pressure, total protein and albumin concentrations were unchanged throughout the protocol, whereas significant decreases in PO2 and blood glucose concentration were observed when Pcuff reached 65 mmHg. Assuming a constant oxygen consumption, this may suggest a reduction in tissue perfusion. 5. This study demonstrates the close correlation between Pcuff and Pv in the saphenous vein. Since the small congestion Pcuff step protocol does not cause significant increase in plasma oncotic pressure, we conclude that Pv, as well as Kf, can be accurately determined with this venous congestion plethysmography protocol.

Adult↗
PubMed1988

Total lung capacity measured by body plethysmography and by the helium dilution method. A comparative study in different patient groups.

The helium dilution method is known to underestimate the total lung capacity (TLC) in patients with poorly or non-ventilated areas in the lungs. The standard plethysmographic method has been reported to overestimate TLC in patients with severe airway obstruction. To determine the magnitude of the difference between the two methods, a comparison was made in different patient groups. In a group of patients with normal lung function tests (n = 20) there was a small but significant average difference in TLC between plethysmography and the helium dilution method, the larger values being obtained with the latter. In patient groups with moderately obstructed airways (n = 23), severely obstructed airways (n = 20), or emphysema (n = 19), there were no significant average differences, although in two patients in the emphysema group the plethysmographic values were considerably larger than those obtained by helium dilution. We conclude that the gas dilution methods and plethysmography with a pressure-compensated volume displacement plethysmograph gave estimates of TLC which agreed even in patients with airway obstruction or emphysema, except in patients with very severe lung disease.

Emphysema↗
PubMed2005

A methodological study of computerized venous strain-gauge plethysmography of the upper extremities.

This study was performed to assess the efficiency of computerized strain-gauge plethysmography for evaluation of venous volume (VV) and outflow capacity of the upper extremities and to receive reference values. For this purpose, we investigated 34 healthy controls; 16 males and 18 females with a mean age of 45 years (range 31-58 years). These results were compared with those obtained in 32 patients with earlier spontaneous deep venous thrombosis (DVT) in the upper extremities. In the control group, there was no difference between right and left arm and none of the variables were influenced by age and gender. Venous volume and rate of venous emptying (VE) were significantly lower in arms with earlier DVT than in those without (VV: DVT arms 3.7+/-0.96 ml 100ml-1 and controls 4.6+/-0.81 ml 100 ml-1; VE: DVT arms 79+/-24 ml 100 ml-1 min-1 and controls 110+/-21 ml 100 ml-1 min-1). Repeated measurements had a coefficient of variation of approximately 10% in both groups. We found the device easy to handle and the results demonstrates that this is a useful method to study venous function in upper extremities. This implicates that computerized strain-gauge plethysmography is an efficient method both for clinical diagnostic routine and research studies of circulatory changes in acute and chronic DVT in the upper extremity.

Adult↗
PubMed1991

Forearm blood flow response to posture change in the very old: non-invasive measurement by venous occlusion plethysmography.

Little is known about the peripheral vascular response to posture change in very elderly people who are vulnerable to the development of orthostatic hypotension. This is due, in part, to the risks of currently utilized invasive vascular monitoring techniques in the elderly population. We studied the forearm vascular response to active standing in 18 healthy young, 10 healthy old, and 19 impaired elderly subjects, using the non-invasive technique of venous occlusion plethysmography. In six subjects this technique was compared to duplex doppler ultrasonography for the measurement of postural changes in forearm blood flow. Forearm blood flow changes determined by venous occlusion plethysmography were 11% larger than doppler measurements, but the two methods strongly correlated (r = 0.90, P less than .001). Mean forearm vascular resistance increased to a significantly greater extent at 1 minute of standing in young subjects than in both groups of old, although the response was quite variable in all groups. Two healthy elderly (20%) and eight impaired elderly (40%) subjects had unexpected forearm vasodilatation at 1 minute of standing. By 3 minutes, forearm vascular resistance had increased by similar amounts in all three groups of subjects. Five impaired elderly and no healthy young or healthy old subjects had orthostatic hypotension, defined as greater than or equal to 10 mm Hg decline in mean arterial blood pressure at 1 or 3 minutes of standing. Forearm vascular resistance changes did not correlate with blood pressure response to standing. Thus, forearm vascular response to 1 minute of active standing is attenuated in many elderly subjects. This abnormality may impair adaptation to orthostatic stress in advanced age.

Adult↗
PubMed2001

Ambulatory abdominal inductance plethysmography: towards objective assessment of abdominal distension in irritable bowel syndrome.

BACKGROUND: Abdominal distension is one of the cardinal features of irritable bowel syndrome (IBS) with patients often ranking it as more intrusive than their pain or bowel dysfunction. If this symptom could be quantified accurately and reliably it would provide, for the first time, an objective way of assessing this disorder. Using the principle of inductance plethysmography we have developed a microprocessor based system capable of recording even minimal changes in girth over 24 hours and we describe its validation and establish normal ranges. METHODS: Twenty four hour recordings were made in 20 healthy female volunteers (aged 23-58 years) to assess changes in abdominal girth with respect to time, posture, meals, and sleep. Normal daily activity was encouraged and meals were standardised. The feeling of abdominal distension was also assessed using a visual analogue scale. FINDINGS: Measurement of abdominal girth using abdominal inductance plethysmography (AIP) at a static point in time showed a close relationship with that measured using a tape measure (rho=0.8910, p<0.001). Furthermore, girth was significantly greater both in the sitting and standing postures compared with lying (p<0.01). Measurement over a 24 hour period showed that girth was significantly greater at the end compared with the beginning of the day, and ingestion of a standard meal also increased its value (p<0.05). Sleep was associated with a reduction in girth (p<0.05). CONCLUSIONS: AIP promises to add an objective dimension to the assessment of IBS which could prove invaluable in clinical trials. Furthermore, it should aid research into the pathogenesis of this symptom for which no satisfactory explanation has yet emerged.

Abdomen↗
PubMed1981

Noninvasive ventilatory monitoring by respiratory inductive plethysmography in conscious sheep.

The respiratory inductive plethysmograph is a noninvasive device that has been used to measure tidal volume (VT) in humans from changes in self-inductance of wire coils excited by an oscillator circuit placed about the rib cage and abdomen. We investigated its accuracy in conscious sheep utilizing a new calibration procedure during quiet breathing and breathing associated with bronchospasm provoked by aerosolized carbachol. Seven sheep were intubated with a nasotracheal tube and an esophageal balloon placed for determination of transpulmonary pressure. Base-line mean pulmonary flow resistance (RL) in the sheep was 1.5 +/- 0.7 (SD) cmH2O X l-1 X s. After carbachol inhalation, mean RL increased to a maximum of 8.8 +/- 2.8 cmH2O X l-1 X s (P less than 0.002). AT base line, mean VT estimated by respiratory inductive plethysmography over a 20-s period fell within +/- 6% of spirometry. After carbachol VT in five of the sheep remained close to the initial validation, but in two, it deviated +/- 11% from spirometry. Analysis of the continuous recording of timing and volume components of the breaths revealed that bronchoprovocation did not significantly alter mean VT or frequency. However, there was a slight increase in both parameters resulting in an increase in minute ventilation from 7.6 +/- 2.4 to 9.6 +/- 2.8 l/min (P less than 0.02). Similarly, a slight decline in inspiratory time coupled with the slight rise in VT produced an increase in mean respiratory flow from a base-line value of 0.35 +/- 0.12 to 0.44 +/- 0.17 l/s (P less than 0.05). These results indicate that the respiratory inductive plethysmography accurately monitors breathing pattern in conscious sheep even during severe bronchospasm.

Animals↗
PubMed1982

Demonstration of failure of body plethysmography in airway obstruction.

To demonstrate the role of extrathoracic airways in the overestimation of lung volumes by body plethysmography in airway obstruction, we induced in six normal subjects an artificial airway stenosis by inflating a balloon in the lower trachea. We measured thoracic gas volume in a body plethysmograph simultaneously from mouth pressure (Pm) vs. plethysmographic volume (Vbox) (TGVm) and from esophageal pressure (Pes) vs. Vbox (TGVes). During control measurements there was no difference between TGVm and TGVes (P greater than 0.1) in any subject. Balloon inflation (B) resulted in a significant (P less than 0.01) decrease of specific airway conductance (sGaw) from a mean value of 0.199 +/- 0.66 (SD) to 0.025 +/- 0.01 cmH2O-1 . s-1. TGVm significantly (P less than 0.02) exceeded TGVes in every subject (mean diff 1.24 +/- 0.56 liters) and Pm lagged behind Pes. In two subjects studied at different levels of airway obstruction we found a significant (P less than 0.05) correlation between TGVm-TGVes difference and sGaw. Bypassing the extrathoracic airways by a cuffed endotracheal tube resulted in each case in a degree of airway obstruction comparable to that during balloon inflation (sGaw 0.019 +/- 0.004 cmH2O-1 . s-1), but no difference between TGVm and TGVes (P greater than 0.1). We conclude that lung volume is overestimated by plethysmography in airway obstruction. The overestimation is due to the presence of a compliant extrathoracic airway, and it probably depends on both the degree of airway obstruction and the value of compliance of the extrathoracic airway.

Adult↗
PubMed1988

What does inductance plethysmography really measure?

Inasmuch as it has been claimed that inductance plethysmography can measure cross-sectional area changes, we tested this assumption. We present experimental and computed relationships between self-inductance (L) of coils and areas (A) included inside for a coil with a well-defined side wavy pattern (triangular or sinusoidal) and for a real belt (Respitrace) placed on elliptical or rectangular configurations. The results are applied to the physiological field using measurements obtained from a computed tomography experiment. We demonstrate that the L-A relationships vary not only with shape or ellipticity of the cross section but also with the wavy pattern shape. This last parameter is critical because it is difficult to actually control. When the coil wavy pattern remains steady, there are some physiological situations where inductance plethysmography can more accurately estimate area changes: when the configuration shape is constant, the correspondence between delta L and delta A is almost linear with a shape-dependent sensitivity; when the configuration is nearly circular (ellipticity in the range 0.8-1), the relative error in delta A estimation is less than 5%.

Humans↗
PubMed1995

Beat-by-beat forearm blood flow with Doppler ultrasound and strain-gauge plethysmography.

Simultaneous Doppler ultrasound estimates of brachial artery mean blood velocity (MBV) and venous occlusion strain-gauge plethysmography measures of forearm blood flow (FBF) were performed to determine the beat-by-beat relationship between the two methods and provide a method for flow calibration of Doppler MBV estimates. Such a calibration of Doppler MBV eliminates the need for knowledge of vessel cross-sectional area and angle of insonation while allowing for the quantification of limb blood flow. Six healthy subjects (5 men and 1 woman) performed 40 s of isometric forearm contraction at 35% maximal voluntary contraction with arterial inflow occluded. This resulted in elevated blood flow on relaxation and cuff deflation, and simultaneous beat-by-beat Doppler MBV and strain-gauge FBF measurements were then made over a period of 2-3 min as flow gradually decreased to resting levels. The r2 values for the fitted regression lines over a wide range of flows ranged from 0.87 to 0.98, and the mean square error terms ranged from 0.88 to 3.07 ml.100 ml-1.min-1. Significant day-to-day variation of the fitted regression parameters within subjects indicated that quantitative estimates of FBF from Doppler MBV require a calibration to be performed for each experiment. The finding of a strong linear relationship between Doppler MBV and venous occlusion strain-gauge plethysmography, as well as the marked beat-by-beat effect of cuff inflation on blood flow, confirms the importance of calibration on the same beats, not on adjacent segments of beats.

Adult↗
PubMed2002

A reevaluation of the validity of unrestrained plethysmography in mice.

Presently, unrestrained plethysmography is widely used to assess bronchial responsiveness in mice. An empirical quantity known as enhanced pause is derived from the plethysmographic box pressure [P(b)(t), where t is time] and assumed to be an index of bronchoconstriction. We show that P(b)(t) is determined largely by gas conditioning when normal mice breathe spontaneously inside a closed chamber in which the air is at ambient conditions. When the air in the chamber is heated and humidified to body conditions, the changes in P(b)(t) are reduced by about two-thirds. The remaining changes are thus due to gas compression and expansion within the lung and are amplified when the animals breathe through increased resistances. We show that the time integral of P(b)(t) over inspiration is accurately predicted by a term containing airway resistance, functional residual capacity, and tidal volume. We conclude that unrestrained plethysmography can be used to accurately characterize changes in airway resistance only if functional residual capacity and tidal volume are measured independently and the chamber gas is preconditioned to body temperature and humidity.

Airway Resistance↗
PubMed2006

Restrained whole body plethysmography for measure of strain-specific and allergen-induced airway responsiveness in conscious mice.

The mouse is the most extensively studied animal species in respiratory research, yet the technologies available to assess airway function in conscious mice are not universally accepted. We hypothesized that whole body plethysmography employing noninvasive restraint (RWBP) could be used to quantify specific airway resistance (sRaw-RWBP) and airway responsiveness in conscious mice. Methacholine responses were compared using sRaw-RWBP vs. airway resistance by the forced oscillation technique (Raw-FOT) in groups of C57, A/J, and BALB/c mice. sRaw-RWBP was also compared with sRaw derived from double chamber plethysmography (sRaw-DCP) in BALB/c. Finally, airway responsiveness following allergen challenge in BALB/c was measured using RWBP. sRaw-RWBP in C57, A/J, and BALB/c mice was 0.51 +/- 0.03, 0.68 +/- 0.03, and 0.63 +/- 0.05 cm/s, respectively. sRaw derived from Raw-FOT and functional residual capacity (Raw*functional residual capacity) was 0.095 cm/s, approximately one-fifth of sRaw-RWBP in C57 mice. The intra- and interanimal coefficients of variations were similar between sRaw-RWBP (6.8 and 20.1%) and Raw-FOT (3.4 and 20.1%, respectively). The order of airway responsiveness employing sRaw-RWBP was AJ > BALBc > C57 and for Raw-FOT was AJ > BALB/c = C57. There was no difference between the airway responsiveness assessed by RWBP vs. DCP; however, baseline sRaw-RWBP was significantly lower than sRaw-DCP. Allergen challenge caused a progressive decrease in the provocative concentration of methacholine that increased sRaw to 175% postsaline values based on sRaw-RWBP. In conclusion, the technique of RWBP was rapid, reproducible, and easy to perform. Airway responsiveness measured using RWBP, DCP, and FOT was equivalent. Allergen responses could be followed longitudinally, which may provide greater insight into the pathogenesis of chronic airway disease.

Administration, Inhalation↗
PubMed2004

Comparison of two plethysmography systems in assessment of forearm blood flow.

Venous occlusion plethysmography is widely used to assess forearm blood flow (FBF). We compared the established Hokanson system (HEC4) with a newly developed Filtrass 2001 system (F2001). The HEC4 uses mercury-in-Silastic strain gauges, whereas F2001 detects volume changes with a nonmercury linear displacement device. The aim of this study was to evaluate the new F2001 against the HEC4 in terms of repeatability and systematic bias. Ten subjects were studied on 4 separate days in random order using either the HEC4 on both arms, the F2001 on both arms, the HEC4 on the right arm with the F2001 on the left, or the F2001 on the right arm and the HEC4 on the left. Stroop's colored word conflict test and postocclusive hyperemia were used to increase FBF, and lower body negative pressure was used to lower FBF. Stroop's colored word conflict test and lower body negative pressure increased (24.6 +/- 1.5%, n = 240, P < 0.0001) and decreased (18.7 +/- 0.8%, n = 240, P < 0.0001) FBF, respectively. Postocclusive hyperemia after occlusion times of 5, 8, and 13 min substantially increased FBF by 390 +/- 86, 756 +/- 217, and 851 +/- 132%, respectively. Repeatability was not different between the devices (0.10 +/- 2.37 vs. -0.47 +/- 1.92 l/min, n = 125, P > 0.05), and there was no systematic bias. The F2001 is a newly developed plethysmography system that does not utilize mercury and is suitable for assessing changes of FBF in physiological studies.

Adult↗
PubMed1993

Whole-body plethysmography in the clinical assessment of infants with bronchopulmonary diseases.

Infant whole-body plethysmography offers a unique possibility of measuring end-expiratory resting level (thoracic gas volume; TGV), and hence lung volume in its close interrelationship to airway function (airway resistance; R(aw), its reciprocal value, airway conductance, Gaw). Therefore, this technique is a valuable aid for objective evaluation of lung diseases in infants. This article gives an overview of the physiological background of this particular measuring technique and its usefulness in the clinical routine. Plethysmographic data obtained in infant survivors of the infant respiratory distress syndrome (iRDS), in infants with cystic fibrosis (CF) and in the so-called 'wheezy infants' are presented. Special emphasis is given to the fact that in such infants the interrelationship between changes in end-expiratory resting level and the deficit in airway mechanics is of great importance and, consequently, for the determination of functional lung derangement in each particular case of lung disease, both TGV and the closely related R(aw) and Gaw have to be evaluated. This recommendation has to be kept in mind when the different diagnostic tools for evaluation of treatment facilities are applied in this particular young age group of patients with lung disease. In children as in adult patients, inhalative treatment must be considered the mainstay of all therapeutic measures. However, in infants, the efficacy of such treatment regimens must first be evaluated by adequate functional investigations. Infant whole-body plethysmography offers one such possibility.

Bronchitis↗
PubMed1976

Impedance plethysmography using the occlusive cuff technique in the diagnosis of venous thrombosis.

Impedance plethysmography using the cuff technique has been compared with venography in 346 consecutive patients with suspected venous thromboembolism. The limbs were classified according to the venographic results as no thrombosis, proximal (popliteal, femoral, or iliac) vein thrombosis, and calf thrombosis. A discriminant analysis was performed. The impedance plethysmographic result was normal in 386 of 397 limbs which were normal on venography, a specificity of 97%, and abnormal in 124 of 133 limbs which showed proximal vein thrombosis, a sensitivity of 93%. Seventy-three of 88 limbs with calf vein thrombi and a normal impedance plethysmographic result. The sensitivity in 29 limbs with asymptomatic proximal vein thrombosis was 83%. Impedance plethysmography is an accurate method for detecting proximal vein thrombosis but has limitations which include the possibility of false positive results due to arterial insufficiency and muscle tension.

Adolescent↗
PubMed1997

Noninvasive measurement of airway responsiveness in allergic mice using barometric plethysmography.

To study the mechanisms and kinetics underlying the development of increased airway responsiveness (AR) after allergic sensitization, animal models have been invaluable. Using barometric whole-body plethysmography and increases in enhanced pause (Penh) as an index of airway obstruction, we measured responses to inhaled methacholine in conscious, unrestrained mice after sensitization and airway challenge with ovalbumin (OVA). Sensitized and challenged animals had significantly increased AR to aerosolized methacholine compared with control animals. AR measured as Penh was associated with increased IgE production and eosinophil lung infiltration. In a separate approach we confirmed the involvement of the lower airways in the response to aerosolized methacholine using tracheotomized mice. Increases in Penh values after methacholine challenge were also correlated with increased intrapleural pressure, measured via an esophageal tube. Lastly, mice demonstrating AR using a noninvasive technique also demonstrated increased pulmonary resistance responses to aerosolized methacholine when measured using an invasive technique the following day in the same animals. The increases in Penh values were inhibited by pretreatment of the mice with a beta 2-agonist. These data indicate that measurement of AR to inhaled methacholine by barometric whole-body plethysmography is a valid indicator of airway hyperresponsiveness after allergic sensitization in mice. The measurement of AR in unrestrained, conscious animals provides new opportunities to evaluate the mechanisms and kinetics underlying the development and maintenance of airway hyperresponsiveness and to assess various therapeutic interventions.

Airway Resistance↗
PubMed1982

Validation of respiratory inductive plethysmography using different calibration procedures.

We devised a new calibration procedure [least squares method (LSQ)] for respiratory inductive plethysmography (RIP) and compared it with our previously reported simultaneous equation method (SEQ) of analyzing data in 2 body positions and with the method of Stagg and associates using the analysis of individual breaths in a single body position. The values from RIP were compared with simultaneous spirometry (SP) in 20 normal subjects placed in the standing (STD), supine (SUP), sitting, prone, semi-recumbent, right lateral decubitus, and left lateral decubitus postures. The LSQ gave the most accurate results followed closely by SEQ. In addition, LSQ was compared with the isovolume angle maneuver (ISV) calibration procedure in supine (ISV-SUP) and standing (ISV-STD) postures. Each of the 10 normal subjects breathed at tidal volumes of 250, 750, and 1,250 ml in the SUP and STD postures. Of the values obtained by the LSQ method, 93% were within +/- 10% of SP in SUP and STD positions. Without a change in the posture in which the calibration was made, 83% of values with ISV-SUP and 90% of values with ISV-STD were within +/- 10% of SP. When body position was changed, 65% of the values obtained with ISV-SUP and 38% of the values obtained with ISV-STD were within +/- 10% of SP. With the LSQ, 45% of isovolume angles in SUP and STD position were within 45 +/- 3 degrees; 40% of isovolume angles with ISV-SUP and 60% with ISV-STD were within 45 +/- 3 degrees when body position was changed from position calibrated. In estimating fractional contribution of rib cage and abdominal compartments. LSQ was comparable to ISV in the standing posture but generally gave lesser values for the rib cage contribution in the supine posture than ISV. The optimal calibration procedure for respiratory inductive plethysmography in terms of accuracy and ease of subject performance is the least squares calibration procedure.

Calibration↗
PubMed1986

Inductive plethysmography--a facilitated postural calibration technique for rapid and accurate tidal volume determination in low birth weight premature newborns.

Inductive plethysmography is a noninvasive method of measuring lung volumes in infants. This technique, however, has had very limited use in premature newborns because of the difficulty of calibrating the device with regard to the small tidal volumes (VT) in such infants. The present study describes a facilitated calibration of the inductive plethysmograph in low birth weight infants. The technique depends on generating significantly different compartmentalization of VT into rib cage and abdominal components by changing the infant's position from supine to upright. Linear regression analyses were performed to compare VT measurements made in 9 premature infants with the inductive plethysmograph and the pneumotachygraph; an overall Z-transformed correlation of 501 breath-to-breath comparisons yielded an r value of 0.80; the mean VT (pneumotachygraph) was 13.9 +/- 4.7 ml SD; the mean VT (inductive plethysmograph) was 14.3 +/- 5.1 ml SD. It is concluded that inductive plethysmography is an accurate method to measure VT in small premature infants. Moreover, the ease of the two-position technique for calibration of the device gives the inductive plethysmograph greater utility as a clinical and research tool for measuring lung volumes in premature infants.

Calibration↗
PubMed2004

The birth of clinical body plethysmography: it was a good week.

Nearly fifty years ago, Arthur B. DuBois, Julius H. Comroe Jr., and their colleagues published two papers on the use of body plethysmography to measure lung volume and airway resistance. These two articles in the JCI are almost the most-cited doublet in the Journal's entire archive. Remarkably, the methods described then are still in use today in clinical pulmonary function laboratories. Though body plethysmography had been used before, there were serious technical problems; it was extraordinary that DuBois managed to solve most of these in one week. Times have changed and molecular medicine now dominates the JCI, but these articles remind us that biomedical research goes beyond the molecular.

Airway Resistance↗