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PubMed1981

Thoracic gas volume measured by body plethysmography during anesthesia and muscle paralysis: description and validation of a method.

A method based on body plethysmography for the assessment of thoracic gas volume (TGV) in the anesthetized, paralyzed subject is presented. The compression of thoracic gas following inflation is detected by measuring the difference between the inflation volume and the "box volume" change caused by the expansion of the chest. Model experiments showed good agreement between true and measured volumes with a residual standard deviation of 2 per cent. In studies on human subjects with healthy lungs during halothane anesthesia, the coefficient of variation of repeated measurements was 5 per cent. Comparative measurements with resting lung volume (FRC) determined by multiple breath nitrogen washout disclosed a larger volume by the box technique, a difference which was reduced but not eliminated by deep breathing during the nitrogen washout. This difference, amounting to 0.2 liters on the average, may be explained by abdominal gas and by the detection of trapped gas by the box technique but not by the nitrogen washout.

Adult↗

PubMed1988

Calibration of respiratory inductive plethysmography in lambs receiving intermittent mandatory mechanical ventilation.

Respiratory inductive plethysmography (RIP) is a noninvasive method of assessing breathing pattern. We employed a single-position graphic (SPG) calibration technique for gain factor calculation in 38 studies on five sedated lambs who were receiving intermittent mandatory mechanical ventilation (IMV). The SPG technique uses selection of two breaths from a 20-sec run of breaths with different ribcage/pneumotachograph (PNT) and abdomen/PNT ratios for gain calculation. Validation of gains was performed by comparing volumes obtained simultaneously by RIP and PNT. The mean tidal volume (VT) measured by RIP corresponded well with mean VT measured by PNT with animals receiving 42.2 +/- 13.2 (SD) % of breaths over 1 min by IMV. Time for calibration and validation ranged between 15 and 30 min. The results of this study suggest that the SPG calibration technique provides an accurate method of calibration of RIP in sedated lambs receiving IMV.

Animals↗

PubMed2001

Estimation of end-expiratory lung volume variations by optoelectronic plethysmography.

OBJECTIVE: To test the capability of optoelectronic plethysmography (OEP) to monitor positive end-expiratory pressure (PEEP)-induced changes of end-expiratory lung volume (EELV) changes in mechanically ventilated paralyzed patients. DESIGN: Laboratory and clinical investigation. SETTING: Intensive care unit of the Ospedale Maggiore Policlinico di Milano. PATIENTS: A total of eight patients with respiratory failure of various degrees, sedated and paralyzed. INTERVENTIONS: PEEP variations (+/-5 cm H2O) relative to the baseline PEEP of 10 cm H2O. MEASUREMENTS AND MAIN RESULTS: In the model protocol, we tested the reproducibility of the OEP by repeating volume measurements of a plastic torso model over a 21-hr period, every 30 mins. The variations of OEP measurements of the torso model (9337 mL value) were encountered in a range of 16 mL (sd = 4 mL). In the patient protocol, we measured the end-expiratory volume of the chest wall (EEVCW) breath-by-breath by OEP before, during, and after the PEEP increase/decrease and we compared its variations with the corresponding variations of EELV measured by helium dilution technique. The regression line between EELV changes measured by helium and EEVCW changes measured by OEP resulted very close to the identity line (slope 1.06, intercept -0.02 L, r(2) = 0.89) and their difference was not related to their absolute magnitude. After PEEP increase, the new steady state of EEVCW was reached approximately in 15 breaths; and, after PEEP decrease, in 3-4 breaths. The slow increase in EEVCW was mainly because of the abdominal compartment. CONCLUSION: OEP measurements of EEVCW accurately reflect the changes of EELV. Furthermore, OEP allows a continuous compartmental analysis, even during unsteady conditions.

Adult↗

PubMed2001

Identification of optimal lung volume during high-frequency oscillatory ventilation using respiratory inductive plethysmography.

OBJECTIVES: First, to define the relationships between critical opening and closing pressures and oxygenating efficiency, and second, to address whether respiratory inductive plethysmography (RIP) could be used to monitor changes in thoracic volume that follow changes in mean airway pressure during high- frequency oscillatory ventilation (HFOV). DESIGN: Prospective, interventional animal study. SETTING: University research laboratory. SUBJECTS: Five anesthetized, paralyzed, and ventilated pigs. INTERVENTIONS: The animals were ventilated by using HFOV after lung injury. Pre- and post-HFOV pressure-volume curves were obtained by supersyringe. A pressure-volume curve was constructed during HFOV as mean airway pressure was increased from 10 to 40 cm H(2)O and then weaned back down to the minimum sustainable. Hemodynamic and oxygenation data were obtained at each data point. MEASUREMENTS AND MAIN RESULTS: RIP-derived thoracic volumes correlated with known lung volumes during supersyringe (r(2) =.78, p <.00001). During HFOV, three of five animals had an identifiable critical opening pressure of the lung, and four of five had an identifiable critical closing pressure. No consistent relationship between critical opening and critical closing pressures was observed. During the weaning phase of HFOV, a relative decrease in RIP-measured volume of >10% predicted the decrease in oxygenation associated with reaching the critical closing pressure. CONCLUSIONS: The ability of RIP to detect optimal lung volume during the weaning of mean airway pressure may allow clinicians to more directly monitor lung volume changes during HFOV and use the lowest possible airway pressures after lung recruitment.

Animals↗

PubMed1985

Comparison of blood pressure ratio by Doppler velocimetry and by plethysmography during treatment with ketanserin, a 5-HT2 receptor antagonist: a measure of improved collateral and microcirculatory flow.

We could demonstrate a progressive and significant increase in blood pressure ratio (thigh/arm) in 42 patients with intermittent claudication, treated with ketanserin for 9 months, which confirms our earlier double-blind placebo-controlled findings. In an additional experiment comparing blood pressure ratio with Doppler velocimetry and with plethysmography, an upwards shift was observed for the plethysmographic values as compared with the Doppler values during ketanserin therapy, and only at the level of the thigh, which suggests an improvement of the collateral and microcirculatory flow.

Aged↗

PubMed2000

Validation of air displacement plethysmography for assessing body composition.

PURPOSE: The purpose of this study was to verify the validity of an air displacement plethysmography device (Bod Pod) for estimating body density (Db). METHODS: The Db from the Bod Pod (DbBP) was compared with the Db from hydrostatic weighing (DbHW) at residual lung volume in a heterogeneous sample of 30 black men who varied in age (32.0 +/- 7.7 yr), height (180.3 +/- 7.5 cm), body mass (84.2 +/- 15.0 kg), body fatness (16.1 +/- 7.5%), and self-reported physical activity level and socioeconomic status. The Db for each method was converted to relative body fat (%BF) using race-specific conversion formulas and subsequently compared with %BF obtained from dual-energy x-ray absorptiometry (%BFDXA). RESULTS: Linear regression, using DbHW as the dependent variable and DbBP as the predictor, produced an R2 = 0.84 and SEE = 0.00721 g x cc(-1). However, the mean difference between the two methods (0.00450 +/- 0.00718 g x cc(-1) was significant (P < 0.01). The Bod Pod underestimated the Db of 73% of the sample. The %BF estimates from the Bod Pod, HW, and DXA differed significantly (P < 0.01). The average %BFBP (17.7 +/- 7.4%) was significantly greater than %BFHW (15.8 +/- 7.5%) and %BFDXA (16.1 +/- 7.5%); however, there was no significant difference between %BFHW and %BFDXA. CONCLUSION: The Bod Pod significantly and systematically underestimated Db, resulting in an overestimation of %BF. More cross-validation research is needed before recommending the Bod Pod as a reference method.

Absorptiometry, Photon↗

PubMed2001

Use of air displacement plethysmography for estimating body fat in a four-component model.

PURPOSE: To compare measurements of body density (D(b)) obtained from air displacement plethysmography (AP) and hydrostatic weighing (HW) and to determine the accuracy of substituting D(b) via AP (D(b)-AP) for D(b) via HW (D(b)-HW) in estimating body fatness (%Fat(4C)) and the composition and density of the fat-free mass (Dffm) from a four-component model (fat, mineral, water, and protein). METHODS: D(b) was measured in 50 young adults using AP and HW. Total body water via deuterium dilution, bone mineral content via dual-energy x-ray absorptiometry, and D(b) were used to estimate %Fat(4C). RESULTS: D(b)-AP and D(b)-HW were highly correlated (r = 0.89, SEE = 0.008 g x mL(-1)), but D(b)-AP (1.065 +/- 0.003 g x mL(-1)) was significantly higher (P < 0.05) than D(b)-HW (1.058 +/- 0.003 g x mL(-1)), resulting in a mean difference of 2.8%fat. Differences between %Fat(4C-AP) (17.8 +/- 1.2%) and %Fat(4C-HW) (19.3 +/- 1.2%) were significant (P < 0.05), but the SD of the differences (2.3%) was low. When D(b)-AP was used in a four-component model in place of D(b)-HW, the calculated Dffm was significantly higher (1.109 +/- 0.002 vs 1.105 +/- 0.002 g x mL(-1)) based on a higher (P < 0.05) protein fraction (22.0 +/- 0.4% vs 20.6 +/- 0.4%) and lower (P < 0.05) water (71.1 +/- 0.4% vs 72.4 +/- 0.4%) and mineral fractions (7.0 +/- 0.1% vs 7.1 +/- 0.1%). CONCLUSIONS: AP yields a higher D(b) than HW and may not be a valid method for measuring D(b) or estimating %fat using densitometry. However, due to relatively small bias and low individual error, D(b)-AP is an acceptable substitute for D(b)-HW when estimating %fat with a four-component model in young adults.

Adipose Tissue↗

PubMed1993

Regional distribution of 201Tl during one-leg exercise: comparison with leg blood flow by plethysmography.

To validate the use of 201Tl distribution as an estimate of regional blood flow in the legs, 201Tl leg uptake was compared by whole body scintigraphy and simultaneously measured leg blood flow by plethysmography during one-leg exercise in 11 male subjects. 201Tl leg uptake ratio and leg blood flow ratio were also compared to exclude the effect of cardiac output variation in each subject. There was a good correlation between 201Tl leg uptake and leg blood flow (r = 0.85, P < 0.01, y = 0.28x + 1.00). Moreover, there was a highly linear correlation between these ratios (r = 0.98, P < 0.01, y = 0.75x + 0.13), although the 201Tl leg uptake ratio somewhat underestimated the leg blood flow ratio as exercise became strenuous. It is concluded that 201Tl leg uptake reflects regional blood flow in the legs during exercise.

Aged↗

PubMed1980

Diagnosing deep vein thrombosis by Doppler ultrasound and impedance plethysmography.

To evaluate the diagnostic accuracy of Doppler ultrasound (DU) and impedance plethysmography (IPG) in deep vein thrombosis (DVT), hospital records of 904 patients having 1,084 studies of blood flow in the lower extremities were retrospectively reviewed, and 544 were found abnormal. In 128, both DU and IPG showed abnormalities, 86 had only DU evidence of abnormalities, and 330 had only IPG abnormalities. Fifty-one patients with abnormal results of both DU and IPG studies had ascending phlebography, which in 47 documented the presence of DVT, for a diagnostic accuracy of 92%. On the basis of DU/IPG testing, or extenuating clinical circumstances, 135 patients considered at high risk for pulmonary emboli had ventilation-perfusion lung scans. Of these, 44 had roentgenographic evidence of pulmonary emboli. While ascending phlebography remains the definitive study for documenting the presence of DVT, DU/IPG testing has a high accuracy rate, is noninvasive, readily reproducible, inexpensive, and simple to perform. When results of DU/IPG studies are abnormal a baseline ventilation lung scan should be done which, if questionable, should be followed by pulmonary arteriography.

Humans↗

PubMed1981

Forearm plethysmography in normotensive and hypertensive pregnant women.

Forearm plethysmography affords a simple noninvasive method of studying dynamic changes in the microcirculation. This technic was used to study the peripheral circulation of normotensive nongravid women and normotensive and untreated hypertensive pregnant women during the third trimester. The variables of forearm blood flow, vascular resistance, venous capacitance, and capillary filtration coefficient were measured in the resting state and during and after exercise. The pregnant women demonstrated an increase in forearm blood flow over the nonpregnant women. As expected, vascular resistance was higher in the hypertensive pregnant patients than in normotensive pregnant women. The possible predictive value of these findings is discussed.

Female↗

PubMed1990

Photoelectric plethysmography in monitoring skin circulation.

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

Amplifiers, Electronic↗

PubMed1994

Comparison of venography, duplex imaging, and bilateral impedance plethysmography for diagnosis of lower extremity deep vein thrombosis.

Twenty-four consecutively hospitalized patients with clinical evidence of lower extremity deep vein thrombosis (DVT) had blinded ipsilateral ultrasonographic duplex imaging (US), contrast venography (VG), and a one-time bilateral impedance plethysmography (IPG) examination. The cases of eight (33%) of the study patients were thought to be complicated due to a prior history of DVT or the presence of ipsilateral inguinal adenopathy. Interpretable test results were obtained for 100% of the US examinations, 88% of the VG studies, and 75% of the IPGs. One additional subject, included in our study for statistical analysis, had an unblinded false-negative US examination; in this case DVT was shown by VG but could not be seen on US despite the radiologist's prior knowledge. The sensitivities, specificities, and 95% confidence intervals for the three studies were as follows: US, 92% (81% to 103%) sensitivity, 100% (99% to 101%) specificity; VG, 100% (99% to 101%) sensitivity, 75% (58% to 96%) specificity; IPG, 50% (30% to 70%) sensitivity, 83% (68% to 98%) specificity. Of the six indeterminate IPG studies, four (67%) occurred in complicated cases. These data suggest that US should be the first-line noninvasive screening study done for evaluation of suspected DVT, especially in complicated cases.

Adult↗

PubMed1981

A peripheral vascular insufficiency test using photocell plethysmography.

A preliminary laboratory study seeking an objective test for vascular insufficiency of the fingertips (Raynaud's syndrome) is described. In a limited number of subjects, circulatory changes in the vascular bed of one hand were examined by photocell plethysmography while the opposite had was immersed in ice water. The time to complete recovery after cessation of the cold stimulus was significantly longer with primary Raynaud's patients than with the control subjects (p = 0.0045). The analysis of another parameter, the relative change in pulse amplitude during cold immersion, was confounded by age and sex differences between the Raynaud's and the control group. A follow-up investigation of the application of this technique to a population of vibration-exposed chipper and grinder and control workers is in progress.

Adult↗

PubMed1993

Venous occlusion plethysmography using a fiber-optic sensor.

This paper presents the results of comparative testing of a fiber-optic sensor used as an alternative to the mercury strain-gauge in a clinically well-established technique for limb blood flow assessment, venous occlusion plethysmography. In this research the measurement of volume changes following venous occlusion has been performed with a variety of methods including the commonly used mercury strain-gauge. Temperature drift and long-term instability are problems associated with the mercury strain-gauge. In addition, environmental protection authorities are prohibiting the marketing of mercury sensors, beginning in 1993. Evaluation and optimization of the fiber optic microbending sensor is described in detail. Comparison with the mercury strain-gauge sensor is made for in lower limb blood flow measurements.

Equipment Design↗

PubMed1984

Minoxidil stimulates cutaneous blood flow in human balding scalps: pharmacodynamics measured by laser Doppler velocimetry and photopulse plethysmography.

In a double-blind study with randomly assigned topical solutions of 0%, 1%, 3%, or 5% minoxidil, the blood flow in balding scalps of 16 human volunteers was measured by the noninvasive techniques of both laser Doppler velocimetry (LDV) and photopulse plethysmography (PPG). On two consecutive days, an 0.25-ml volume of the assigned minoxidil formulation was spread uniformly over a 100-cm2 area of each side of the bald scalp and cutaneous blood flow was recorded for the following 4 h. Both measurement techniques showed that the 5% minoxidil solution stimulated the microcirculation of the bald scalp. Increased blood flow was greater with the 5% minoxidil solution than with the other treatments. Measured by LDV on day 1, the increase (p less than 0.0001) in blood flow occurred within 15 min of application of the 5% solution of minoxidil and was maintained at least through hour 1. On day 2, LDV showed blood flow stimulation with the 5% solution was 3-fold (p less than 0.0001) within 15 min of application and was so maintained for about 1 h. Measured by PPG, the only statistically significant (p less than 0.01) response occurred with the day 2 application of the 5% minoxidil solution. PPG is dependent on local blood volume and is only weakly correlated to cutaneous blood flow, which makes it unsuitable for this kind of study. Analysis of vital signs for days 1 and 2 revealed no systemic effect from treatment with minoxidil, suggesting that the blood flow stimulation was directly related to the topical application of minoxidil.

Administration, Topical↗

PubMed1978

Non-invasive methods for evaluating the importance of heart rate and atrial activity in cardiac pacing. Results of ballistocardiography and digital plethysmography studies in six patients with heart block.

Ultralow frequency ballistocardiography (UFB) and digital pulse plethysmography (DPP) were performed in six patients with an external artificial pacemaker system. UFB was used mainly to evaluate the force of contraction of the left ventricle (IJ amplitude) and DPP for evaluating relative changes in the peripheral pulse volume. Four patients were studied at 40, 50, 60, 70, 80, 90 and 100 beats/min. There was a significant decrease (p less than 0.001) in LJ and pulse amplitudes when the heart rate increased from 40 to 100 beats/min. A positive correlation between relative IJ and pulse amplitude was observed in all cases studied. In beat-to-beat analysis it was found that the importance of the PR interval for the IJ and pulse amplitudes varied between patients. It is concluded that both UFB and DPP may be of value in clinical practice for evaluating hemodynamics in patients with slow spontaneous heart rate. The methods may be of help in selecting the most effective type of pacemaker for the individual patient.

Aged↗

PubMed2005

A comparison of plethysmography, spirometry and oscillometry for assessing the pulmonary effects of inhaled ipratropium bromide in healthy subjects and patients with asthma.

AIMS: We have compared the ability of plethysmography (sGaw), impulse oscillometry (IOS) and spirometry (FEV(1), MMEF) to detect bronchodilation in response to an anticholinergic. METHODS: IOS (R5, R20, X5, RF), sGaw and spirometry were measured in 12 healthy subjects and 12 asthmatics. Variability was assessed by performing two measurements, 30 min apart and the effect of increasing the number of readings for each sGaw measurement was also studied. Ipratropium bromide (IB) 10, 20, 100 and 200 microg was administered and the sensitivity of the methods compared by determining the lowest dose that caused changes greater than variability. RESULTS: In healthy subjects significant changes (P < or = 0.05) occurred at 10 microg for FEV(1) (mean [95% CI]; 1.3%[0.3-2.3]), R5 (mean [95% CI]; -7.9%, [-13.2-2.6]) and R20 (mean [95% CI], -6.4%, [-11.4-1.4]). No significant change was detected when the mean of 3 sGaw readings was used, but with 10 readings significant change was observed at 20 microg; (mean increase [95% CI] 15.2%[8.3-22.1]). In asthmatics significant changes (P < or = 0.05) occurred with IB 10 microg for sGaw (mean [95% CI] 25.6%[11.1-40.1]), R5 (mean [95% CI]-11.3%, [-15.5-7.2]), RF (mean [95% CI] 11.7%[6.1-16.3]), FEV(1) (mean [95% CI] 5.1%[2.6-7.7]) and MMEF (mean [95% CI] 12.3%[2.3-22.2]). CONCLUSION: IOS and spirometry are more sensitive than sGaw in healthy subjects, but the sensitivity of sGaw improved when the number of readings was increased. The most sensitive method for assessing bronchodilation in asthmatics was sGaw.

Adult↗

PubMed2005

Reproducibility of forearm vasodilator response to intra-arterial infusion of calcitonin gene-related peptide assessed by venous occlusion plethysmography.

AIMS: To assess the reproducibility of the forearm blood flow (FBF) response to intra-arterial infusion of calcitonin-gene related peptide (CGRP), measured by venous occlusion plethysmography. In addition, to compare different ways of expressing the FBF response and perform sample size calculations. METHODS: On two separate visits, CGRP (10 ng min(-1) dl(-1) forearm) was infused for 45 min into the brachial artery of six healthy subjects. Reproducibility was assessed by calculating mean difference, repeatability coefficient, within-subject coefficient of variation (WCV) and intraclass correlation coefficient. RESULTS: CGRP increased FBF from 2.8 +/- 0.4 and 3.2 +/- 0.7 (at baseline) to 15.4 +/- 1.4 and 15.2 +/- 1.5 ml min(-1) dl(-1) forearm (at 45 min) on visits 1 and 2, respectively (P < 0.0001 for both visits). Mean difference in FBF at 45 min between both visits was 0.3 ml min(-1) dl(-1) forearm (repeatability coefficient: 4.1 ml min(-1) dl(-1) forearm). This FBF response appeared to be more reproducible when expressed as absolute FBF in the infused arm (WCV 11%) compared with absolute FBF-ratio between both arms (WCV 37%), percentage change from baseline in FBF in the infused arm (WCV 29%) and percentage change from baseline in FBF-ratio (WCV 40%). When expressed as absolute FBF, a sample size of five (95% confidence interval: 2-12) subjects gives 90% power at a type I error probability of 0.05 to detect a 25% shift in FBF response. CONCLUSIONS: Intra-arterial infusion of CGRP results in a forearm vasodilator response which is reproducible between days. This response is most reproducible when expressed as absolute FBF. The presented methodology provides a suitable pharmacodynamic model to assess the in vivo activity of CGRP-receptor antagonists in a small number of subjects.

Adult↗