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At least 343 records · Page 19Linked to original sources
PubMed2005

Body composition predicted from skinfolds in African women: a cross-validation study using air-displacement plethysmography and a black-specific equation.

Skinfold thickness (SF) measurements are commonly used for the indirect assessment of body composition. It is necessary to know how large the bias is when using Caucasian SF-based prediction equations Africans, as no specific equations exist. Our first aim was to test the validity of the equation of Durnin & Womersley for predicting body density from SF in Africans. The second aim was to determine the effect of calculating percentage body fat (%BF) from body density using a black-specific formula rather than the Siri equation, thus taking into account the higher fat-free mass (FFM) density in blacks than in whites. A total of 196 African women volunteered. Mean age was 29.5 (sd 8.7) years and mean BMI was 22.5 (sd 4.6) kg/m2. We compared body density values predicted from SF with those measured by air-displacement plethysmography, and %BF values obtained from body density using the Siri equation or the black-specific calculation. The bias (reference minus prediction) was 0.0100 kg/cm3 in body density (P<10(-4)) and 6.5 % BF (P<10(-4)), and the error (sd of the bias) 0.0097 kg/l and 4.5 % BF. With the black-specific equation, the bias was reduced by 1.9 % BF, while error remained similar. As the %BF prediction required an SF-based equation followed by a body density-based calculation, the lack of validity we observed in Africans may be due to known differences between blacks and whites in the distribution of subcutaneous adipose tissue and, as demonstrated, in the FFM density. Equations thus need to be established using SF values specific to Africans.

Adipose Tissue↗
PubMed1977

Reactive hyperaemia in the calf of trained and untrained subjects: a study with strain gauge plethysmography.

Postischaemic reactive hyperaemia in the calf was investigated by strain gauge plethysmography in three pairs of trained and untrained groups of different ages. Maximal flow and repayment in the trained adults were greater than in corresponding untrained groups. This may be due to training effect on the arterioles and a relatively great muscle volume and vascular bed in athletes. The 58-year-old trained men revealed a postischaemic hyperaemic response of approximately the same magnitude as the 25-year-old athletes. Training in old age may result in less degeneration of vascular smooth muscle as well as striated muscle and may induced a relatively great cardiac stroke volume, factors which probably influence reactive hyperaemia in the calf. Hyperaemia in 13-year-old children of different conditions of training was approximwtely the same. It is concluded that the influence of training state on postischaemic calf flow may be considered when reactive hyperaemia is used as a test of the peripheral circulation.

Adolescent↗
PubMed1979

Biphasic venous emptying from the calves in venous-occlusion plethysmography.

The pathophysiological significance of the biphasic venous emptying curves from the lower limbs in venous occlusion plethysmography was examined in three patients peroperatively by clamping the iliac veins in different locations. The clinical significance of biphasic curves was analysed in fifty-four patients, thirty-one of whom were pregnant and twenty-three had a suspected deep vein thrombosis. It was found that the primary venous emptying time (PVET) was helfpul in locating the obstruction. Patients with femoral and pelvic vein thrombosis had shorter PVET than patients with pregnancy or other pelvic vein obstructions. With PVET of 0.5 sec, or shorter, thrombosis should be strongly suspected. The ratio between the slow and fast emptying phases was useless in localization of the intrapelvic process.

Adult↗
PubMedDate not supplied

Statistical validation of air-displacement plethysmography for body composition assessment in children.

BACKGROUND: Body composition assessment of children has been hindered by the absence of a safe, quick, and easily tolerated gold standard technique. Existing validation studies of air-displacement plethysmography (ADP) have been based on small, narrowly defined samples, using simple linear regression or Bland-Altman analyses. AIM: Correlations within a multitrait-multimethod matrix (MTMM) and factor analytic methodologies were used to evaluate ADP as a valid and reliable body composition technique for children. SUBJECTS AND METHODS: Fat mass (FM), fat-free mass (FFM) and per cent body fat (%BF) were measured in 139 children, 7-10 years old, by ADP, dual energy X-ray absorptiometry (DXA) and anthropometry (ANTH). MTMM and factor analysis were used to compare assessment techniques. RESULTS: Reliability estimates were lower for ADP than for either ANTH or DXA. Convergent and discriminant correlations between ADP and ANTH or DXA were high for identical as well as non-identical measures. Two body composition factors (Fatness, Leanness) and two technique-related factors (Bod Pod, Anthropometry) were identified. CONCLUSION: ADP offers a valid and reliable means of assessing body composition in children but does not perform as well as ANTH or DXA. MTMM and factor analytic methodologies offer an effective alternative to assessing body composition.

Absorptiometry, Photon↗
PubMed1989

Workplace measurement of respirator effects using respiratory inductive plethysmography.

A useful system to study the cardiopulmonary effects of respirators in the workplace would be reliable, portable, and lightweight and would not encumber the nose or mouth or require modification to the respirator. Twenty men using such a system (which measured ventilatory parameters by respiratory inductive plethysmography [RIP]) were studied. The subjects all performed their usual jobs which involved some work with and some without a respirator. Twelve subjects used airline respirators and eight used air-purifying respirators. The RIP equipment measurements included respiratory frequency, tidal volume (VT), minute ventilation (V), and heart rate (HR). The RIP data from 20 other subjects was lost because of equipment malfunction, primarily lead separation in those whose jobs involved climbing around large workpieces. In general, the workers' cardiopulmonary parameters increased during respirator wear, probably because of a combination of factors, including the increased exercise of most respirator-requiring tasks and the weight and heat stress associated with the respirator and protective clothing. When the ventilatory parameters with and without a respirator were compared at the same heart rates, no significant differences were noted in VT for the entire group. Respiratory frequency, however, and V increased with respirator wear. The effects of respirators alone were found to be commonly confounded in the workplace by changes in protective clothing, exercise requirements, and ambient heat stress. Further improvements in the portable RIP system are needed before it can be accepted as a reliable ventilatory measurement device in the workplace.

Adult↗
PubMed1981

Photoelectric plethysmography--some fundamental aspects of the reflection and transmission method.

In photoelectric plethysmography a distinction is made between the reflection methods. Uncertainties still exist, especially regarding the origin of the reflected signal: some investigators attach quantitative value to the amplitude of the plethysmogram. The various findings are reconsidered. Various fluids are pulsatingly pumped through an in vitro circuit. Flow, pressure and volume pulsations are measured, as is the total light intensity detected by a photoelectric plethysmograph with the small variations caused in it by the pulsations in flow. Both phase and amplitude of the resulting plethysmogram are studied and the results compared with those found in vivo at the fingers and auricles. In vitro, the variations in light reflection are in phase with the volume pulsations: this can only be ascribed to reflection by orienting erythrocytes. In vivo, however, the light reflection, like the light transmission, is in anti-phase with the volume excursions, thus eliminating the determinative effect of light reflection by orienting erythrocytes--the strong reflection from surrounding tissues completely dominates reflection from erythrocytes. Since erythrocytes also have absorptive properties, and the light reflection is in anti-phase with the volume excursions, it is concluded that this absorptivity can manifest itself over the strong reflection from surrounding tissue. In vivo, therefore, the reflection plethysmogram is, in principle, an absorption measurement. The relationship between intensity of detected light and resultant voltage may not be linear: this nonlinearity may not be neglected when amplitude changes are compared. Amplitude changes of different plethysmograms may only be compared quantitatively if there is no difference in their light-voltage relationship.

Blood Physiological Phenomena↗
PubMed1986

Effective airway resistance: a reliable variable from body plethysmography.

Since the introduction of whole-body plethysmography in pulmonary function routines, airway resistance measurements by this method have been plagued by a side-effect of the ventilation process. Warming up and humidifying of inspired air and the cooling and condensation of expired air lead to a change in volume of the gas in the system and thus to a change in pressure in the body box which is superimposed on the regular box pressure. One generally applied solution is to compensate electronically for the disturbing pressure change. However, the required adjustment of the size of the compensating signal is difficult or impossible to obtain with patients who have obstructive lung diseases. In this paper we show that if no correction at all is applied the measurement error in the effective airway resistance remains relatively small. Moreover the magnitude of the error appears to depend on certain symmetrical and asymmetrical properties of the mouth flow curve. The maximum error in the effective resistance, as computed from a number of measured flow patterns, was found to be -18% for the normal persons and -9% for patients with obstructive lung diseases. We conclude that the uncorrected effective airway resistance is reasonably accurate. Alternatively, a good accuracy can be obtained with only a coarse adjustment of the correction circuit.

Airway Resistance↗
PubMed1999

Inductive plethysmography components analysis and improved non-invasive postoperative apnoea monitoring.

Twenty-nine patients were monitored overnight for breathing distress patterns during postoperative analgesia. Nasal flow apnoea monitoring and pulse oximetry data were recorded at 50 Hz. Respiratory inductive plethysmography (RIP) tracked tidal volume (TV) thoracoabdominal motion, and supplemented the flow monitoring by identifying detected apnoea type. TVs were computed from linear combinations of the RIP signals, but calibrations showed that multiple regression approaches with fitting errors <1% had highly variable coefficients and estimate precisions. Simple least squares theory showed that unstable parameter calculation and coefficient variation with signal conditions were inherent in RIP calibration models. Principal components (PC) methods were well suited to mitigating these problems because the RIP signals were highly correlated. The two PCs tracked the relative changes in TVs and indicated the degree of signal asynchrony, enabling improved uncalibrated monitoring. For accurately measuring RIP phase differences, the cross-correlation function was calculated. A simple version of PC analysis is developed, avoiding matrices, to help clarify how RIP calibration problems can be addressed. The methods are illustrated for calibration in normal breathing, and for postoperative monitoring during Cheyne-Stokes breathing. Sum and difference combinations of the RIP signals could discriminate central from obstructive apnoeas to help improve flow monitoring efficacy on-line.

Analgesia↗
PubMed2002

Key to better qualitative diagnostic calibrations in respiratory inductive plethysmography.

Least-squares estimates for coefficients of linear models that predict tidal volume (VT) via respiratory inductive plethysmography (RIP) are given. The qualitative diagnostic calibration sum formula M(RC + KAbd) arises for idealized thoracoabdominal co-ordination within this model-fitting framework. For a normal synchronous breath K is then optimally determined from the ratio of its associated ribcage (RC) and abdomen (Abd) movement standard deviations, not from a ratio that applied to a previously measured breath. M merely rescales relative changes in (RC + KAbd) to absolute changes in VT for correct proportioning. RC and Abd move in complete antipathy during an obstructive apnoea, so use of optimal K ensures (RC + KAbd) tends to zero for such unproductive breathing efforts. The interpretation is extended to more general breathing patterns by using a complementary difference expression M(RC-KAbd) to help identify any antagonistic respiratory actions. The two new constructs are equivalent to the principal components of the combined ribcage and abdomen movements. Together they demonstrate versatile capability in uncalibrated RIP applications for obstructive apnoea detection and tracking relative changes in VT during paradoxical or variable natural breathing. Calibration is appropriate for model-fitting quality assessment but otherwise usually too patient demanding, unnecessary or detrimental to prediction monitoring efficacy.

Apnea↗
PubMed2002

A device for 24 hour ambulatory monitoring of abdominal girth using inductive plethysmography.

Inductive plethysmography (IP) sensors and oscillator modules were assessed for their potential use in the ambulatory monitoring of abdominal girth in subjects with irritable bowel syndrome (IBS) in order to objectively quantify their bloating symptoms. A dedicated microprocessordata logger was designed to record over 24 h the frequency output of IP oscillators connected to a belt around the subject's lower abdomen. Posture was also recorded via tilt switches (standing, sitting and lying). The system was separately calibrated by placing the belts around a variable rectangular phantom and measuring the frequency of oscillation. A theoretical geometric model was devised to convert measured frequency into circumference and account for changes caused by variations in shape. Using the calibration factors, it was found that the circumference of a circular phantom could be measured accurately (mean difference 1.27 cm and SD 0.25 cm). The system has been tested over 24 h with 20 volunteers. Movement introduced variations in measured girth larger than those found during periods of non-movement during sleep. We conclude that IP promises to be a useful and quantitative tool suitable for ambulatory monitoring of abdominal girth, a hitherto relatively unexplored symptom of IBS.

Abdomen↗
PubMed2002

Carbon dioxide accumulation during small animal, whole body plethysmography: effects on ventilation, indices of airway function, and aerosol deposition.

Barometric (whole body) plethysmography is used to examine changes in ventilation and breathing pattern in unrestrained animals during exposure to therapeutic or toxic aerosols. Whole body plethysmographs (WBP) may be operated with a bias flow in order to maintain an adequate supply of oxygen and remove expired CO(2). However, some aerosol generation and delivery methods may require operation of the WBP without bias flow, which would artificially deplete aerosol concentration. Under these conditions, expired CO(2) accumulates in the plethysmograph and stimulates ventilation, increasing total aerosol deposition, shifting regional deposition, and significantly altering some airway function indices. We characterized these effects in guinea pigs using a commercially available 4.5-L WBP, with and without a 1 L/min bias flow. CO(2)-induced changes in breathing frequency (f), tidal volume (Vt), minute ventilation (Ve), and indices of airway function -- including enhanced pause (penh), flow derived parameter (FDP), and respiratory duty cycle -- were measured. Without bias flow, CO(2) in the plethysmograph increased steadily to 5.4% after 30 min compared to a steady state 0.9% with bias flow. This resulted in a moderate suppression of f, and significant increases in Vt and Ve by factors of 1.5 and 1.4, respectively. Changes in regional deposition were stimulated for 300 mg/m(3) polydisperse aerosols with mass median aerodynamic diameters of 0.3, 1, 3, or 7 microm and geometric standard deviations of 1.7. Percent increase in aerosol deposition from CO(2) inhalation ranged from 24% to 90%, by mass, depending on aerosol size distribution and respiratory tract region. In addition, fractional deposition shifted toward the pulmonary region. Empirical indices of airway constriction, penh and FDP, also were increased significantly to 1.7 and 1.3 times their respective baseline values. The study quantifies the effect of inadvertent coexposure to CO(2) on ventilation, aerosol deposition, and airway function in WBP evaluation of aerosol effects in airway function.

Administration, Inhalation↗
PubMed2001

Calibration and validation of an air-displacement plethysmography method for estimating percentage body fat in an elderly population: a comparison among compartmental models.

BACKGROUND: The use of hydrostatic weighing (HW) to measure body composition in the elderly can be difficult and is based on the assumption of constancy of body compartments. OBJECTIVE: We calibrated and validated a new air-displacement plethysmography (AP) method for measuring body composition in the elderly. DESIGN: A 4-compartment equation for calculating percentage body fat (%BF) that used body density (D(b)), total body water, and bone mineral content was used as the criterion for evaluating %BF estimated by the 2- and 3-compartment models. D(b) was measured by HW [D(b(HW))] and by use of the AP instrument [D(b(AP))] in 30 elderly men and 28 elderly women aged 70-79 y. RESULTS: D(b(AP)) was not significantly different from D(b(HW)). However, analysis of variance showed a significant two-way interaction between sex and compartment model (P < 0.02), indicating that the comparisons between the sexes were different across all compartment models. The %BF calculated for the women was significantly higher than that calculated for the men by both HW and AP and for all compartment models. CONCLUSION: Our data indicate that D(b(AP)) was not significantly different from D(b(HW)). Although differences were seen in %BF between the sexes, we observed no significant differences among the compartment models within each sex for this group of older individuals.

Adipose Tissue↗
PubMed2002

Body-composition assessment via air-displacement plethysmography in adults and children: a review.

Laboratory-based body-composition techniques include hydrostatic weighing (HW), dual-energy X-ray absorptiometry (DXA), measurement of total body water (TBW) by isotope dilution, measurement of total body potassium, and multicompartment models. Although these reference methods are used routinely, each has inherent practical limitations. Whole-body air-displacement plethysmography is a new practical alternative to these more traditional body-composition methods. We reviewed the principal findings from studies published between December 1995 and August 2001 that compared the BOD POD method (Life Measurement, Inc, Concord, CA) with reference methods and summarized factors contributing to the different study findings. The average of the study means indicates that the BOD POD and HW agree within 1% body fat (BF) for adults and children, whereas the BOD POD and DXA agree within 1% BF for adults and 2% BF for children. Few studies have compared the BOD POD with multicompartment models; those that have suggest a similar average underestimation of approximate 2-3% BF by both the BOD POD and HW. Individual variations between 2-compartment models compared with DXA and 4 -compartment models are partly attributable to deviations from the assumed chemical composition of the body. Wide variations among study means, -4.0% to 1.9% BF for BOD POD - HW and -3.0% to 1.7% BF for BOD POD - DXA, are likely due in part to differences in laboratory equipment, study design, and subject characteristics and in some cases to failure to follow the manufacturer's recommended protocol. Wide intersubject variations between methods are partly attributed to technical precision and biological error but to a large extent remain unexplained. On the basis of this review, future research goals are suggested.

Absorptiometry, Photon↗
PubMed1985

Photo-electric plethysmography as a monitoring device in anaesthesia. Application and interpretation.

The optical principle of photo-electric plethysmography is described and the clinical significance of changes in the amplitude of the plethysmogram discussed. Physiologically, changes in blood volume pulsations depend on the distensibility of the vessel wall as well as on the intravascular pulse pressure. The importance of both factors in the interpretation of changes in the arterial pulse amplitude is illustrated by examples from 500 continuous recordings. In addition, it is shown that changes in the height of ventilatory waves may be of diagnostic significance.

Anesthesia↗
PubMed1987

Acute ventilatory changes during i.v. induction of anaesthesia with thiopentone or propofol in man. Studies using inductance plethysmography.

We have compared the acute ventilatory changes during induction of anaesthesia with equipotent doses of thiopentone and propofol in 12 premedicated female patients. Using ventilatory inductance plethysmography we have shown that both agents depress respiration to a similar and significant degree (P less than 0.001). However, although the functional residual capacity was reduced in patients receiving propofol, it increased slightly after induction with thiopentone (P less than 0.05).

Adult↗
PubMed2006

Stimulation induced variability of pulse plethysmography does not discriminate responsiveness to intubation.

BACKGROUND: Hypnotic depth but not haemodynamic response to painful stimulation can be measured with various EEG-based anaesthesia monitors. We evaluated the variation of pulse plethysmography amplitude induced by an electrical tetanic stimulus (PPG variation) as a potential measure for analgesia and predictor of haemodynamic responsiveness during general anaesthesia. METHODS: Ninety-five patients, ASA I or II, were randomly assigned to five groups [Group 1: bispectral index (BIS) (range) 40-50, effect site remifentanil concentration 1 ng ml(-1);Group 2: BIS 40-50, remifentanil 2 ng ml(-1); Group 3: BIS 40-50, remifentanil 4 ng ml(-1); Group 4: BIS 25-35, remifentanil 2 ng ml(-1); Group 5: BIS 55-65, remifentanil 2 ng ml(-1)]. A 60 mA tetanic stimulus was applied for 5 s on the ulnar nerve. From the digitized pulse oximeter wave recorded on a laptop computer, linear and non-linear parameters of PPG variation during the 60 s period after stimulation were computed. The haemodynamic response to subsequent orotracheal intubation was recorded. The PPG variation was compared between groups and between responders and non-responders to intubation (anova). Variables independently predicting the response were determined by logistic regression. RESULTS: The probability of a response to tracheal intubation was 0.77, 0.47, 0.05, 0.18 and 0.52 in Groups 1-5, respectively (P<0.03). The PPG variability was significantly higher in responders than in non-responders but it did not improve the prediction of the response to tracheal intubation based on BIS level and effect site remifentanil concentration. CONCLUSION: Tetanic stimulation induced PPG variation does not reflect the analgesic state in a wide clinical range of surgical anaesthesia.

Adult↗
PubMed2005

Need for optimal body composition data analysis using air-displacement plethysmography in children and adolescents.

Air-displacement plethysmography (ADP) is now widely used for body composition measurement in pediatric populations. However, the manufacturer's software developed for adults leaves a potential bias for application in children and adolescents, and recent publications do not consistently use child-specific corrections. Therefore we analyzed child-specific ADP corrections with respect to quantity and etiology of bias compared with adult formulas. An optimal correction protocol is provided giving step-by-step instructions for calculations. In this study, 258 children and adolescents (143 girls and 115 boys ranging from 5 to 18 y) with a high prevalence of overweight or obesity (28.0% in girls and 22.6% in boys) were examined by ADP applying the manufacturer's software as well as published equations for child-specific corrections for surface area artifact (SAA), thoracic gas volume (TGV), and density of fat-free mass (FFM). Compared with child-specific equations for SAA, TGV, and density of FFM, the mean overestimation of the percentage of fat mass using the manufacturer's software was 10% in children and adolescents. Half of the bias derived from the use of Siri's equation not corrected for age-dependent differences in FFM density. An additional 3 and 2% of bias resulted from the application of adult equations for prediction of SAA and TGV, respectively. Different child-specific equations used to predict TGV did not differ in the percentage of fat mass. We conclude that there is a need for child-specific equations in ADP raw data analysis considering SAA, TGV, and density of FFM.

Adolescent↗
PubMed1989

Assessment of the optimal atrio-ventricular delay in DDD paced patients by impedance plethysmography.

The beneficial haemodynamic effects of sequential atrioventricular (AV) pacing have been clearly established and are dependent on the AV delay and pacing rate. However, the optimal AV delay is difficult to determine in each particular patient. We used a modified impedance plethysmographic method to assess variations in stroke volume for different AV delay and pacing rate settings. Impedance measurements showed a good correlation with CO2 rebreathing stroke volume measurements in VVI patients. Impedance variations were then used to set the optimal AV delay at different pacing rates in DDD patients. The inverse relationship between the optimal AV delay and the pacing rate has been accurately identified in most of the patients but is not predictable. In all cases, the cardiac output was higher in DDD mode at the optimal AV delay than in VVI mode. In some patients with a damaged myocardium, the stroke volume appeared to be highly sensitive to multiple AV delay settings. Impedance plethysmography can permit such repetitive non-invasive quick measurements, increasing the accuracy of optimal AV delay determination and is well suited for routine examination of patients with cardiac dual chamber pacemakers.

Atrioventricular Node↗