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PubMedDate not supplied

[The use of impedance plethysmography in the forensic medical diagnosis of the time of death].

Diagnosis of the time of death (DTD) is a pressing problem of forensic medicine. For defining the criteria of DTD by impedance plethysmography, electric conductivity of tissues was studied in 45 corpses of male subjects aged 18-44 years who died from craniocerebral injuries. Autolytic changes were characterized by a wave-like pattern, with periods of stability replaced by necrobiotic processes. This allows recording residual activity of surviving cells and tissues in a corpse during the early postmortem period. Based on these data, a model of postmortem changes in tissues can be created for DTD.

Adult↗
PubMed1993

Computerized photo-plethysmography of the finger.

A microcomputer system for studying photo-plethysmography of the finger (PPF) was designed and applied to 50 non-premedicated healthy boys (one to ten years old) undergoing general anaesthesia (halothane in 70% N2O, with mechanical ventilation) for outpatient inguinal hernia repair. The purpose of this study was to assess the accuracy of computerized estimations of the photo-plethysmographic (arterial waves) amplitude and to evaluate whether or not PPF allows discrimination between two different surgical stimuli (skin incision, and manipulation of the spermatic cord). When anaesthesia was stable for at least five minutes (end-tidal halothane = 1.25-1.5%; PETCO2 = 32-38 mmHg; SpO2 > or = 98%; rectal temperature = 36.3-37 degrees C; ambient operating room temperature = 20-21 degrees C), and immediately before the skin incision, computerized estimations of the photo-plethysmographic (arterial waves) amplitudes (PPA) were recorded and saved for later comparison with direct (manual) measurements of the plethysmographic tracing, using an arbitrary scale of 0-255 units. Also, the values of PPA, systolic blood pressure, and pulse rate recorded immediately before the skin incision were later compared with the maximum changes in these same values recorded 30-90 sec after skin incision, and 30-90 sec after manipulation (traction+dissection) of the spermatic cord. Six boys (three to ten years old) stayed quiet enough, during induction of anaesthesia by mask, to allow regression analysis of PPA, systolic blood pressure, and pulse rate (Y) on end-tidal halothane/70% N2O (X). Computerized estimations tended to give a higher reading, by between 0.2 to 0.8 units, than direct measurements.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Inhalation↗
PubMed1998

[Exhale nitric oxide (NO) and respiratory function measured with body plethysmography in children].

BACKGROUND: Exhaled nitric oxide (NO) may be a marker of airway inflammation. Previous studies in adults have shown that the level of NO in exhaled air is influenced by several factors (breath holding, exercise, etc), or by several disease (asthma, congestive heart failure, diseases of the upper respiratory tract, cystic fibrosis, etc). However, few studies have been performed in children less than 3 years of age. The aim of this study was to determine endogenous NO levels in children with various diseases during lung volume measurements. PATIENTS AND METHODS: Fifty-two children aged 18.3 +/- 9.5 months were studied. The population was divided in two groups, according to the underlying disease: a group of 39 children with cystic fibrosis (n = 7), bronchopulmonary dysplasia (n = 17), asthma (n = 7) or recurrent respiratory tract infections (n = 8) and a second group of 13 children without respiratory disease. Lung function was measured by whole body plethysmography and several respiratory parameters were calculated (functional residual capacity [FRC], compliance and resistances of the respiratory system, trapped volume). NO production was measured on a chemiluminescence analyzer from mixed exhaled air collected into a bag, over a period of 5 minutes. RESULTS: NO production was related to disease: exhaled NO levels were three times higher in bronchopulmonary dysplasia and cystic fibrosis, compared to NO levels in children without respiratory disease. They were higher in asthma. They were not altered in recurrent respiratory tract infections. No correlation was found between respiratory parameters and NO production. However, exhaled NO levels were correlated to trapped volume, which defined dynamic part of pulmonary hyperinflation. CONCLUSION: Levels of endogenous NO in infants were similar to those measured in adults with and without inflammatory respiratory disease. Lung distention influenced exhaled NO production.

Biomarkers↗
PubMed1978

The noninvasive diagnosis of thrombophlebitis in the lower extremities: clinical value of plethysmography combined with augmentation methods and a new scoring system.

Venous impedance plethysmography and respiratory-compression Doppler augmentation responses have proved to be diagnostically valuable in suspected thrombophlebitis of the lower extremities. These noninvasive methods can provide quantitative and reproducible data on the basis of which the presence of increased deep venous resistance can be confirmed, suspected, or doubted. A new scoring system for the composite evaluation of data from 100 consecutive patients with possible thrombophlebitis, pulmonary embolism, or both, is presented. These procedures assume added importance in view of the diagnostic limitations, and even potential hazards, of other methods. These methods indluce lung scanning, radioactive fibrinogen scanning, venography, and pulmonary angiography. Serial studies can be performed with impunity for following highrisk patients and evaluating various therapeutic or prophylactic measures. The importance of monitoring the femoral-popliteal segment is emphasized, because of the greater propensity for massive pulmonary thromboembolism from thrombi in these veins than in the calf vessels. Clinical observations coupled with these studies underscore the fallacy of several widely-held diagnostic biases pertaining to deep venous thrombosis and pulmonary thromboembolism. The long-term followup of 12 patients in whom inferior vena cava unbrellas has been inserted for life-threatening pulmonary embolism is presented. The possible propensity to deep vein thrombosis from vitamin E therapy is raised.

Adult↗
PubMed2004

Assessment of body composition by air-displacement plethysmography: influence of body temperature and moisture.

BACKGROUND: To investigate the effect of body temperature and moisture on body fat (%fat), volume and density by air-displacement plethysmography (BOD POD). METHODS: %fat, body volume and density by the BOD POD before (BOD PODBH) and immediately following hydrostatic weighing (BOD PODFH) were performed in 32 healthy females (age (yr) 33 +/- 11, weight (kg) 64 +/- 14, height (cm) 167 +/- 7). Body temperature and moisture were measured prior to BOD PODBH and prior to BOD PODFH with body moisture defined as the difference in body weight (kg) between the BOD PODBH and BOD PODFH measurements. RESULTS: BOD PODFH %fat (27.1%) and body volume (61.5 L) were significantly lower (P </= 0.001) and body density (1.0379 g/cm3) significantly higher (P </= 0.001) than BOD PODBH %fat (28.9%), body volume (61.7 L), and body density (1.0341 g/cm3). A significant increase in body temperature (~0.6 degrees C; P </= 0.001) and body moisture (0.08 kg; P </= 0.01) were observed between BOD PODBH and BOD PODFH. Body surface area was positively associated with the difference in %fat independent of changes in body temperature and moisture, r = 0.30, P < 0.05. CONCLUSION: These data demonstrate for the first time that increases in body heat and moisture result in an underestimation of body fat when using the BOD POD, however, the precise mechanism remains unidentified.

Journal Article↗
PubMed2005

Effect of short schemes on body composition measurements using air-displacement plethysmography.

BACKGROUND: Air-displacement plethysmography (ADP) is becoming a popular method to assess body composition. Several studies have shown certain types of clothing can affect measurements of body density, however no study has specifically investigated the effect of cotton gym shorts and spandex bicycle shorts on body density. METHODS: Thirty-seven males (23.0 +/- 3.2 yr., 177.3 +/- 5.4 cm., 74.8 +/- 7.5 kg.) and thirty-eight females (23.7 +/- 5.3 yr., 163.6 +/- 8.4 cm., 57.1 +/- 7.0 kg.) had their body density measured by ADP in three clothing schemes: 1) a tight fitting Speedo swim suit (criterion measure), 2) cotton gym shorts, and 3) spandex bicycle shorts. The clothing was provided by the University of Oklahoma Body Composition Laboratory and the testing schemes were performed in random order. RESULTS: The regression of body density by the criterion measure against body density while wearing cotton gym shorts for the entire group (y = 0.001 + 0.991x, SEE = 0.003 g/cm3) and the females (y = 0.059 + 0.934x, SEE = 0.003 g/cm3) did not significantly deviate from the line of identity. However in males the regression significantly deviated from the line of identity (y = 0.052 + 0.944x, SEE = 0.002 g/cm3). Body density by the criterion measure and body density while wearing spandex bicycle shorts did not significantly differ from the line of identity for the entire group (y = -0.018 + 1.013x SEE = 0.003 g/cm3), in males (y = -0.002 + 1.001x, SEE = 0.003 g/cm3), or females (y = 0.073 + 0.925x, SEE = 0.003 g/cm3). Residual plot analysis revealed no group or gender bias in either the cotton gym shorts or in the spandex bicycle shorts. CONCLUSION: It would appear bicycle spandex shorts are an acceptable alternative to a Speedo like swim suit, however we advise that subjects adhere to the strict clothing protocol that is recommended by the manufacturer.

Journal Article↗
PubMed2006

Validity of air-displacement plethysmography in the assessment of body composition changes in a 16-month weight loss program.

OBJECTIVE: To compare the accuracy of air displacement plethysmography (ADP) and dual energy x-ray absorptionmetry (DXA) in tracking changes in body composition after a 16 month weight loss intervention in overweight and obese females. METHODS: 93 healthy female subjects (38.9 +/- 5.7 yr, 159.8 +/- 5.6 cm, 76.7 +/- 9.9 kg, 30.0 +/- 3.4 kg/m2) completed a 16 month weight loss intervention. Eligible subjects attended 15 treatment sessions occurring over the course of 4 months with educational content including topics relating to physical activity and exercise, diet and eating behavior, and behavior modification. In the remaining 12 months, subjects underwent a lifestyle program designed to increase physical activity and improve eating habits. Before and after the intervention, subjects had their percent body fat (%fat), fat mass (FM), and fat-free mass (FFM)) assessed by DXA and ADP. RESULTS: Significant differences (p < or = 0.001) were found between DXA and ADP at baseline %fat (46.0 % fat vs. 42.0 % fat), FM (35.3 kg vs. 32.5 kg) and FFM (40.8 kg vs. 44.2 kg) as well as at post intervention for %fat (42.1% fat vs. 38.3 % fat), FM (30.9 kg vs. 28.4 kg) and FFM (41.7 kg vs. 44.7 kg). At each time point, ADP %fat and total FM was significantly lower (p < or = 0.001) than DXA while FFM was significantly higher (p < or = 0.001). However, both techniques tracked %fat changes similarly considering that there were no differences between the two means. Furthermore, a Bland-Altman analysis was performed and no significant bias was observed, thus demonstrating the ability of ADP to measure body fat across a wide range of fatness. CONCLUSION: At baseline and post weight loss, a significant difference was found between ADP and DXA. However, the results indicate both methods are highly related and track changes in %fat similarly after a weight loss program in overweight and obese females. Additionally, the mean changes in %fat were similar between the two techniques, suggesting that ADP can be translated to its use in clinical practice and research studies as DXA currently is used.

Journal Article↗
PubMed2006

A method for exposing rodents to resuspended particles using whole-body plethysmography.

BACKGROUND: Epidemiological studies have reported increased risks of cardiopulmonary-related hospitalization and death in association with exposure to elevated levels of particulate matter (PM) across a wide range of urban areas. In response to these findings, researchers have conducted animal inhalation exposures aimed at reproducing the observed toxicologic effects. However, it is technically difficult to quantitate the actual amount of PM delivered to the lung in such studies, and dose is frequently estimated using default respiration parameters. Consequently, the interpretation of PM-induced effects in rodents exposed via whole-body inhalation is often compromised by the inability to determine deposited dose. To address this problem, we have developed an exposure system that merges the generation of dry, aerosolized particles with whole-body plethysmography (WBP), thus permitting inhalation exposures in the unrestrained rat while simultaneously obtaining data on pulmonary function. RESULTS: This system was validated using an oil combustion-derived particle (HP12) at three nominal concentrations (3, 12, and 13 mg/m3) for four consecutive exposure days (6 hr/day); a single 6-hour exposure to 13 mg/m3 of HP12 was also conducted. These results demonstrated that the system was both reliable and consistent over these exposure protocols, achieving average concentrations that were within 10% of the targeted concentration. In-line filters located on the exhaust outlets of individual WBP chambers showed relative agreement in HP12 mass for each day and were not statistically different when compared to one another (p = 0.16). Temperatures and relative humidities were also similar between chambers during PM and air exposures. Finally, detailed composition analyses of both HP12 filter and bulk samples showed that grinding and aerosolization did not change particle chemistry. CONCLUSION: The results of this study demonstrate that it is possible to expose rodents to resuspended, dry PM via whole-body inhalation while these animals are maintained in WBP chambers. This new methodology should significantly improve the ability to assess dosimetry under minimally stressful exposure conditions.

Journal Article↗
PubMed1995

Time-frequency spectral analysis of electric field plethysmography signals.

Cardiac activity contaminates respiratory electric field plethysmography (EFPG) signals, and vice versa, and is usually treated as an artefact. On the other hand, simultaneous information on respiration and cardiac activity is often required in clinical practice. Hence, we use time-frequency spectral analysis (TFSA) by means of the spectrogram (SG) to investigate the instantaneous cardio-respiratory information contained in EFPG-signals and show that it is a practical means of extracting this information out of a single EFPG-signal. Comparisons with a Wigner distribution reveal sufficient time-frequency resolution of the SG for detection of physiological events in EFPG-signals. SG-analysis indicates spectral peaks related to respiration and cardiac activity (depending on the electrode configuration, up to the third and fifth harmonic, respectively) and the possibility to detect respiratory sinus arrhythmia by means of EFPG-measurements. Intermodulation products cause overlaps of respiratory and cardiac spectra pointing out nonlinear relationships. Additionally, SG-analysis supplies essential information for the separation of EFPG-signals into respiratory and cardiac components, by means of filter techniques.

Adolescent↗
PubMedDate not supplied

Electric field plethysmography signals of the human thorax as determined by a 2-D FE-model.

Electric field plethysmography (EFPG) signals of the human thorax consist of a baseline component, a respiratory component and a cardiac component. This paper investigates to what extent a two-dimensional finite-element model of the human thorax can serve as a tool for signal prediction allowing for both optimisation of electrode position and effective signal interpretation. In the model inspiration is taken into account by decreasing lung conductivity. Modelling of cardiac activity involves heart geometry changes and lung conductivity increase. Comparison with experiments shows that the model is more effective for strip than spot electrodes for current injection. Modelling results suggest that the thorax behaves approximately as a homogeneous structure with an inspiratory conductivity increase of about 5%. Two electrode pairs are preferable for monitoring respiration in general. As cardiac activity involves two counter-acting signal sources in the thorax, optimum electrode position is obtained using four separated electrodes. However, recommendable positions for two electrode pairs are on the left sternal and right parasternal line. The investigation shows that in providing a proper modelling of respiration and cardiac activity, a 2-D model provides a practical tool for modelling EFPG signals with the cost of a few structural and systematical restrictions.

Cardiography, Impedance↗