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At least 847 records · Page 47Linked to original sources
PubMed1993

Pre-term infant volume measurements by acoustic plethysmography.

An acoustic plethysmograph has been developed to provide routine total body volume measurements of pre-term (1.5-3.0 kg) infants. It operates near 50 Hz and is excited by band-limited 25 Hz span noise. Excitation, measurement, analysis, and environment are computer controlled for greater accuracy, speed, and objectivity in volume determinations. Performance tests produced volume measurements with a mean per cent error (+/- SD) of 0.77 +/- 0.66% for two phantoms with volumes of 2880 and 2130 cm3. Ten, one-minute volume measurements were obtained for 14 infants over a 20 to 30 min period. Their mean density was 1.061 +/- 0.028 g cm-3 and their weight ranged from 1294 to 2025 g.

Body Composition↗
PubMed1987

Quantitative evaluation of arterial pulsatile flow and pressure, applying impedance plethysmography to a human arterial model incorporating anatomical branching and scale.

This paper presents the theoretical basis of a new noninvasive method for obtaining arterial pulsatile flow and pressure. The proposed technique uses a model of the human arterial system based on the anatomical branching structure of the arterial tree. Arteries are divided into segments represented by uniform thin-walled elastic tubes with realistic arterial dimensions and wall properties. A simple mathematical model equivalent to electrical transmission lines is developed which is able to fit the electrical impedance plethysmograph waveform produced by the subjects throughout the complete cardiac cycle. Ensemble averaging is suggested as an option for processing of the impedance data. This technique provides artifact-free impedance data which enables the model to be used during exercise as well as quiet breathing. The proposed model provides an enhanced capability for measuring pulsatile blood flow and pressure in both clinical and research applications.

Arteries↗
PubMed1991

Using LabVIEW to facilitate calibration and verification for respiratory impedance plethysmography.

A system for calibrating the Respitrace impedance plethysmograph was developed with the capacity to quantitatively verify the accuracy of calibration. LabVIEW software was used on a Macintosh II computer to create a user-friendly environment, with the added benefit of reducing development time. The system developed enabled a research assistant to calibrate the Respitrace within 15 min while achieving an accuracy within the normally accepted 10% deviation when the Respitrace output is compared to a water spirometer standard. The system and methods described were successfully used in a study of 10 subjects smoking cigarettes containing marijuana or cocaine under four conditions, calibrating all subjects to 10% accuracy within 15 min.

Analog-Digital Conversion↗
PubMed1988

Assessment of airway reactivity in guinea pigs: comparison of methods employing whole body plethysmography.

Airway reactivity of guinea pigs was assessed while animals were in whole body plethysmographs by measurement of responses to histamine aerosol. Histamine was delivered using 2 protocols: one employed exposure to a single concentration, the other utilized 1.5-fold stepped concentrations. Both protocols were tested while animals inhaled ambient air, and again when the air contained 10% CO2. Exposures to single concentrations of histamine in air produced increases in both respiratory frequency (f) and plethysmograph pressure (delta P). The latter increase was shown to coincide with a decrease in tidal volume and with the onset of airway constriction. The time to reach a doubling in delta P represented a quantitative measure of airway reactivity. Exposures using the single concentration method in conjunction with 10% CO2 also demonstrated a dose-dependent time to reach the endpoint, in this case a 33% decrease in delta P from the maximum CO2-induced increase. The endpoints for the stepped concentration protocols were the concentration required to double delta P (PC2.delta P) or, in the presence of 10% CO2, the concentration that induced a 33% decline from the maximum delta P (PC33 (CO2]. Mean values for PC2.delta P and PC33 (CO2) were 2.1 mg/m3 and 0.58 mg/m3, respectively. These endpoints were comparable based on the dose received as calculated from the minute volume of animals when breathing the above atmospheres. The intersubject variability, assessed using both stepped concentration protocols, was comparable to that reported for PC20 FEV1 in human studies. Both stepped concentration protocols, conducted in air, or the 10% CO2 atmospheres, proved suitable for determination of airway reactivity of the unrestrained, unanesthetized guinea pigs. However, by not requiring use of CO2, the histamine in air approach is easier to perform, requires less time, and provides a clear endpoint representing early airway constriction.

Aerosols↗
PubMed2006

The application of surface plethysmography for heart rate variability analysis after GSM radiofrequency exposure.

The aim of the present study was to test whether the electromagnetic field emitted by standard GSM mobile phones results in changes in heart rate (HR) and heart rate variability (HRV) of 35 healthy young male and female subjects. Two parallel signals, electrocardiogram and infrared surface plethysmogram were recorded and compared to test their validity for the analysis. Plethysmographic recording is proved to be a fast and reliable method for HRV measurements. In the radiofrequency (RF) exposure study, there was no significant difference in the values of HR and HRV between the RF and the sham groups. Our preliminary study demonstrates that, in our experimental conditions, RF fields emitted by cellular phones do not cause observable effects on the regulation of heart rate of healthy, young adults.

Adult↗
PubMed2005

Canine awake head-out plethysmography (HOP): characterization of external resistive loading and spontaneous laryngeal paralysis.

We applied a novel head-out plethysmographic (HOP) method to study awake canine responses to external resistive loading and natural laryngeal paralysis. Measurements of inspiratory and expiratory specific airway resistance (sRaw(insp), sRaw(exp)) were obtained before and after uni- and bidirectional loading (R(add) = 5 cmH(2)O/L/s) in large-breed dogs (n = 9). Mean sRaw(insp) after inspiratory, and sRaw(exp) after expiratory loading were 31.4 and 33.3 cmH(2)Os, respectively. Bidirectional loads induced a significantly greater rise in both sRaw(insp) and sRaw(exp) (55.1 and 61.3 cmH(2)Os) compared to unidirectional loading (P < 0.001). Yet, type of loading did not affect flow-volume indices. The mean R(aw) of dogs was 4.81 cmH(2)O/L/s. Expiratory loading resulted in a significant 8.8% increase in functional-residual-capacity (FRC), compared to FRC(baseline) (76.7 ml/kg). Dogs (n = 5) with laryngeal paralysis demonstrated a significant increase in sR(aw) and R(aw) compared to controls without changes in FRC. In conclusion, HOP precisely characterized sR(aw) in response to external resistive loading. Hence, we could accurately quantify airway obstruction in awake dogs with laryngeal paralysis.

Airway Resistance↗
PubMed1983

Computerized body plethysmography: an algorithm for minimizing drift and hysteresis.

The use of linear regression for on-line data processing of airway resistance measurements in the body plethysmograph may be difficult. When airflow (V) is plotted against plethysmographic pressure (Pbox), the resulting loop exhibits hysteresis and may drift along the PBox axis. Although the slope of the V-PBox loop can be estimated visually, computer calculations of the slope are difficult if baseline drift is present. Taking the derivatives of V and PBox eliminates the effect of drift and reduces the loops to a series of essentially parallel lines from which the slope can be readily calculated using linear regression. The identical technique can be employed when mouth pressure is plotted against plethysmographic pressure, enabling on-line calculation of thoracic gas volume.

Airway Resistance↗
PubMedDate not supplied

Continuous assessment of multiple vital physiological functions in conscious freely moving rats using telemetry and a plethysmography system.

The general pharmacologist in the pharmaceutical industry is challenged to generate physiologically relevant data on possible safety liabilities or on secondary therapeutic uses as early as possible in drug development. This implies the need for efficient use of usually only small supplies of test article. For this reason, we have developed a new animal model combining various elements to provide a broad spectrum of data focussing on the so-called vital physiological functions: cardiovascular, respiratory, and central nervous system. This system uses rats chronically implanted with transmitters for the measurement of arterial pressure, ECG, and body temperature. Modification of the transmitters also allows for the simultaneous assessment of locomotor activity. Studies are performed with these rats in plethysmographs placed directly over the antenna units thus allowing for the additional assessment of respiratory function in the same studies. Using this system, we can generate simultaneously a wide range of relevant physiological parameters in conscious rats with a modest requirement for test article. Such an approach is highly useful for getting early safety readouts of potential drug development candidates as well as for detecting possible secondary therapeutic actions of a drug.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMedDate not supplied

Pulmonary function assessment by whole-body plethysmography in restrained versus unrestrained mice.

INTRODUCTION: The evaluation of pulmonary physiological measurements in laboratory animals is an essential tool in many biomedical and toxicological research areas. Recently, an unrestrained single chambered whole-body plethysmograph that utilizes a barometric analysis technique to quantify pulmonary physiological values has gained widespread use. However, results generated with the single chamber plethysmograph have come under increased scrutiny because airflow in the lung is indirectly measured. The purpose of the present study was to use mice with known interstrain differences in pulmonary physiology (A/J, BALB/c, CD-1, and B6C3F1) and compare the physiological data generated with a single chamber plethysmograph to data obtained in the widely accepted double chamber noninvasive airway mechanics (NAM) plethysmograph in which the animals are restrained. METHODS: Animals were placed into the plethysmographs and baseline physiological data acquired. The mice were then subjected to challenge with aerosols generated from isotonic saline (control) and methacholine solutions of increasing concentration (2.5-320 mg/ml) for 3 min for determination of the concentration of methacholine that induced a 200% increase in airway resistance (PC(200)R). RESULTS: Repeated physiological measurements on the same animals in both the single and double chamber plethysmographs demonstrated that each instrument generated reproducible baseline physiological data. However, comparison of physiological data generated with the double-chambered instrument to that generated with the single chamber plethysmograph revealed several significant differences. While the single chamber plethysmograph appeared to give inaccurate measurements of tidal volume, it provided much better analysis of airway reactivity based on PC(200)R results. In contrast, the double chamber plethysmograph provided accurate physiological data such as tidal volume and respiratory rate, but provided inaccurate and irreproducible airway reactivity results based on PC(200)R. DISCUSSION: Our results indicate that the choice of single or double chamber plethysmograph for physiological measurements should be linked to the study objectives and the type of data required.

Administration, Inhalation↗
PubMed1999

Reliability of infrared plethysmography in BVP biofeedback therapy and the relevance for clinical application.

Biofeedback methods are well established as behavioral techniques for the therapy of various psychophysiological diseases. The forms of feedback generally employed are muscle activity (electromyogram), skin temperature, brain activity (electroencephalogram), and vasomotoricity. The latter technique, which employs plethysmographic feedback, has been studied most extensively in the therapy of migraine (vasoconstriction training, blood volume pulse training). Although the clinical efficacy has been demonstrated in several studies, little is known about the psychometric properties of this technique. This study examined the intrasession and intersession reliability of the pulse volume amplitude (PVA). The results showed that the PVA measurements within a single biofeedback session were highly reliable. Repositioning of the probe within the session resulted in a lower correlation coefficient, but one that was still sizable and significant. The PVA values from different sessions were not reliable (or comparable).

Adult↗
PubMed1981

Digital plethysmography for assessing erythrityl tetranitrate bioavailability.

The bioavailability or oral, sublingual, and chewable tablets or erythrityl tetranitrate (ETN) was evaluated in 15 normal men. In a randomized, complete crossover investigation with nitroglycerin and placebo controls, drug-induced changes in the diastolic amplitude response intensity were measured with a digital plethysmogram. Values for area under the response intensity curve (AUC), maximum response intensity (Imax), and time lapse from dosing to peak response (tmax) were obtained by computer processing and converted to intensity values and AUC segments for specific time intervals. Sublingual nitroglycerin induced a response (p less than 0.05) from placebo within the first hour. Although somewhat slower in reaching peak intensity, all forms of ETN induced significant responses over placebo (p less than 0.05) for 2 hr, with oral (swallowed) ETN different 6 hr. Our results indicate that all the ETN dosage forms were bioavailable, with the longest duration of effect by the oral form.

Administration, Oral↗