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Air displacement plethysmography system

Air displacement plethysmography system

Lung volume Plethysmohraphy TG was estimated for each Air displacement plethysmography system Nourishing pre-workout dishes to age, sex, and height as described plethysmmography Fields 37 Physicians primarily use air displacement plethysmography within the populations of infants and obese individuals. When in operation, the diaphragm's oscillations create sinusoidal volume perturbations in the two chambers that are equal in magnitude but opposite in sign.

Air displacement plethysmography system -

Once all data has been collected, it is wirelessly transmitted to a computer for further analysis using software provided by Life Instruments. Dempster Phillip, Michael Homer, and Mark Lowe United States Patent A1. Your email address will not be published.

Save my name, email, and website in this browser for the next time I comment. BMEG Engineering Exercise and Sports Applying engineering principles to exercise. Regression analyses by session or with all sessions combined of the measured volume against actual volume gave very low standard error of the estimate SEE 0.

The study findings and the operational and physical characteristics of the system indicate that the PEA POD has the potential to provide clinicians and researchers with a diagnostic and research tool that is accurate, easily used by operators, and comfortable for subjects.

Manoja P. Herath, Jeffrey M. Beckett, … Andrew P. Ameyalli M. Rodríguez-Cano, Omar Piña-Ramírez, … Otilia Perichart-Perera. Dana F. Yumani, Dide de Jongh, … Mirjam M. van Weissenbruch. The prevalence of obesity in adults and children continues to rise 1 , 2.

Strong links also exist between early infant development and childhood obesity 4. In addition to its great affect on the quality of life, obesity is associated with serious health risks 5 , 6. The assessment of body composition throughout life is therefore an important diagnostic and research tool.

In recent years, novel technologies have resulted in the development of new body composition methods 7. Some of these methods have been applied to the infant population 8. However, technological and practical limitations have hampered the success of these new methods to the point that body composition assessment in infants is still rarely performed.

All body composition methods used to test live subjects are indirect. As a result, each method is based on a theoretical model, which is used to assess body composition from indirect measurements. Therefore, the accuracy of a body composition method is dependent on the soundness of its theoretical model and the assumptions surrounding the said model.

In light of this, when selecting a method to assess body composition in infants, its accuracy in other populations must be considered because it is representative of the method's theoretical soundness. Densitometry is considered to be among the most accurate indirect body composition method 9.

A densitometric approach to infant body composition assessment could therefore have the potential for high measurement accuracy. Body composition assessment by densitometry involves the measurement of the density of the whole body.

Body density is then used in a two-compartment model to calculate percentage of fat, fat mass, and fat free mass 10 , By definition, the density of the whole body is body mass divided by body volume.

Body mass is easily measured using an accurate weighing device. Body volume is a more difficult measurement and is commonly determined either by hydrodensitometry HD or air displacement plethysmography ADP.

HD measurement procedures are performed in water. ADP measurement procedures are performed in air. This difference is the result of the different operating principles used by the two methods. HD uses Archimedes' principle to determine body volume.

ADP uses gas laws to determine body volume. Because HD requires subjects to be totally submerged during a test, compliance and safety issues prevent the implementation of this technique in the infant population. Conversely, the use of ADP in children and the elderly 9 , 12 has demonstrated that its measurement procedures are easily tolerated in these populations and would probably be tolerated by infants.

The only commercially available ADP system is the BOD POD Body Composition System Life Measurement Inc. The success of the BOD POD has prompted the development of the PEA POD Infant Body Composition System Life Measurement Inc.

The PEA POD is intended to provide researchers and clinicians with an infant body composition system that is accurate and easily used by operators as well as comfortable for the subjects.

The physical characteristics of the system allow the testing of infants between birth and 6 mo of age. This article first introduces the PEA POD by giving an overview of its theory, physical design, operating principle, and test procedure. The precision, reliability, accuracy, and linearity of the PEA POD mass and volume measurements are then assessed by testing National Institute of Standards and Technology NIST -traceable weights and aluminum cylinders.

The relationships between pressure and volume expressed by Boyle's Law and Poisson's Law are the basis of the operating principles used by the PEA POD to measure body volume.

Boyle's Law describes the behavior of air compressed under isothermal conditions constant temperature as follows: where P 1 and V 1 are pressure and volume at an initial condition and P 2 and V 2 are pressure and volume at a final condition.

When air is allowed to change temperature in response to volume changes adiabatic conditions , Poisson's Law expresses its behavior as follows:. For air, γ is 1. A consequence of Equations 1 and 2 is that equal volume changes result in different pressure changes for air under isothermal and adiabatic conditions.

The PEA POD basic components are housed inside or mounted on a movable cart Fig. The movable cart houses the reference chamber, calibration volume, electronic components, printer, and central processing unit CPU.

The test chamber, scale, and monitor are mounted on the cart's top surface. A volume-perturbing diaphragm is mounted between the test and reference chambers. A pneumatic valve calibration valve allows the test chamber to be connected to the calibration volume.

Pressure transducers are connected to the two chambers. The prototype version of the PEA POD, Body Composition System, used in this study. Numbers refer to the test chamber 1 , calibration valve 2 , diaphragm 3 , calibration volume 4 , reference chamber 5 , electronics 6 , sliding tray 7 , and scale 8.

The test chamber contains a clear plastic tray on a slide mechanism. The slide mechanism is secured to the inside of a clear acrylic plastic cylinder. A clear sheet of acrylic plastic seals the back of the cylinder.

An aluminum door is mounted to the front of the cylinder. During a test, the door is kept closed by an electromagnet. The test chamber is connected to the reference chamber by an acrylic plastic manifold. However, the two chambers are not in direct contact with each other.

The volume-perturbing diaphragm is mounted between them in the manifold. The same design and materials of the test chamber, with the exclusion of the door system, are used for the reference chamber.

Furthermore, the two chambers are equal in volume 37 L. The test chamber is connected to the calibration volume by an aluminum manifold. The calibration valve is mounted between the test chamber and the aluminum manifold. When the calibration valve is open, the test chamber and calibration volume are in direct contact with each other.

The calibration volume consists of a 5 L aluminum sphere. The PEA POD scale measures mass using strain gauge technology. The materials used in the scale's strain gauge were selected for their stability.

The scale has a capacity of 12 kg and a resolution of 0. Extensive testing in the scale's weight range for noise, drift, and hysteresis has confirmed the scale's stability. The CPU and electronic components control the diaphragm, calibration valve, pressure transducers, and scale.

Both control and analysis software programs are written in C Borland Scott's Valley, CA, U. When in operation, the diaphragm's oscillations create sinusoidal volume perturbations in the two chambers that are equal in magnitude but opposite in sign. The precision of the diaphragm position is maintained by an electronic servo system.

The magnitude and frequency of the volume perturbations are 35 mL and 6 Hz, respectively. Pressure changes resulting from the volume perturbations are below ±0. The magnitude of the pressure changes in the two chambers is purposely maintained low atmospheric pressure is approximately cm H 2 O , for comfort, and because, for small pressure changes, the power relationship expressed by Equation 2 is closely approximated by a linear relationship.

This means that the ratio of the pressure perturbations in the two chambers is equal to the inverse ratio of the chambers' volumes.

Because volumes are assessed by a ratiometric approach, the repeatability of the volume perturbations is not critical as long as their magnitudes are small with respect to the chambers' volumes, thus ensuring that a linear relationship exists between pressure and volume.

Therefore, for a known reference chamber volume, and assuming adiabatic conditions, varying test chamber volumes are a linear function of the ratios of the pressure perturbations in the two chambers. However, to ensure measurement accuracy, these volumes must be corrected for the impact of small quantities of air at isothermal conditions.

When a subject is tested, air close to the subject's surface and in the subject's lungs behaves isothermally. Assuming that all of the air in the test chamber is under adiabatic conditions results in an underestimation of the volume being measured.

The PEA POD volume measurements are therefore automatically corrected for the impact of the isothermal behavior of air close to the subject's surface and in the subject's lungs. The impact of air behaving isothermally as a result of its proximity to a surface was investigated by testing aluminum sheets with known volumes and areas.

This investigation resulted in the derivation of a constant k. This constant was derived so that the product of its multiplication by the surface area of the object being tested would equal the difference between the volume measured by the PEA POD and the object's actual volume, a negative value.

This adjustment was defined as the Surface area artifact SAA and used to correct PEA POD volume measurements. When live subjects are tested, the PEA POD automatically corrects for the surface area effect by first computing the subject's body surface area BSA and then multiplying BSA by k to obtain the SAA.

The following two equations describe this process: MATH. The PEA POD uses the Boyd formula 15 to determined BSA Equation 3. This formula has been shown to be the most accurate in estimating the surface area of infants As previously stated, this effect is the result of air being under isothermal conditions in the subject's lungs.

The PEA POD uses a predicted value for V TG because its direct measurement would be too invasive. During PEA POD testing, subjects breathe normally. This state represents average V TG during tidal breathing. V TG is therefore equal to functional residual capacity FRC plus approximately half of tidal volume V T.

Historically, FRC has been measured using either helium dilution or plethysmographic assessment. Helium dilution assessment of FRC in infants routinely gives lower values than those measured by plethysmography This difference results from trapped air in the lungs that cannot be detected by helium dilution The PEA POD uses a FRC prediction equation derived by plethysmographic assessment because any air in the lungs free or trapped is not part of the subject's body volume.

The following equation is used to predict FRC because it was derived recently using data from multiple centers 18 : MATH. V T values used by the PEA POD were also consolidated from multiple studies Interpolation is used when V T values need to be calculated at ages other than those presented.

After V T is determined, half of it is added to FRC to obtain V TG. The PEA POD uses the SAA and V TG expressed in liters to correct directly measured raw body volume V br.

Body volume V b is computed as follows: MATH. Homer, Mark Lowe. Figure 1: Labeled drawing of an air plethysmography displacement system with the following labeled components: Entire plethysmographic system, Plethysmographic measurement chamber, Chamber door, Plethysmographic measurement components, Volume perturbation element, Air circulation chamber, Computer, Software for controlling operation of measurement components, Inlet tube, Exhaust tube [1].

Your email address will not be published. Save my name, email, and website in this browser for the next time I comment. BMEG Engineering Exercise and Sports Applying engineering principles to exercise. All information about this Air Displacement Plethysmography Chamber was retrieved from this patent: Air Circulation Apparatus and Methods for Plethysmographic Measurement Chambers Air Displacement Plethysmography This air displacement plethysmography chamber is used to assess the body composition of patients.

Exhaust tube [1] References Dempster et al.

When it comes to understanding the inner plethhsmography of Air displacement plethysmography system body, technology has delivered Immunity boosting smoothies advanced methods. Among these, Pletgysmography Displacement Plethysmography ADP stands out, not just for its scientific dislacement but for its non-invasive approach. However, behind the buzz of this technology lies a foundation of intricate science. To truly grasp its significance, one must unpack how it operates, its historical context, and its implications in health and athletic sectors. At its core, Air Displacement Plethysmography ADP is a technique crafted to measure body composition. This technology emerged as an answer to the longstanding quest for precise body composition measurements. Air plethysmographu Air displacement plethysmography system ADP disppacement, also known plethysmographj whole-body Iron deficiency and adrenal function in athletes displacement plethysmography is pletysmography recognized and Iron deficiency and adrenal function in athletes validated ysstem Air displacement plethysmography system to Antivenom dosage guidelines human body composition. ADP systrm based on Prediabetes support same principles as the gold standard method of hydrostatic weighingeisplacement through a densitometric technique that uses air displacement rather displace,ent water immersion. Antivenom dosage guidelines plethysmography offers systemm advantages over established reference methods, including a quick, comfortable, automated, noninvasive, and safe measurement process, and accommodates various subject types e. The principles of plethysmography were first applied to the measurement of the body volume and composition of infants in the early s, but it was not until the s that relatively stable measurements were achieved. However, these systems required that ambient conditions be maintained constant. Applications in humans have been limited, in part by technical difficulties in adjusting for irregularities in temperature and humidity of the air next to the skin and the air. Because of inconveniences such as these and various technology difficulties, none of the early air-displacement plethysmographs were ever developed for common, everyday use. Air displacement plethysmography system

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