Studies of Pulmonary Capacity and Mixing With the Nitrogen Meter 1

Wolfe, William A.; Carlson, Loren D.

doi:10.1172/jci102398

Cited by 15 publications

(4 citation statements)

References 10 publications

(8 reference statements)

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“…The participants were weighed underwater a minimum of 6 times, and the mean of the 3 heaviest weights was used to calculate body density. Residual lung volume was measured before underwater weighing using the closed-circuit nitrogen dilution technique 29. Total percentage of body fat (%BF) was calculated from body mass density using Siri’s equation for Caucasians and Hispanics or Schutte’s equation for African Americans, and fat mass and fat free mass were calculated from body weight 30,31…”

Section: Research Methods and Proceduresmentioning

confidence: 99%

Seasonal Changes in Amount and Patterns of Physical Activity in Women

Buchowski¹,

Choi²,

Majchrzak³

et al. 2009

Journal of Physical Activity and Health

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Section: Research Methods and Proceduresmentioning

confidence: 99%

Seasonal Changes in Amount and Patterns of Physical Activity in Women

Buchowski¹,

Choi²,

Majchrzak³

et al. 2009

Journal of Physical Activity and Health

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“…To date, no method has been wholly satisfactory (3). One approach has been by study of the time course of equilibration of alveolar gas with a "foreign" inspired gas, such as H2 (4), He (5-7) or pure 02 (8)(9)(10)(11)(12)(13)(14)(15). A principal difficulty has been to differentiate between the effects of an enlarged respiratory dead space and of uneven alveolar ventilation, both of which can retard the completion of equilibration.…”

mentioning

confidence: 99%

Lung Function Studies. Viii. Analysis of Alveolar Ventilation by Pulmonary N2 Clearance Curves 12

Fowler¹,

Cornish²,

Kety³

1952

J. Clin. Invest.

218

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A comprehensive analysis of pulmonary fuinction must include measurements of pulmonary ventilation, diffusion, and circulation. An accurate measurement of alveolar ventilation, independent of diffusion and circulation, is desirable. To date, no method has been wholly satisfactory (3). One approach has been by study of the time course of equilibration of alveolar gas with a "foreign" inspired gas, such as H2 (4) Most simply, the lungs could be represented by a bellows which is uniformly ventilated, i.e., inspired gas is distributed evenly to and mixed instantly with all the gas previously present in the bellows. For simplicity, it will be assumed for the moment that inspired gas contains no N,, and that there is no transfer of N2 from blood and tissue.

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“…VN 2 bag can be found by multiplying the bag nitrogen fraction with the total volume accumulated in the bag. With the advent of the nitrogen analyzer [ 2 ], the mass spectrometer [ 3 ] and the use of high precision spirometers the washout could be followed on a breath-by-breath basis [ 4 ]. This refinement eliminated the need for the bag and replaced the numerator in Equation ( 1 ) with the expired volumes of nitrogen summed over the number of breaths.…”

Section: Introductionmentioning

confidence: 99%

Validation and Clinical Application of a First Order Step Response Equation for Nitrogen Clearance During FRC Measurement

Choncholas

Søndergaard

Heinonen

2007

J Clin Monit Comput

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ObjectiveTo derive a difference equation based on mass conservation and on alveolar tidal volumes for the calculation of Functional Residual Capacity. Derive an equation for the FRC from the difference equation. Furthermore, to derive and validate a step response equation as a solution of the difference equation within the framework of digital signal processing where the FRC is known a priori.MethodsA difference equation for the calculation of Functional Residual Capacity is derived and solved as step response of a first order system. The step response equation calculates endtidal fractions of nitrogen during multiple breath nitrogen clearance. The step response equation contains the eigenvalue defined as the ratio of FRC to the sum of FRC and alveolar tidal ventilation. Agreement of calculated nitrogen fractions with measured fractions is demonstrated with data from a metabolic lung model, measurements from patients in positive pressure ventilation and volunteers breathing spontaneously. Examples of eigenvalue are given and compared between diseased and healthy lungs and between ventilatory settings.ResultsComparison of calculated and measured fractions of endtidal nitrogen demonstrates a high degree of agreement in terms of regression and bias and limits of agreement (precision) in Bland & Altman analysis. Examples illustrate the use of the eigenvalue as a possible discriminator between disease states.ConclusionThe first order step response equation reliably calculates endtidal fractions of nitrogen during washout based on a Functional Residual Capacity. The eigenvalue may be a clinically valuable index alone or in conjunction with other indices in the analysis of respiratory states and may aid in the setting of the ventilator.

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Studies of Pulmonary Capacity and Mixing With the Nitrogen Meter 1

Cited by 15 publications

References 10 publications

Seasonal Changes in Amount and Patterns of Physical Activity in Women

Seasonal Changes in Amount and Patterns of Physical Activity in Women

Lung Function Studies. Viii. Analysis of Alveolar Ventilation by Pulmonary N2 Clearance Curves 12

Validation and Clinical Application of a First Order Step Response Equation for Nitrogen Clearance During FRC Measurement

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