Influence of Fluid Compressibility and Movements of the Swash Plate Axis of Rotation on the Volumetric Efficiency of Axial Piston Pumps

This paper describes the design of a swash plate axial piston pump and the theoretical models describing the bulk modulus of aerated and non-aerated fluids. The dead space volume is defined and the influence of this volume and the fluid compressibility on the volumetric efficiency of the pump is considered. A displacement of the swash plate rotation axis is proposed to reduce the dead space volume for small swash plate swing angles. A prototype design of a pump with a displaced axis of rotation of a swash plate with two directions of delivery is presented, in which the capacity is changed by means of a valve follow-up mechanism. Comparative results for a pump with a displaced and a non-displaced swash plate rotation axis are presented, which confirm that displacement of the swash plate rotation axis causes an increase in volumetric efficiency that is apparent for high pressure discharge and small swash plate angles. The determined characteristics were compared with a mathematical model taking into account the compressibility of the fluid in the dead space volume and a satisfactory consistency was obtained.

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Estimating the Dead Space Volume Between a Headform and N95 Filtering Facepiece Respirator Using Microsoft Kinect

Journal of Occupational and Environmental Hygiene ◽

10.1080/15459624.2015.1019078 ◽

2015 ◽

Vol 12 (8) ◽

pp. 538-546

Author(s):

Ming Xu ◽

Zhipeng Lei ◽

James Yang

Keyword(s):

Dead Space ◽

Microsoft Kinect ◽

Dead Space Volume ◽

The Dead ◽

Space Volume

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Time and volume dependence of dead space in healthy and surfactant-depleted rat lungs during spontaneous breathing and mechanical ventilation

Journal of Applied Physiology ◽

10.1152/japplphysiol.00299.2013 ◽

2013 ◽

Vol 115 (9) ◽

pp. 1268-1274 ◽

Cited By ~ 3

Author(s):

Constanze Dassow ◽

David Schwenninger ◽

Hanna Runck ◽

Josef Guttmann

Keyword(s):

Mechanical Ventilation ◽

Tidal Volume ◽

Dead Space ◽

Spontaneous Breathing ◽

Small Animals ◽

Single Breath ◽

Dead Space Volume ◽

The Dead ◽

Gas Volume ◽

Space Volume

Volumetric capnography is a standard method to determine pulmonary dead space. Hereby, measured carbon dioxide (CO2) in exhaled gas volume is analyzed using the single-breath diagram for CO2. Unfortunately, most existing CO2 sensors do not work with the low tidal volumes found in small animals. Therefore, in this study, we developed a new mainstream capnograph designed for the utilization in small animals like rats. The sensor was used for determination of dead space volume in healthy and surfactant-depleted rats ( n = 62) during spontaneous breathing (SB) and mechanical ventilation (MV) at three different tidal volumes: 5, 8, and 11 ml/kg. Absolute dead space and wasted ventilation (dead space volume in relation to tidal volume) were determined over a period of 1 h. Dead space increase and reversibility of the increase was investigated during MV with different tidal volumes and during SB. During SB, the dead space volume was 0.21 ± 0.14 ml and increased significantly at MV to 0.39 ± 0.03 ml at a tidal volume of 5 ml/kg and to 0.6 ± 0.08 ml at a tidal volume of 8 and 11 ml/kg. Dead space and wasted ventilation during MV increased with tidal volume. This increase was mostly reversible by switching back to SB. Surfactant depletion had no further influence on the dead space increase during MV, but impaired the reversibility of the dead space increase.

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Dead Space Volume in N95 Masks

Archivos de Bronconeumología ◽

10.1016/j.arbres.2020.11.006 ◽

2020 ◽

Author(s):

Santiago C. Arce ◽

Fernando Chiodetti ◽

Eduardo L. De Vito

Keyword(s):

Dead Space ◽

Dead Space Volume ◽

Space Volume

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High-frequency ventilation

Physiological Reviews ◽

10.1152/physrev.1984.64.2.505 ◽

1984 ◽

Vol 64 (2) ◽

pp. 505-543 ◽

Cited By ~ 81

Author(s):

J. M. Drazen ◽

R. D. Kamm ◽

A. S. Slutsky

Keyword(s):

Experimental Data ◽

Gas Exchange ◽

Dead Space ◽

Gas Transport ◽

Physical Models ◽

High Frequency Ventilation ◽

General Description ◽

Wide Range ◽

Dead Space Volume ◽

Space Volume

Complete physiological understanding of HFV requires knowledge of four general classes of information: 1) the distribution of airflow within the lung over a wide range of frequencies and VT (sect. IVA), 2) an understanding of the basic mechanisms whereby the local airflows lead to gas transport (sect. IVB), 3) a computational or theoretical model in which transport mechanisms are cast in such a form that they can be used to predict overall gas transport rates (sect. IVC), and 4) an experimental data base (sect. VI) that can be compared to model predictions. When compared with available experimental data, it becomes clear that none of the proposed models adequately describes all the experimental findings. Although the model of Kamm et al. is the only one capable of simulating the transition from small to large VT (as compared to dead-space volume), it fails to predict the gas transport observed experimentally with VT less than equipment dead space. The Fredberg model is not capable of predicting the observed tendency for VT to be a more important determinant of gas exchange than is frequency. The remaining models predict a greater influence of VT than frequency on gas transport (consistent with experimental observations) but in their current form cannot simulate the additional gas exchange associated with VT in excess of the dead-space volume nor the decreased efficacy of HFV above certain critical frequencies observed in both animals and humans. Thus all of these models are probably inadequate in detail. One important aspect of these various models is that some are based on transport experiments done in appropriately scaled physical models, whereas others are entirely theoretical. The experimental models are probably most useful in the prediction of pulmonary gas transport rates, whereas the physical models are of greater value in identifying the specific transport mechanism(s) responsible for gas exchange. However, both classes require a knowledge of the factors governing the distribution of airflow under the circumstances of study as well as requiring detail about lung anatomy and airway physical properties. Only when such factors are fully understood and incorporated into a general description of gas exchange by HFV will it be possible to predict or explain all experimental or clinical findings.

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Gas transport during high-frequency ventilation

Journal of Applied Physiology ◽

10.1152/jappl.1983.55.2.472 ◽

1983 ◽

Vol 55 (2) ◽

pp. 472-478 ◽

Cited By ~ 15

Author(s):

V. Brusasco ◽

T. J. Knopp ◽

K. Rehder

Keyword(s):

Stroke Volume ◽

Dead Space ◽

High Frequency ◽

Oscillation Frequency ◽

High Frequency Ventilation ◽

Dead Space Volume ◽

Entire Lung ◽

Frequency Ventilation ◽

Gas Volume ◽

Space Volume

During high-frequency small-volume ventilation (HFV), the transport rate of gas from the mouth to a lung region is a function of two conductances (conductance is the transfer rate of a gas divided by its partial pressure difference): regional longitudinal gas conductance along the airways (Grlongi) and gas conductance between lung regions (Ginter). Grlongi per unit regional lung (gas) volume [Grlongi/(Vr beta g)] was determined during HFV in 11 anesthetized paralyzed dogs lying supine. The distribution of Grlongi/(Vr beta g) was nearly uniform during HFV when stroke volumes were less than approximately two-thirds of the Fowler dead-space volume. By contrast, the distribution of Grlongi/(Vr beta g) was nonuniform when the stroke volume exceeded approximately two-thirds of the Fowler dead-space volume and the oscillation frequency was 5 Hz. Gas conductance along the airways per unit lung gas volume [average Glongi/(V beta g)], for the entire lung, increased with stroke volume at all frequencies, but for a given product of oscillation frequency and stroke volume, the average Glongi/(V beta g) was greater when stroke volume was large and oscillation frequency was low. The average Glongi/(V beta g) increased with frequency up to a maximal value; the frequency at which the maximum occurred depended on the kinematic viscosity of the inspired gas mixture.

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Reductions in dead space ventilation with nasal high flow depend on physiological dead space volume: metabolic hood measurements during sleep in patients with COPD and controls

European Respiratory Journal ◽

10.1183/13993003.02251-2017 ◽

2018 ◽

Vol 51 (5) ◽

pp. 1702251 ◽

Cited By ~ 19

Author(s):

Paolo Biselli ◽

Kathrin Fricke ◽

Ludger Grote ◽

Andrew T. Braun ◽

Jason Kirkness ◽

...

Keyword(s):

Respiratory Rate ◽

Dead Space ◽

Minute Ventilation ◽

High Flow ◽

Physiological Dead Space ◽

Copd Patients ◽

Dead Space Volume ◽

Anatomical Dead Space ◽

Dead Space Ventilation ◽

Space Volume

Nasal high flow (NHF) reduces minute ventilation and ventilatory loads during sleep but the mechanisms are not clear. We hypothesised NHF reduces ventilation in proportion to physiological but not anatomical dead space.11 subjects (five controls and six chronic obstructive pulmonary disease (COPD) patients) underwent polysomnography with transcutaneous carbon dioxide (CO2) monitoring under a metabolic hood. During stable non-rapid eye movement stage 2 sleep, subjects received NHF (20 L·min−1) intermittently for periods of 5–10 min. We measured CO2 production and calculated dead space ventilation.Controls and COPD patients responded similarly to NHF. NHF reduced minute ventilation (from 5.6±0.4 to 4.8±0.4 L·min−1; p<0.05) and tidal volume (from 0.34±0.03 to 0.3±0.03 L; p<0.05) without a change in energy expenditure, transcutaneous CO2 or alveolar ventilation. There was a significant decrease in dead space ventilation (from 2.5±0.4 to 1.6±0.4 L·min−1; p<0.05), but not in respiratory rate. The reduction in dead space ventilation correlated with baseline physiological dead space fraction (r2=0.36; p<0.05), but not with respiratory rate or anatomical dead space volume.During sleep, NHF decreases minute ventilation due to an overall reduction in dead space ventilation in proportion to the extent of baseline physiological dead space fraction.

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Labeled carbon dioxide (C18O2): an indicator gas for phase II in expirograms

Journal of Applied Physiology ◽

10.1152/japplphysiol.01360.2003 ◽

2004 ◽

Vol 97 (5) ◽

pp. 1755-1762 ◽

Cited By ~ 9

Author(s):

Holger Schulz ◽

Anne Schulz ◽

Gunter Eder ◽

Joachim Heyder

Keyword(s):

Carbon Dioxide ◽

Phase Ii ◽

Dead Space ◽

Moment Analysis ◽

Cumulative Distribution ◽

Breath Holding ◽

Power Moment ◽

Single Breath ◽

Dead Space Volume ◽

Space Volume

Carbon dioxide labeled with 18O (C18O2) was used as a tracer gas for single-breath measurements in six anesthetized, mechanically ventilated beagle dogs. C18O2 is taken up quasi-instantaneously in the gas-exchanging region of the lungs but much less so in the conducting airways. Its use allows a clear separation of phase II in an expirogram even from diseased individuals and excludes the influence of alveolar concentration differences. Phase II of a C18O2 expirogram mathematically corresponds to the cumulative distribution of bronchial pathways to be traversed completely in the course of exhalation. The derivative of this cumulative distribution with respect to respired volume was submitted to a power moment analysis to characterize volumetric mean (position), standard deviation (broadness), and skewness (asymmetry) of phase II. Position is an estimate of dead space volume, whereas broadness and skewness are measures of the range and asymmetry of functional airway pathway lengths. The effects of changing ventilatory patterns and of changes in airway size (via carbachol-induced bronchoconstriction) were studied. Increasing inspiratory or expiratory flow rates or tidal volume had only minor influence on position and shape of phase II. With the introduction of a postinspiratory breath hold, phase II was continually shifted toward the airway opening (maximum 45% at 16 s) and became steeper by up to 16%, whereas skewness showed a biphasic response with a moderate decrease at short breath holding and a significant increase at longer breath holds. Stepwise bronchoconstriction decreased position up to 45 ± 2% and broadness of phase II up to 43 ± 4%, whereas skewness was increased up to twofold at high-carbachol concentrations. Under all circumstances, position of phase II by power moment analysis and dead space volume by the Fowler technique agreed closely in our healthy dogs. Overall, power moment analysis provides a more comprehensive view on phase II of single-breath expirograms than conventional dead space volume determinations and may be useful for respiratory physiology studies as well as for the study of diseased lungs.

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