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

2013 ◽  
Vol 115 (9) ◽  
pp. 1268-1274 ◽  
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.

Gas transport during high-frequency ventilation

1983 ◽  
Vol 55 (2) ◽  
pp. 472-478 ◽  
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.

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

2004 ◽  
Vol 97 (5) ◽  
pp. 1755-1762 ◽  
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.

Alveolar gas exchange during exercise: a single-breath analysis

1984 ◽  
Vol 57 (6) ◽  
pp. 1704-1709 ◽  
Author(s):  
C. J. Allen ◽  
N. L. Jones ◽  
K. J. Killian
Keyword(s):  
Tidal Volume ◽  
Dead Space ◽  
Heavy Exercise ◽  
Single Breath ◽  
Arterial Blood ◽  
Co2 Output ◽  
Dead Space Volume ◽  
Airway Dead Space ◽  
Male Subjects ◽  
Alveolar Gas Exchange

Changes in expired alveolar O2 and CO2 were measured breath-by-breath in six healthy male subjects (mean age 30 yr, mean weight 80 kg) at rest, 600 kpm/min, and 1,200 kpm/min. Changes were expressed in relation to expired volume (liters) and time (s) and separated into an initial dead-space component using the Fowler method applied to expired CO2 and O2, and alveolar slope. The alveolar slopes with respect to time (dPACO2, dPAO2, Torr/s) increased in relation to CO2 output (VCO2, 1/min, STPD) and O2 intake (VO2, 1/min, STPD) but were reduced by increasing tidal volume (VT, liters, BTPS): dPACO2 = 2.7 + 4.6(VCO2) - 1.9(VT) (r = 0.97); and dPAO2 = 2.3 + 5.5(VO2) - 1.9(VT) (r = 0.96). From the alveolar slopes, tidal volume, and airway dead-space volume, mean expired alveolar PO2 and PCO2 (PAO2, PACO2) were calculated. There was no change in arterialized capillary PCO2 (PaCO2) between rest (38.9 +/- 0.66 Torr) and heavy exercise (38.2 +/- 2.18 Torr), but mean PACO2 rose from 36.7 +/- 0.55 to 40.8 +/- 1.67 Torr during heavy exercise. There was no change in arterialized capillary (mean = 84.3 +/- 0.7 Torr) or alveolar (mean = 107.2 +/- 1.03 Torr) PO2. Exercise increases the fluctuations in alveolar gas composition leading to discrepancies between the PCO2 in mean alveolar gas and arterial blood to an extent that is dependent on VCO2 and VT.

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

Energies ◽  
2022 ◽  
Vol 15 (1) ◽  
pp. 298
Author(s):  
Paweł Załuski
Keyword(s):  
Dead Space ◽  
Rotation Axis ◽  
Volumetric Efficiency ◽  
Axis Of Rotation ◽  
Swash Plate ◽  
Plate Rotation ◽  
Dead Space Volume ◽  
The Dead ◽  
Axial Piston ◽  
Space Volume

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.

Effect of salicylates on ventilatory response to inhaled carbon dioxide in normal subjects

1960 ◽  
Vol 15 (5) ◽  
pp. 826-828 ◽  
Author(s):  
Philip Samet ◽  
Eugene M. Fierer ◽  
William H. Bernstein
Keyword(s):  
Tidal Volume ◽  
Dead Space ◽  
Ventilatory Response ◽  
Normal Subjects ◽  
The Other ◽  
Compressed Air ◽  
Arterial Blood ◽  
Dead Space Volume ◽  
Basic Purpose ◽  
Space Volume

The basic purpose of this investigation was to determine whether salicylates increase the sensitivity of the respiratory center to inhaled CO2. The problem was approached by noting the effect of salicylates upon ventilation and arterial blood Co2 tension and pH during inhalation of compressed air and 3% and 5% Co2 in air. These studies were performed in 30 subjects, 15 of whom ingested 2.1 gm salicylate; the other 15 ingested 3.6 gm. The results demonstrate that the ventilatory response to CO2 was increased only by the larger dose of salicylate. Variations in dead-space volume secondary to increments in tidal volume were observed. Dead-space volume increased in approximately linear fashion with increase in tidal volume. Submitted on October 28, 1959

Prediction of the Physiological Dead-Space in Resting Normal Subjects

1973 ◽  
Vol 45 (3) ◽  
pp. 375-386 ◽  
Author(s):  
E. A. Harris ◽  
Mary E. Hunter ◽  
Eve R. Seelye ◽  
Margaret Vedder ◽  
R. M. L. Whitlock
Keyword(s):  
Tidal Volume ◽  
Multiple Regression ◽  
Dead Space ◽  
Predictive Accuracy ◽  
Volume Ratio ◽  
Normal Subjects ◽  
Physiological Dead Space ◽  
Dead Space Volume ◽  
Made In ◽  
Space Volume

1. Two-hundred and forty duplicate estimations of physiological dead-space volume (VD) were made in forty-eight healthy subjects (twenty-four men and twenty-four women) aged from 20 to 74 years, to assess the predictive accuracy of various standards. 2. The VD/VT (physiological dead-space volume/tidal volume) ratio standard was least precise, but could be improved by allowing for sex and age. 3. The best prediction could be made by multiple regression of VD on age, height, tidal volume (VT) and the reciprocal of respiratory frequency (f), which gave an estimate with a standard deviation of 24·7 ml. 4. Theoretical and practical arguments favour the abandonment of the VD/VT ratio standard. Simple regression of VD on VT also is unsatisfactory, giving a much less precise estimate of VD than a multiple regression on VT and other variables.

Dead Space Volume in N95 Masks

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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