Gas mixing in lung model ventilated by high frequency oscillation: Effect of tidal volume, frequency and molecular diffusivity

1991 ◽  
Vol 29 (1) ◽  
pp. 75-78 ◽  
Author(s):  
A. Ben-Jebria
Keyword(s):  
Tidal Volume ◽  
High Frequency ◽  
Lung Model ◽  
High Frequency Oscillation ◽  
Gas Mixing ◽  
Frequency Oscillation ◽  
Oscillation Effect ◽  
Molecular Diffusivity

Pendelluft and mixing in a single bifurcation lung model during high-frequency oscillation

1988 ◽  
Vol 65 (1) ◽  
pp. 146-155 ◽  
Author(s):  
J. S. Ultman ◽  
R. G. Shaw ◽  
D. C. Fabiano ◽  
K. A. Cooke
Keyword(s):  
Bifurcation Point ◽  
High Frequency ◽  
Direct Relationship ◽  
Lung Model ◽  
High Frequency Oscillation ◽  
Frequency Oscillation ◽  
Mixing Coefficients ◽  
Longitudinal Mixing ◽  
Flow Oscillations ◽  
Bell Shaped Curve

A single bifurcation with an adjustable daughter branch compliance ratio (VR) was used to simultaneously study pendelluft and longitudinal mixing during flow oscillations at frequencies (f) of 1-15 Hz and amplitudes (VOp) of 25-150 ml/s. Mixing coefficients (Deff) were determined from the dispersion of a CO2 bolus centered at the bifurcation point, and pendelluft volume was computed as a fraction of mother branch tidal volume (PVF) using measurements of airflow in the daughter branches. Plotted against frequency, PVF was a bell-shaped curve insensitive to the value of VOp. When VR = 2, a PVF peak of 0.25 appeared at f = 3 Hz, and when VR = 5, a PVF peak of 0.75 appeared at f = 4 Hz. After normalization by control values at VR = 1, Deff curves were also bell shaped, insensitive to the value of VOp and with peaks appearing at the same frequencies as the PVF peaks. The normalized Deff peak values were 1.7 when VR = 2 and 4.0 when VR = 5. The similarities in the PVF and Deff curves imply a direct relationship between pendelluft and enhanced mixing.

Mechanically Induced Pendelluft Flow in a Model Airway Bifurcation During High Frequency Oscillation

1991 ◽  
Vol 113 (3) ◽  
pp. 342-347 ◽  
Author(s):  
K. C. High ◽  
J. S. Ultman ◽  
S. R. Karl
Keyword(s):  
Tidal Volume ◽  
High Resistance ◽  
High Frequency ◽  
Volume Fraction ◽  
Reynolds Numbers ◽  
High Frequency Oscillation ◽  
Optimal Frequency ◽  
Frequency Oscillation ◽  
Parameter Values ◽  
Airway Bifurcation

A single bifurcation with adjustable branch compliances, resistances and inertances was used to study the generation of pendelluft flows during ventilation at tidal volumes of 5–15 ml and frequencies of 6–26 Hz, corresponding to parent branch Reynolds numbers of 400–8000 and Womersley parameter values of 12–25. Pendelluft was quantified by the ratio of tidal volume sum in sibling branches to tidal volume in the parent branch. This tidal volume fraction being greater than one in all experiments where an asymmetry in branch mechanics was imposed, indicated that some degree of pendelluft was always present. Asymmetries in compliance and in inertance produced much greater pendelluft than an asymmetry in resistance. The largest tidal volume fraction, equal to 2.75, was recorded when inertance in both sibling branches was high, resistance was low, and compliances differed by a factor of five. Tidal volume fraction always peaked at an optimal frequency between 12–24 Hz, similar to the frequencies at which physiologic transport optima have previously been observed.

High-frequency ventilation in dogs with three gases of different densities

1991 ◽  
Vol 70 (5) ◽  
pp. 2188-2192 ◽  
Author(s):  
M. J. Jaeger
Keyword(s):  
Tidal Volume ◽  
High Frequency ◽  
Kinematic Viscosity ◽  
Blood Gases ◽  
High Frequency Oscillation ◽  
High Frequency Ventilation ◽  
Gas Mixture ◽  
Frequency Oscillation ◽  
Frequency Ventilation ◽  
Arterial Po2

Dogs were ventilated with a high-frequency oscillation device varying the frequency (5-15 Hz), the tidal volume (25-100 ml), and the resident gas (He, N2, SF6). Tidal volume was measured with a body plethysmograph. Blood gases were measured after a quasi-steady state was established. The kinematic viscosity of the breathing gas mixture, which changed by 1,700%, was found to have little effect on arterial PO2 and PCO2. The results are consistent with findings in a branched model that consisted of tubes with a diameter of 1 cm and with the theory of Taylor-type diffusion in turbulent flow. In addition, experiments were performed reducing and increasing the equipment dead space. This resulted in changes of PO2 and PCO2 that were appreciably less than those resulting from variations of tidal volume of the same magnitude.

Measurement of tidal volume using a pneumotachometer during high-frequency oscillation

1990 ◽  
Vol 18 (6) ◽  
pp. 651-653 ◽  
Author(s):  
SHERRY E. COURTNEY ◽  
KAYE R. WEBER ◽  
WILLIAM A. SPOHN ◽  
SETH W. MALIN ◽  
CHARLES V. BENDER ◽  
...  
Keyword(s):  
Tidal Volume ◽  
High Frequency ◽  
High Frequency Oscillation ◽  
Frequency Oscillation

Alveolar ventilation during high-frequency oscillation: core dead space concept

1984 ◽  
Vol 56 (3) ◽  
pp. 700-707 ◽  
Author(s):  
D. Isabey ◽  
A. Harf ◽  
H. K. Chang
Keyword(s):  
Tidal Volume ◽  
Dead Space ◽  
High Frequency ◽  
Alveolar Ventilation ◽  
High Frequency Oscillation ◽  
High Frequency Ventilation ◽  
Frequency Oscillation ◽  
Simple Physical Model ◽  
Small Tube ◽  
The Dead

To assess the role of direct alveolar ventilation during high-frequency ventilation, we studied convective gas mixing during high-frequency oscillation with tidal volumes close to the dead space volume in a simple physical model. A main conduit representing a large airway was connected with a rigid sphere (V = 77, 517, and 1,719 cm3) by a small circular tube (d = 0.3 and 0.5 cm; L = 5, 10, and 20 cm). The efficiency of sinusoidal oscillations (f = 5, 20, and 40 Hz) applied at one end of the main conduit was assessed from the washout of a CO2 mixture from the sphere; to flush CO2 from the main fluid line, a constant flow of air was used. The decay in CO2 concentration measured in the sphere was exponential and therefore characterized by a measured time constant (tau m). Taking the small tube volume as the ventilatory dead space (VD), an effective tidal volume (VT*) was computed from tau m and compared with the tidal volume (VT) obtained separately from the pressure variation in the sphere. The discrepancy between these two tidal volumes has been found to be uniquely dependent on the ratio VT/VD within the range of VT/VD studied (0.5–2.2). For VT/VD less than 1.2, VT* was larger than VT, indicating that the conventional concept of alveolar ventilation does not apply. From the partition of the oscillatory flow in the small tube into two regions, the core and the unsteady boundary layer, we theoretically computed the proportions of the sinusoidal flow (or tidal volume) and the dead space for each region.(ABSTRACT TRUNCATED AT 250 WORDS)

Determinants of tidal volume during high-frequency oscillation*

2003 ◽  
Vol 31 (1) ◽  
pp. 227-231 ◽  
Author(s):  
Khaled A. Sedeek ◽  
Muneyuki Takeuchi ◽  
Klaudiusz Suchodolski ◽  
Robert M. Kacmarek
Keyword(s):  
Tidal Volume ◽  
High Frequency ◽  
High Frequency Oscillation ◽  
Frequency Oscillation

A new system for ventilating with high-frequency oscillation

1982 ◽  
Vol 53 (6) ◽  
pp. 1638-1642 ◽  
Author(s):  
Y. K. Ngeow ◽  
W. Mitzner
Keyword(s):  
Tidal Volume ◽  
High Frequency ◽  
Airway Pressure ◽  
Ventilation System ◽  
High Frequency Oscillation ◽  
High Frequency Ventilation ◽  
Mean Airway Pressure ◽  
Frequency Oscillation ◽  
Frequency Ventilation ◽  
New System

We describe simple high-frequency oscillation systems that incorporate a CO2 absorber and supply O2 on a need basis. These systems have the advantage of easy control of mean airway pressure and airway hydration and negligible loss of oscillatory tidal volume. Experiments done at constant tidal volume showed that as frequency (and hence total ventilation) increased, arterial CO2 tension (PaCO2) decreased. The fall in PaCO2 occurred until frequency reached approximately 20 Hz; above 20 Hz further increases in frequency had little or no effect on PaCO2. Because of their practical advantages the techniques described here may be quite useful in a clinical setting where an oscillator, rather than jet-type high-frequency, ventilation system is desired.

High-Frequency Oscillation and Chronic Lung Disease in Very Low Birth Weight Infants

PEDIATRICS ◽  
2001 ◽  
Vol 108 (1) ◽  
pp. 212-214
Author(s):  
J. P. Shenai; ◽  
P. Rimensberger; ◽  
U. Thome ◽  
F. Pohlandt; ◽  
P. Rimensberger
Keyword(s):  
Birth Weight ◽  
Low Birth Weight ◽  
Lung Disease ◽  
Chronic Lung Disease ◽  
High Frequency ◽  
Very Low Birth Weight ◽  
High Frequency Oscillation ◽  
Frequency Oscillation ◽  
Low Birth Weight Infants
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