A network theory of bronchial gas mixing applied to single breath nitrogen washout

Lung ◽  
1980 ◽  
Vol 158 (1) ◽  
pp. 201-220 ◽  
Author(s):  
P. W. Scherer ◽  
F. R. Haselton
Keyword(s):  
Network Theory ◽  
Gas Mixing ◽  
Nitrogen Washout ◽  
Single Breath

Changes in the single-breath nitrogen washout curve on exposure to 17,600 ft

1975 ◽  
Vol 39 (4) ◽  
pp. 652-656 ◽  
Author(s):  
G. W. Gray ◽  
D. M. McFadden ◽  
C. S. Houston ◽  
A. C. Bryan
Keyword(s):  
Lung Lesion ◽  
Phase Iii ◽  
Base Line ◽  
Gas Mixing ◽  
Nitrogen Washout ◽  
Single Breath ◽  
Base Camp ◽  
Subsequent Exposure ◽  
Acclimatization Period ◽  
Washout Curves

Seventeen volunteers were exposed to 17,600 ft after an acclimatization period, at 9,800 ft. Single-breath nitrogen washout curves were done at base camp (2,600 ft), on days 2 and 4 at 9,800 ft, and on days 1, 2,3 4, and 7 at 17,600 ft. There was a significant 39% increase in the slope of phase III on day 2 at 9,800 ft, accompanied by a 125 ml mean increase in anatomic dead space (Vd) and a marked decrease in cardiac oscillations. By day 4 at 9,800 ft phase III slopes were reduced and were not significantly different from base-line controls, while cardiac oscillations were increased and Vd decreased from day 2. Subsequent exposure to 17,600 ft produced another significant increase in phase III slope to 87% above control, which by day 7 had decreased significantly to 63% above control. Cardiac oscillations were again diminished and Vd increased. These changes cannot be accounted for by changes in gas density, nor by the decrease in PIOO2 per se, since this alone would decrease the range of PaNN2. They suggest a pathophysiologic lung lesion which impairs gas mixing and increases asynchronous emptying during early altitude exposure. high-altitude pulmonary edema; gas-mixing impairment at altitude Submitted on November 7, 1974

Computerized single-breath nitrogen washout: Predicted values in a rural French community

Lung ◽  
2004 ◽  
Vol 174 (1) ◽  
Author(s):  
D.B. Teculescu ◽  
M.-C. Daniel ◽  
E. Costantino ◽  
O. Buhler ◽  
A.B. Bohadana ◽  
...  
Keyword(s):  
Nitrogen Washout ◽  
Single Breath ◽  
Predicted Values

Inflection point on transpulmonary pressure-volume curves and closing volume

1975 ◽  
Vol 38 (2) ◽  
pp. 228-235 ◽  
Author(s):  
M. Demedts ◽  
J. Clement ◽  
D. C. Stanescu ◽  
K. P. van de Woestijne
Keyword(s):  
Inflection Point ◽  
Vital Capacity ◽  
Transpulmonary Pressure ◽  
Bronchial Obstruction ◽  
Closing Volume ◽  
Lung Volumes ◽  
Nitrogen Washout ◽  
Single Breath ◽  
Space Effect ◽  
Washout Curves

In 20 healthy subjects and 18 patients with bronchial obstruction, closing volume (CV) on single-breath nitrogen washout curves and inflection point (IP) on transpulmonary pressure-volume curves were recorded simultaneously during slow expiratory vital capacity maneuvers. IP and CV did not occur at identical lung volumes, IP being systematically larger than CV for small CV values. This discrepancy could not be attributed to an esophageal or mediastinal artifact. It is suggested that, though CV and IP both express “airway closure,” their sensitivity to closure may differ: CV underestimates closure because of a dead space effect; the latter may vary individually. On the other hand, IP may not reflect the true beginning of closure, particularly when it occurs at higher lung volumes.

Mode shift of an inhaled aerosol bolus is correlated with flow sequencing in the human lung

2002 ◽  
Vol 92 (3) ◽  
pp. 1232-1238 ◽  
Author(s):  
Christopher N. Mills ◽  
Chantal Darquenne ◽  
G. Kim Prisk
Keyword(s):  
Vital Capacity ◽  
Normal Subjects ◽  
Phase Iii ◽  
Mode Shift ◽  
Nitrogen Washout ◽  
Single Breath ◽  
Posture Change ◽  
Supine Posture ◽  
Residual Capacity ◽  
Phase Iii Slope

We studied the effects on aerosol bolus inhalations of small changes in convective inhomogeneity induced by posture change from upright to supine in nine normal subjects. Vital capacity single-breath nitrogen washout tests were used to determine ventilatory inhomogeneity change between postures. Relative to upright, supine phase III slope was increased 33 ± 11% (mean ± SE, P < 0.05) and phase IV height increased 25 ± 11% ( P < 0.05), consistent with an increase in convective inhomogeneity likely due to increases in flow sequencing. Subjects also performed 0.5-μm-particle bolus inhalations to penetration volumes (Vp) between 150 and 1,200 ml during a standardized inhalation from residual volume to 1 liter above upright functional residual capacity. Mode shift (MS) in supine posture was more mouthward than upright at all Vp, changing by 11.6 ml at Vp = 150 ml ( P < 0.05) and 38.4 ml at Vp = 1,200 ml ( P < 0.05). MS and phase III slope changes correlated positively at deeper Vp. Deposition did not change at any Vp, suggesting that deposition did not cause the MS change. We propose that the MS change results from increased sequencing in supine vs. upright posture.

Can Single Breath Nitrogen Washout Test Reflect the Severity of Emphysema?

CHEST Journal ◽  
2017 ◽  
Vol 152 (4) ◽  
pp. A803
Author(s):  
Michael Hanna ◽  
Zeron Ghazarian ◽  
Raminderjit Sekhon ◽  
Tapan Pandya ◽  
Zainab Syed ◽  
...  
Keyword(s):  
Nitrogen Washout ◽  
Single Breath

Single-Breath Nitrogen Washout

CHEST Journal ◽  
1979 ◽  
Vol 76 (1) ◽  
pp. 83-88 ◽  
Author(s):  
Faiq J. Al-Bazzaz
Keyword(s):  
Nitrogen Washout ◽  
Single Breath

Effect of breathing pattern on gas mixing in a model with asymmetrical alveolar ducts

1985 ◽  
Vol 58 (1) ◽  
pp. 18-26 ◽  
Author(s):  
C. L. Bowes ◽  
J. D. Richardson ◽  
G. Cumming ◽  
K. Horsfield
Keyword(s):  
Breathing Pattern ◽  
Breath Holding ◽  
Gas Mixing ◽  
Breathing Patterns ◽  
Discrete Elements ◽  
Finite Difference Technique ◽  
Single Breath ◽  
Pulmonary Airways ◽  
Conducting Airways ◽  
And Diffusion

A model of the pulmonary airways was used to study three single-breath indices of gas mixing, dead space (VD), slope of the alveolar plateau, and alveolar mixing inefficiency (AMI). In the model, discrete elements of airway volume were represented by nodes. Using a finite difference technique the differential equation for simultaneous convection and diffusion was solved for the nodal network. Conducting airways and respiratory bronchioles were modeled symmetrically, but alveolar ducts asymmetrically, permitting interaction between convection and diffusion. VD, alveolar slope, and AMI increased with increasing flow. Similar trends were seen with inspired volume, although slope decreased at high inspired volumes with constant flow. VD was affected most by inspiratory flow and AMI and alveolar slope by expiratory time. VD fell approximately exponentially with time of breath holding. Eight different breathing patterns were compared. They had a small effect on alveolar slope and AMI and a greater effect on VD. The model shows how series and parallel inhomogeneity occur together and interact in asymmetrical systems: the old argument as to which is the more important should be abandoned.

Convective and diffusive gas mixing in human lungs: experiments and model analysis

1976 ◽  
Vol 40 (3) ◽  
pp. 362-371 ◽  
Author(s):  
R. S. Sikand ◽  
H. Magnussen ◽  
P. Scheid ◽  
J. Piiper
Keyword(s):  
Gas Exchange ◽  
Compartment Model ◽  
Model Analysis ◽  
Lung Model ◽  
Breath Holding ◽  
Gas Mixing ◽  
Single Breath ◽  
Human Lungs ◽  
Three Compartment Model ◽  
Residual Gas

Equilibration of inspired with lung residual gas was studied by a single-breath technique for varying breath-holding time with He, Ar, and SF6 as test gases. The ratio of end-expired (FE‣) to mean lung concentration after expiration (FL) was always below unity, indicating imperfect mixing of gas in the lung. The ratio of FL/FE‣ for all gases increased with tB, for any tB the ratio was smallest for SF6 and greatest for He. Similarly, Bohr dead space (VD) at any given tB was greatest for SF6 and smallest for He, with VD decreasing toward an asymptotic value common for all gases as tB increased. The results were analyzed quantitatively on a serial three-compartment model of the lung. Model analysis suggests that both diffusion and convection are effective in equilibrating test gases in the lung during breath holding. Further, stratified inhomogeneities in the absence of convective gas mixing in the alveolar space would seriously limit alveolar respiratory gas exchange; with convection, however, stratification is likely to impose only moderate constraints on resting gas exchange.

Intra-airway gas transport during high-frequency chest vibration with tracheal insufflation in dogs

1995 ◽  
Vol 79 (1) ◽  
pp. 243-250 ◽  
Author(s):  
N. Gavriely ◽  
D. M. Eckmann ◽  
J. B. Grotberg
Keyword(s):  
High Frequency ◽  
Gas Transport ◽  
Gas Mixing ◽  
Catheter Position ◽  
Distribution Width ◽  
High Frequency Vibration ◽  
Single Breath ◽  
Peak Enhancement ◽  
Airway Opening ◽  
Tracheal Insufflation

High-frequency external chest vibration with tracheal insufflation (high-frequency vibration ventilation) has previously been shown to be an effective mode of artificial ventilation in experimental animals. To investigate the intra-airway gas mixing during high-frequency vibration ventilation (frequency 30 Hz, amplitude 0.4 cm), we used an analysis of the single-breath washout curve that gives the vibration-induced mixing coefficient distribution relative to the no-vibration situation. Data from four anesthetized dogs were collected during constant-flow insufflation at six rates (0.05–0.4 l.min-1.kg-1), at three insufflation durations (2, 4, and 7 s), and with the insufflation catheter outlet at three positions (carina, trachea, and a bronchus) while the vibration was on and off. Vibration enhanced intra-airway gas mixing 14.1 +/- 3.9-fold, with the peak of the enhancement distribution located 125 +/- 29 ml from the airway opening and a distribution width of 121 +/- 29 ml. As insufflation flow increased, the position of the peak enhancement shifted toward the alveolar zone and diminished in peak amplitude. Changing the insufflation duration and the catheter position did not affect the intra-airway mixing induced by vibration. External chest vibration causes a substantial increase of intra-airway gas mixing, bringing alveolar gas to central airways. This leads to overall increased pulmonary gas transport when fresh gas is insufflating the tracheal carina area.

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