Investigation of computer lung model-predicted DLCO during single-breath maneuvers

1994 ◽  
Vol 76 (5) ◽  
pp. 2210-2215 ◽  
Author(s):  
M. Brenner ◽  
A. Babusis ◽  
V. Tran ◽  
L. Bellusa ◽  
E. Pinderski ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Computer Model ◽  
Dead Space ◽  
Normal Subjects ◽  
Gas Absorption ◽  
Lung Model ◽  
Alveolar Volume ◽  
Single Breath ◽  
Three Phase ◽  
Model Predictions

A computer model based on the theoretical gas absorption equations of Martonen and Wilson (J. Math. Biol. 14: 203–220, 1982) was developed to predict changes in single-breath diffusing capacity of the lung for carbon monoxide (DLCO) with alterations in anatomic dead space, alveolar volume, and inspiratory time. The computer model predictions were compared with results obtained from normal subjects performing DLCO maneuvers under correspondingly altered conditions to assess the validity of the Martonen-Wilson equations. In normal subjects, a theoretical “ideal” single-breath DLCO was derived from measured DLCO and adjusted to instantaneous inspiratory and expiratory times with this three-phase computer model. Clinical single-breath DLCO measurements with increased external dead space and inspiratory and expiratory times in normal subjects correlated well with our mathematical model predictions (all r > 0.80, P < 0.001) but did not correlate closely with the predicted effects of alveolar volume on DLCO. This study demonstrates that uniform gas absorption equations of Martonen and Wilson closely predict changes in observed DLCO with systematic variation of inspiratory and expiratory time in normal subjects at full lung volume and appear to be a reasonable estimation of normal physiological events during single-breath carbon monoxide absorption.

The effect of conductive ventilation heterogeneity on diffusing capacity measurement

2008 ◽  
Vol 104 (4) ◽  
pp. 1094-1100 ◽  
Author(s):  
Sylvia Verbanck ◽  
Daniel Schuermans ◽  
Sophie Van Malderen ◽  
Walter Vincken ◽  
Bruce Thompson
Keyword(s):  
Carbon Monoxide ◽  
Vital Capacity ◽  
Experimental Situation ◽  
Normal Subjects ◽  
Diffusing Capacity ◽  
Capacity Measurement ◽  
Alveolar Volume ◽  
Estimation Errors ◽  
Single Breath ◽  
Ventilation Heterogeneity

It has long been assumed that the ventilation heterogeneity associated with lung disease could, in itself, affect the measurement of carbon monoxide transfer factor. The aim of this study was to investigate the potential estimation errors of carbon monoxide diffusing capacity (DlCO) measurement that are specifically due to conductive ventilation heterogeneity, i.e., due to a combination of ventilation heterogeneity and flow asynchrony between lung units larger than acini. We induced conductive airway ventilation heterogeneity in 35 never-smoker normal subjects by histamine provocation and related the resulting changes in conductive ventilation heterogeneity (derived from the multiple-breath washout test) to corresponding changes in diffusing capacity, alveolar volume, and inspired vital capacity (derived from the single-breath DlCO method). Average conductive ventilation heterogeneity doubled ( P < 0.001), whereas DlCO decreased by 6% ( P < 0.001), with no correlation between individual data ( P > 0.1). Average inspired vital capacity and alveolar volume both decreased significantly by, respectively, 6 and 3%, and the individual changes in alveolar volume and in conductive ventilation heterogeneity were correlated ( r = −0.46; P = 0.006). These findings can be brought in agreement with recent modeling work, where specific ventilation heterogeneity resulting from different distributions of either inspired volume or end-expiratory lung volume have been shown to affect DlCO estimation errors in opposite ways. Even in the presence of flow asynchrony, these errors appear to largely cancel out in our experimental situation of histamine-induced conductive ventilation heterogeneity. Finally, we also predicted which alternative combination of specific ventilation heterogeneity and flow asynchrony could affect DlCO estimate in a more substantial fashion in diseased lungs, irrespective of any diffusion-dependent effects.

Error due to dead-space admixture in single-breath method for estimation of pulmonary blood flow

1985 ◽  
Vol 58 (3) ◽  
pp. 1034-1039 ◽  
Author(s):  
J. Gronlund ◽  
P. Christensen
Keyword(s):  
Blood Flow ◽  
Dead Space ◽  
Pulmonary Blood Flow ◽  
Normal Subjects ◽  
Measurement Noise ◽  
Lung Model ◽  
Analytical Relationship ◽  
Single Breath ◽  
The Dead ◽  
Single Breath Method

The single-breath method of Kim et al. (J. Appl. Physiol. 21: 1338–1344, 1966) for the estimation of pulmonary blood flow is based on a single-alveolus lung model for which an analytical relationship has been established between the kinetic behavior of the alveolar O2 and CO2 tensions and the pulmonary blood flow. The analysis is based on the assumption that the dead-space contribution to the expirate is negligible after expiration of a predefined volume. We have examined the influence of this assumption on the estimation of pulmonary blood flow by computer simulation in a lung model that incorporates deadspace contribution to the expirate. Data on the fractional contribution of the dead space to the expired gas were obtained from Tsunoda et al.'s study (J. Appl. Physiol. 32: 644–649, 1972) on the emptying pattern of normal adult lungs. The results show that failure to take account of the dead-space contribution can cause an underestimation in the pulmonary blood flow of greater than 30%. The error can be reduced by ignoring the first part of the expiration but only at the cost of an increase in the sensitivity of the single-breath method to measurement noise. This property of the system is demonstrated experimentally. The error due to dead-space admixture depends on the total volume of dead-space gas, the measurement noise, the pulmonary blood flow, and the emptying characteristics of the dead-space compartment during expiration. In normal subjects it is possible to optimize the experimental design so that the systematic error is less than 5% and the coefficient of variation is less than 10%.

Assessment of cardiorespiratory function using oscillating inert gas forcing signals

1994 ◽  
Vol 76 (5) ◽  
pp. 2130-2139 ◽  
Author(s):  
E. M. Williams ◽  
J. B. Aspel ◽  
S. M. Burrough ◽  
W. A. Ryder ◽  
M. C. Sainsbury ◽  
...  
Keyword(s):  
Blood Flow ◽  
Nitrous Oxide ◽  
Dead Space ◽  
Confidence Limit ◽  
Pulmonary Blood Flow ◽  
Mean Difference ◽  
Alveolar Volume ◽  
Single Breath ◽  
Cardiorespiratory Function ◽  
Airway Dead Space

A theoretical model (Hahn et al. J. Appl. Physiol. 75: 1863–1876, 1993) predicts that the amplitudes of the argon and nitrous oxide inspired, end-expired, and mixed expired sinusoids at forcing periods in the range of 2–3 min (frequency 0.3–0.5 min-1) can be used directly to measure airway dead space, lung alveolar volume, and pulmonary blood flow. We tested the ability of this procedure to measure these parameters continuously by feeding monosinusoidal argon and nitrous oxide forcing signals (6 +/- 4% vol/vol) into the inspired airstream of nine anesthetized ventilated dogs. Close agreement was found between single-breath and sinusoid airway dead space measurements (mean difference 15 +/- 6%, 95% confidence limit), N2 washout and sinusoid alveolar volume (mean difference 4 +/- 6%, 95% confidence limit), and thermal dilution and sinusoid pulmonary blood flow (mean difference 12 +/- 11%, 95% confidence limit). The application of 1 kPa positive end-expiratory pressure increased airway dead space by 12% and alveolar volume from 0.8 to 1.1 liters but did not alter pulmonary blood flow, as measured by both the sinusoid and comparator techniques. Our findings show that the noninvasive sinusoid technique can be used to measure cardiorespiratory lung function and allows changes in function to be resolved in 2 min.

Factors affecting expired waveform for carbon monoxide

1984 ◽  
Vol 56 (3) ◽  
pp. 708-715
Author(s):  
D. Z. Rubin ◽  
S. M. Lewis ◽  
C. Mittman
Keyword(s):  
Carbon Monoxide ◽  
Normal Subjects ◽  
Lung Model ◽  
Repeated Testing ◽  
Factors Affecting ◽  
Sensitivity Tests ◽  
Standard Parameter ◽  
Expired Gas ◽  
End Tidal ◽  
Computer Simulation Studies

We previously presented a method based on a computer lung model for determining the distribution of both specific ventilation and specific diffusing capacity. These argon and carbon monoxide (CO) washin and washout studies were obtained in 12 normal subjects and 24 patients with varying degrees of obstructive lung disease. In addition to end-tidal and mixed expired gas concentrations, the expired waveform for both gases was sampled. In patients we found that this method failed to adequately describe CO dynamics during the early part of expiration; predicted concentrations were higher than actual data. Modifications of the original model that satisfy all data are presented. This new model suggests that CO uptake occurs in spaces with ventilatory properties of dead space. The accuracy and reliability of these observations were established by computer simulation studies as well as by repeated testing in one subject. These proved to be highly reproducible over a period of 5 mo. Standard parameter sensitivity tests showed parameters to vary by less than 10% and to be stable even when realistic levels of noise were added to the data. We conclude that studies involving ventilation of insoluble gases are insufficient to describe gas exchange in the lung. The addition of an exchangeable gas adds significant understanding of lung function, particularly in disease.

Distribution of ventilation and diffusing capacity in the normal and diseased lung

1981 ◽  
Vol 51 (6) ◽  
pp. 1463-1470 ◽  
Author(s):  
S. M. Lewis ◽  
D. Z. Rubin ◽  
C. Mittman
Keyword(s):  
Normal Subjects ◽  
Lung Model ◽  
Uniform Structure ◽  
Model Parameters ◽  
Diffusing Capacity ◽  
Single Breath ◽  
Steady State Method ◽  
Noise Measurements ◽  
End Tidal ◽  
And Diffusion

Conventional tests of diffusing capacity (DL) consider the lung to be a uniform structure with regard to both ventilation and diffusion. These assumptions are incorrect even in normal subjects. We present a method for determining the distribution of both specific ventilation (SV) and DL from the washin and washout of C18O and simultaneous washout of argon. Both end-tidal and mixed-expired data are fit to a two-compartment lung model; parameters that define SV and DL are assigned to each compartment. From data generated by a model, the parameters recovered were found to be relatively insensitive to realistic levels of noise. Measurements in one subject were highly repeatable. We examined 15 normal subjects and 16 subjects with varying degrees of obstructive lung disease. In both groups the better ventilated spaces generally showed a higher DL. The sum of the total two-compartmental DL's correlated with, but was found to exceed, the value obtained using the steady-state method and generally exceeded the single-breath result. We conclude that this method has potential advantages over conventional methods and is worthy of further study.

The Effect of Human Pregnancy on the Pulmonary Transfer Factor for Carbon Monoxide as Measured by the Single-Breath Method

1977 ◽  
Vol 53 (3) ◽  
pp. 271-276 ◽  
Author(s):  
J. A. Milne ◽  
R. J. Mills ◽  
J. R. T. Coutts ◽  
M. C. Macnaughton ◽  
F. Moran ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Transfer Factor ◽  
Post Partum ◽  
Previous History ◽  
Haemoglobin Concentration ◽  
First Trimester ◽  
Alveolar Volume ◽  
Single Breath ◽  
Pregnant State ◽  
Single Breath Method

1. The pulmonary transfer factor for carbon monoxide was measured by the single-breath method in 21 pregnant women with no previous history of cardiac or respiratory disease. Measurements were made at monthly intervals throughout pregnancy and once post partum. 2. The transfer factor was higher in the first trimester of pregnancy than in the non-pregnant state. There was a fall in the transfer factor during pregnancy until 26 weeks gestation, after which no further decrease was observed. 3. The changes in transfer factor were not explained by alterations in haemoglobin concentration or alveolar volume. 4. Simultaneous serial estimations of plasma 17β-oestradiol were performed in all the subjects. There was no obvious direct relation between changes in the concentration of this hormone and transfer factor measurements.

Improved accuracy and precision of single-breath CO diffusing capacity measurements

1981 ◽  
Vol 51 (5) ◽  
pp. 1306-1313 ◽  
Author(s):  
B. L. Graham ◽  
J. T. Mink ◽  
D. J. Cotton
Keyword(s):  
Normal Subjects ◽  
Single Equation ◽  
Lung Model ◽  
New Method ◽  
Breath Holding ◽  
Diffusing Capacity ◽  
Single Breath ◽  
Accuracy And Precision ◽  
Conventional Methods ◽  
The Way

Using three conventional methods and a new method we measured the single-breath diffusing capacity for carbon monoxide [DLCO(SB)] in a group of normal subjects. Whereas the conventional methods calculated DLCO(SB) from a single equation valid only for breath holding, the new method used three equations, one for each phase of the single-breath maneuver, i.e., inhalation, breath holding, and exhalation. We found that while the conventional methods of calculating DLCO(SB) were greatly affected by variations in the way in which the single-breath maneuver was performed and/or the way in which the alveolar gas sample was collected, these variations had little effect on the calculations of DLCO(SB) using the new method. These results were in close agreement with results from a computerized mathematical lung model in which the diffusing capacity did not change with lung volume. We concluded that the new method significantly improves the accuracy and precision of DLCO(SB) measurements while reducing the effects of maneuver variability. For these reasons comparisons of DLCO(SB) values between patients and normal subjects or between two groups with different pulmonary function may be more valid using the new method than using conventional methods.

Respiratory dead space measurements in a model lung and healthy human subjects according to the single breath method

1959 ◽  
Vol 14 (4) ◽  
pp. 517-520 ◽  
Author(s):  
Gösta Birath
Keyword(s):  
Standard Deviation ◽  
Dead Space ◽  
Human Subjects ◽  
Lung Model ◽  
Quiet Breathing ◽  
Healthy Human ◽  
Single Breath ◽  
Healthy Human Subjects ◽  
The Dead ◽  
Single Breath Method

Observations on the dead space (Fowler's method) in a lung model were compared to observations on three human subjects. Corresponding to the theoretical gas front between dead space O2 and alveolar N2, a point in the model experiment was found dividing the S-shaped form of the N2 curve in a ratio of 2:3. The washout volume for the model dead space was about twice its volume. Similar findings were noted in the human subjects. Washout time did not influence the dead space values at flow rates of 5–37 l/min. In the human subjects the dead space values increased by 2.4–3.3 ml/100 ml of increasing end-inspiratory lung volume. The values for the dead space fell during an inspiratory pause even in the normal interval of quiet breathing. The accuracy of the method in tests on the model with a known dead space of 190 ml was 189 ± 1.4 ml with a standard deviation of ±7.0 ml. In human subjects the standard deviation was about 10%. Submitted on August 21, 1958

Effect of nitroglycerin on DL of normal subjects at rest and during exercise

1982 ◽  
Vol 52 (4) ◽  
pp. 851-856 ◽  
Author(s):  
B. Nemery ◽  
L. Piret ◽  
L. Brasseur ◽  
A. Frans
Keyword(s):  
Carbon Monoxide ◽  
Healthy Subjects ◽  
Normal Subjects ◽  
Lung Perfusion ◽  
Sublingual Nitroglycerin ◽  
Sitting Position ◽  
Diffusing Capacity ◽  
Single Breath ◽  
Pulmonary Capillary ◽  
Lateral Decubitus

By use of the single-breath diffusing capacity for carbon monoxide (DL) as an index of the pulmonary capillary filling, the effects of 3 mg sublingual nitroglycerin (NTG) were studied in eight healthy subjects at rest and during exercise. At rest, NTG induced a significant and persistent decrease of DL when subjects were sitting or supine (60 min of observation) and also when they were in the lateral decubitus or supine with legs up position (30 min of observation). Subjects in the supine positions showed more pronounced percentage decreases in DL than when sitting. In the sitting position 1 mg NTG also induces a decrease of DL. During a moderate upright cycloergometer exercise, NTG also induces a significant decrease of DL; the decrease is smaller and of shorter duration (less than 15 min) than at rest, but it reappears as soon as the exercise is stopped. The decrease of DL may be attributed to an outward shift of blood from the thorax to the periphery or to a redistribution of lung perfusion consequent to changes in pulmonary vascular pressures.

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