Effect of ventilation inhomogeneity on "intrabreath" measurements of diffusing capacity in normal subjects

1993 ◽  
Vol 75 (2) ◽  
pp. 927-932 ◽  
Author(s):  
D. J. Cotton ◽  
M. B. Prabhu ◽  
J. T. Mink ◽  
B. L. Graham
Keyword(s):  
Lung Volume ◽  
Hold Time ◽  
Normal Subjects ◽  
Phase Iii ◽  
Breath Hold ◽  
Diffusing Capacity ◽  
Ventilation Inhomogeneity ◽  
Single Breath ◽  
The Mean ◽  
And Diffusion

In normal seated subjects we increased single-breath ventilation inhomogeneity by changing both the preinspiratory lung volume and breath-hold time and examined the ensuing effects on two different techniques of measuring the diffusing capacity of the lung for carbon monoxide (DLCO). We measured the mean single-breath DLCO using the three-equation method (DLCOSB-3EQ) and also measured DLCO over discrete intervals during exhalation by the "intrabreath" method (DLCOexhaled). We assessed the distribution of ventilation using the normalized phase III slope for helium (SN). DLCOSB-3EQ was unaffected by preinspiratory lung volume and breath-hold time. DLCOexhaled increased with increasing preinspiratory lung volume and decreased with increasing breath-hold time. These changes correlated with the simultaneously observed changes in ventilation inhomogeneity as measured by SN (P < 0.01). We conclude that measurements of DLCOexhaled do not accurately reflect the mean DLCO. Intrabreath methods of measuring DLCO are based on the slope of the exhaled CO concentration curve, which is affected by both ventilation and diffusion inhomogeneities. Although DLCOexhaled may theoretically provide information about the distribution of CO uptake, the concomitant effects of ventilation nonuniformity on DLCOexhaled may mimic or mask the effects of diffusion nonuniformity.

Effects of ventilation inhomogeneity on DLcoSB-3EQ in normal subjects

1992 ◽  
Vol 73 (6) ◽  
pp. 2623-2630 ◽  
Author(s):  
D. J. Cotton ◽  
M. B. Prabhu ◽  
J. T. Mink ◽  
B. L. Graham
Keyword(s):  
Lung Volume ◽  
Vital Capacity ◽  
Hold Time ◽  
Airflow Obstruction ◽  
Normal Subjects ◽  
Phase Iii ◽  
Mixing Efficiency ◽  
Breath Hold ◽  
Ventilation Inhomogeneity ◽  
Single Breath

In patients with airflow obstruction, we found that ventilation inhomogeneity during vital capacity single-breath maneuvers was associated with decreases in the three-equation single-breath CO diffusing capacity of the lung (DLcoSB-3EQ) when breath-hold time (tBH) decreased. We postulated that this was due to a significant resistance to diffusive gas mixing within the gas phase of the lung. In this study, we hypothesized that this phenomenon might also occur in normal subjects if the breathing cycle were altered from traditional vital capacity maneuvers to those that increase ventilation inhomogeneity. In 10 normal subjects, we examined the tBH dependence of both DLcoSB-3EQ and the distribution of ventilation, measured by the mixing efficiency and the normalized phase III slope for helium. Preinspiratory lung volume (V0) was increased by keeping the maximum end-inspiratory lung volume (Vmax) constant or by increasing V0 and Vmax. When V0 increased while Vmax was kept constant, we found that the tBH-independent and the tBH-dependent components of ventilation inhomogeneity increased, but DLcoSB-3EQ was independent of V0 and tBH. Increasing V0 and Vmax did not change ventilation inhomogeneity at a tBH of 0 s, but the tBH-dependent component decreased. DLcoSB-3EQ, although independent of tBH, increased slightly with increases in Vmax. We conclude that in normal subjects increases in ventilation inhomogeneity with increases in V0 do not result in DLcoSB-3EQ becoming tBH dependent.

Measurement of temporal changes in DLSBCO-3EQ from small alveolar samples in normal subjects

1994 ◽  
Vol 76 (4) ◽  
pp. 1494-1501 ◽  
Author(s):  
G. R. Soparkar ◽  
J. T. Mink ◽  
B. L. Graham ◽  
D. J. Cotton
Keyword(s):  
Hold Time ◽  
Normal Subjects ◽  
Gas Diffusion ◽  
Phase Iii ◽  
Mixing Efficiency ◽  
Breath Holding ◽  
Breath Hold ◽  
Inspiratory Capacity ◽  
Ventilation Inhomogeneity ◽  
Single Breath

The dynamic changes in CO concentration [CO] during a single breath could be influenced by topographic inhomogeneity in the lung or by peripheral inhomogeneity due to a gas mixing resistance in the gas phase of the lung or to serial gradients in gas diffusion. Ten healthy subjects performed single-breath maneuvers by slowly inhaling test gas from functional residual capacity to one-half inspiratory capacity and slowly exhaling to residual volume with target breath-hold times of 0, 1.5, 3, 6, and 9 s. We calculated the three-equation single-breath diffusing capacity of the lung for CO (DLSBCO-3EQ) from the mean [CO] in both the entire alveolar gas sample and in four successive equal alveolar gas samples. DLSBCO-3EQ from the entire alveolar gas sample was independent of breath-hold time. However, with 0 s of breath holding, from early alveolar gas samples DLSBCO-3EQ was reduced and from late alveolar gas samples it was increased. With increasing breath-hold time, DLSBCO-3EQ from the earliest alveolar gas sample rapidly increased, whereas from the last alveolar gas sample it rapidly decreased such that all values from the small alveolar gas samples approached DLSBCO-3EQ from the entire alveolar sample. These changes correlated with ventilation inhomogeneity, as measured by the phase III He concentration slope and the mixing efficiency, and were larger for maneuvers with inspired volumes to one-half inspiratory capacity vs. total lung capacity.(ABSTRACT TRUNCATED AT 250 WORDS)

Single-breath washout experiments in rat lungs

1991 ◽  
Vol 71 (3) ◽  
pp. 855-862 ◽  
Author(s):  
N. Gonzalez Mangado ◽  
G. Peces-Barba ◽  
S. Verbanck ◽  
M. Paiva
Keyword(s):  
Lung Volume ◽  
Strong Correlation ◽  
Wistar Rats ◽  
Hold Time ◽  
Tracheobronchial Tree ◽  
Breath Hold ◽  
Single Breath ◽  
Lung Structure ◽  
Diffusion And Convection ◽  
Diffusion Convection

Single-breath washouts were performed on 30 Wistar rats postmortem in studies in which breaths of 90% O2–5% He-5% SF6 were given. We investigated the effects of variations in preinspiratory lung volume, inspired volume, end-inspiratory breath-hold time, and inspiratory and expiratory flows on the alveolar plateau slopes for N2, He, and SF6. The main result is that the slope for He was always larger than the slope for SF6, except for large breath-hold times (approximately 15 s), contrary to previous findings in other species. Slopes for the three gases decreased with increasing inspiratory and expiratory flows when flows were greater than 1 ml/s. There was a strong correlation between the magnitude of a slope and its curvilinearity, suggesting that the concentration heterogeneity in the lung that causes the slope is due to interaction between diffusion and convection. The results seem incompatible with heterogeneities of parenchymal elasticity, which have been said to contribute to alveolar slopes in dog lungs but appear to be completely explainable as the result of diffusion-convection interaction in an asymmetric lung structure that has acini widely spread along the tracheobronchial tree.

Single-breath breath-holding estimate of pulmonary blood flow in man: comparison with direct Fick cardiac output

1989 ◽  
Vol 76 (6) ◽  
pp. 673-676 ◽  
Author(s):  
A. H. Kendrick ◽  
A. Rozkovec ◽  
M. Papouchado ◽  
J. West ◽  
G. Laszlo
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Pulmonary Blood Flow ◽  
Hold Time ◽  
Normal Subjects ◽  
Breath Holding ◽  
Breath Hold ◽  
Single Breath ◽  
Significant Difference ◽  
Cardiac Disorders

1. Resting pulmonary blood flow (Q.), using the uptake of the soluble inert gas Freon-22 and an indirect estimate of lung tissue volume, has been estimated during breath-holding (Q.c) and compared with direct Fick cardiac output (Q.f) in 16 patients with various cardiac disorders. 2. The effect of breath-hold time was investigated by comparing Q.c estimated using 6 and 10 s of breath-holding in 17 patients. Repeatability was assessed by duplicate measurements of Q.c in the patients and in six normal subjects. 3. Q.c tended to overestimate Q.f, the bias and error being 0.09 l/min and 0.59, respectively. The coefficient of repeatability for Q.c in the patients was 0.75 l/min and in the normal subjects was 0.66 1/min. For Q.f it was 0.72 l/min. There was no significant difference in Q.c measured at the two breath-hold times. 4. The technique is simple to perform, and provides a rapid estimate of Q., monitoring acute and chronic changes in cardiac output in normal subjects and patients with cardiac 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.

scholarly journals Reference equations for pulmonary diffusing capacity of carbon monoxide and nitric oxide in adult Caucasians

2018 ◽  
Vol 52 (1) ◽  
pp. 1500677 ◽  
Author(s):  
Mathias Munkholm ◽  
Jacob Louis Marott ◽  
Lars Bjerre-Kristensen ◽  
Flemming Madsen ◽  
Ole Find Pedersen ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Carbon Monoxide ◽  
Hold Time ◽  
Specific Conductance ◽  
Breath Hold ◽  
Diffusing Capacity ◽  
Single Breath ◽  
Capillary Membrane ◽  
Reference Equations ◽  
Hb Concentration

The aim of this study was to determine reference equations for the combined measurement of diffusing capacity of the lung for carbon monoxide (CO) and nitric oxide (NO) (DLCONO). In addition, we wanted to appeal for consensus regarding methodology of the measurement including calculation of diffusing capacity of the alveolo-capillary membrane (Dm) and pulmonary capillary volume (Vc).DLCONO was measured in 282 healthy individuals aged 18–97 years using the single-breath technique and a breath-hold time of 5 s (true apnoea period). The following values were used: 1) specific conductance of nitric oxide (θNO)=4.5 mLNO·mLblood−1·min−1·mmHg−1; 2) ratio of diffusing capacity of the membrane for NO and CO (DmNO/DmCO)=1.97; and 3) 1/red cell CO conductance (1/θCO)=(1.30+0.0041·mean capillary oxygen pressure)·(14.6/Hb concentration in g·dL−1).Reference equations were established for the outcomes of DLCONO, including DLCO and DLNO and the calculated values Dm and Vc. Independent variables were age, sex, height and age squared.By providing new reference equations and by appealing for consensus regarding the methodology, we hope to provide a basis for future studies and clinical use of this novel and interesting method.

scholarly journals Implementing the Three-Equation Method of Measuring Single Breath Carbon Monoxide Diffusing Capacity

1996 ◽  
Vol 3 (4) ◽  
pp. 247-257 ◽  
Author(s):  
Brian L Graham ◽  
Joseph T Mink ◽  
David J Cotton
Keyword(s):  
Carbon Monoxide ◽  
Lung Volume ◽  
Equation Method ◽  
Breath Holding ◽  
Breath Hold ◽  
Diffusing Capacity ◽  
Flow Rates ◽  
Single Breath ◽  
Conventional Methods ◽  
Made In

Conventional methods of measuring the single breath diffusing capacity of the lung for carbon monoxide (DLcoSB) are based on the Krogh equation, which is valid only during breath holding. Rigid standardization is used to approximate a pure breath hold manoeuvre, but variations in performing the manoeuvre cause errors in the measurement of DLcoSB. The authors previously described a method of measuring DLcoSBusing separate equations describing carbon monoxide uptake during each phase of the manoeuvre: inhalation, breath holding and exhalation. The method is manoeuvre-independent, uses all of the exhaled alveolar gas to improve estimates of mean DLcoSBand lung volume, and is more accurate and precise than conventional methods. A slow, submaximal, more physiological single breath manoeuvre can be used to measure DLcoSBin patients who cannot achieve the flow rates and breath hold times necessary for the standardized manoeuvre. The method was initially implemented using prototype equipment but commercial systems are now available that are capable of implementing this method. The authors describe how to implement the method and discuss considerations to be made in its use.

Pulmonary diffusing capacity in the presence of ventilation inhomogeneity

1987 ◽  
Vol 63 (6) ◽  
pp. 2438-2449 ◽  
Author(s):  
G. M. Saidel ◽  
M. Modarreszadeh
Keyword(s):  
Membrane Transport ◽  
Lung Volume ◽  
Human Subjects ◽  
Optimization Procedure ◽  
Diffusing Capacity ◽  
Capillary Transport ◽  
Ventilation Inhomogeneity ◽  
Single Breath ◽  
Residual Capacity ◽  
Alveolar Capillary

A model has been developed to quantify the effectiveness of alveolar-capillary transport in the presence of ventilation inhomogeneity. The exhalation dynamics of carbon monoxide (CO), argon (Ar), and lung volume from a single-breath experiment are analyzed simultaneously. A membrane transport coefficient (MTCO) that does not vary with lung volume is evaluated by a two-stage optimization procedure and related to diffusing capacity. Also, the model allows for a decrease in membrane transport rate associated with reduced lung volume. The model is tested by simulation studies and experiments with human subjects having normal or diseased (mainly obstructed) lungs. The MTCO provides a clear distinction between normal and obstructed lungs with respect to alveolar-capillary transport, whereas the semilog slope of the Ar alveolar plateau characterizes the ventilation inhomogeneity. Only when the diffusing capacity is corrected by the Ar slope, DLCO(Ar), do the breathing maneuvers performed from different preinflation volumes (residual volume or functional residual capacity) yield the same results for lungs with ventilation inhomogeneity. The uncorrected DLCO overestimates the effectiveness of alveolar-capillary transport in the presence of ventilation inhomogeneity.

Convection- and diffusion-dependent ventilation maldistribution in normal subjects

1985 ◽  
Vol 59 (3) ◽  
pp. 838-846 ◽  
Author(s):  
A. B. Crawford ◽  
M. Makowska ◽  
M. Paiva ◽  
L. A. Engel
Keyword(s):  
Dead Space ◽  
Sulfur Hexafluoride ◽  
Normal Subjects ◽  
Branch Points ◽  
Single Breath ◽  
The Mean ◽  
The Difference ◽  
Lung Periphery ◽  
And Diffusion ◽  
Dependent Mechanism

We performed multiple-breath N2 washouts (MBNW) with tidal volumes of 1 liter at 8–16 breaths/min and constant flow rates in six normal subjects. For each breath we computed the slope of the alveolar plateau, normalized by the mean expired N2 concentration (Sn), the Bohr dead space (VDB), an index analogous to the Fowler dead space (V50), and the normalized slope of phase II (S2). In four subjects helium (He) and sulfur hexafluoride (SF6) were washed out after equilibration with a 5% gas mixture of each tracer. The Sn for He and SF6 increased in consecutive breaths, but the difference (delta Sn) increased only over the first five breaths, remaining constant thereafter. In all six subjects Sn, VDB, and V50 increased progressively in consecutive breaths of the MBNW, the increase in Sn being the greatest, approximately 290% from the first to the 23–25th breath. In contrast, S2 was unchanged initially and decreased after the sixth breath. The results indicate that after the fifth breath the increase in Sn during a MBNW is diffusion independent and may constitute a sensitive index of convection-dependent inhomogeneity (CDI). Subtraction of this component from the first breath suggests that Sn in a single-breath washout is largely due to a diffusion-dependent mechanism. The latter may reflect an interaction of convection and diffusion within the lung periphery, whereas CDI may comprise ventilation inequality among larger units, subtended by more centrally located branch points.

Effect of breath-hold time on DLCO(SB) in patients with airway obstruction

1985 ◽  
Vol 58 (4) ◽  
pp. 1319-1325 ◽  
Author(s):  
B. L. Graham ◽  
J. T. Mink ◽  
D. J. Cotton
Keyword(s):  
Hold Time ◽  
Phase Iii ◽  
Breath Holding ◽  
Breath Hold ◽  
Single Breath ◽  
Incomplete Mixing ◽  
Capillary Membrane ◽  
Phase Iii Slope ◽  
Alveolar Capillary ◽  
Short Breath

The single-breath diffusing capacity of the lung for CO [DLCO(SB)] is considered a measure of the conductance of CO across the alveolar-capillary membrane and its binding with hemoglobin. Although incomplete mixing of inspired gas with alveolar gas could theoretically influence overall diffusion, conventional calculations of DLCO(SB) spuriously overestimate DLCO(SB) during short breath-holding periods when incomplete mixing of gas within the lung might have the greatest effect. Using the three-equation method to calculate DLCO(SB) which analytically accounts for changes in breath-hold time, we found that DLCO(SB) did not change with breath-hold time in control subjects but increased with increasing breath-hold time in both patients with asthma and patients with emphysema. The increase in DLCO(SB) with increasing breath-hold time correlated with the phase III slope of the single-breath N2 washout curve. We suggest that in patients with ventilation maldistribution, DLCO(SB) may be decreased for the shorter breath-hold maneuvers because overall diffusion is limited by the reduced transport of CO from the inspired gas through the alveolar gas prior to alveolar-capillary gas exchange.

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