Uneven gas mixing during rebreathing assessed by simultaneously measuring dead space

1982 ◽  
Vol 53 (4) ◽  
pp. 930-939 ◽  
Author(s):  
M. F. Petrini ◽  
B. T. Peterson ◽  
R. W. Hyde ◽  
V. Lam ◽  
M. J. Utell ◽  
...  
Keyword(s):  
Dead Space ◽  
Sulfur Hexafluoride ◽  
Breath Holding ◽  
Gas Mixing ◽  
Pulmonary Tissue ◽  
Pulmonary Capillary Blood Flow ◽  
Pulmonary Capillary Blood ◽  
Anatomical Dead Space ◽  
The Difference ◽  
Uneven Ventilation

To evaluate the rate of gas mixing in human lungs during rebreathing maneuvers used to measure pulmonary tissue volume (Vt) and pulmonary capillary blood flow (Qc), we devised a method to determine the dead space during rebreathing (VRD). Required measurements are initial concentration of a foreign inert insoluble gas in the rebreathing bag, first mixed expired concentration, equilibrated concentration, volume inspired, and volume of the first expired breath. In subjects breathing rapidly at 30 breaths/min with inspired volumes in excess of 2 liters, VRD had values three or more times greater than the predicted anatomical dead space (VD). Breath holding after the first inspiration progressively diminished VRD so that after 10–15 s, it approximately equaled predicted VD. VRD measured with helium was smaller than VRD measured with sulfur hexafluoride. The reported degree of uneven ventilation from gravitational forces in normal humans can account for only about one-third of the difference between VRD and VD. These findings support the concept that mixing by diffusion between peripheral parallel airways is incomplete at normal breathing rates in humans and can result in errors as high as 25% in Vt and Qc.

A New Equal Area Method to Calculate and Represent Physiologic, Anatomical, and Alveolar Dead Spaces

2006 ◽  
Vol 104 (4) ◽  
pp. 696-700 ◽  
Author(s):  
Yongquan Tang ◽  
Martin J. Turner ◽  
A Barry Baker
Keyword(s):  
Carbon Dioxide ◽  
Dead Space ◽  
Graphical Method ◽  
Mean Difference ◽  
Equal Area ◽  
Area Method ◽  
Physiologic Dead Space ◽  
Anatomical Dead Space ◽  
The Mean ◽  
The Difference

Background Physiologic dead space is usually estimated by the Bohr-Enghoff equation or the Fletcher method. Alveolar dead space is calculated as the difference between anatomical dead space estimated by the Fowler equal area method and physiologic dead space. This study introduces a graphical method that uses similar principles for measuring and displaying anatomical, physiologic, and alveolar dead spaces. Methods A new graphical equal area method for estimating physiologic dead space is derived. Physiologic dead spaces of 1,200 carbon dioxide expirograms obtained from 10 ventilated patients were calculated by the Bohr-Enghoff equation, the Fletcher area method, and the new graphical equal area method and were compared by Bland-Altman analysis. Dead space was varied by varying tidal volume, end-expiratory pressure, inspiratory-to-expiratory ratio, and inspiratory hold in each patient. Results The new graphical equal area method for calculating physiologic dead space is shown analytically to be identical to the Bohr-Enghoff calculation. The mean difference (limits of agreement) between the physiologic dead spaces calculated by the new equal area method and Bohr-Enghoff equation was -0.07 ml (-1.27 to 1.13 ml). The mean difference between new equal area method and the Fletcher area method was -0.09 ml (-1.52 to 1.34 ml). Conclusions The authors' equal area method for calculating, displaying, and visualizing physiologic dead space is easy to understand and yields the same results as the classic Bohr-Enghoff equation and Fletcher area method. All three dead spaces--physiologic, anatomical, and alveolar--together with their relations to expired volume, can be displayed conveniently on the x-axis of a carbon dioxide expirogram.

Measurement of pulmonary blood flow during exercise using nitrous oxide

1962 ◽  
Vol 17 (4) ◽  
pp. 579-586 ◽  
Author(s):  
Margaret R. Becklake ◽  
C. J. Varvis ◽  
L. D. Pengelly ◽  
S. Kenning ◽  
M. McGregor ◽  
...  
Keyword(s):  
Blood Flow ◽  
Steady State ◽  
Dilution Technique ◽  
Fick Principle ◽  
Pulmonary Capillary Blood Flow ◽  
Time Period ◽  
Pulmonary Capillary ◽  
Wide Range ◽  
Pulmonary Capillary Blood ◽  
The Difference

Pulmonary capillary blood flow (Qc) in the exercising subject was calculated from the rate of disappearance of N2O during steady state breathing of an N2O-He-O2 mixture. Measurements were made after alveolar rinsing (reciprocal of N2 washout) had occurred, and up to 30 sec, a time period accompanied by minimal recirculation, since FaNN2O during this period did not rise significantly. Repeatability of the method, judged as the difference of a second estimate from a first on the same subject, was comparable to that reported for the direct Fick technique in resting subjects (31 of 33 paired observations agreed within 20%). Results over a wide range agreed with almost simultaneous measurements by a dye dilution technique (24 of 26 paired observations agreed within 20%), and when related to pulse rate and to Vo2, were comparable to those of the other workers whose subjects were studied in a similar posture. Indeed, this technique (using the indirect Fick principle under “steady state” conditions) probably attains its greatest accuracy during exercise when other methods become less easily applicable. Submitted on December 18, 1961

Gas mixing in dog lungs studied by single-breath washout of He and SF6

1983 ◽  
Vol 55 (6) ◽  
pp. 1795-1802 ◽  
Author(s):  
M. Meyer ◽  
C. Hook ◽  
H. Rieke ◽  
J. Piiper
Keyword(s):  
Gas Exchange ◽  
Lung Volume ◽  
Dead Space ◽  
Sulfur Hexafluoride ◽  
Breath Holding ◽  
Concentration Difference ◽  
Alveolar Plateau ◽  
Variable Time ◽  
Single Breath ◽  
Constant Rate

Simultaneously measured helium (He) and sulfur hexafluoride (SF6) single-breath washout was studied in 16 anesthetized paralyzed dogs ventilated with a special hydraulically operated ventilatory servo system. After equilibration of lung gas with 1% He and 1% SF6, the maneuver consisting of inspiration of a test gas-free mixture at constant rate (VI), a variable time of breath holding, and an expiration at constant rate (VE), was performed. Fractional concentrations of He and SF6, recorded against expired volume, were analyzed in terms of slope of the alveolar plateau (S) and series (Fowler) dead space (VD). In control conditions (VI = 0.5 l/s, VE = 0.1 l/s) S was about 10% of alveolar-to-inspired concentration difference per liter expirate both for He and SF6. Both SHe and SSF6 were inversely related to VI and VE, the relative changes being more pronounced with varying VE. SHe/SSF6 was higher or lower than unity depending on VI and VE. Both SHe and SSF6 decreased with increasing preinspiratory lung volume. Breath holding up to 10 s slightly decreased SHe and SSF6 while SHe/SSF6 was unchanged. The contribution of continuing gas exchange to S assessed from comparative measurements using the reversed (single breath washin) technique ranged from 6 to 23% in the various conditions. The VDHe/VDSF6 ratio was 0.84 and was little affected in the various settings. Results indicate that the substantial alveolar gas inhomogeneity in the dog lung and the mechanism accounting for S are little diffusion dependent. By exclusion sequential filling and emptying of lung units is believed to constitute the most important mechanism responsible for the sloping alveolar plateau.

Bronchospirometric studies of lung volumes, ventilation/perfusion ratios and diffusion

1965 ◽  
Vol 20 (1) ◽  
pp. 79-86 ◽  
Author(s):  
E. M. Cree ◽  
H. K. Rasmussen ◽  
F. Wright ◽  
J. K. Curtis
Keyword(s):  
Breath Holding ◽  
Physiological Changes ◽  
Diffusing Capacity ◽  
Lung Volumes ◽  
Nitrogen Washout ◽  
Pulmonary Capillary Blood Flow ◽  
Pulmonary Capillary ◽  
Pulmonary Capillary Blood ◽  
First Time ◽  
And Diffusion

Bilateral bronchospirometric nitrogen washout studies were used for the first time to calculate ventilation/perfusion ratios for the well and poorly ventilated areas in individual lungs. Results were compared with washout studies on both lungs measured together. Data suitable for analysis were obtained from seven patients with chronic lung disease. It was demonstrated that this technique for determining simultaneous ventilation/perfusion ratios for each lung gave accurate and detailed physiological changes. Comparison of the sum of average values for pulmonary capillary blood flow when both lungs were measured together by the same nitrogen washout technique showed a variation within the accepted 10% error for cardiac output. Diffusion for the separate lungs, measured by the carbon monoxide breath-holding method, gave values which correlated with lung volumes. bronchospirometry; nitrogen washout; diffusing capacity Submitted on November 22, 1963

Rebreathing techniques for pulmonary capillary blood flow and tissue volume

1980 ◽  
Vol 49 (5) ◽  
pp. 910-915 ◽  
Author(s):  
M. A. Sackner ◽  
G. Markwell ◽  
N. Atkins ◽  
S. J. Birch ◽  
R. J. Fernandez
Keyword(s):  
Blood Flow ◽  
Dimethyl Ether ◽  
Capillary Blood ◽  
Ethyl Iodide ◽  
Capillary Blood Flow ◽  
Pulmonary Tissue ◽  
Pulmonary Capillary Blood Flow ◽  
Pulmonary Capillary ◽  
Capillary Blood Volume ◽  
Pulmonary Capillary Blood

The variability of three methods of calculating pulmonary capillary blood flow (Qc) and pulmonary tissue plus capillary blood volume (Vt) during rebreathing was assessed in normal humans by using as markers acetylene, ethyl iodide, and dimethyl ether. The methods of analysis were as follows. Method I, the timing of the disappearance curves of the soluble gases was corrected by assuming that the C18O-disappearance curve intercepted at unity at time O. Method II, it was assumed that the acetylene Qc calculated by method I was correct; ethyl iodide and dimethyl ether Vt were solved by an equation using the disappearance slopes of these gases and the acetylene Qc value, thereby avoiding dependence on extrapolated intercept values. Method III, Vt was calculated by solving for a unique value of Qc between pairs of disappearance slopes of acetylene and dimethyl ether, acetylene and ethyl iodide, and ethyl iodide and dimethyl ether. Among the three methods, method I gave the most reproducible values for Vt as determined with acetylene or dimethyl ether. Using method I, both acetylene and dimethyl ether were equally acceptable gases for measurement of Vt; acetylene was a better marker for Qc measurements.

Respiratory dead space and arterial to end-tidal CO2 tension difference in anesthetized man

1960 ◽  
Vol 15 (3) ◽  
pp. 383-389 ◽  
Author(s):  
J. F. Nunn ◽  
D. W. Hill
Keyword(s):  
Tidal Volume ◽  
Dead Space ◽  
Artificial Respiration ◽  
Physiological Dead Space ◽  
Anatomical Dead Space ◽  
The Subject ◽  
The Mean ◽  
The Difference ◽  
End Tidal ◽  
End Tidal Co2

Observations were made during both spontaneous and artificial respiration on 12 fit patients anesthetized for routine surgical procedures. Above a tidal volume of 350 ml (BTPS), the anatomical dead space was close to the predicted normal value for the subject. Below 350 ml, it was reduced in proportion to the tidal volume. The physiological dead space (below the carina) approximated to 0.3 times the tidal volume for tidal volumes between 163 and 652 ml (BTPS). Throughout the range the physiological dead space was considerably in excess of the anatomical dead space measured simultaneously. The difference (alveolar dead space) varied from 15 to 231 ml, being roughly proportional to the tidal volume. The mean arterial to end-tidal CO2 tension difference was 4.6 (S.D. ±2.5) mm Hg and not related to tidal volume or arterial CO2 tension. None of the findings appeared to depend on whether the respiration was spontaneous or artificial. Submitted on September 25, 1959

Effects of water immersion to the neck on pulmonary circulation and tissue volume in man

1976 ◽  
Vol 40 (3) ◽  
pp. 293-299 ◽  
Author(s):  
R. Begin ◽  
M. Epstein ◽  
M. A. Sackner ◽  
R. Levinson ◽  
R. Dougherty ◽  
...  
Keyword(s):  
Water Immersion ◽  
Normal Subjects ◽  
Capillary Blood ◽  
Alveolar Volume ◽  
Pulmonary Tissue ◽  
Fourfold Increase ◽  
Pulmonary Capillary Blood Flow ◽  
Capillary Blood Volume ◽  
Pulmonary Capillary Blood ◽  
Residual Capacity

Utilizing the rebreathing of a gas mixture containing C2H2, C180, He O2, and N2, we obtained serial measurements of the pulmonary capillary blood flow (Qc), diffusing capacity per unit of alveolar volume (DL/VA), functional residual capacity (FRC), pulmonary tissue plus capillary blood volume (VTPC), and O2 comsumption (VO2) in five normal subjects under the following conditions: 1) 6 h of sitting, 2) 4 h of sitting while immersed in thermoneutral water to the neck, and 3) 4 h of lying in thermoneutral water to the neck. Water immersion (NI) was preceded and followed by 1-h prestudy and 1-h recovery periods. The measurements were made at 30-min intervals. Seated NI produced a fourfold increase in sodium excretion (UNaV), a 25–36% increase in Qc, a 45–59% increase in DL/VA, and a 30–36% decrease in FRC. This occurred as early as the 1st h of NI and persisted throughout the 4-h period of study. Throughout the seated control and NI periods, VO2, heart rate, and VTPC remained constant. During supine NI, Qc, HR, DL/VA, FRC, and VO2 did not differ significantly from supine prestudy. These date demonstrate that seated NI causes a significant increase of Qc and DL/VA which persists throughout the immersion period. Furthermore, the lack of change of VTPC suggests that the central vascular engorgement induced by seated NI is not accompanied by extravasation of fluid into the pulmonary interstitial space.

Determination of pulmonary parenchymal tissue volume and pulmonary capillary blood flow in man

1959 ◽  
Vol 14 (4) ◽  
pp. 541-551 ◽  
Author(s):  
Leon Cander ◽  
Robert E. Forster
Keyword(s):  
Blood Flow ◽  
Capillary Blood ◽  
Capillary Blood Flow ◽  
Breath Holding ◽  
Tissue Volume ◽  
Parenchymal Tissue ◽  
Pulmonary Capillary Blood Flow ◽  
Pulmonary Capillary ◽  
Alveolar Level ◽  
Pulmonary Capillary Blood

The rates of disappearance of SF6, N2O, C2H2, diethyl ether and acetone from alveolar air during breath holding, following a single deep inspiration of a mixture containing one of these gases and about 15% helium, was studied in five normal seated subjects. SF6 is so insoluble that no significant change in its concentration relative to helium was found. Ether and acetone are so soluble that they dissolve in the tissues around the respiratory dead space during inspiration and evaporate during expiration, contaminating the expired alveolar gas to such an extent that the exchange of these gases cannot be properly measured at the alveolar level. N2O and C2H2 showed a) a rapid (less than 1.5 sec.) initial fall in relative alveolar concentration and b) a subsequent more gradual decrease; a) presumably results from the solution of the foreign gas in the pulmonary parenchymal tissues and can be used to calculate the pulmonary parenchymal tissue volume (Vt); b) can be used to calculate the pulmonary capillary blood flow (Qc), provided observations are not extended beyond 21 sec. The average values obtained were 3.31 l/min/m2 and 606 ml for Qc and Vt, respectively. Submitted on December 4, 1958

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