Comparison of cardiac output during exercise by single-breath and CO2-rebreathing methods

1985 ◽  
Vol 58 (4) ◽  
pp. 1372-1377 ◽  
Author(s):  
M. D. Inman ◽  
R. L. Hughson ◽  
N. L. Jones
Keyword(s):  
Cardiac Output ◽  
Partial Pressure ◽  
Co2 Rebreathing ◽  
Single Breath ◽  
Partial Pressure Of Co2 ◽  
The Difference ◽  
End Tidal ◽  
Rebreathing Method ◽  
Single Breath Method

Cardiac output (Q) was estimated in supine rest and in upright cycling at several work rates up to 200 W in five male and one female subjects. At least four repetitions of both the CO2-rebreathing plateau method (Collier, J. Appl. Physiol. 9:25–29, 1956) and the Kim et al. (J. Appl. Physiol. 21: 1338–1344, 1966) single-breath method were performed at each work rate, in a steady state of O2 consumption and heart rate. At supine rest and low work rates, estimates of Q were similar by the two methods. However, at higher work rates, the single-breath method significantly (P less than 0.05) underestimated the value obtained by CO2 rebreathing. The reason for the difference in estimates of Q by the two methods was traced to the determination of arterial partial pressure of CO2 (PaCO2) and mixed venous partial pressure of CO2 (PvCO2). The estimate of PaCO2 from the single-breath method was approximately 88.5% of the estimate from end-tidal PCO2 used with the rebreathing method (P less than 0.001). The oxygenated PvCO2 calculated from the single-breath Q averaged approximately 92.5% of the PvCO2 from CO2 rebreathing (P less than 0.0001). The difference in estimates of Q was not eliminated by using a logarithmic form of the CO2 dissociation curve with the single-breath method.

Comparison of CO2 rebreathing and acetylene methods for cardiac output

1965 ◽  
Vol 20 (4) ◽  
pp. 763-766 ◽  
Author(s):  
K. Klausen
Keyword(s):  
Cardiac Output ◽  
Partial Pressure ◽  
Venous Blood ◽  
Mixed Venous Blood ◽  
Co2 Rebreathing ◽  
Arterial Blood ◽  
Co2 Output ◽  
Partial Pressure Of Co2 ◽  
Douglas Bag ◽  
Rebreathing Method

The cardiac output during rest and work was determined by a CO2 rebreathing method as suggested by Defares. The partial pressure of CO2 in the mixed venous blood (PvCOCO2) was calculated from the rise of the CO2 percent in a Grollman bag during rebreathing. In the rest experiments the partial pressure of CO2 in arterial blood (PaCOCO2) was obtained from analysis of alveolar samples taken by the Haldane-Priestley direct sampling method. In the work experiments the PaCOCO2 was calculated using the Bohr formula and a dead space estimated from Asmussen and Nielsen's data. The metabolic rate including both O2 uptake and CO2 output was determined by the Douglas bag method. In each experiment the acetylene method as described by Christensen was applied after the CO2 rebreathing method. The values obtained by the two methods were almost identical, the standard deviation for all experiments being ±7.3%, and were of the same magnitude as those obtained by others with the dye-dilution or direct Fick method both during rest and work. cardiac output at rest and work; arterial Pco2 and venous Pco2 at rest and work; stroke volume at rest and work Submitted on November 25, 1964

Voluntary breath-holding in the morning and in the evening

2004 ◽  
Vol 106 (4) ◽  
pp. 347-352 ◽  
Author(s):  
Gerardo BOSCO ◽  
Alessandro IONADI ◽  
Piergiorgio G. DATA ◽  
Jacopo P. MORTOLA
Keyword(s):  
Partial Pressure ◽  
Statistical Significance ◽  
Breath Holding ◽  
Sitting Position ◽  
Voluntary Hyperventilation ◽  
Partial Pressure Of Co2 ◽  
The Difference ◽  
End Tidal ◽  
Male Subjects ◽  
Voluntary Breath Holding

The aim of the present study was to determine whether or not voluntary breath-holding time (BHT) changes with the time of the day. BHT with airways closed at end-expiration was measured in six male subjects in the sitting position during the morning (08.00–12.00 hours, on days 1, 6, 7 and 8) and evening (20.00–24.00 hours, on days 2 and 4). BHT increased with the number of days of testing and, at day 8, the morning values averaged 160% of those on day 1. Also, ΔPACO2 [the difference between end-tidal partial pressure of CO2 (PCO2) and alveolar PCO2 (PACO2) at the breaking point] increased in proportion to BHT. Hence the BHT/ΔPACO2 ratio remained nearly constant. Voluntary hyperventilation prolonged BHT and increased ΔPACO2. Conversely, in hypoxia (13% O2 for 1–2 h), BHT and ΔPACO2 were reduced proportionally. During the evening sessions, most of the BHT/ΔPACO2 ratios in normoxia, hypoxia or after hyperventilation were higher than the corresponding morning values, with the group difference reaching statistical significance for the measurements in normoxia and hypoxia. In conclusion, voluntary BHT varies in both duration and its relationship with ΔPACO2 between the morning and evening hours. The results should also imply that, with an interruption of breathing, changes in alveolar and arterial gases are not the same at different times of the day.

Comparison of Cardiac Output Determined by a Carbon Dioxide-Rebreathing and Direct Fick Method at Rest and during Exercise

1978 ◽  
Vol 55 (5) ◽  
pp. 445-452 ◽  
Author(s):  
T. Reybrouck ◽  
A. Amery ◽  
L. Billiet ◽  
R. Fagard ◽  
H. Stijns
Keyword(s):  
Cardiac Output ◽  
Haemoglobin Concentration ◽  
Systematic Difference ◽  
Dissociation Curve ◽  
Co2 Rebreathing ◽  
Carbon Dioxide Rebreathing ◽  
Large Dispersion ◽  
Graded Exercise ◽  
End Tidal ◽  
Rebreathing Method

1. To study the validity of a CO2-rebreathing method at rest and during graded exercise, cardiac output was measured simultaneously on 59 occasions in 16 subjects with normal pulmonary function with the CO2-rebreathing method and the direct Fick method for oxygen. The correlation coefficient between the results of both methods was significantly higher during exercise than at rest. 2. No systematic difference was shown between (a-v̄)CO2 content difference determined on whole blood and end-tidal gas, which justified the exclusion of a correction factor for blood to alveolar gas Pco2 gradients. 3. In the calculation of cardiac output by the direct Fick method for CO2 and by CO2 rebreathing, a standard CO2 dissociation curve was preferred to a synthetic CO2 dissociation curve, constructed by allowance for changes in haemoglobin concentration, pH and oxygen saturation. The latter curve tended to increase values for cardiac output and induced a large dispersion around the line of identity, when compared with simultaneous cardiac output estimates by the direct Fick method for oxygen.

scholarly journals A Simple and Accurate Approach for Determining the VFA Concentration in Anaerobic Digestion Liquors, Relying on Two Titration Points and an External Inorganic Carbon Analysis

2021 ◽  
Vol 5 (2) ◽  
pp. 15
Author(s):  
Paz Nativ ◽  
Yonatan Gräber ◽  
Yaron Aviezer ◽  
Ori Lahav
Keyword(s):  
Partial Pressure ◽  
Volatile Fatty Acids ◽  
Inorganic Carbon ◽  
Strong Acid ◽  
Direct Analysis ◽  
Anaerobic Digesters ◽  
Acid Titration ◽  
Partial Pressure Of Co2 ◽  
Ph Range

A new analytic approach is presented for determining the total volatile fatty acids (VFAT) concentration in anaerobic digesters. The approach relies on external determination of the inorganic carbon concentration (CT) in the analyzed solution, along with two strong-acid titration points. The CT concentration can be determined by either a direct analysis (e.g., by using a TOC device) or by estimating it from the recorded partial pressure of CO2(g) in the biogas (often a routine analysis in anaerobic digesters). The titration is carried out to pH 5.25 and then to pH 4.25. The two titration results are plugged into an alkalinity-mass-based equation and then the two terms are subtracted from each other to yield an equation in which VFAT is the sole unknown (since CT is known and the effect of the total orthophosphate and ammonia concentrations is shown to be small at this pH range). The development of the algorithm and its verification on four anaerobic reactor liquors is presented, on both the raw water and on acetic acid-spiked samples. The results show the method to be both accurate (up to 2.5% of the expected value for VFAT/Alkalinity >0.2) and repetitive when the total orthophosphate and ammonia concentrations are known, and fairly accurate (±5% for VFAT >5 mM) when these are completely neglected. PHREEQC-assisted computation of CT from the knowledge of the partial pressure of CO2(g) in the biogas (and pH, EC and temperature in the liquor) resulted in a very good estimation of the CT value (±3%), indicating that this technique is adequate for the purpose of determining VFAT for alarming operators in case of process deterioration and imminent failure.

Respiratory physiology teaching: determination of residual volume by applying the indicator-dilution technique.

1998 ◽  
Vol 274 (6) ◽  
pp. S53
Author(s):  
H Heller ◽  
K Granitza ◽  
B Eixmann
Keyword(s):  
Indicator Dilution ◽  
Respiratory Physiology ◽  
Successful Outcome ◽  
Residual Volume ◽  
Dilution Technique ◽  
Laboratory Courses ◽  
Single Breath ◽  
Indicator Dilution Technique ◽  
Single Breath Method

Apart from the current teaching of spirometric methods in laboratory courses on respiratory physiology, we have included an experiment in which medical students determine their own residual volume by applying the indicator-dilution technique. For hygienic reasons we used a bag-in-the-box system to dilute helium within alveolar space by performing the single-breath method. Although each participant independently underwent only one single-breath maneuver, we gained a reliable relationship between residual volume and subjects' height and body weight in 68 female (r = 0.6, P < 0.0001) and 99 male (r = 0.42, P < 0.0001) students. From this successful outcome and with the opportunity to discuss the limitations of the single-breath method as well, we inferred that this experiment affords a transparent and instructive approach to interpreting the determination of lung volumes on the basis of the indicator-dilution technique.

Single-breath CO diffusing capacity influenced by initial alveolar partial pressure of CO

1998 ◽  
Vol 275 (1) ◽  
pp. R339-R342
Author(s):  
Hartmut Heller ◽  
Klaus-Dieter Schuster
Keyword(s):  
Mass Spectrometry ◽  
Partial Pressure ◽  
Breath Holding ◽  
Gas Mixture ◽  
Residual Volume ◽  
Diffusing Capacity ◽  
Time Intervals ◽  
Single Breath ◽  
Identical Manner ◽  
End Tidal

The purpose of this study was to assess the influence of incorrect determinations of the initial alveolar partial pressure of carbon monoxide (CO) at the beginning of breath holding (Pia CO) on the pulmonary CO diffusing capacity of the lung (Dl CO). Single-breath maneuvers were performed on 14 anesthetized and artificially ventilated rabbits, using 0.2% CO in nitrogen as the indicator gas mixture. Inflation and deflation procedures were carried out in an identical manner on each animal, with inflation always starting from residual volume. End-tidal partial pressure of CO was determined by respiratory mass spectrometry and was used to calculate Dl CO values with the application of the three-equation ( method 1), as well as the conventional ( method 2), solution. In each rabbit, method 2 caused Dl CO values to be overestimated when compared with method 1, and this overestimation decreased with increasing time intervals of CO uptake. Because we were able to recalculate this deviation using Pia COvalues that were obtained by taking the diffusive removal of CO during inflation into account, we concluded that errors in estimating Pia CO by applying method 2 significantly contribute to the discrepancy between both methods.

Expiratory and arterial partial pressure relations under different ventilation-perfusion conditions

1983 ◽  
Vol 54 (6) ◽  
pp. 1745-1753 ◽  
Author(s):  
A. Zwart ◽  
S. C. Luijendijk ◽  
W. R. de Vries
Keyword(s):  
Partial Pressure ◽  
Dead Space ◽  
Gas Analysis ◽  
Lung Model ◽  
Breathing Patterns ◽  
Tracer Gas ◽  
Physiological Dead Space ◽  
Arterial Partial Pressure ◽  
The Difference ◽  
End Tidal

Inert tracer gas exchange across the human respiratory system is simulated in an asymmetric lung model for different oscillatory breathing patterns. The momentary volume-averaged alveolar partial pressure (PA), the expiratory partial pressure (PE), the mixed expiratory partial pressure (PE), the end-tidal partial pressure (PET), and the mean arterial partial pressure (Pa), are calculated as functions of the blood-gas partition coefficient (lambda) and the diffusion coefficient (D) of the tracer gas. The lambda values vary from 0.01 to 330.0 inclusive, and four values of D are used (0.5, 0.22, 0.1, and 0.01). Three ventilation-perfusion conditions corresponding to rest and mild and moderate exercise are simulated. Under simulated exercise conditions, we compute a reversed difference between PET and Pa compared with the rest condition. This reversal is directly reflected in the relation between the physiological dead space fraction (1--PE/Pa) and the Bohr dead space fraction (1--PE/PET). It is argued that the difference (PET--Pa) depends on the lambda of the tracer gas, the buffering capacity of lung tissue, and the stratification caused by diffusion-limited gas transport in the gas phase. Finally some determinants for the reversed difference (PET--Pa) and the significance for conventional gas analysis are discussed.

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