Competitive inhibition of carbon monoxide transport: evidence against a carrier

1981 ◽  
Vol 50 (5) ◽  
pp. 1061-1064 ◽  
Author(s):  
D. Z. Rubin ◽  
D. Fujino ◽  
C. Mittman ◽  
S. M. Lewis
Keyword(s):  
Carbon Monoxide ◽  
Competitive Inhibition ◽  
Normal Adult ◽  
Gas Mixture ◽  
Diffusing Capacity ◽  
Constant Amount ◽  
Pulmonary Diffusing Capacity ◽  
Co Concentration ◽  
Carrier Molecule ◽  
Co Concentrations

The existence of a saturable carbon monoxide (CO) carrier in the lung remains controversial. The carrier hypothesis was invoked to explain data that indicated that pulmonary diffusing capacity for CO (DLCO) decreases with increasing CO concentration. To test this hypothesis, we measured DLCO in 14 normal adult subjects at three alveolar CO concentrations (60, 660, and 2,060 ppm). Each mixture contained a constant amount of labeled C18O (60 ppm) and a balance of unlabeled C16O. If a saturable carrier exists at increasing CO concentrations, the unlabeled CO would compete for most of the sites on the carrier molecule, effectively inhibiting the uptake of the labeled C18O. C18O diffusing capacities (mean +/- SD) for the three levels of CO were 34.9 +/- 5.6, 33.0 +/- 6.0, and 34.7 +/- 7.8. There were no significant differences (P greater than 0.2) among the three levels. In another group of subjects we repeated the study using a gas mixture containing 130 ppm C18O. No significant differences were found. As a result, we find no evidence to support a CO carrier hypothesis.

CO concentration-dependent changes in pulmonary diffusing capacity in humans

1982 ◽  
Vol 53 (2) ◽  
pp. 505-509 ◽  
Author(s):  
A. Sybert ◽  
R. Ayash ◽  
M. Chatham ◽  
G. H. Gurtner
Keyword(s):  
Treadmill Exercise ◽  
Transport Systems ◽  
Diffusing Capacity ◽  
Mechanically Ventilated ◽  
Pulmonary Diffusing Capacity ◽  
Carrier Mediated Transport ◽  
Saturation Kinetics ◽  
Co Concentration ◽  
End Tidal ◽  
Co Concentrations

Steady-state CO pulmonary diffusing capacity (DLCO) was measured at different inspired CO concentrations in seven males and one female during light treadmill exercise. As the CO level is increased. DLCO increases, reaches a maximum at an end-tidal CO concentration of approximately 100 ppm, and then decreases. The maximum DLCO is up to twice as large as the DLCO measured at an inspired CO concentration of approximately 1,780 ppm. These results are consistent with the presence of saturation kinetics, one of the basic properties of carrier-mediated transport systems. A similar relationship between DLCO and CO concentration was found in previous studies of mechanically ventilated dogs. Thus there is evidence for carrier-mediated transport of CO in the lungs of both humans and dogs.

Pulmonary diffusing capacity for CO independent of alveolar CO concentration

1981 ◽  
Vol 51 (3) ◽  
pp. 571-576 ◽  
Author(s):  
M. Meyer ◽  
W. Lessner ◽  
P. Scheid ◽  
J. Piiper
Keyword(s):  
Mass Spectrometer ◽  
Human Subjects ◽  
Normal Subjects ◽  
Facilitated Transport ◽  
Diffusing Capacity ◽  
Mean Values ◽  
Initial Concentration ◽  
Pulmonary Diffusing Capacity ◽  
Co Concentration ◽  
Co Concentrations

Pulmonary diffusing capacity for CO (DCO) was measured in human subjects at various CO concentrations using a rebreathing procedure. Two stable CO isotopes, 12C18O and 13C18O, were used. These isotopes could be simultaneously and continuously recorded by a respiratory mass spectrometer. For 13C18O the initial concentration in the rebreathing bag was constant at 0.00016, whereas it was varied for 12C18O from 0 to 0.00224. DCO was calculated for both isotopes. In five normal subjects, both D12C18O and D13C18O were independent of the rebreathing CO concentration, with mean values of 31.0 and 30.2 ml . min-1 . Torr-1, respectively. These results, which are at variance with those of Mendoza et al. (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 43: 880–884, 1977), are compatible with the assumption that diffusion is the sole mechanism of alveolocapillary CO transport; in particular, there is no evidence for facilitated transport.

Rate of uptake of carbon monoxide at different inspired concentrations in humans

1982 ◽  
Vol 52 (1) ◽  
pp. 109-113 ◽  
Author(s):  
H. A. Jones ◽  
J. C. Clark ◽  
E. E. Davies ◽  
R. E. Forster ◽  
J. M. Hughes
Keyword(s):  
Carbon Monoxide ◽  
Transport System ◽  
Human Lung ◽  
Normal Subjects ◽  
Facilitated Transport ◽  
Diffusing Capacity ◽  
Normal Human ◽  
The Mean ◽  
Co Concentrations

The rate of uptake of carbon monoxide (CO) in the lungs of normal subjects were measured at inspired concentrations of less than 1, 300, and 3,000 ppm (less than 0.0001–0.3%) using radioactive CO (11CO). In nine subjects the rate of uptake was monitored at the mouth during rebreathing. At inspired CO concentrations of approximately 1, 300, and 3,000 ppm and a mean alveolar O2 fraction of 0.15, the mean lung diffusing capacity was 25.8, 26.4, and 25.3 ml . min-1. Torr-1, respectively. In seven subjects the measurements were repeated after a period of O2 breathing, giving a mean alveolar O2 fraction of 0.78. The calculated membrane diffusing capacity was 31.9, 33.7, and 32.0 ml . min-1. Torr-1 at less than 1, 300, and 3,000 ppm inspired CO. We conclude that there is no difference in the rate of uptake of CO over the range of concentrations studied in these experiments. No evidence for the presence of a facilitated transport system for CO in the normal human lung was found.

Lung diffusing capacity: rebreathing method, applicability in nonuniform ventilation

1965 ◽  
Vol 20 (1) ◽  
pp. 99-102 ◽  
Author(s):  
P. S⊘lvsteen
Keyword(s):  
Carbon Monoxide ◽  
Nonuniform Distribution ◽  
Diffusing Capacity ◽  
Carbon Monoxide Concentration ◽  
Straight Line ◽  
Co Concentration ◽  
Concentration Changes ◽  
Rectilinear Section ◽  
Rebreathing Method

We have calculated how the carbon monoxide concentration changes when subjects with different distributions of ventilation and lung diffusing capacity (Dl) respire in a small bag. The curve [loge CO concentration in the bag] versus [time] will sooner or later appear as a straight line. Dl is calculated from the slope of the rectilinear section of the curve and from lung and bag volume. If the curve becomes rectilinear within the period considered, Dl is calculated too low. In some cases the curve will not be rectilinear until more than 45 sec have passed, but will appear to be rectilinear during the period from 30 to 45 sec. If such an experiment is discontinued when 45 sec (the usual duration of experiment) have passed, Dl can be calculated at too high, at correct, or at too low values. nonuniform distribution of lung diffusing capacity Submitted on February 18, 1964

DlCO measurements with gas chromatography

1962 ◽  
Vol 17 (6) ◽  
pp. 856-860 ◽  
Author(s):  
Josef R. Smith ◽  
Lyle H. Hamilton
Keyword(s):  
Gas Chromatography ◽  
Normal Subjects ◽  
Inert Gas ◽  
Breath Holding ◽  
Gas Mixture ◽  
Diffusing Capacity ◽  
Gas Chromatograph ◽  
Excellent Correlation ◽  
Pulmonary Diffusing Capacity ◽  
The Mean

A gas chromatograph has been used to analyze gases for the measurement of pulmonary diffusing capacity using the breath-holding technique. The gas mixture used for the measurement consisted of carbon monoxide in air with neon as the insoluble inert gas. The calculated DlCO was unaffected when sulphur hexafloride (SF6) or He was substituted for Ne in the mixture, but since CO and Ne could be most simply and rapidly analyzed, this combination was preferred for the gas mixture used to measure DlCO. The mean DlCO for ten normal subjects was 25.8 ± 4.2 ml/min mm Hg. These results were comparable to values reported in the literature when established methods of analysis were used. An excellent correlation was found between calculated DlCO and the clinical condition of patients with impaired pulmonary diffusing capacity. Submitted on February 14, 1962

scholarly journals Effect of hyperlipidaemia on pulmonary diffusing capacity for carbon monoxide.

Thorax ◽  
1979 ◽  
Vol 34 (2) ◽  
pp. 265-268 ◽  
Author(s):  
M R Partridge ◽  
J M Hughes ◽  
G R Thompson
Keyword(s):  
Carbon Monoxide ◽  
Diffusing Capacity ◽  
Pulmonary Diffusing Capacity

scholarly journals Increased heme catabolism in critically ill patients: correlation among exhaled carbon monoxide, arterial carboxyhemoglobin, and serum bilirubin IXα concentrations

2006 ◽  
Vol 290 (1) ◽  
pp. L114-L119 ◽  
Author(s):  
Hiroshi Morimatsu ◽  
Toru Takahashi ◽  
Kyoichiro Maeshima ◽  
Kazuyoshi Inoue ◽  
Tomoko Kawakami ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Critically Ill ◽  
Critically Ill Patients ◽  
Linear Regression Analysis ◽  
Multivariate Linear Regression Analysis ◽  
Arterial Blood ◽  
Exhaled Air ◽  
Co Concentration ◽  
Exhaled Carbon Monoxide ◽  
Co Concentrations

It has been reported that exhaled carbon monoxide (CO) concentrations and arterial carboxyhemoglobin (CO-Hb) concentration in blood may be increased in critically ill patients. However, there was no study that examined correlation among amount of CO in exhaled air, CO-Hb concentrations in erythrocytes, and bilirubin IXα (BR) in serum, i.e., the three major indexes of heme catabolism, within the same subject. Here, we examined CO concentrations in exhaled air, CO-Hb concentrations in arterial blood, and BR levels in serum in 29 critically ill patients. Measurements of exhaled CO, arterial CO-Hb, and serum total BR have been done in the intensive care unit. As control, exhaled CO concentration was also measured in eight healthy volunteers. A median exhaled CO concentration was significantly higher in critically ill patients compared with control. There was significant correlation between CO and CO-Hb and CO and total BR level. We also found CO concentrations correlated with indirect BR but not direct BR. Multivariate linear regression analysis for amount of exhaled CO concentrations also showed significant correlation with CO-Hb and total BR, despite the fact that respiratory variables of study subjects were markedly heterogeneous. We found no correlation among exhaled CO, patients’ severity, and degree of inflammation, but we found a strong trend of a higher exhaled CO concentration in survivors than in nonsurvivors. These findings suggest there is an increased heme breakdown in critically ill patients and that exhaled CO concentration, arterial CO-Hb, and serum total BR concentrations may be useful markers in critically ill conditions.

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