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Query: UMLS:C0020440 (hypercapnia)
 7,939 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In vitro, the affinity of Hb for O2 depends on pH and capnia by the intermediate of the 2-3 DPG level, the concentration of which lowers in the case of acidosis and hypercapnia. Thus, an increase in the affinity results, but while Bohr's effect is immediate, on the contrary the 2-3 DPG effect is slow. Authors have verified the importance of this modification by studying the affinity of Hb for O2 thanks to the P50 technique in 15 normal non-smokers subjects and in 10 subjects with compensated or not respiratory acidosis but normally saturated thanks to continuous O2 administration.
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PMID:[Study of P50 in patients under continuous O2 inhalation and during chronic respiratory acidosis]. 0 19

Blood and tissue gas exchange properties of mole rats in normoxic and hypoxic-hypercapnic conditions were compared to the common mammalian pattern. RBC count was 14.0 +/- 1.2-10(6)/microliter. Hb concentration was 15.0 +/- 0.4g/100 ml. P50 (at pH 7.4 and 37 degrees C) was 29.5 +/- 0.5 mm Hg. Oxygen capacity averaged 20.2 +/- 0.4 vol% and the Hill coefficient was 2.9 +/- 0.1. The Bohr effect was -0.53 +/- 0.02 (deltalog P/deltapH). The temperature coefficient was 0.0152 +/- 0.0014 (deltalog P/delta degrees C). The Haldane effect was 4.8 +/- 0.5 (deltaCCO2 vol%)at PCO2 =40 mm Hg. Steady-state partial pressures in gas pockets were PO2 = 15.1 +/- 1.4 mm Hg and PCO2 = 85.8 +/- 3.9 mm Hg in normoxia, and 11.5 +/- 3.0 and 101.8 +/- 3.5 repectively in hypoxia-hypercapnia (PIO2 congruent to 85 mm Hg). Under the same conditions 2,3-DPG dropped from 0.87 and 0.88 to 0.62 and 0.65 (mol/mol Hb) in the rat and in the white rat, respectively. Heart muscle myoglobin concentration of the mole rat (1.44 mg/g) did not differ significantly from that of the white rat (1.96 mg/g), whereas masseter myoglobin was 4.0 mg/g--significantly different from the rat (1.21 mg/g). Results indicate that the strategy used by the mole rat to maintain a normal metabolic rate under variable atmospheric conditions, besides having high oxygen affinity, is to expand the physiological range of the oxygen dissociation curve to very low oxygen tensions, at the expense of its acid-base regulation. The regulation of the shape of the oxygen dissociation curve is discussed.
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PMID:Blood-gas properties and function in the fossorial mole rat under normal and hypoxic-hypercapnic atmospheric conditions. 1 98

The effects on hemoglobin oxygen transport of acute respiratory acidosis have been studied in dogs inhaling a gaseous mixture with 12% CO2 (O2 21%) for two to five hours. In a first series of experiments, it was shown that the shape of the oxyhemoglobin dissociation curve (ODC) was not modified by severe acidosis (pH congruent to 7) lasting for two and a half hours. The Hill number (N equals 2.6) did not change significantly. The aim of the second experimental series was to stuey the Bohr effect and the hemoglobin oxygen affinity (P50). The control value for the respiratory Bohr coefficient (B) was --0.54; neither after two hours (--0.52), nor after five hours of hypercapnia (--0.55) was it significantly modified. The P50 expressed at arterial pH was much increased in acidosis (congruent to 45 torr); when expressed at standard p/ 7.4, it was slightly but significantly decreased (congruent to 1 torr) at the fifth hour. At the same time there was a decrease (p smaller than 0.05) in the erythrocyte 2,3-DPG approaching 15 p. cent; on the other hand the ATP concentration did not change significantly. No significant individual correlation was found between P50(7.4), 2,3-DPG and mean hemoglobin corpuscular concentration. These results suggest that during severe respiratory acidosis neither a change in the shape of ODC, nor a change in Bohr effect do affect the hemoglobin oxygen transport. The main characteristic remains the decrease in oxygen affinity of hemoglobin, due to the erythrocyte [H+] increase induced by hypercapnia ; this phenomenon is observed as long as the 2,3-DPG decrease stays moderate.
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PMID:[Hemoglobin oxygen transport during experimental acute hypercapnia (author's transl)]. 23 80

Multivariate analysis of P50 changes in hypoxia, hypercapnia and polycythaemia was performed in an heterogeneous group of forty three patients: hypoxic subjects with or without hypercapnia, with or without polycythaemia and polycythaemic subjects without hypoxia. A statistical analysis was undertaken using comparison of the means, study of the correlations, principal component analysis, multiple regression and correspondence analysis. In the patients studied, P50 changes were not wholly explained by those of 2-3 DPG and pH; PaCO2, per se, did not play an important part. Haemoglobin concentration and P50 value would represent an adaptative mechanism to hypoxia: when hypoxia is moderate (80 greater than PaO2 greater than or equal to 65 torr) and isolated, oxygen haemoglobin affinity decreases (P50 increases); when hypoxia is severe (PaO2 less than 65 torr) and combined with hypercapnia and disturbed acid-base equilibrium, P50 comes back to normal range but haemoglobin increases, restoring thus, the normal blood oxygen content.
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PMID:Changes of P50 in hypoxaemia, hypercapnia and polycythaemia: multivariate analysis. 60 4

2,3-DPG and P50 were measured in 23 patients with chronic obstructive lung disease. All patients had a chronic hypercapnia (PaCO2 greater than or equal to 45 Torr). They are shared in 3 groups, according to hemoglobin content [Hb] and hypoxia : group I(PaO2 = 48.0 +/- 2.4 Torr ; [Hb] = 15.9 +/- 0.3 g. 100 ml-1; n = 9), (M +/- 1 SE); group II (PaO2 = 46.4 +/- 5.0 Torr; [Hb] = 11.6 +/- 0.7 g. 100 m[-1; n = 7); group III(PaO2 = 61.4 +/- 2.4 Torr; [Hb] = 13.3 +/- 0.4 g. 100 ml-1; n = 7). 2,3-DPG (group I : 1.05 +/- 0.06 mole.moleHb-1; group II : 1.02 +/- 0.08; group III : 1.11 +/- 0.08) was not significantly different of 2,3-DPG value of 12 control subjects (0.96 +/- 0.04). P50 of group I (26.9 +/- 0.9 Torr) and group III patients (28.1 +/- 1.6 Torr) was not significantly different of control value of P50 (27.4 +/- 0.5 Torr). P50 of group II patients (29.6 +/- 0.8 Torr) was significantly higher than P50 control and group I values (p less than 0.05). All the patients of group II died. These results suggest that in patients with chronic obstructive lung disease : 1) P50 value is different with various clinical conditions; 2) P50 increase is a compensatory mechanism in severe hypoxemia with anemia, but is not sufficient; 3) [Hb] is the best data for clinical prognosis.
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PMID:[Study of P50 and 2,3-diphosphoglycerate in 23 bronchoemphysema patients as a function of hypoxia and hemoglobin concentration]. 89 17

In order to study the effect of the decrease in P-Pi caused by low pH on hemoglobin-oxygen affinity, we measured P-Pi,2,3-diphosphoglycerate (2,3-DPG), and oxygen tension at 50% saturation (P50) in 36 cases with acute exacerbation of chronic respiratory failure with hypercapnia. The cases were classified into two groups by arterial blood pH values obtained on the day of admission. Group A: pH less than or equal to 7.35 and Group B: pH greater than or equal to 7.36. P50 was calculated by a modification of Severinghaus' equation developed by Yusa and Kohsaka, and it was corrected by applying the carboxy-hemoglobin (COHb) coefficient. On the day of admission (stage I), 2,3-DPG and P50 in both groups were slightly higher than in the control group. In Group A, a week after admission (stage II), these values decreased and became significantly lower than they had been at stage I. Especially 2,3-DPG in stage II was even lower than those of the control group. Approximately 14 days after admission, in stage III, it was found that these values had risen to the initial level at stage I. In Group A, similar changes were also observed for P-Pi. The value of P-Pi was low in stage II and recovered to the initial value in stage III. On the other hand, we found that the urinary excretion of phosphorus (U-Pi) increased at stage I in Group A. It was supposed that the increase in U-Pi at stage I caused a decrease in P-Pi, which caused the decrease in 2,3-DPG, in stage II.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Hemoglobin-oxygen affinity in acute exacerbation of chronic respiratory failure]. 207

The burrow-dwelling woodchuck (Marmota monax) (mean body wt. = 4.45 +/- 1 kg) was compared to a similar-sized (5.87 +/- 1.5 kg) but arboreal rodent, the porcupine (Erithrizon dorsatum), in terms of its ventilatory and heart rate responses to hypoxia and hypercapnia, and its blood characteristics. VT, f, T1 and TE were measured by whole-body plethysmography in four awake individuals of each species. The woodchuck has a longer TE/TTOT (0.76 +/- 0.03) than the porcupine (0.61 +/- 0.03). The woodchuck had a higher threshold and significantly smaller slope to its CO2 ventilatory response compared to the porcupine, but showed no difference in its hypoxic ventilatory response. The woodchuck P50 of 27.8 was hardly different from the porcupine value of 30.7, but the Bohr factor, -0.72, was greater than the porcupine's, -0.413. The woodchuck breathing air has PaCO2 = 48 (+/- 2) torr, PaO2 = 72 (+/- 6), pHa = 7.357 (+/- 0.01); the porcupine blood gases are PaCO2 = 34.6 (+/- 2.8), PaO2 = 94.9 (+/- 5), pHa = 7.419 (+/- 0.03), suggesting a difference in PaCO2/pH set points. The woodchuck exhibited no reduction in heart rate with hypoxia, nor did it have the low normoxic heart rate observed in other burrowing mammals.
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PMID:Cardiorespiratory responses of the woodchuck and porcupine to CO2 and hypoxia. 251 13

The effects of body temperature and hypercapnia (7% inspired CO2) on arterial blood gases, plasma pH, and the characteristics of the blood oxygen dissociation curve were determined in Tegu lizards (Tupinambis nigropunctatus). Arterial pH fell from 7.59 to 7.50 when body temperature was increased from 25 to 35 degrees C. The pH/temperature coefficient (delta pH/delta t = -0.009 U/degrees C) was half of that predicted on the basis of 'constant relative alkalinity' and the alphastat hypothesis. The fall in plasma pH resulted from a decrease in plasma [HCO3-], and a rise in plasma Pco2. The O2 affinity of Tegu blood, expressed by the partial pressure at half saturation (P50), decreased with temperature in vitro from 42.3 to 49.6 torr at pH 7.4. The apparent enthalpy (delta H = -3.1 kcal/mol) is about 1/4 of that of human blood. In vivo, the arterial blood oxygen saturation decreased from 89% at 25 degrees to 82% at 35 degrees C. Arterial Po2 increased from 61 to 71 torr as expected from the right-shift of the oxygen dissociation curve. During environmental hypercapnia (7% CO2, 21% O2, 72% N2 inspired concentrations), arterial pH decreased to 7.28. Arterial O2 saturation remained constant and arterial Po2 increased from 61 to 85 torr due to the right-shift of the oxygen dissociation curve. The comparatively small effect of changes in temperature on the oxygen affinity of Tegu blood (directly according to the delta H value, and indirectly via changes in blood pH) results in a relatively small right shift of the oxygen dissociation curve, and accordingly in relatively high arterial and tissue Po2 values also at higher temperatures.
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PMID:Respiratory properties of blood and arterial blood gases in the tegu lizard: effects of temperature and hypercapnia. 311 84

1. Measurements of certain hematological and morphological characteristics were made in burrowing owls and bobwhite in search of features that could be associated with the previously described ventilatory adaptations of the burrowing owl to hypoxia and hypercarbia. 2. Values for burrowing owls and bobwhite, respectively, were: P50 = 44.9, 46.0 torr; Hct = 36.6, 38.8 vol%, Hb = 12, 12.3 (g/100 ml); RBC = 2.72 X 10(6), 3.02 X 10(6); log P50/pH = -0.412, -0.485; delta log PCO2/delta pH = -1.39, -1.585. 3. The owls had greater heart weights and smaller tracheal volumes than the bobwhite or the predicted value. 4. No hematological characteristics of the burrowing bird distinguish it from the non-burrowing bird.
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PMID:Blood characteristics, tracheal volume and heart mass of burrowing owls (Athene cunicularia) and bobwhite (Colinus virginianus). 613 13

In order to compare high and low oxygen affinity blood under conditions of severe respiratory failure, the effects of a high or low P50 were evaluated in two groups of newborn lambs (P50, 20 mmHg versus 30 mmHg), under conditions of hypoxic hypoxia (Fio2, 10%) and hypercapnic hypoxia (Fio2, 10% and Fico2, 10%). Data on cardiovascular function, blood gas parameters, and tissue oxygenation were collected under normoxic conditions and during severe hypoxia. During hypoxic hypoxia, a higher arterial oxygen content was noted in the high affinity group throughout the experiment; however, there were no significant differences detected in the remainder of the parameters studied. During hypercapnic hypoxia, the position of the oxygen dissociation curve did not cause any significant differences. When, however, hypercapnic hypoxia was compared to hypoxic hypoxia, there was a significant increase in cardiac output and myocardial contraction during hypercapnia.
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PMID:The effect of high or low oxygen affinity red cells on tissue oxygenation and myocardial function in hypoxic newborn lambs with or without hypercapnia. 662 98


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