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

Arterial (PaCO2), alveolar (PACO2), mixed expired (PECO2) CO2 pressures, CO2 production (VCO2) as well as arterial O2 saturation (SaO2) were measured on 20 severely hypoxic and hypercapnic patients breathing air (A) and 100% O2 (HO). On HO, mean PaCO2 increased to 56.6 torr from 50.8 torr on A, whereas there was no significant change in PACO2 (38.3 on A, 38.6 on HO), so that the arterial-alveolar gradient (aADCO2) increased from 12.5 to 18.0 torr. PECO2 remained essentially the same. There was a statistically significant correlation between the increase in PaCO2 on HO and the arterial unsaturation (100 - SaO2) on A and also between PaCO2 on A and its increment on HO. When the rise in PaCO2 and aADCO2 were estimated which resulted from the shift in the Co2 dissociation curve due to complete oxygenation of hemoglobin on HO (Haldane effect), 78% of the observed change in PaCO2 could be accounted for. The deadspace/tidal volume ratio (VD/VT) increased from 0.59 on A to 0.64 and 87% of this difference could be attributed to the Haldane effect. The results emphasize the importance of considering this effect when interpreting alterations in PaCO2, aADCO2 and VD/VT on transition from air to hyperoxia, particularly in patients with severe hypoxemia and hypercapnia.
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PMID:Contribution of the Haldane effect to the rise of arterial Pco2 in hypoxic patients breathing oxygen. 678 Feb 65

In patients with metabolic alkalosis, compensatory alveolar hypoventilation may induce hypercapnia and hypoxemia. In edematous or normally-hydrated patients without electrolyte deficiencies, acetazolamide--a carbonic anhydrase inhibitor--has been advocated to correct the primary acid-base disturbance, thereby preventing hypoxemia. The hemodynamic consequences and the effect on oxyhemoglobin dissociation of acetazolamide, were studied. Twelve critically ill patients with metabolic alkalosis were given 15 mg/kg body wt. acetazolamide intravenously. Cardiovascular performance was completely unchanged. The P50 was 26.6 mm Hg at the beginning and the end of the study, indicating that hemoglobin-oxygen affinity is unaffected by acetazolamide. In six patients, investigated after open-heart surgery, the arterial oxygen tension increased by 10-45%. This was probably related to the combined effects of slight reductions in total body oxygen consumption or shunting of venous blood through the lungs. Eight of the 12 patients were on controlled ventilation. After acetazolamide there was a mean increase in mixed venous carbon dioxide tension (PvCO2) of 4.5 mm Hg, with no increase in arterial carbon dioxide tension (PaCO2), indicating only a limited interference with carbon dioxide uptake and release of the carbonic anhydrase inhibition. No other adverse reactions were observed.
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PMID:Cardiovascular performance and oxyhemoglobin dissociation after acetazolamide in metabolic alkalosis. 681 46

The effects of fetal hypoxemia on blood coagulation (platelet count, prothrombin time, partial thromboplastin time, fibrinogen, factors II, V, VI, VIII, IX, X, XI, XII, XIII and von Willebrands activities, fibrin degradation products, and fibrin monomer) were evaluated in nine chronically catheterized fetal lambs early in the third trimester of pregnancy (107-110 days gestation). Seven chronically catheterized fetal lambs of similar gestational ages served as controls. The hypoxemic episode (pO2 14 mm Hg) was maintained for 1 hr in the experimental group during which time there were only minimal changes in PCO2, arterial pressure, heart rate, and pH. Epinephrine and norepinephrine levels increased significantly in stressed animals--22 pg/ml pre- to 1025 pg/ml postepinephrine, and 475 pg/ml pre- to 2292 pg/ml postnorepinephrine. There were no significant changes in blood coagulation factor activities related to the hypoxic stress although, one fetus who experienced acidemia did develop a transient increase in fibrin monomer. Slight through significant increases in VIII coagulant activity activity (4.0%), von Willebrand activity (5.9%), and factor XII activity (4.3%) occurred in both the hypoxemic and control fetal lambs. These changes were associated with minimal increases in the white blood cell count (15%) and slight decreases in the mean arterial pressure (3.9 mm Hg) hemoglobin (1.2 g), and hematocrit (2.9%) and may have been related to the blood loss of 25% that occurred as a result of sampling in both groups. There were no differences between the hypoxic and control animals' levels of coagulation factor activities when measured during an 18-day follow-up period except for a slight increase in factor X activity (10%) in the control animals not apparent in the nine hypoxic animals. Thus an episode of severe fetal hypoxemia in the absence of hypotension, acidosis, and hypercarbia does not lead to acute or chronic alterations in blood coagulation factor activities in the fetal lamb.
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PMID:Blood coagulation changes after hypoxemia: a fetal lamb model. 707 Aug 80

Effect of increased blood O2 affinity on cardiac output and its distribution was studied in conscious sedated rats by the microsphere-reference sample method. After a preliminary measurement of cardiac output and its distribution, rats were exchange transfused with normal blood or low-P50 (PO2 at which hemoglobin is half-saturated with O2) blood; other groups were made anemic with and without a simultaneous reduction in P50. Reduction in P50 from 38 to 17 Torr did not change cardiac output, pulse, or blood pressure but caused, after allowance for changes in controls, a 102% increase in coronary blood flow and an 88% increase in cerebral blood flow. Anemia (hematocrit = 22%) produced similar changes in coronary and cerebral flow. When anemia was combined with a 12-Torr reduction in P50, coronary and cerebral flow increased by 297 and 209%, respectively. These increases in coronary and cerebral flow were not attributable to increased cardiac work or hypercapnia. It is concluded that a left shift of the O2 dissociation curve induces increased blood flow to brain and heart, probably in compensation for decreased tissue O2 pressure.
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PMID:Effect of increased oxygen affinity and anemia on cardiac output and its distribution. 717 22

Pulmonary diffusion capacity (D) for O2 and CO was determined from alveolar-mixed venous equilibration kinetics of 16O2, 18O2, and C18O measured during rebreathing by mass spectrometry. During the rebreathing maneuver (15 s) the ventilation was extremely high (about 100 1 X min-1) and PO2 and PCO2 in lung gas were close to their mixed venous values (aveolar hypoxia and hypercapnia). The following mean values (+/- SD) were found in six healthy males (20-33 yr) sitting on a bicycle ergometer (in ml X min-1 X Torr-1): 1) without work load, D18O2 = 54 +/- 10, Dc18O = 47 +/- 11; 2) with the highest work load tested (150 W, O2 uptake 2.1 l X min-1), D18O2 = 62 +/- 12, Dc18O = 54 +/- 8. The ratio D16O2/D18O2 averaged 1.07. The ratio D18O2/Dc18O, averaging 1.2 at rest and at all exercise levels, was close to the estimated O2/CO ratio of Krogh's diffusion constants for tissue and, therefore, was in agreement with the diffusion limitation model. An analysis of the various factors affecting the DO2/DCO ratio does not allow to reliably assess the role of diffusion in red blood cells and reaction with hemoglobin in limiting alveolar-capillary O2 transfer.
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PMID:Pulmonary diffusion capacities for O2 and CO measured by a rebreathing technique. 731 94

Ten splenectomized and ten nonsplenectomized conscious dogs were subjected to hemorrhage of 41% of their blood volume over a 15-minute period. Hemodynamic and metabolic variables were monitored for 4 hours after hemorrhage. Mortality (100%) occurred in the splenectomized group. Significant (P < 0.001) hemodynamic responses after hemorrhage included hypotension, tachycardia, low central venous pressure, and decreased ECG voltage of the R wave. Tachypnea was noted in the absence of hypoxia, hypercapnia, and acidosis inthe nonsplenectomized dogs. Significant (P < 0.001) hypocapnia and mean PCO2 values of 13.9 MM of Hg and 23.5 mm of Hg in splenectomized and nonssplenectomized dogs, respectively, was noted. Mean hemoglobin levels were significantly (P < 0.001) decreased after hemorrhage in the splenectomized dogs. The absence of a change in hemoglobin in thenonsplenectomized dogs was attributed to the translocationof extracellular fluid into the vascular space which diluted the high concentration of RBC from splenic contraction. Other changes noted after hemorrhage were hyperglycemia, increased blood cortisol, and increased pyruvate and lacte levels. Changes were not noted in pyruvate-to-lactate ratios.
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PMID:Experimental hemorrhage in splenectomized and nonsplenectomized dogs. 740 89

A Shimazu OM-100A near infrared spectrophotometer was used to monitor the cerebral oxygenated hemoglobin (Oxy-Hb), deoxygenated hemoglobin (Deoxy-Hb) and total hemoglobin (Total-Hb) in 3 patients with a) massive hemorrhage, b) ruptured aneurysm in the abdominal aorta, or c) hypercapnia. The hematocrit value of the patient with massive hemorrhage decreased rapidly to 18 %; the Total-Hb and Oxy-Hb also decreased significantly. Red blood cell transfusion raised the Oxy-Hb level, indicating an improvement in cerebral oxygenation. In the patient with a ruptured aneurysm, changes in blood flow brought about by clamping or declamping of the abdominal aorta were immediately reflected by corresponding changes in Total-Hb and Oxy-Hb. Oxy-Hb increased significantly and correlated well with the PETCO2 value in the patient with hypercapnia. Thus, NIR spectrophotometry is a useful non-invasive tool which can monitor metabolic and hemodynamic changes in the brain in various pathological conditions.
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PMID:[Non-invasive monitoring of cerebral oxygenation by NIR spectrophotometry (clinical trial)]. 763 65

To analyze quantitatively the performance of the intravenacaval blood gas exchanger (IVOX), we developed a right atrium-pulmonary artery venovenous extracorporeal bypass circuit. Oxygen transfer and carbon dioxide removal were calculated at different blood flow rates, different hemoglobin levels, and during permissive hypercapnia. Oxygen transfer increased linearly with blood flow up to 41 mL/min. Likewise, O2 transfer increased linearly with hemoglobin levels up to 7.5 g/dL, but no further increases were achieved above this level. Carbon dioxide removal increased linearly as flow increased from 1.0 to 3.0 L/min but did not increase further for higher flows. Carbon dioxide removal was 45 mL/min at blood carbon dioxide tension of 42 mm Hg but increased to a maximum of 81 mL/min at a carbon dioxide tension of 90 mm Hg. We conclude that IVOX is a diffusion-limited device dependent on blood flow, hemoglobin content, and the gas pressure gradient across the membrane. Further engineering improvements are needed to improve the gas exchange performance of IVOX.
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PMID:Performance of an intravenous gas exchanger (IVOX) in a venovenous bypass circuit. 801 Jul 91

An echo planar linewidth mapping technique, Shufflebutt, has allowed temporal measurements of changes in linewidth caused by static inhomogeneities (delta LWSI) and transverse relaxation rate (delta R2) in models of hypoxia and hypercapnia. We demonstrate these changes are due to intravascular susceptibility differences/(delta chi) between the blood and tissue. Contrast agent injections at a delta chi equivalent to that of deoxygenated blood showed a twofold difference between the contrast agent and physiological anoxia values. Hypercapnia decreased both delta LWSI and delta R2 consistent with an increase in blood oxygenation. We attribute these findings to constant oxygen extraction during an increase in blood flow, resulting in less deoxygenated venous blood and thus reduced delta chi. For in vivo perturbations we found that delta R2/delta R2' approximately 0.33, a ratio much different from that measured in whole blood phantoms (delta R2/delta R2' approximately 2). This demonstrates that signal changes in these studies are produced predominantly by dephasing of extravascular protons due to field inhomogeneities produced by intravascular deoxygenated hemoglobin (deoxyHb).
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PMID:Measurement of regional blood oxygenation and cerebral hemodynamics. 813 53

The hemoglobin-oxygen dissociation curve and the relationships between the parameters of tension, saturation, capacity, affinity and concentration of oxygen in the course of respiratory failure in chronic obstructive lung diseases (COLD) were studied. The study included 141 patients divided into four basic groups according to the value of pO2 (a): patients with normoxia, mild, moderate and severe arterial hypoxia. The blood-gas status was determined using the ABL-330 and OSM-3 analyzers (Radiometer A/S, Denmark). It is concluded that: 1. Presence of normoxia (pO2 and sO2 in norm) in COLD patients does not exclude abnormalities in their arterial blood oxygen transport and increased risk of tissue hypoxia. 2. Total oxygen concentration in respiratory failure is relatively stable and "independent" from the stepwise decrease of the arterial pO2, which results from the compensatory increase of the total and effective hemoglobin. 3. There are phase fluctuations of the ctO2/pO2 dissociation curve in the reference interval, expressed in the "lowering" of P50 and p90 in mild hypoxia and the "centering" or "raising" of their values in severe hypoxia. Such fluctuations are more pronounced in the p90 than in the p50. 4. The oxygen extraction tension lowers progressively (without reaching the anaerobic threshold) and the oxygen compensation factor elevates with the pO2 (a) reduction and the arising of hypercapnia and acidemia. 5. The calculated 2,3-diphosphoglycerate (2,3-DPG) concentration values are significantly higher in hypercapnics with COHb > 1% than in those with COHb < 1%. The relationships between hypoxia, oxygen affinity, hemoglobinemia and oxygen affinity as well as the dissociation curve properties in chronic respiratory failure are discussed.
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PMID:Relationships between blood oxygen parameters in patients with chronic obstructive lung disease. 819 1


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