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At least 19 recordsLinked to original sources
PubMed1990

The oxygen status of the arterial blood revised: relevant oxygen parameters for monitoring the arterial oxygen availability.

The new generation of very accurate multi-wavelength oximeters, e.g. OSM3, for in vitro measurement of the hemoglobin oxygen saturation, total hemoglobin concentration, and carboxy- and methemoglobin fractions opens new aspects of oxygen monitoring. Combined with the data from the blood gas analyzer (e.g. ABL300) these very accurate measurements allow the calculation of several derived oxygen parameters on the basis of a set of newly developed calculation algorithms. The traditional parameters obtained from an arterial sample are the oxygen tension (pO2) and the hemoglobin oxygen saturation (sO2). Clinical examples illustrate that the pO2 and the sO2 even in combination may give misleading information. The new algorithm calculates three extra oxygen parameters. 1) The oxygen extraction tension, px, defined as the tension required to extract 2.3 mmol of oxygen per liter blood. It signals the mixed venous pO2 level on the assumption that the arterio-venous oxygen difference is normal (2.3 mmol/L). 2) The concentration of extractable oxygen, cx, defined as the concentration of oxygen extracted at a tension of 5.0 kPa. 3) The oxygen compensation factor, Qx, derived as (2.3 mmol/L)/cx. It may be interpreted as the increase in cardiac output necessary to maintain a normal mixed venous pO2 of 5 kPa. These three parameters indicate the oxygen availability of the blood and summarize important properties of the arterial blood in relation to oxygen supply of the tissues, including the arterial pO2, the 'active' hemoglobin concentration (equivalent to the oxygen capacity), and the hemoglobin oxygen affinity (p50). The set of data measured with the blood gas analyzer, e.g. the ABL300 combined with the data measured with the OSM3 contains much more information than is routinely utilized. This information is extracted and summarized by our calculation algorithm. Omitting the calculation of the extra oxygen parameters involves a risk of losing valuable information.

Arteries↗
PubMed1989

[Oxygen status of arterial blood including uncompensated mixed venous oxygen tension and cardial oxygen compensation factor. Reevaluation on the basis of 250 arterial punctures].

In arterial blood from 250 patients we measured pH, pco2, and po2 (electrochemically) together with total-hemoglobin concentration, oxygen saturation, carboxy- and methemoglobin fractions (spectrometrically). With a previously published algorithm we calculated the effective hemoglobin concentration, total-oxygen concentration, half saturation tension, erythrocyte 2,3-diphosphoglycerate concentration, and two new oxygen parameters: uncompensated mixed venous oxygen tension and cardiac oxygen compensation factor. 11% of the patients have normal arterial oxygen tension, but nevertheless risk of tissue hypoxia judged from the two new oxygen parameters. This is due to a low hemoglobin concentration and/or low half saturation tension (increased hemoglobin oxygen affinity). Some patients have decreased arterial oxygen tension but normal uncompensated mixed venous oxygen tension (15%) or normal cardiac oxygen compensation factor (9%). This is due to a high hemoglobin concentration and/or increased half saturation tension. The latter varies from 2.6 to 5.2 kPa (ref.: 3.3-3.9 kPa); 36% have decreased, 27% increased values. The 2,3-diphospho-glycerate concentration varies from 2.0 to 7.9 mmol/l (ref.: 3.6-5.1 mmol/l); 14% have decreased, 30% increased values. Uncompensated mixed venous oxygen tension varies from 1.8 to 5.7 kPa (ref.: 4.5-5.5 kPaf). The cardiac oxygen compensation factor varies from 0.9 to infinity (ref.: 0.8-1.6). We conclude that the variation in the different oxygen parameters is so significant that it justifies routine calculation for all arterial blood samples where the measurement on a conventional blood gas analyzer is supplemented with measurement on one of the new multi-wavelength hemoximeters. The calculation algorithm permits calculation of all the oxygen parameters for the majority of arterial samples (84%) where the oxygen saturation is less than or equal to 0.970.

Adult↗
PubMed1989

Oxygen transport and oxygen consumption during supplemental oxygen administration in patients with chronic obstructive pulmonary disease.

PURPOSE: Oxygen consumption (VO2) is independent of oxygen delivery (DO2) above a critical level of DO2. VO2 may become dependent on DO2 when oxygen demand exceeds oxygen supply. We studied DO2 VO2, and exercise capacity in 12 stable, ambulatory patients with chronic obstructive pulmonary disease (COPD) receiving ambient air and 26% oxygen to ascertain whether VO2 is dependent on DO2 in this patient sample. PATIENTS AND METHODS: An exercise protocol consisting of a symptom-limited, low-level treadmill test with progressive increments in workload was performed twice, once with patients breathing ambient air and once with patients breathing 26% oxygen. Expired gas, arterial and mixed venous blood values, and recordings of systemic and pulmonary artery pressures were obtained after a 10-minute period of rest (while standing) and during the last minute of each three-minute exercise level. RESULTS: Five patients had an increase in exercise capacity, defined as an increase in the maximal VO2 greater than 25%, using supplemental oxygen. In these patients, oxygen delivery increased from 10.9 +/- 3.4 to 13.8 +/- 4.7 mL/minute/kg (p = 0.008) at rest and from 16.2 +/- 5.0 to 24.7 +/- 2.7 mL/minute/kg (p = 0.046) during exercise with supplemental oxygen administration. VO2 increased from 0.329 +/- 0.065 to 0.436 +/- 0.109 L/minute (p = 0.029) at rest and from 0.776 +/- 0.275 to 1.119 +/- 0.482 L/minute (p = 0.048) during exercise. Three of these five patients had an arterial oxygen pressure greater than 55 mm Hg at rest. Seven patients had little or no increase in exercise capacity with supplemental oxygen. This patient group had no increase in VO2 at rest. The DO2 failed to increase at rest despite an increase in arterial oxygen content because of a reduction in cardiac output. CONCLUSION: These data demonstrate that DO2 may fail to increase in some patients with COPD and resting or exertional hypoxemia when supplemental oxygen is administered because of a reduction in cardiac output; that patients who fail to increase their DO2 are less likely to increase exercise capacity; and that some stable, ambulatory patients with COPD who do not qualify for supplemental oxygen at rest by current standards may have inadequate DO2 to meet physiologic needs.

Aged↗
PubMed1991

Oxygen transport in adult respiratory distress syndrome and other acute circulatory problems: relationship of oxygen delivery and oxygen consumption.

OBJECTIVE: To evaluate the evidence that oxygen consumption (VO2) is pathologically dependent on oxygen delivery (DO2). DATA SOURCES: Studies published since 1972 with their relevant bibliographies and computerized search of MEDLINE. STUDY SELECTION: All clinical papers reporting the relationship of: VO2 to DO2 in the adult respiratory distress syndrome (ARDS), sepsis, other critically ill patients, and normal individuals; cardiac output determined by measured VO2 to calculated VO2 from the arterial-mixed venous oxygen difference; blood lactate to DO2; and selected basic science studies. DATA EXTRACTION: Study quality was assessed and all pertinent data were summarized. RESULTS OF DATA EXTRACTION: Normal individuals display physiologic dependence of VO2 at very low levels of DO2 (330 mL/min.m2). Pathologic dependence of VO2 on DO2 entails two concepts: a) VO2 varies directly with DO2 over a wide range of DO2 and b) of particular import, tissue oxygen extraction is compromised. This pathologic supply dependence was initially identified in patients with ARDS; subsequently, it has been demonstrated in patients with sepsis and in a variety of other critically ill individuals. There are substantial, but not uniform, data documenting this dependence of VO2 on DO2 in ARDS. In some studies, this relationship correlates best with increased lactate concentrations. However, increased blood lactate concentrations do not accurately track other evidence of tissue hypoxia. Some researchers have attributed the finding of this supply dependency to artifact, when VO2 is determined by the arterial-mixed venous oxygen difference. However, when these methods are compared, the correlation is excellent. Others have raised the concern that appreciable changes in VO2, even over short periods of time, may result in physiologic increases in DO2. However, when "control" groups have been contemporaneously compared with patients with ARDS using the same methodology, they have not shown supply dependency. Interwoven throughout the studies reviewed is overwhelming and uniform evidence that both mixed venous oxygen tension (PVO2) and mixed venous oxygen content (CVO2) correlate poorly with cardiac output, DO2, or VO2. The inconsistencies in identifying pathologic DO2 dependency may well reflect the unknown variables that exist in patients with ARDS, perhaps better labeled, multiple organ system failure. CONCLUSIONS: Pathologic dependence of VO2 on DO2, especially the inability to increase tissue oxygen extraction, is present in most patients with ARDS and many other critically ill individuals. PVO2 and CVO2 are both unreliable indicators of cardiac output, DO2, or VO2.

Biological Transport↗
PubMed1987

Effects of variable oxygenation and gradual withdrawal of oxygen during the recovery phase in oxygen-induced retinopathy: kitten model.

The effects of two types of prolonged oxygen supplementation were tested in the kitten model of oxygen induced retinopathy. Thirty-one litters were placed in 80% oxygen for 65 h starting the 3rd day after birth to initiate a moderately severe retinopathy. One-half of each litter thereafter served as controls, remaining in room air during the development of the retinopathy. In the remaining half, the retinopathy was allowed to develop in either a variably hyperoxic/hypoxic environment (one-half of each of 16 litters) or in an oxygen environment that was gradually reduced to room air by 4 wk (one-half of each of 15 litters). The retinopathy scores in the controls were comparable in both studies and the same as in previous experience with this model. Kittens exposed to the variable oxygen recovery environment had significantly less severe retinopathy than their room air recovery littermates (p less than 0.05). The retinopathy scores in the group with gradually withdrawn oxygen did not differ from the littermate controls (power greater than 80%). These data support the hypothesis that conditions of oxygenation during the recovery process from an acute oxygen-induced vascular injury have a significant effect on the healing process.

Animals↗
PubMed1978

The relationships among arterial oxygen flow rate, oxygen binding by hemoglobin, and oxygen utilization in chronic cardiac decompensation.

We have examined the interrelationships among CaO2, blood flow, oxygen binding by hemoglobin, and VO2 in cardiac patients with and without chronic cardiac decompensation. We have quantified the role that decreased oxygen-binding to hemoglobin may play in maintaining VO2 in the presence of low systemic blood flow rates. The volume rate of oxygen delivery to tissues was expressed as the OFIa, the product of CO2 and blood flow. OFIa varied from 738 to 262 ml/min/m2, whereas VO2 varied from 170 to 117 ml/min/m2. Thus, in the patients with lowest OFIa (63% below the highest OFIa), VO2 was only down 19%. VO2 was maintained because the extraction of oxygen rose from about 20% to 50% in close association with the decrease in OFIa. Oxygen binding to hemoglobin was lower in patients with the lowest OFIa--and therefore, at in vivo conditions of pH, PCO2, and temperature, P50 in vivo was higher. The resulting facilitation of oxygen release at the PO2 of tissue capillaries could explain about one third of the observed increment in oxygen extraction in patients with low OFIa. An alternative interpretation is that a high P50 in vivo minimizes the reduction in PVO2 needed to maintain VO2 when increased proportional extraction of O2 compensates for decreased OFIa.

Aged↗
PubMed1988

Predicted and measured oxygen concentrations in the circle system using low fresh gas flows with oxygen supplied by an oxygen concentrator.

An oxygen concentrator based on a zeolitic molecular sieve has been used to supply piped oxygen in a District General Hospital; such oxygen contains 5% argon. If concentrator oxygen is used in the closed circuit, argon accumulates. The present investigation defines the extent and time course of argon accumulation in partially and fully closed breathing systems. A theoretical model is presented which predicts the extent and rate of inert gas accumulation. The predictions have been tested in a volunteer under laboratory conditions and in five anaesthetized patients. It is recommended that concentrator oxygen may be used for low flow anaesthesia of indefinite duration, provided the fresh oxygen flow to the circuit is at least twice the oxygen consumption. If the circuit is totally closed, periodic opening of the circuit is necessary.

Adult↗
PubMed1990

Evaluating oxygen delivery and oxygen utilization with mixed venous oxygen saturation monitoring: a case study approach.

Three cases studies are presented to demonstrate clinical application of mixed venous oxygen saturation (SvO2) monitoring in critical care nursing practice. Examples of critically ill patients are used to demonstrate how SvO2 monitoring can be used in clinical practice to reflect an imbalance between oxygen delivery and oxygen utilization. In the first case, the patient had a problem with oxygen delivery. Continuous SvO2 data aided nurses in guiding, adjusting, and assessing therapy. The second case demonstrates how SvO2 monitoring can provide an early sign of a life-threatening complication. The final case is one in which the patient had a problem with oxygen utilization. In all the cases, continuous SvO2 data provided important information about the balance between oxygen delivery and oxygen utilization.

Adolescent↗
PubMed1977

Simultaneous determination of hemoglobin derivatives, oxygen content, oxygen capacity, and oxygen saturation in 10 microliters of whole blood.

We describe a new method for simultaneous determination of four hemoglobin derivatives (deoxyhemoglobin, Hb; oxyhemoglobin, HbO2; methemoglobin, Hb+; and carbon monoxide hemoglobin, HbCO) and total oxygen content in 10 microliters of whole blood. Percentage HbO2, HbCO, Hb+, total hemoglobin (Hbt), and oxygen capacity can also be obtained from the experimental data by simple calculations. Total analysis time is 1 min. Blood is diluted 100-fold with a buffer contained in a quasi-anaerobic cuvette, where simultaneous measurements of oxygen pressure (by a po2 electrode) and adsorbance (at 497, 565, and 620 nm) are made. The decrease of oxygen pressure, as recorded by the oxygen electrode, is proportional to the amount of deoxyhemoglobin. The concentrations of HbO2, HbCO, and Hb+ can be obtained from absorbance measurements at the specified wavelengths. The new method eliminates the use of short-path optical cells and, due to the low sample volume requirement, makes possible the automated measurement of hemoglobin derivatives and oxygen saturation in arterialized capillary blood.

Carboxyhemoglobin↗
PubMed1989

Oxygen delivery, oxygen consumption and hemoglobin-oxygen affinity in acute myocardial infarction.

The interrelations of oxygen delivery (DO2), oxygen consumption (VO2) and hemoglobin-oxygen affinity assessed by P50 were investigated in 43 patients with acute myocardial infarction. As DO2 declined due to low cardiac output, a significant decrease in VO2 (r = 0.75, p less than 0.001) and a significant increase in P50 (r = -0.74, p less than 0.001) were observed. In the DO2 range between 300 and 450 ml/min/m2, in which the DO2 of 32 survivors and 11 nonsurvivors overlapped, the P50 of nonsurvivors was significantly higher than that of survivors (31.5 +/- 1.6 vs 27.9 +/- 1.5 torr, p less than 0.001), but there were no significant differences in any other oxygen transport variable. As a result of differences in P50, VO2 in this range was significantly higher in nonsurvivors compared to survivors (169 +/- 17 vs 148 +/- 13 ml/min/m2, p less than 0.001). These data suggest that a normal or increased VO2 alone does not ensure survival in patients with acute myocardial infarction, and increased P50 leads to an increase in VO2. Nevertheless, the interpretation of an increased P50 in patients with acute myocardial infarction must be made with caution, even with adequate DO2 and VO2, because it may imply a precarious oxygen transport/requirement balance in peripheral tissue and, hence, a fatal outcome.

Aged↗
PubMed1988

Hyperbaric oxygenation for experimental bladder tumor. I. Tissue oxygen tension of the rabbit bladder during hyperbaric oxygenation.

Although considerable advances have been made in the application of hyperbaric oxygenation (HBO) on tumor treatment in the recent past, many difficulties persist due to conflicting results and the understanding of its mechanism. We tested whether HBO treatment in clinical use could really influence the tissue concentration of oxygen in bladder or circulatory condition in animals. Eleven rabbits were treated with 1-3 atmospheric absolute pressures under an environment of air saturating 30-35% of oxygen for 90 min. Ten control animals were placed in the same chamber without providing HBO treatment. The tissue oxygen pressure in trigone or dome of the in HBO-treated group was significantly higher than that of the control group. A similar tendency was also noted in the arterial oxygen concentration to a greater extent, while regional blood flow in the bladder, mean arterial blood pressure and plasma volume were not significantly changed following HBO treatment. The use of HBO appears to offer some possibilities for the treatment of bladder tumor in the future.

Animals↗
PubMed1990

Dependence of oxygen consumption on oxygen delivery in children with hyperdynamic septic shock and low oxygen extraction.

We studied the effect of increasing systemic oxygen delivery (DO2) by packed RBC (PRBC) transfusion on oxygen consumption (VO2) in children with hyperdynamic septic shock. After routine resuscitation with volume loading and pharmacologic support, patients were studied if they had significant derangements of oxygen transport variables defined as: baseline VO2 less than 180 ml/min.m2 and oxygen extraction (O2 extr) less than 24%. Eight studies were performed. PRBC transfusion increased DO2 from 636 +/- 167 to 828 +/- 266 ml/min.m2 (p less than .01) without increasing cardiac index (5.2 +/- 1.3 vs. 5.0 +/- 1.4 L/min.m2). VO2 increased from 112 +/- 36 to 157 +/- 60 ml/min.m2 (p less than .01) while O2 extr was unchanged (18 +/- 3% vs. 19 +/- 6%). Despite initial low O2 extr, VO2 can be increased in pediatric septic shock by a further increase in DO2. Since VO2 correlates with survival, one should consider enhancing DO2 further despite initial low O2 extr and high DO2. Effects on morbidity and mortality require further study.

Adolescent↗
PubMed1991

Tissue oxygenation in hemorrhagic shock measured as transcutaneous oxygen tension, subcutaneous oxygen tension, and gastrointestinal intramucosal pH in pigs.

BACKGROUND AND METHODS: Tissue oxygenation, measured in peripheral tissue as transcutaneous PO2 (PtCO2) and subcutaneous PO2, was compared with the oxygenation in GI mucosa, which was measured as intramucosal wall pH (pHi), during experimental hemorrhagic shock and resuscitation in pigs. The pigs were hemorrhaged stepwise to a BP of 80 and 45 mm Hg, followed by retransfusion. PtCO2 was measured in the groin and subcutaneous PO2 was measured in the hip region. Intraluminal PCO2 was measured in the stomach, in the small intestine, and the sigmoid colon using silicone catheters. A simultaneous determination of arterial blood HCO3 concentration allowed pHi to be calculated using Henderson-Hasselbalch equation. Cardiac output was determined by thermodilution, and oxygen delivery (DO2) was calculated. RESULTS: Early indications of shock were decreases in PtCO2 and intestinal pHi (p less than .01). All measured variables decreased at the second step of bleeding. PtCO2 and subcutaneous PO2 was correlated to DO2 through the entire experiment (r2 = .25 and .49, respectively). Also, the pHi of the small intestine and the sigmoid colon correlated with DO2 (r2 = .36 and .25, respectively). PtCO2 and subcutaneous PO2 correlated with pHi in the small intestine and sigmoid colon. CONCLUSIONS: PtCO2 and pHi in the small intestine and sigmoid colon were the variables that most rapidly indicated blood volume loss. Subcutaneous PO2 and PtCO2, and small intestine and sigmoid colon pHi were correlated to total body oxygen transport. Peripheral tissue perfusion followed intestinal perfusion to some extent.

Animals↗
PubMed1990

Compliance, alveolar-arterial oxygen difference, and oxygenation index changes in patients managed with extracorporeal membrane oxygenation.

Eighteen patients with meconium aspiration syndrome who failed conventional management were treated with extracorporeal membrane oxygenation (ECMO) for reversible respiratory failure. Dynamic lung compliance measurements were made prior to, during, and after ECMO support. P(A-a)O2 and oxygenation index (OI) measurements were calculated prior to and after ECMO support. Lung compliance decreased significantly comparing before-ECMO to during-ECMO, and increased significantly comparing during- to after-ECMO, but not comparing before- to after-ECMO measurements. P(A-a)O2 and OI decreased significantly from before to after ECMO. The improvement in oxygenation allowing removal from ECMO does not appear to be related to improved pulmonary mechanics, but may rather be secondary to increased effective pulmonary capillary blood flow.

Extracorporeal Membrane Oxygenation↗
PubMed1988

Involvement of oxo-bridged binuclear iron centers in oxygen transport, oxygen reduction, and oxygenation.

The occurrence of an oxo-bridged binuclear iron site is well-established for the oxygen transport protein, hemerythrin, and strongly implicated in ribonucleotide reductase, purple acid phosphatase, ferritin, and methane monooxygenase. Key identifying characteristics are an antiferromagnetic interaction between the two iron atoms, an Fe-O-Fe vibrational mode in the resonance Raman spectrum, and an S = 1/2 EPR signal upon one-electron reduction. In hemerythrin the oxo bridge serves as a hydrogen bond acceptor which stabilizes the bound hydroperoxide. In ribonucleotide reductase both the binuclear iron center and a protein tyrosine undergo oxidation in the presence of molecular oxygen, whereas in methane monooxygenase a binuclear iron moiety may activate O2 for substrate oxygenation.

Iron↗
PubMed1988

Extracorporeal membrane oxygenation selection criteria: partial pressure of arterial oxygen versus alveolar-arterial oxygen gradient.

Extracorporeal membrane oxygenation (ECMO) has dramatically increased the survival rate of hypoxemic neonates who are unresponsive to maximum conventional medical therapy. Because ECMO involves multiple risks, including ligation of the right common carotid artery and right internal jugular vein, ECMO candidates should be neurologically intact neonates with a high probability of death despite maximum conventional ventilatory support. Currently, criteria based on the calculated alveolar-arterial oxygen gradient (A-aDO2) have replaced the neonatal pulmonary insufficiency index for predicting mortality and, thus, ECMO eligibility. A retrospective review of death prediction for the 26 months prior to the initiation of an ECMO program revealed a sensitivity of 67% and a specificity of 96% using the criterion of a PaO2 of less than 50 mm Hg for four hours. An equivalent A-aDO2 criterion of greater than or equal to 630 for four hours produced a sensitivity of 61% and a specificity of 96%. Prediction of mortality in neonates with sepsis was poor regardless of the criteria used. Excluding the deaths due to sepsis increased the sensitivity to 86% and 79% using criteria based on PaO2 and A-aDO2, respectively. It is concluded that the use of criteria based on PaO2 is equivalent to criteria based on A-aDO2 for predicting mortality. Criteria based on PaO2 may, however, decrease both the false-negative rate (patients with an elevated PCO2) and the false-positive rate (patients with intentionally induced hypocarbia secondary to hyperventilation alkalosis).

Blood Gas Analysis↗
PubMed1989

Oxygenation during chest physiotherapy of very-low-birth-weight infants: relations among fraction of inspired oxygen levels, number of hand ventilations, and transcutaneous oxygen pressure.

Chest physiotherapy (CPT) to clear the airway of infants requiring assisted ventilation is a routine procedure in neonatal intensive care units. This study was done to describe the relationships between fraction of inspired oxygen (FiO2) levels and the number of hand ventilations (independent variables) and variations of transcutaneous oxygen pressure (TcPO2) from baseline among intubated very-low-birth-weight (VLBW) infants receiving CPT. The study consisted of 30 observations of 13 intubated VLBW infants receiving CPT. Data were obtained by observations during routine CPT procedures performed by the nurses in charge of the infants. Stepwise multiple regression showed that hand ventilations and FiO2 levels significantly accounted for the variability in TcPO2 levels during CPT. Pearson correlation analysis showed that there was a negative correlation between FiO2 and TcPO2 and between the number of hand ventilations and TcPO2.

Blood Gas Monitoring, Transcutaneous↗
PubMed1990

The relationship between oxygen demand, oxygen uptake, and oxygen supply.

Results of the relationships between oxygen supply, demand, and uptake can be used to interpret cardiac output values, identify types of acute circulatory failure, guide attempts to improve cellular function, and thus prevent the development of multiple organ failure and death. Five steps in the interpretation of cardiac output values are recommended: (1) relate cardiac output to the patient's size; (2) determine the presence of anemia or hypoxemia; (3) measure mixed venous O2 saturation and (4) blood lactate levels; and (5) evaluate O2 uptake before and after a transient increase in cardiac output.

Animals↗