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At least 163 records · Page 9Linked to original sources
PubMed1994

Changes in oxygen saturation in the 72 hours after hip surgery: the effect of oxygen therapy.

The aim of this study was to investigate changes in oxygen saturation (SpO2) occurring during the three days following hip surgery in patients in this hospital and to determine to what extent SpO2 might be improved by oxygen therapy for 24 or 72 hours. Eighty-three patients (aged 43-96 years) scheduled for elective total hip replacement or emergency surgery for hip fractures were studied. Forty-four patients had 24 hour postoperative oxygen prescribed by their anaesthetist or surgeon; we randomized these to either continue oxygen for a total of three days (Group 1) or to discontinue oxygen after Day 1 (Group 2). Patients not prescribed oxygen by the surgeon or anaesthetist (n = 39) were randomly assigned either to receive oxygen for three days (Group 3) or not to receive oxygen (Group 4). Oxygen was administered through nasal cannulae at a flow of 2 l.min-1. SpO2 was measured every 10 seconds for three days and stored on computer disc. Percentage of time spent with SpO2 below 90% was used as an index of desaturation. Patients receiving oxygen had significantly improved SpO2. In patients not receiving oxygen, desaturation was most severe on Days 1 and 2, improving somewhat on Day 3. On Day 2 desaturation was similar in Groups 2 and 4. When oxygen was not being administered males were significantly more desaturated than females. Our investigations indicate that following hip surgery poor saturation continues for at least two days and can be improved by oxygen therapy.

Adult↗
PubMed1991

Effect of oxygen therapy on increasing arterial oxygen tension in hypoxemic patients with stable chronic obstructive pulmonary disease while breathing ambient air.

Recertification for long-term oxygen therapy (LTOT) has been recommended for patients who are clinically unstable when home oxygen therapy is begun. Periods of observation for clinical stability have ranged from three weeks to three months in large multicenter clinical trials. There is concern, however, that an increase in arterial oxygen tension occurring after three months may be related to the beneficial effects of oxygen rather than to continued changes in clinical stability. In a review of 20 patients receiving transtracheal oxygen (TTO2) therapy, it was found that four (20 percent) did not qualify for oxygen therapy at the end of six months because the PaO2 breathing ambient air had increased to levels above 55 mm Hg. All patients were clinically stable at the time of insertion of the transtracheal catheter and all had been receiving nasal oxygen for at least seven months (mean, 25.8 months) before entering the study. A retrospective analysis of data published by Weitzenblum et al disclosed that four (25 percent) of 16 patients had a similar increase in PaO2 when reexamined after one year of oxygen therapy. All of the patients had been studied at least one year before oxygen therapy was initiated and each had three consecutive arterial blood gas measurements done monthly to ensure clinical stability. The increase in PaO2 to levels above 55 mm Hg observed in patients receiving TTO2 therapy was associated with a reduction in alveolar-arterial oxygen gradient; however, arterial oxygen desaturation with walking persisted. The specific mechanisms for improvement in PaO2 during oxygen therapy require further study. Any recommendation for recertification of LTOT must recognize that an increase in PaO2 after three months may be due to the beneficial effects of the oxygen therapy and does not provide prima facie justification for termination of therapy.

Aged↗
PubMed2005

The effect of different doses of oxygen administration on oxygen saturation in patients with stroke.

INTRODUCTION: American Stroke guidelines suggest that oxygen saturation after acute stroke should be maintained at 95% or higher. European recommendations include a dose of 2 to 4 L/minute via nasal cannulae. These recommendations are not based on controlled clinical studies. No consensus exists among stroke physicians regarding how much oxygen should be administered and which route should be selected. The aim of this study was to assess the effects of different doses and routes of oxygen administration on oxygen saturation in patients with stroke. METHODS: Patients were recruited within 72 hours of admission with acute stroke. Oxygen saturation was assessed by pulse oximetry (Minolta Pulsox 3i) for 30 minutes on room air (baseline), 2 and 3 L/minute of oxygen via nasal cannulae, 24 and 35% oxygen via face mask, and, finally, on room air. Patients were asked about their preferred route of oxygen administration. RESULTS: Twenty-one patients with a mean age of 72.3 years (range: 46-87 years) were recruited. A total of 24% oxygen (face mask) increased saturation by 1%, 2 L/minute (nasal cannulae) and 35% (face mask) led to a 2% increase, and 3 L/minute (nasal cannulae) resulted in a 3% increase in saturation compared to baseline (p < 0.001). Oxygen saturations were similar in the first and last half-hours. Oxygen treatment has no significant effect on respiratory and heart rates. Most patients (71%) preferred nasal cannulae to face masks. CONCLUSIONS: In our patient population, there was a close dose-response relationship between the amount of oxygen given and the resultant changes in oxygen saturation.

Aged↗
PubMed2002

The generation of oxygen radicals after drinking of oxygenated water.

UNLABELLED: It has been speculated whether ingestion of oxygenated water can lead to an enhanced generation of oxygen radicals. The purpose of three prospective randomized blinded clinical studies was therefore to measure if, when and at which oxygen content in the water,drinking of oxygenated water induces the generation of radicals. Moreover in the fourth prospective,randomized, blinded study possible longterm effects of drinking oxygenated water were examined. METHODS: Altogether 66 volunteers were drinking 300 ml oxygenated or tap water within 15 minutes. Before drinking, altogether 15 ml of blood from the antecubital vein was collected for determination of ascorbyl radicals with ESR, routine laboratory data (hemoglobin, erythrocytes, hematocrit, leukocytes, thrombocytes, uric acid) and the vitamins A,C,E by HPLC. After drinking the ascorbyl radical measurements were repeated from blood of the antecubital vein. In the longterm study ( fourth study) the volunteers had to undergo the same procedure, as described above, at day 1 and day 21. In the meantime they were drinking per day three times 300 ml either oxygenated water or tap water. RESULTS: All subjects exhibited normal vitamin levels in all three studies. Concommitantly in the fourth study there was no statistically relevant alteration of vitamin concentrations during the observation period of three weeks in the verum and placebo-group. 30 minutes after drinking oxygenated water the concentration of ascorbyl radicals increased significantly by median 42 % from median 48 to 65 nmol/l. This increase of ascorbyl radicals after 30 minutes was reproducible in all studies. The levels of ascorbyl radicals remained elevated for 60 minutes after drinking and returned to normal after 120 minutes. This increase was independent of the oxygen concentration in the water, beginning at 30 mg oxygen/l. Water containing 15 mg oxygen/l did not lead to an enhanced radical formation. Longterm consumption of oxygenated water attenuated the ascorbyl radical increase normally observed, thus the initial increase of ascorbyl radicals at day 1 could not be observed after day 21, if the subjects were drinking oxygenated water regularly during the observation period. CONCLUSION: Drinking of oxygenated water possibly leads to a time-limited, yet very moderate, systemic generation of radicals. Regular consumption of oxygenated water over a longer period of time seems to attenuate this effect. The mechanisms leading to this effect and adaptation are unknown.

Adult↗
PubMed2005

Randomised trial of ambulatory oxygen in oxygen-dependent COPD.

Long-term oxygen therapy may limit a patient's ability to remain active and may be detrimental to the rehabilitation process. This study aimed to determine the effect of ambulatory oxygen on quality of life and exercise capacity in patients with chronic obstructive pulmonary disease fulfilling the usual criteria of long-term oxygen therapy. In a 1-yr, randomised, three-period, crossover trial, 24 patients (mean age 68 yrs; mean arterial partial pressure of oxygen at rest 7.1 kPa (53 mmHg)) were allocated to one of the six possible sequences generated by three interventions: 1) standard therapy (home oxygen therapy with an oxygen concentrator only); 2) standard therapy plus as-needed ambulatory oxygen; and 3) standard therapy plus ambulatory compressed air. The comparison of ambulatory oxygen versus ambulatory compressed air was double blind. The main outcomes were quality of life (Chronic Respiratory Questionnaire), exercise tolerance (6-min walk test) and daily duration of exposure to oxygen therapy. The trial was stopped prematurely after an interim analysis. On average, the patients used few ambulatory cylinders (7.5 oxygen cylinders versus 7.4 compressed air cylinders over a 3-month study period). Ambulatory oxygen had no effect on any of the outcomes. In conclusion, the current results do not support the widespread provision of ambulatory oxygen to patients with oxygen-dependent chronic obstructive pulmonary disease.

Aged↗
PubMed1985

Oxygen consumption by portal-drained viscera of cattle: comparison of analytical methods and relationship to whole body oxygen consumption.

Two experiments were conducted to compare methods of determining oxygen consumption by portal-drained viscera and to relate this consumption to total oxygen consumption by lactating dairy cows. Oxygen consumption was the product of portal blood flow (determined by dilution of dye infused into a mesenteric vein) and portal-arterial concentration differences of oxygen. In Experiment 1, portal-arterial concentrations of oxygen were determined in samples from three cows using equations based on blood pH, hemoglobin, partial pressure of carbon dioxide, and partial pressure of oxygen (method 1) or by direct oxygen determination with an oximeter (method 2). Overall, there were no differences in oxygen concentrations or oxygen consumption by portal-drained viscera between methods. In Experiment 2, oxygen consumption by portal-drained viscera (method 2) and total oxygen consumption were measured in two lactating cows. Oxygen consumption by portal-drained viscera accounted for 18% of total oxygen consumption.

Abdomen↗
PubMed1982

One-lung anesthesia: percent shunt and arterial oxygen tension during continuous insufflation of oxygen to the nonventilated lung.

Twenty-four male patients scheduled for elective pulmonary resection were studied to determine whether continuous insufflation of oxygen to the nonventilated lung would reduce intrapulmonary shunting (Qs/Qt) and arterial oxygen desaturation. Measurements of physiologic variables were made using pulmonary arterial and peripheral arterial catheters. Blood was sampled for analysis and Qs/Qt and other hemodynamic variables were calculated. Significant differences were observed in Qs/Qt and arterial oxygen tensions (PaO2) between patients insufflated and those in whom oxygen was not insufflated. Patients with oxygen insufflation had significantly lower Qs/Qt and consistently higher PaO2. Statistically significant differences in Qs/Qt became apparent after 15, 30, and 45 minutes of one-lung ventilation compared with values for patients not receiving oxygen insufflation. Six of 12 patients without oxygen insufflation had peak Qs/Qt levels greater than 50%, whereas none of the patients in whom oxygen was insufflated had levels that exceeded this amount. Of 12 patients given oxygen insufflation, one had a PaO2 of less than 100 torr at the point of maximum decrease in arterial oxygen tension, compared with six of 12 patients in whom oxygen was not insufflated. These findings suggest that continuous oxygen insufflation of the nonventilated lung during periods of one-lung ventilation reduces Qs/Qt and minimizes arterial oxygen desaturation.

Adult↗
PubMed1995

Supplemental oxygen during endoscopic variceal ligation: effects on arterial oxygenation and cardiac arrhythmia.

OBJECTIVES: Endoscopic variceal ligation may affect cardiopulmonary function. The aim of this study was to determine the effect of either nasal oxygen (2 L/min) or no oxygen on arterial oxygenation and cardiac arrhythmia during variceal ligation. METHODS: A prospective, endoscopy team-blinded, randomized, cross-over study (first session vs second session) was conducted in 30 cirrhotic patients undergoing variceal ligation. Oxygen saturation (SaO2) and cardiac arrhythmia were assessed by a pulse oximeter. In this study, 15 patients received supplemental oxygen in the first sessions, and 15 received oxygen in the second sessions. RESULTS: Oxygen desaturation (nadir SaO2 < 90%) occurred in 23% of patients breathing room air but was prevented by oxygen (p < 0.01), and the nadir SaO2 was significantly lower in patients breathing room air than in those receiving oxygen (93.2 +/- 0.7% vs 98.3 +/- 0.3%, p < 0.01). During the procedure, premature ventricular contraction was more frequently observed in patients breathing room air than in those receiving oxygen (14.0 +/- 3.2/h vs 5.4 +/- 1.5/r, p < 0.05). CONCLUSIONS: These data suggest that oxygen desaturation and cardiac arrhythmia are common in patients undergoing variceal ligation and that low flow nasal oxygen can alleviate these events. Supplemental oxygen is therefore advisable to avoid potential serious cardiopulmonary accidents in patients undergoing variceal ligation.

Administration, Intranasal↗
PubMedDate not supplied

Is percentage of predicted maximal exercise oxygen consumption a better predictor of survival than peak exercise oxygen consumption for patients with severe heart failure?

BACKGROUND: Peak exercise oxygen consumption provides valuable short-term prognostic information in patients with heart failure. However, peak exercise oxygen consumption is determined not only by the cardiac output response to exercise but also by age, gender, and muscle mass. We investigated whether percentage of predicted maximal exercise oxygen consumption rather than an absolute value may be a better predictor of survival. METHODS: Peak exercise oxygen consumption was measured and percentage of predicted maximal exercise oxygen consumption was derived from two standard formulas (Wasserman and Astrand) in 272 ambulatory patients referred for transplant evaluation. The predictive ability of these variables was determined by comparison of Kaplan-Meier curves, univariable proportional-hazards models, and receiver operating characteristic curves. RESULTS: Neither method of determining percentage of predicted maximal exercise oxygen consumption significantly improved the prediction of survival over peak exercise oxygen consumption alone. Overall model discrimination, as assessed by area under the receiver operating characteristic curve, was not significantly improved with percentage of predicted maximal exercise oxygen consumption (Wasserman) rather than weight-normalized peak exercise oxygen consumption (0.71 +/- 0.04 versus 0.66 +/- 0.04; Z = 1.60, p = 0.11). All of the difference between percentage of predicted maximal exercise oxygen consumption-Wasserman and peak exercise oxygen consumption resulted from differences in women (areas under receiver operating characteristic curve = 0.68 +/- 0.09 and 0.74 +/- 0.09; p = 0.14); results for men were the same (both areas = 0.68 +/- 0.04). CONCLUSIONS: Normalization of peak exercise oxygen consumption for predicted values adds only minimal prognostic information. A peak exercise oxygen consumption < 14 ml/kg/min remains a reasonable guideline by which to time heart transplantation.

Adult↗
PubMed1995

The mechanisms by which hyperbaric oxygen and carbogen improve tumour oxygenation.

Hyperbaric oxygen (HBO) has been proposed to reduce tumour hypoxia by increasing the amount of dissolved oxygen in the plasma. That this actually occurs has not been verified experimentally. This study was performed to explore changes in tumour oxygenation induced by treatment with normobaric and hyperbaric oxygen and carbogen. R3230Ac mammary adenocarcinomas were implanted into Fisher 344 rats. Arterial blood gases, blood pressure and heart rate were monitored. Tumour oxygenation was measured polarographically in five sets of animals. They received either normobaric 100% oxygen, hyperbaric (3 atmospheres; atm) 100% oxygen, normobaric carbogen or hyperbaric (3 atm) carbogen (HBC) +/- bretylium. HBO reduced the mean level of low pO2 values (< 5 mmHg) from 0.49 to 0.07 (P = 0.0003) and increased the average median pO2 from 8 mmHg to 55 mmHg (P = 0.001). HBC reduced the level of low pO2 values from 0.82 to 0.51 (P = 0.002) an increased median pO2 from 2 mmHg to 6 mmHg (P = 0.05). Normobaric oxygen and carbogen did not change tumour oxygenation significantly. Sympathetic blockade with bretylium before HBC exposure improved oxygenation significantly more than HBC alone (low pO2 0.55-0.17, median pO2 4-17 mmHg). HBO and hyperbaric carbogen improved tumour oxygenation in this model, while normobaric oxygen or carbogen had no effect. Sympathetic-mediated vasoconstriction during hyperbaric carbogen caused it to be less effective than HBO. This mechanism also appeared to operate during normobaric carbogen breathing.

Adenocarcinoma↗
PubMed2002

Effects of high inspired oxygen fraction during elective caesarean section under spinal anaesthesia on maternal and fetal oxygenation and lipid peroxidation.

BACKGROUND: Oxygen supplementation is given routinely to parturients undergoing Caesarean section under regional anaesthesia. While the aim is to improve fetal oxygenation, inspiring a high oxygen fraction (FIO2) can also increase free radical activity and lipid peroxidation in both the mother and baby. In this prospective, randomized, double-blind study, we investigated the effect of high inspired oxygen fraction (FIO2) on maternal and fetal oxygenation and oxygen free radical activity in parturients having Caesarean section under spinal anaesthesia. METHODS: Forty-four healthy parturients were randomized to breathe either 21% (air group) or 60% oxygen (oxygen group) intraoperatively via a ventimask. Maternal arterial blood was collected at 5-min intervals from baseline until delivery, and umbilical arterial and venous blood was collected at delivery. We measured blood gases and the products of lipid peroxidation (8-isoprostane, malondialdehyde (MDA), hydroperoxide (OHP)) and purine metabolites. RESULTS: At delivery, the oxygen group had greater maternal arterial PO2 [mean 30.0 (SD 6.3) vs 14.2 (1.9) kPa; mean difference 15.8 kPa, 95% confidence interval 12.9-18.7 kPa, P<0.001] and greater umbilical venous PO2 [4.8 (1.0) vs 4.0 (1.4) kPa; mean difference 0.8 kPa, 95% confidence interval 0.0-1.5 kPa, P=0.04] compared with the air group. Maternal and umbilical plasma concentrations of lipid peroxides (8-isoprostane, MDA, OHP) were greater in the oxygen group than in the air group (P<0.05). CONCLUSIONS: We conclude that breathing high FIO2 modestly increased fetal oxygenation but caused a concomitant increase in oxygen free radical activity in both mother and fetus.

Adult↗
PubMed2005

A wet-primed extracorporeal membrane oxygenation circuit with hollow-fiber membrane oxygenator maintains adequate function for use during cardiopulmonary resuscitation after 2 weeks on standby.

OBJECTIVE: To assess the durability of wet-preprimed extracorporeal membrane oxygenation (ECMO) circuits for potential use in resuscitation after a 2-wk period of storage. DESIGN: Experimental laboratory study. SETTING: Tertiary care pediatric cardiac intensive care unit. SUBJECTS: None. INTERVENTIONS AND MEASUREMENTS: 14 ECMO circuits (polyvinyl chloride and super-Tygon tubing with hollow-fiber oxygenator, Medos Hilite 800LT) were primed with crystalloid under sterile conditions and stored for 0 (control, n = 4), 7 (n = 5) and 14 (n = 5) days and maintained at 8 degrees C on pump at 10 rpm and gas flow at 0.2 L/min. Daily samples were inspected for plasticizers by means of high-performance liquid chromatography and for microorganisms by culture and polymerase chain reaction techniques. After storage, the oxygenators were primed with red blood cells (hemoglobin, 12 g/dL) and tested in vitro with a deoxygenator according to Association for Advancement of Medical Instrumentation standards. Oxygen and CO(2) transfer rates were calculated by standard formulae at maximum blood flow (800 mL/min) and maximum sweep gas flow (1.6 L/min). MAIN RESULTS: Oxygen transfer was linearly related to venous oxygen saturation, increasing by 11 mL/min for each 10% decrease in venous oxygen saturation. Estimated oxygen transfer at venous oxygen saturation of 60% was 45.8 mL/min (95% confidence interval [CI], 43.5-48.1) for controls, 51.0 mL/min (95% CI, 48.9-53.2) for 7-day oxygenators, and 49.0 mL/min (95% CI, 47.8-50.1) for 14-day oxygenators. CO(2) transfer declined to 29.2 mL/min at 14 days of storage, a mean fall of 11.5 mL/min (95% CI, 4.2-18.7) in comparison with 7-day storage. All circuits were free from microbes/microbial DNA. Plasticizer levels fell below the lower limit of detection (0.003 microg/mL) at 7 and 14 days. CONCLUSIONS: A wet-preprimed ECMO circuit with hollow-fiber membrane oxygenator can be stored for up to 2 wks with adequately preserved function if prepared appropriately. These data may improve safe access to rapid-response ECMO support.

Biological Transport↗
PubMedDate not supplied

[Age-dependence of oxygen transport into body tissues and the favorable modification of this transport by multistep oxygen therapy].

The routine determination of the oxygen flux into body's tissues (= resting oxygen uptake) should gain more attention in practice, because its magnitude can be considered a kind of characteristic value for the energetic state of the entire organism. The determination of this value has deserved special interest since we discouvered a "switch mechanism" of blood microcirculation, which depends on the oxygen state of the body. A high value of pO2 (greater than or equal to 50 mm of Hg) at the venous ends of the capillaries, attainable by the procedures of the Oxygen Multistep Therapy and by powerful physical exercise as well, results in an increase of the blood microcirculation and, consequently, in a permanent elevation of the oxygen influx and uptake, respectively. This effect can persist for weeks, months or even years. If the oxygen state gets worse and declines below a certain threshold, e. g. in progressing age or after long-term distress, the cross sections of the capillaries shrink by swelling of the endothelial cells, and the blood microcirculation is diminished for an extended period of time. The utilization of the above-mentioned switch mechanism for permanent improvement of the oxygen flux into all the tissues of the organism is therefore of decisive importance for fighting against the common cause of many diseases, disorders and complaints going often along with increasing age due to insufficient oxygen (energy) supply for general metabolism. As can be taken from measurements described in this paper, the main contribution to this deterioraction comes from the age-dependent diminution of the cardiac minute or stroke volume, respectively, since eta--the percent exhaustion of the oxygen-binding capacity of blood--increases even with progressing age, as was found by us. Numerous determinations of the arterial and venous pO2 resting levels have shown that the values of eta can almost be doubled easily by the procedures of the Oxygen Multistep Therapy, whereby--as a rule--the age-dependent decrease of the cardiac output is overcompensated. Within the schedule of the Oxygen Multistep Therapy, the third step prescribes a temporary enhancement of the blood circulation by physical exercise. With respect to this measure, there was made progress of principal importance by the idea to increase the minute volume by application of sympathicomimetics during the single treatment units under moderately enhanced oxygen inhalation, but with due consideration of the known contraindications.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1991

Gastric and colonic oxygen tension measured with a vacuum-fixed oxygen electrode.

A new electrode system for determination of visceral oxygen tension is presented. The system consists of a transcutaneous oxygen electrode (E5242 Radiometer A/S. Copenhagen), which is screwed into a suction ring and fixed to the organ by applying a vacuum. The electrode membrane is then in contact with the organ surface via a fluid layer with a thickness of a few micrometres, without interference from atmospheric air and without mechanical disturbance of the membrane. The electrode system was tested on the gastric and colonic wall in six pigs. As reference, a silicone tonometer was placed subserously beneath the vacuum-fixed electrode. The silicone tonometer was connected to a second transcutaneous oxygen electrode. The tissue oxygen tension was changed by subjecting the animals to various inspiratory concentrations of oxygen and to hypovolaemia. The oxygen tension measured by the vacuum-fixed electrode (PO2vac) was compared with the oxygen tension measured by the tonometer (PO2tono). A good correlation was demonstrated between PO2vac and PO2tono, the correlation coefficient being 0.8619, confirming that the suction-fixed oxygen electrode measures tissue oxygen. The lowest possible vacuum to hold the electrode unit in place was between 4.0 and 6.7 kPa. Provided the measuring time did not exceed 3 min. vacuum had only slight influence on the measured oxygen values. The mean change in PO2vac induced by varying the vacuum from 7 to 26 kPa, and 26 to 7 kPa, was only +0.23 kPa (-1.2 to +1.9) and +0.19 kPa (-0.3 to +1.3), respectively. The mean stabilization time, defined as the time from electrode application until achieving 95% of the equilibration value, was 66 sec (SEM, 3.4 sec) and 57 sec (SEM, 3.0 sec) on the gastric and colonic wall, respectively. The measured values of PO2vac varied significantly between different areas on the gastric wall (p less than 0.001). When several surface measurements were performed throughout the investigated area, the mean oxygen tension approached the oxygen tension measured by the tonometer. It is concluded that the vacuum-fixed electrode constitutes a reliable, easy and, noninvasive method for measurements of the oxygen tension in the gastric and colonic tissue.

Animals↗
PubMed1986

Effect of hyperbaric oxygen exposure on oxygen tension within the medullary canal in the rabbit tibial osteomyelitis model.

The effect on intramedullary oxygen tension of 100% oxygen exposure at 1, 2, 2.4, and 3 atm pressure was studied in 12 New Zealand white rabbits with chronic right tibial osteomyelitis. The model, modified from that described by others, incorporates a multipuncture silastic closure plug placed transcortically in the proximal tibial metaphysis through which platinum needle, polarographic electrode oxygen tension determinations can be made without repeat surgical exposure. In 40% of the control, left, noninfected tibial metaphyses the baseline oxygen tension with the animals breathing room air at sea level was suboptimal for leukocyte bacterial killing. This oxygen tension was depressed further in the infected right tibia. Medullary canal oxygen tension increased in response to hyperbaric oxygen exposure in both the infected and noninfected tibiae. Whereas the amount of the oxygen tension increase varied with the presence of infection and depth of dive, neither the time for oxygen tension to plateau nor the time required for return to baseline tension after completion of hyperbaric oxygen exposure varied with the presence of infection or depth of dive. After completion of hyperbaric oxygen exposure, the oxygen tension within the medullary canal returned to baseline within 15 min.

Animals↗
PubMed1992

Effect of maternal oxygen administration on fetal oxygenation during graded reduction of umbilical or uterine blood flow in fetal sheep.

OBJECTIVE: Effects of maternal oxygen administration on fetal blood gases and on oxygen delivery and consumption during reduced uterine and reduced umbilical blood flows were examined. STUDY DESIGN: In eight pregnant sheep (gestational age 133 +/- 4 days) flow transducers were applied to a uterine and the common umbilical artery. Graded reductions in uterine and umbilical blood flows were achieved by a hypogastric artery snare and a balloon cuff encircling the umbilical cord. Fetal femoral arterial and umbilical venous oxygen contents and flows were measured at varying flow reductions with the ewe breathing air or oxygen. RESULTS: During 75% reduction in umbilical blood flow maternal oxygen administration significantly increased fetal oxygen delivery (6.4 +/- 2.5 to 7.7 +/- 2.3 ml/min/kg) and oxygen consumption (4.3 +/- 1.2 to 5.0 +/- 0.8 ml/min/kg). With similar reduction of uterine flow oxygen administration increased oxygen delivery from 8.3 +/- 2.4 to 12.3 +/- 3.6 and oxygen consumption from 3.3 +/- 0.8 to 4.7 +/- 1.6 ml/min/kg. CONCLUSION: Maternal oxygen inhalation improves fetal oxygenation during umbilical but especially during uterine blood flow reduction.

Animals↗
PubMed1997

Isovolemic hemodilution with a bovine hemoglobin-based oxygen carrier: effects on hemodynamics and oxygen transport in comparison with a nonoxygen-carrying volume substitute.

OBJECTIVE: Stroma-free hemoglobin solutions have been shown to maintain oxygen transport in the absence of red blood cells. This study was designed to investigate the impact of such solutions on hemodynamics and oxygen transport during progressive isovolemic hemodilution within and even beyond a clinically relevant range of hematocrit values. DESIGN: Prospective, randomized experimental study comparing a bovine hemoglobin-based oxygen carrier (bHBOC) with a conventional nonoxygen-carrying volume substitute (hydroxyethyl starch [HES]). SETTING: Animal laboratory of a university cardiovascular research center. PARTICIPANTS: Splenectomized full-grown foxhounds, anesthetized with pentobarbital and piritramid. INTERVENTIONS: Twelve splenectomized foxhounds were anesthetized and mechanically ventilated. Catheters were placed for hemodilution, arterial and venous blood sampling, and hemodynamic measurements. The baseline hematocrit (Hct) value was adjusted to 0.35 by an initial isovolemic exchange of blood for identical volumes of HES (10% HES 200/0.5). Thereafter, the hematocrit was progressively reduced by isovolemic hemodilution using either HES (n = 6) or bHBOC (n = 6). MEASUREMENTS AND MAIN RESULTS: Hemodynamic and laboratory parameters of oxygen transport were measured at Hct values of 0.30, 0.20, and 0.10. Oxygen content was directly estimated using an oxygen-specific fuel cell. Arterial oxygen content at an Hct value of 0.10 nearly doubled in bHBOC-treated dogs as compared with HES-diluted animals (p < 0.001). This gain in oxygen-carrying capacity was completely negated by a decrease in cardiac output (-32% Hct 0.35 v Hct 0.30; p < 0.001) immediately on the first infusion of bovine hemoglobin. Thus, oxygen delivery was significantly lower as compared with HES-treated dogs at Hct 0.30 and 0.20, but remained stable at a level of 60% of baseline until Hct was 0.10. Both the pulmonary and the systemic vascular resistances increased. CONCLUSIONS: Isovolemic hemodilution with bHBOC did not improve systemic oxygen delivery in comparison with a nonoxygen-carrying diluent (HES) in a range of Hct values down to 0.10. Unchanged mixed venous lactate levels and stable oxygen consumption indicate sufficiently maintained oxygen delivery. This might become advantageous in patients who are unable to adequately increase cardiac output during hemodilution.

Animals↗
PubMed2003

Influence of oxygen administration on pulmonary haemodynamics and tissue oxygenation during exercise in COPD patients with different ACE genotypes.

We previously found that the angiotensin-converting enzyme (ACE) DD genotype is associated with exaggerated pulmonary hypertension and disturbance of tissue oxygenation during exercise in chronic obstructive pulmonary disease (COPD) patients. This study was designed to compare the effect of oxygen administration on pulmonary haemodynamics and tissue oxygenation during exercise in COPD patients with different ACE genotypes. Forty-three COPD patients (II=16, ID=12, DD=15) underwent right heart catheterization, and then performed an exercise test with room air or oxygen. We measured pulmonary haemodynamic variables and indices of tissue oxygenation such as mixed venous oxygen tension (PVO2) and arterial lactate concentration, both at rest and after exercise. The magnitude of difference in mean pulmonary arterial pressure and pulmonary vascular resistance after exercise between breathing of room air and breathing of oxygen did not significantly differ among the three groups. PVO2 after exercise with room air or oxygen was significantly higher in patients with the II genotype than in those with the ID or DD genotype. In contrast, lactate concentration after exercise with room air or oxygen was significantly lower in patients with the II genotype than in those with the ID or DD genotype. Moreover, the magnitude of difference in PVO2 and lactate concentration after exercise between breathing of room air and breathing of oxygen was the II>ID>DD genotype. These findings suggest that the ability of oxygen administration to improve tissue oxygenation during exercise is associated with the ACE genotypes in COPD patients.

Administration, Inhalation↗