Pump Oxygenator Research Articles

DEVELOPMENT OF AN IMPLANTABLE OXYGENATOR WITH CROSS FLOW PUMP

The resistance of the implantable oxygenator to the right ventricle would become very large and might cause cardiac failure if an implantable oxygenator is connected to PA-LA and blood is circulated without a pump. We developed an integrated implantable pump oxygenator using a Cross Flow Pump (CFP). It is difficult to produce an uniform inflow to the oxygenator with centrifugal pump. The CFP can produce a wide uniform flow to the oxygenator because it has a wide impeller and outlet. An uniform flow is vital to avoid turbulence in the inlet part. Therefore, an implantable oxygenator with CFP can provide anti-thrombogenicity and high gas exchange performance. In this study, we evaluated effects on the oxygenator performance by the uniformity of blood velocity at the hollow fiber membrene part using the CFP. The oxygenator had a hollow fiber density of 40% and a membrane surface area of 1.3m2. And two types of oxygenators are used. One oxygenator is the prototype oxygenator, and the other is the improved oxygenator with improved uniformity of blood velocity at the hollow fiber membrane part. The O2 and the CO2 gas transfer performance of prototype oxygenator were 200mL/min and 137mL/min (V/Q=1) respectively at a blood flow rate of 4L/min. The improved oxygenator indicated 200mL/min and 157mL/min. CO2 gas transfer performance of the improved oxygenator was increased by 14.6%. The result of our experiments suggests CFP, that produces a wide uniform flow to the oxygenator is effective to attain the high gas exchange performance.

Characteristics of an HC sensor using a Pr 6O 11 electrode

The characteristics of an HC sensor consisting of a gas-detection cell and an oxygen pump cell have been investigated. A Pt active electrode and a Pr 6O 11 inactive electrode were formed on YSZ in the gas-detection cell using a sputtering technique, and the concentration of hydrocarbon gases was determined from the electromotive force generated between these two electrodes. The pump cell was assembled such that the oxygen concentration in the gas-detection space was decreased. At 800 °C, the gas-detection cell showed high output sensitivity for hydrocarbon gases such as CH 4 and C 3H 8. However, the sensitivity was low for H 2 and CO. The sensor output increased when the pump cell was operated in C 3H 8/O 2/N 2. This result shows that decreasing the oxygen concentration in the gas-detection space by using the pump cell is an effective technique for improving the detection sensitivity of the sensor.

Preparation of BiMeVO x (Me = Cu, Ti, Zr, Nb, Ta) compounds as solid electrolyte and behavior of their oxygen concentration cells

A group of complex metal oxides, BiMeVO x , which a fraction ( x) of V in Bi 4V 2O 11 is replaced by foreign metal, has been reported to be oxide-ionic conductors. The various kinds of oxides in this group, Me = Cu ( x = 0.1), Zr ( x = 0.1), Ti ( x = 0.4), Nb ( x = 0.15) and Ta ( x = 0.15), were investigated for electrochemical characterization based on oxygen concentration battery. The powders of BiMeVO x , their structural phases to the high temperature phase (γ) of Bi 4V 2O 11, were obtained by calcining at 700–850 °C. Each sample was compacted into a disk, and installed into an oxygen concentration cell. The oxygen concentration cells using the resulting disks of BiMeVO x , especially Me = Cu, were found to work as an oxygen sensor fairly well at 700 °C: the number of reaction electrons ( n) associated with the reduction of O 2 was close to the theoretical one (4). With lowering operating temperature, however, the O 2-responding properties degraded rather quickly: it was far larger at 500 °C. Such degradation was confirmed to be owing to decrease the rate of electrode reactions through the measurement of Faraday efficiency of oxygen pumping current. As a result, the performances of the cells were found to depend very much on the kinds of electrode materials. The use of a perovskite-type oxide, La 0.6Sr 0.4Co 0.8Fe 0.2O 3, instead of Pt as a electrode was found to enable the cell to work at 400 °C and above.

Heart Failure in Children - Mechanical Assistance

The use of mechanical circulatory support for the treatment of heart failure in the pediatric population has become increasingly important in pediatric heart surgery units; however, the treatment options for the pediatric population have not attained the same level of technological development as we have seen for the adult population. The use of mechanical assistance as a bridge to transplantation or a bridge to recovery are the main indications for mechanical circulatory support in infants and children. The problem of organ donor shortage is even worse compared to the situation in the field of adult heart transplantations. Especially in Europe however, newly developed pulsatile, paracorporeal ventricular assist devices designed for long-term assist in children have demonstrated their ability to provide excellent results beyond the abilities of extracorporeal membrane oxygenation and centrifugal pumps, which are still the mainstay of mechanical support in children worldwide. Especially in the group of the smallest patients, the use of the most appropriate form of circulatory assistance has to be carefully considered as the co-incidence of respiratory failure as well as other complex physiological situations will severely influence the outcome.

Amperometric NO X sensor based on oxygen pumping current by using LaGaO 3-based solid electrolyte for monitoring exhaust gas

An amperometric NO sensor using a LaGaO 3 base solid electrolyte was investigated based on the difference of catalytic activity of the electrode. It was found that oxygen pumping current increased upon exposure to NO when Sr 0.6La 0.4Mn 0.8Ni 0.2O 3 and La 0.5Sr 0.5MnO 3 (LSM 55) were used as active and inactive electrodes for NO oxidation, respectively. Effects of electrolyte on the sensitivity were investigated and the sensitivity to NO becomes higher with increasing oxide ion conductivity for electrolyte. By applying LaGaO 3 doped with Ni or Co, the sensitivity of the sensor becomes 1842 μA per decade of NO concentration at 823 K. The oxygen pumping current linearly increased with increasing NO concentration and the sensor responded NO and recovered to the original level within 1 min. The appearance of mixed potential in potentiometric study suggests that oxidation of NO to NO 2 mainly occurs on Sr 0.6La 0.4Mn 0.8Ni 0.2O 3 electrode. Although oxygen pumping current of this sensor was slightly affected by change in oxygen partial pressure ( P O 2 ), influence by P O 2 change is negligibly small. Cross-sensitivity study revealed that NO in exhaust gas can be selectively detected in presence of coexisting gases.

Behavior of oxygen concentration cells using BiCuVO x oxide-ion conductor

The mixed oxide, Bi 2Cu 0.1V 0.9O 5.35 often abbreviated as BiCuVO x , is known as an oxide-ionic conductor. The applicability of this oxide to a potentiometric oxygen sensor was investigated. Oxygen concentration cells were fabricated by using a disk of this oxide to test the EMF response to changes in oxygen concentration between 10% and 100% at various temperatures between 300 and 700 °C. As a result, the performances of the cells were found to depend very much on the kinds of electrode materials. When attached with Pt electrodes, the cell produced the EMF response fairly good only at 600 °C and above, whereas the oxide-ion transport number was close to unity even at 500 °C as evaluated from the Faraday efficiency of oxygen pumping current. The use of a perovskite-type oxide (La 0.6Sr 0.4Co 0.8Fe 0.2O 3) instead of Pt was found to enable the cell to work at 400 °C and above. Especially excellent performances were observed when the oxide was mixed with BiCuVO x powder prior to being applied on the BiCuVO x disk as the electrodes.

Leukocyte filtration and miniature perfusion during arrested heart CABG on a Jehovah’s Witness patient

Bloodless surgery and a reduction in the use of allogeneic blood products has long been the standard of care in medicine. Many individuals in our communities have demanded this form of surgical treatment for personal and religious reasons. On 6 December 2002, a 72-year-old male patient was admitted to our institution as a critical air flight transfer. The patient's height was 190.5 cm and weight was 59.3 kg (body surface area 1.83 m2). His preliminary diagnosis was chest pain with myocardial infarction as evidenced by elevated blood cardiac isoenzymes. His principle diagnosis was subendocardial infarction with paroxysmal ventricular tachycardia. Cardiac catheterization was performed and demonstrated severe triple vessel disease with an ejection fraction of 30%. He was evaluated and accepted as a candidate for coronary artery bypass grafting. Multidisciplinary consultation concluded that a safe and effective method of perioperative treatment would involve the use of arrested heart support with cold blood cardioplegia using a low prime miniature perfusion circuit as no blood products would be considered for use. Additionally, the combined modalities of perfusion interventions to minimize hemodilution consisted of intraoperative autologous blood collection totaling 500 mL and rapid autologous priming of the miniature perfusion circuit. The miniature perfusion system was a low prime Cardiovention (Santa Clara, CA) CORx device which includes a hollow-fiber oxygenator and integral centrifugal pump with a surface area of 1.2 m2. This system also incorporates an air sensing solenoid which triggers rapid air evacuation in a bolus range of 1 mL or greater. Kinetic venous drainage is another feature of this device as the centrifugal pump is integrated into the oxygenator. We believed that a miniature extracorporeal circuit would enhance the desired clinical outcome as opposed to the risk of: (1) off-pump coronary artery bypass (OPCAB) approach and the concern of emergent transition to an on-pump procedure and (2) use of larger surface area with conventional systems that impose a greater hemodilutional effect. Leukocyte filtration was employed as the patient had a significant past medical history of chronic obstructive pulmonary disease. We herein report our clinical experience with this method of treatment on a patient who refused the use of blood products in his surgical treatment. It is our belief that the multiple modalities utilized in combination during this procedure resulted in positive clinical outcomes as demonstrated by an intubation time of 8 hours 35 min with a discharge on the fifth postoperative day.

Oxidation of C 2–C 4 alkanes over MoO 3–V 2O 5 supported on a YSZ-aided membrane reactor

An electrochemical reactor Au|YSZ|Ag, using yttria-stabilized zirconia (YSZ) as a solid electrolyte, has been employed for the partial oxidation of C 2–C 4 alkanes at 773 K. Catalyst films of Mo–V mixed oxide with various Mo/V compositions were prepared by simultaneous deposition of MoO 3 and V 2O 5 on the Au anode of the electro-chemical cell. A stable MoV 2O 8 mixed oxide formed as the active phase in the catalyst film. When oxygen was pumped onto the catalyst film through the YSZ, ethane and propane were selectively dehydrogenated to ethene and propene, respectively, while isobutane gave a small amount of methacrolein. Preferential orientation of crystal growth of MoV 2O 8 was observed depending on the Mo/V composition, resulting in structure-sensitive alkane oxidation. The diffraction lines 0 0 1 and 1 1 0 of MoV 2O 8 appeared most strongly for the V content of 43.7 and 53.4%, and the formation of propene and ethene were most efficiently catalyzed on the former and the latter, respectively. The active species is considered to be V atoms on the surface. The (0 0 1) plane of MoV 2O 8 is composed of flat terrace planes, while the (1 1 0) planes consist of many steps, where co-ordinatively unsaturated V atoms appeared more intensively than on the (0 0 1) plane on the surface. It is considered that ethane possessing a primary C–H bond requires more active sites for the C–H activation than propane that possesses a secondary C–H bond. Use of the electrochemical oxygen pumping system onto the MoV 2O 8 catalyst film caused a drastic enhancement in the oxidative dehydrogenation of ethane and propane compared to use of the conventional gas-flow reactor with the fixed-bed, probably due to sufficient supply of dissociated oxygen species through the YSZ.

Electrochemical solid electrolyte gas sensors — hydrocarbon and NOx analysis in exhaust gases

For the in situ measurement of the free oxygen concentration and the equilibrium oxygen partial pressure oxygen sensors based on zirconia solid electrolytes are widely used in order to monitor and control technical high temperature processes. Similarly combustibles (HC, CO) and NOx can be determined in non equilibrated oxygen containing gas mixtures of exhausts by mixed potential sensors and amperometric solid electrolyte sensors. It is expected that their long-term stability is similar to that of oxygen sensors. In both cases the electrode material with the desired electrochemical and catalytic properties is the key component. Different electrode materials made of perovskites (La1-xSrxCr1-yGayO3-δ) and composites (Au/Metal oxide) were investigated in different combustibles including CO, C3H6/8, C7H8 and CH4. The response behaviour of mixed potential sensors is determined by the catalytic activity of the measuring electrode, which is closely connected with the defect structure and depends on the measuring conditions. Furthermore the electrode response can be understood by electrokinetic data. Gas symmetrical mixed potential sensors with electrodes made of Au/Nb2O5 composites show maximum sensitivity. By using Ptreference electrodes without equilibrium behaviour the sensors are applicable in lean and rich mixtures as well. In the amperometric sensor mode the consecutive determination of oxygen and NOx or combustibles at two working electrodes is possible. The catalytic activity of the oxygen pumping electrode should be low in order to avoid the decomposition of NO and HC respectively. Alternatively, the electrochemical reduction of NO can be performed at a single working electrode, made of materials with improved NO selectivity, without the previous reduction of oxygen.

A Potentiometric Study of the Interaction of Zr(IV) and O(II) Ions in the LiCl-KCl Eutectic Molten Salt

The physical and chemical properties of zirconium chlorides have been studied in fused LiCl-KCl eutectic at 823 K using an electrochemical cell containing two platinum-oxygen electrodes with a solid electrolyte membrane. The first is used as indicator electrode and the second as an oxygen pump which allows us to vary the of the ionic melt by electrolysis. Titration of Zr(IV) chlorocomplex by ions demonstrated the precipitation of and The solubility constants of these compounds were calculated. A Pourbaix type diagram, which summarizes the properties of zirconium species in the melt, was determined. © 2004 The Electrochemical Society. All rights reserved.

Oxidation of C 2–C 4 hydrocarbons over MoO 3 and V 2O 5 supported on a YSZ-aided membrane reactor

An electrochemical reactor, using yttria-stabilized zirconia (YSZ) as a solid electrolyte and gold and silver as the anode and cathode, respectively, has been employed for the selective partial oxidation of C 2–C 4 hydrocarbons at 775 K. MoO 3 or V 2O 5 was deposited as the catalyst film on the Au anode of the electrochemical cell. The reaction was carried out over the catalyst film under oxygen pumping through the cell; the results are compared with those obtained by the reaction with gaseous oxygen. Under oxygen pumping, no alkane was oxidized over MoO 3, while isobutane and propane were partially oxidized to methacrolein and propene, respectively, and ethane was oxidized a little over V 2O 5. It is supposed that CH cleavage is the rate determining step of the alkane oxidation over V 2O 5. Alkenes were partially oxidized over both MoO 3 and V 2O 5, and the selectivities to the oxygenated products, i.e., acetaldehyde, acrolein and methacrolein from ethene, propene, and isobutene, respectively, were higher on the former than on the latter. Over both MoO 3 and V 2O 5, the selectivity to aldehyde was higher in the reaction under oxygen pumping than in that by gaseous oxygen. Over MoO 3, the other oxygenated compounds than aldehyde were observed in the reaction by gaseous oxygen, while this is not the case under oxygen pumping. Under oxygen pumping, the highest selectivity was observed with methacrolein, followed by acrolein and acetaldehyde, among which acetaldehyde was further oxidized to carbon oxides. Over V 2O 5, alkenes were far more rapidly oxidized by gaseous oxygen than under oxygen pumping, and the selectivity to the oxygenated products were still higher under oxygen pumping than by gaseous oxygen. The highest selectivity was observed with methacrolein, and those of both acrolein and acetaldehyde were low. No further oxidation of acetaldehyde was observed over V 2O 5.

Risk assessment of di(2-ethylhexyl)phthalate released from PVC blood circuits during hemodialysis and pump–oxygenation therapy

This study deals with in vitro investigation of the release of di(2-ethylhexyl)phthalate (DEHP) during hemodialysis and pump–oxygenation therapy using medical grade PVC tubing. High resolution GC–MS analysis showed that the release of DEHP was time-dependently increased by circulation of bovine blood into a major system for the hemodialysis that is used in Japan, and the amount of DEHP released into the blood had reached 7.3 mg by 4 h of circulation. No significant difference was observed in the release patterns of DEHP under the conditions with and without fluid removal treatment during hemodialysis, indicating that the treatment seems not to be effective for eliminating DEHP from the blood through the hemodialysis membrane. Mono(2-ethylhexyl)phthalate (MEHP) analysis revealed that a small amount of DEHP (3–4%) was converted to MEHP by hydrolysis during the circulation of blood. A considerable amount of DEHP was also released from the PVC circuit mimicking the pump–oxygenation system, and 7.5–12.1 mg of DEHP had migrated into bovine blood from the circuit by 6 h. It was noticed, however, that the release was obviously suppressed by covalently coating the inner surface of the PVC tubing with heparin, though this effect was not observed with ionic bond type-heparin coating. Covalent bond type-heparin coating of PVC tubing seems to offer the advantage of decreasing the amount of DEHP exposure to patients during treatment using a PVC circuit.

DEVELOPMENT OF INTEGRATED OXYGENATOR USING UNDULATION BLOOD PUMP

Purpose of study: Undulation blood pump is an original blood pump which is designed and developed in our laboratory. The purpose of this study is to develop an integrated oxygenator using undulation pump. This project is supported by the program for promotion of fundamental studies in health sciences of the organization for pharmaceutical safety and research of Japan Materials and Methods: To reduce the priming blood volume and contacting surface area, we designed one piece integrated compact cardiopulmonary bypass system that consists of oxygenator, heat exchanger and undulation blood pump. Results: Undulation pump is modified to use an injection molding membrane for future mass production. Heat exchanger is composed by about seventy thin metal plates. Oxygenator consists of wounded hollow fibers as a mat, and the mat is wrapped around the heat exchanger directly. The hollow fiber is made of polymethylpenten, the outer diameter is 380 micron. The blood stream goes in radial direction from heat exchanger to capillary membrane to reduce the pressure drop. The surface area of capillary membrane is about 2 m2 and the priming volume of whole system is about 200 ml. This integrated oxygenator is expected to be applied as an extracorporeal membrane oxygenation with pulsatility especially in long term support or a percutaneous cardiopulmonary support system as well as one piece conventional extracorporeal circulation.

Advanced (electro) ceramics and innovative energy technologies

The principal drivers of the new direction of research in energy technologies can be exemplified in three major targets: security of supply, environmental pollution issues (with particular reference to the Kyoto protocol), and adherence to the new European legislation related to the deregulation of the energy market. All these drivers contribute to the introduction of new technologies that better fit the requirements of the new scenario in which all the actors in the energy field are working. In this view, the contribution of Advanced Ceramics to such a big effort, with the identification of some development routes needed in terms of new materials and technologies, is analysed. In particular, the possible future trends in Solid Oxide and High Temperature PEM fuel cells, as well as oxygen and hydrogen pumping for hydrogen production connected with R&D in Advanced Ceramics, are discussed.

On the deposition process of silicon suboxides by a RF magnetron reactive sputtering in Ar–O 2 mixtures: theoretical and experimental approach

Magnetron reactive sputtering of silicon oxides produced by Ar–O 2 RF capacitive plasmas has been studied from a theoretical and experimental point of view. In this way a plasma model has been developed, that allows to know the densities of all the species in the discharge, as well as the flow of ions. This model is coupled with a sputtering model, which relates the plasma properties to the deposition process. Therefore, the substrate stoichiometry, as well as the deposition rate, is obtained as a function of the model input parameters, i.e. the argon and oxygen flows, RF power and pumping speed. These results are compared with experimental data on the deposited layers. The stoichiometry of the SiO x layers was determined by Rutherford backscattering spectroscopy and X-ray photoelectron spectroscopy measurements. A good agreement between theoretical predictions and experimental data is found in several deposition conditions. A discussion about these results is carried out.

Effect of Electrochemical Polarization on the Emission of O − Ions from the Surface of YSZ

The effect of electrochemical oxygen pumping on the emission of oxygen negative ions, from the surface of yttria-stabilized zirconia (YSZ) was studied with a quadrupole mass spectrometer capable of detecting negative ions. It was found that ions are emitted into a vacuum from the YSZ surface with a porous platinum electrode. With a potentiostat, the voltage between an air electrode and the platinum electrode on the emission surface was varied during the emission of ions at 925°C: deviation from the rest potential ranged from −750 to +150 mV. Negative ion mass analysis demonstrated that electrochemical polarization affected the emission rate of ions. The effect of electrochemical polarization increased with the magnitude of the polarization. The emission of ions was enhanced with cathodic polarization, whereas it was reduced with anodic polarization. Although oxygen pumping by anodic polarization enhanced the mass flow of oxygen from air into the vacuum chamber, it did not enhance the emission of ions. The variation in the emission rate of ions is due to the variation in the work function of the emission surface by electrochemical polarization. © 2003 The Electrochemical Society. All rights reserved.

History of Extracorporeal Circulation: The Conceptional and Developmental Period

The development of modern techniques in extracorporeal circulation is the result of the combined efforts of physiologists, physicians, and engineers. Early experimental work at the end of the 19th century was accomplished by physiologists, such as von Schröder, von Frey, and Gruber, as well as Jacobj. These scientists laid the foundation for three different artificial oxygenation devices for experimental isolated animal organ perfusion. The developed bubble, film, and isolated lung oxygenation methods developed were later used for the first clinical cardiopulmonary bypass procedures in humans. For continuous perfusion experiments, closed circulation circuits were put into use. In a second step, during the first half of the 20th century, scientists and physicians, such as Brukhonenko, Gibbon, Crafoord, Björk, and Jongbloed were working on the refinement of these methods for intended application during cardiovascular operations in humans. Refined bubble and film oxygenators together with the modern blood pumps in closed circulatory systems were assembled as pump oxygenators, later called heart–lung machines. They were used in the first clinical cases of extracorporeal circulation for heart surgery in the second half of the 20th century by Dennis, Dogliotti and Constantini, and Gibbon.

Nonlinear responses of a rub-impact overhung rotor

For a rotor system with bearings and step-diameter shaft in the oxygen pump of an engine, the contact between the rotor and the case is considered, and the chaotic response and bifurcation are investigated. The system is divided into elements of elastic support, shaft and disk, and based on the transfer matrix method, the motion equation of the system is derived, and solved by Newmark integration method. It is found that hardening the support can delay the occurrence of chaos. When rubbing begins, the grazing bifurcation will cause periodic motion to become quasi-period. With variation of system parameters, such as rotating speed, imbalance and external damping, chaotic response can be observed, along with other complex dynamics such as period- doubling bifurcation and torus bifurcation in the response.

Pulsatile Mechanical Cardiac Assistance in Pediatric Patients with the Berlin Heart Ventricular Assist Device

Mechanical cardiac assistance for neonates, infants, children and adolescents may be accomplished with pulsatile ventricular assist devices (VAD) instead of extracorporeal membrane oxygenation or centrifugal pumps. The Berlin Heart VAD consists of extracorporeal, pneumatically driven blood pumps for pulsatile univentricular or biventricular assistance for patients of all age groups. The blood pumps are heparin-coated. The stationary driving unit (IKUS) has the required enhanced compressor performance for pediatric pump sizes. The Berlin Heart VAD was used in a total number of 424 patients from 1987 to November 2001 at our institution. In 45 pediatric patients aged 2 days–17 years the Berlin Heart VAD was applied for long-term support (1–111 days, mean 20 days). There were three patient groups: Group I: "Bridge to transplantation" with various forms of cardiomyopathy (N = 21) or chronic stages of congenital heart disease (N = 9); Group II: "Rescue" in intractable heart failure after corrective surgery for congenital disease (N = 7) or in early graft failure after heart transplantation (N = 1); and Group III: “Acute myocarditis” (N = 7) as either bridge to transplantation or bridge to recovery. Seventeen patients were transplanted after support periods of between 4 and 111 days with 12 long-term survivors, having now survived for up to 10 years. Five patients (Groups I and III) were weaned from the system with four long-term survivors. In Group II only one patient survived after successful transplantation. Prolonged circulatory support with the Berlin Heart VAD is an effective method for bridging until cardiac recovery or transplantation in the pediatric age group. Extubation, mobilization, and enteral nutrition are possible. For long-term use, the Berlin Heart VAD offers advantages over centrifugal pumps and ECMO in respect to patient mobility and safety.

Oxygen nonstoichiometry of Sr(Co,Fe)O 3− δ-based perovskites : I. Coulometric titration of SrCo 0.85Fe 0.10Cr 0.05O 3− δ by the two-electrode technique

The p(O 2)– T– δ diagram of perovskite-type SrCo 0.85Fe 0.10Cr 0.05O 3− δ was determined by the coulometric titration technique in the temperature range 770–1250 K at oxygen partial pressures from 8 10 −10 to 0.5 atm. Stability of the cubic perovskite phase of SrCo 0.85Fe 0.10Cr 0.05O 3− δ , existing down to the oxygen pressures of 10 −3–10 −5 atm, was found to be slightly higher than that of SrCo 0.80Fe 0.20O 3− δ , probably due to stabilization of oxygen octahedra neighboring Cr 4+ cations. When the oxygen nonstoichiometry of the Cr-containing perovskite decreases from 0.47 to 0.38, the partial molar enthalpy and entropy for overall oxygen incorporation reaction vary in the ranges −165 to −60 kJ mol −1 and 90 to 150 J mol −1 K −1, respectively. Within the stability limits of the single perovskite phase, the p(O 2)– T– δ diagram can be adequately described by equilibrium processes of oxygen incorporation, cobalt disproportionation and interaction of cobalt and iron cations, with the thermodynamic functions independent of defect concentrations. Increasing grain size in SrCo 0.85Fe 0.10Cr 0.05O 3− δ ceramics from submicron size to 100–200 μm has no effect on the oxygen thermodynamics. The two-electrode coulometric titration technique, based on the alternate use of electrodes for oxygen pumping and e.m.f. measurements, is described and verified by studying oxygen nonstoichiometry of La 0.3Sr 0.7CoO 3− δ and PrO x .