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PubMed1987

[Transcutaneous measures of oxygen partial pressure and capillaroscopic parameters as affected by naftidrofuryl in patients with obliterative arteriopathies, Fontaine stages II-IV].

Transcutaneous partial oxygen pressure on dorsum of foot was determined and capillaroscopy of big toes performed before and after infusions of naftidrofuryl (200 mg/l/h) and of 5% levulose to 30 patients with obliterative arterial disease of lower limbs, stages II to IV (10 patients in each stage). Naftidrofuryl provoked an increase in cutaneous partial oxygen pressure of 26.8 to 36.4 mm Hg (p less than 0.001) whereas no significant change was noted after 5% levulose. In addition, density of visible capillaries increased from 23.5 to 26.1/mm2 with naftidrofuryl. Severe stages of ischemia, evaluated as described by Fagrell, were improved by naftidrofuryl treatment. These findings suggest a favorable action of naftidrofuryl on cutaneous microcirculation distal to arterial obliteration at all Fontaine's stages.

Aged↗
PubMed1989

[Intra- and postoperative effect of various plasma substitutes on blood rheology and conjunctival oxygen partial pressure in microsurgical intervertebral disk operations].

In a prospective, randomized, controlled, parallel group study the effect of different infusion solutions (HES 200/0.5 10%, dextran 40 10% and electrolyte solution) during and after intervertebral disc microsurgery on blood fluidity and conjunctival partial oxygen pressure was measured. At the beginning of the operation all patients showed a reduction in conjunctival oxygen pressure - independent of the infusion solution. Both fluidity of blood and oxygen partial pressure changed according to the plasma substitute used. Thus after the administration of medium molecular weight hydroxyethyl starch an improvement in the fluidity of blood with a consecutive significant increase in the conjunctival oxygen pressure could be observed, whereas there was no increase after the administration of electrolyte solution and only a slight one (according to tendency) after infusion of dextran.

Adult↗
PubMed1993

Effect of epinephrine on local partial pressure of oxygen in the ciliary processes.

Local pO2 was measured close to the ciliary process of the rabbit eye using polarographic microelectrodes under microendoscopic observation. The experiments were performed in 5 anaesthetized New Zealand rabbits. Changes in local pO2, intraocular pressure (IOP) and blood flow velocity (BFV) were investigated after intra-arterial and topical application of epinephrine. After intra-arterial epinephrine, a simultaneous decrease in BFV, IOP and local pO2 was found. pO2 decrease was more pronounced in the anterior part of the ciliary processes than in the posterior part. Topical epinephrine lead to similar changes of all parameters mentioned above, the time constants being 10-20 times longer. In these topical experiments, no recovery of local pO2 was found over a period of at least 30 min despite an increase in BFV. Our results indicate that in the hyperemic phase after epinephrine the activity of the ciliary epithelium (and probably the total aqueous formation) is higher than normal. Thus, the decrease in IOP in this phase must be due to an increased outflow facility.

Administration, Topical↗
PubMed1998

Latency of oxygen toxicity of the central nervous system in rats as a function of carbon dioxide production and partial pressure of oxygen.

Oxygen toxicity of the central nervous system (CNS) can occur as convulsions and loss of consciousness, with no warning symptoms. A quantitative study of the effect of metabolic rate on sensitivity to oxygen toxicity was made in the rat. A group of 19 rats were exposed (126 exposures) to 12 combinations of four pressures (456, 507, 608 and 709 kPa) and three ambient temperatures (15, 23 and 29 degrees C) until the appearance of the first electrical discharge (FED) preceding clinical convulsions. Carbon dioxide production (VCO2) was also measured. A thermoneutral zone (mean VCO2 0.87 ml x g(-1) x h(-1)) existed between the temperatures of 24 and 29 degrees C; at temperatures lower than this, the metabolic rate increased by 1.2 to 4 times the resting level. Latency of FED decreased linearly with the increase in VCO2 at all four oxygen pressures. The slopes (absolute value) and intercepts decreased with the increase in oxygen pressure. This linear relationship made possible the derivation of an equation which described latency of the FED as a function of both oxygen pressure and metabolic rate. Various environmental and other physiological factors that have been said to influence sensitivity to CNS oxygen toxicity, enhancing the effect of the partial pressure of oxygen, can be explained by their effect on metabolic rate. It is suggested that in situations where there is a risk of oxygen toxicity of the CNS, that risk would be reduced by a lower metabolic rate.

Animals↗
PubMed1991

[Increase in skin blood circulation and transcutaneous oxygen partial pressure of the top of the foot in lower leg immersion in water containing carbon dioxide in patients with arterial occlusive disease. Results of a controlled study compared with fresh water].

Semi-quantitative Doppler laser flowmetry and measurement of transcutaneous oxygen partial pressure (TCPO2 in mmHg) are reliable, non-invasive methods of continuous measurement suitable for underwater use. We measured the effect of aqueous CO2 (succinate + sodium bicarbonate = Kao Bub; 1400 mg CO2 per kg water) compared with fresh water (both at 34 degrees C, depth of leg immersion 35 cm, immersion time 20 min) on circulation and TCPO2 in the feet of 15 patients with bilateral stage-II occlusion of the Aa. fem. superf. intraindividually in a randomised, crossover trial. Measurements were made at the same time of day on two consecutive days. No change in either cutaneous microcirculation or TCPO2 was observed during immersion in fresh water. During immersion in a CO2 bath both culaneous blood flow (as expressed by Doppler laser flux) and the amplitude of the Doppler laser vasomotion flux increased more than threefold (p less than 0.001, Wilcoxon), while sitting TCPO2 increased by over 10% (from 63 to 71 mmHg; p less than 0.001). The observed changes in oxygen dissociation and cutaneous microcirculation may help to provide an explanation for the well-known therapeutic effect of CO2 baths in all stages of occlusive arterial disease.

Adult↗
PubMed2006

Influence of Ca content and oxygen partial pressure on microstructural evolution of (Co,Ca)O at elevated temperatures.

Ca-doped (1, 1.7, 5 and 10 mol% CaO) cobalt oxide single-crystal samples, with an [001] orientation, were annealed at elevated temperatures of 1000-1200 degrees C for different times and at different oxygen partial pressures. The microstructure was examined by means of transmission light and electron microscopy. High-temperature X-ray diffractometry was used, with the aim of determining the temperature of the CoO <--> Co(3)O(4) transition in these materials. Extensive precipitation of Ca-free Co(3)O(4) spinel crystals was observed with increasing Ca content and oxygen activity. It is suggested that the electrical conductivity changes in this material may be related to this precipitation, because it changes the electronic state of cobalt cations.

Journal Article↗
PubMedDate not supplied

[Effect of low molecular dextran on maternal microrheologic parameters, fetal heart rate and transcutaneous fetal oxygen partial pressure in labor].

The results from animal experimental research have shown that the infusion of dextran 40 increased the uterine blood flow mainly by decreasing the vascular resistance and by this improving the oxygen supply to the fetus. Dextran 40 given in a dosage of 50 ml/min within 10 minutes to 11 pregnant women during parturition showed that the fetal blood PO2 increased if the PO2 before infusion was low and decreased if the PO2 before infusion was high. Therefore the question enhanced if the reduced maternal oxygen capacity results in a reduction of fetal PO2 (tcPo2) too. After informed consent 10 healthy pregnant women at term with a normal pregnancy got an infusion of 500 ml dextran 40 during 30 minutes. The following maternal parameters were measured: heart rate, mean arterial blood pressure, intrauterine pressure and transcutaneous carbon dioxide tension (tcPCO2). Maternal microrheological parameters before and after infusion of dextran 40 were estimated as following: plasma viscosity, erythrocyte aggregation, serum osmolality, colloid osmotic pressure, hemoglobin and haematocrit. The mothers were laying in the side position and their ventilation was controlled by tcPco2 (Dräger, Lübeck). The following fetal parameters were registered: basal fetal heart rate, transcutaneous fetal oxygen partial pressure (tcPo2) and the umbilical cord blood gases. After rupture of the fetal membranes and at a cervix dilatation of about 5-7 cm a tcPo2 electrode (Dräger, Lübeck) was fixed at the fetal scalp with an acrylate glue (Histoacryl) and by this fetal tcPo2 and its "flow" registered.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed2001

Measurements of resistance by the interrupter technique and of transcutaneous partial pressure of oxygen in young children during methacholine challenge.

Measurement of bronchial airway responsiveness requires noninvasive techniques in young children. The study was designed to examine the changes in resistance as measured using the interrupter technique (Rint) at the dose of methacholine (M) that induced a fall in transcutaneous partial pressure in O2 (P(tc)O2) > or = 20% (PD(20)P(tc)O2) in young children. Rint was calculated using the linear back-extrapolation method (Rint(L)) and the end-interrupter method (Rint(EI)). Twenty-two children (mean age, 5.2 +/- 1.1 years; range, 3.4 - 7.1 years) with nonspecific respiratory symptoms (mainly chronic cough, n = 17) were tested. P(tc)O2, Rint(L), and Rint(EI) were measured before the test, after saline challenge (baseline (B)), after each dose of M delivered by a dosimeter, and after bronchodilator (BD) inhalation. P(tc)O2 decreased significantly during M challenge, from 85 +/- 6 mmHg (B) to 62 +/- 9 mmHg (P < 0.05), and increased after BD inhalation, to 82 +/- 8 mmHg. Rint(L) and Rint(EI) increased significantly during M challenge, from 0.94 +/- 0.2 KPa/L/s and 1.11 +/- 0.19 KPa/L/s (B) to 1.27 +/- 0.35 KPa/L/s and 1.47 +/- 0.37 KPa/L/s, respectively (P < 0.05), and decreased after BD inhalation to 0.80 +/- 0.17 KPa/L/s and 0.95 +/- 0.18 KPa/L/s, respectively. Nineteen of 22 children reached the PD(20)P(tc)O2 at a dose of M ranging from 50-400 microg. At the PD(20)P(tc)O2, significant changes in Rint(L) and Rint(EI) (sensitivity index (SI) > or = 2) were found in 79% and 63% of children, respectively. We conclude that: 1) M challenge using P(tc)O2 is safe in young children; and 2) our findings are not in favor of the use of Rint as the only indicator of bronchial reaction in young children during M challenge.

Airway Resistance↗
PubMed1980

[The influence of arterial partial pressure of CO2 and of the arterial value of pH on the oxygen consumption of the whole body during extracorporal circulation (author's transl)].

134 patients with coronary heart disease, with defects of the cardiac values or with inborn heart diseases were studied referring to the influences of the arterial partial pressure of CO2 and the arterial value of pH on oxygen consumption of the whole body during total hypothermic extracorporal circulation. Oxygen consumption of the whole body increases during respiratory or metabolic alkalosis whereas respiratory or metabolic acidosis decreases oxygen consumption significantly. These typical changes of oxygen consumption of the whole body during extraorporal circulation due to alkalosis or acidosis may be explained by different facts. Within the cellular area glycolysis is in relation of value for pH, and phosphofructokinase-reaction slows up due to ATP-level also in relationship of value for pH. In addition to cellular parameters hemodynamic parameters may explain the changes of oxygen consumption due to alkalosis and acidosis. Alkalosis effects a decrease of the total peripheral resistane whereas acidosis effects an increase of the total peripheral resistance. Peripheral oxygen consumption vaires in addition to other parameters in inverse proportion of the level of totalperipheral resistance.

Acid-Base Equilibrium↗
PubMed1978

Intracerebral gas partial pressure changes under vasoactive drugs. A mass spectrometry study.

An original technique based on mass spectrometry has been used to measure simultaneously in undrugged, freely-breathing animals local PO2 and PCO2 in the brain (caudate nucleus) and arterial PO2 and PCO2 in the aorta. Injection of vasoactive drugs brought about significant modifications of the partial pressures of the physiological gases in the brain. The origin of these variations was discussed, based on the combination of 3 possible factors: cerebral vascular changes, systemic metabolic changes (PaO2 and PaCO2) and local metabolic changes. It was demonstrated that local variations of PCO2 cannot be held to be responsible for the modifications of cerebral blood flow induced by papaverine or the sympathomimetic drugs.

Animals↗
PubMed2004

Variations in dark respiration and mitochondrial numbers within needles of Pinus radiata grown in ambient or elevated CO2 partial pressure.

Within-leaf variations in cell size, mitochondrial numbers and dark respiration rates were compared in the most recently expanded tip, the mid-section and base of needles of Pinus radiata D. Don trees grown for 4 years in open-top chambers at ambient (36 Pa) or elevated (65 Pa) carbon dioxide partial pressure (p(CO2)a). Mitochondrial numbers and respiratory activity varied along the length of the needle, with the highest number of mitochondria per unit cytoplasm and the highest rate of respiration per unit leaf area at the base of the needle. Regardless of the location of the cells (tip, middle or basal sections), needles collected from trees grown in elevated p(CO2)a had nearly twice the number of mitochondria per unit cytoplasm as those grown in ambient p(CO2)a. This stimulation of mitochondrial density by growth at elevated p(CO2)a was greater at the tip of the needle (2.7 times more mitochondria than in needles grown in ambient CO2) than at the base of the needle (1.7 times). The mean size of individual mitochondria was unaffected either by growth at elevated p(CO2)a or by position along the needle. Tree growth at elevated p(CO2)a had a variable effect on respiration per unit leaf area, significantly increasing respiration in the tip of the needles (+25%) and decreasing respiration at the mid-section and base of the needles (-14% and -25%, respectively). Although a simple relationship between respiration per unit leaf area and mitochondrial number per unit cytoplasm was found within each CO2 treatment, the variable effect of growth at elevated p(CO2)a on respiration along the length of the needles indicates that a more complex relationship must determine the association between structure and function in these needles.

Carbon Dioxide↗
PubMed1982

Recovery from central apnea: effect of stimulus duration and end-tidal CO2 partial pressure.

The present study was designed to investigate the effect of stimulus duration and chemosensory input on the recovery of central respiratory activity from apnea induced by superior laryngeal nerve (SLN) electrical stimulation. Newborn piglets less than 8 days of age were anesthetized, paralyzed, and mechanically ventilated at differing levels of end-tidal CO2 partial pressure (PCO2). The vagi were cut bilaterally in the neck. Integrated phrenic nerve activity was used as the index of respiratory activity. SLN stimulation caused apnea that persisted after stimulus cessation. The length of apnea following stimulus cessation was directly related to stimulus duration and inversely related to end-tidal PCO2. After apnea, respiratory activity returned gradually to the initial control level. The recovery pattern was well described by a linear regression function using the natural logarithm of time as the independent variable. Prolonging stimulus duration progressively inhibited the amount of initial respiratory activity following apnea. On the other hand, the rate of respiratory recovery was independent of stimulus duration and, except at low end-tidal PCO2 following long (30 s) stimuli, was independent of the end-tidal PCO2 level. These results demonstrate that a long-acting central mechanism regulates recovery from apnea induced by SLN stimulation.

Animals↗
PubMed1996

[Tissue oxygen partial pressure in human head-neck carcinomas during primary radio-chemotherapy].

BACKGROUND: Experimental data have shown that hypoxic areas in tumors can increase their malignant potential and reduce their sensitivity to chemotherapy and radiation treatment. Until now, the only incomplete data on the oxygenation of human tumors during therapy have been available. METHODS: The distribution of partial pressure of oxygen in malignant head and neck processes was measured in four patients with lymph-node metastases by means of invasive computerized histography (system manufactured by Eppendorf). All patients received primary radiation treatment and chemotherapy with a two-week respite after 30 Gy and the first cycle of chemotherapy. The total dose consisted of 70 Gy in the tumor and two cycles of chemotherapy. Oxygen measurements were taken before the onset of treatment, before and after the respite, and after completion of treatment. RESULTS: In three of the four patients, we measured prominent hypoxic areas in the cancers with PO2 values less than 5 mmHg. The average value was between 12 and 46 mmHg. We were impressed by the observation that oxygenation appeared to improve in every cancer during the respite. Only the patient who showed good initial oxygenation without any measurable hypoxic fraction suffered a complete recurrence six weeks after the completion of therapy. CONCLUSIONS: Prominent areas of hypoxic tissue are present in human head and neck cancers. Radiation treatment and chemotherapy can alter the oxygenation. Further studies are required to investigate the significance of the oxygenation of human head and neck cancers and the changes occurring in it during different types of therapy in order to assess its clinical impact.

Adult↗
PubMed2000

[Rapid measurement of water vapor partial pressure at the saturation point with a new hybrid humidity sensor].

A new hybrid humidity sensor comprising a conventional capacitance humidity sensor and a planar heating element is described. Owing to its short response time of only a few milliseconds, its great measuring accuracy, large measuring range, and simplicity in handling, the sensor is suitable for measuring water vapour partial pressure in gases with rapidly changing flow and direction, e.g. in ventilated patients in the fields of anaesthesia and intensive care medicine. The small dimensions permit measurements at almost any location within the ventilation system.

Anesthesia↗
PubMed2005

Measurement of cerebrospinal fluid oxygen partial pressure in humans using MRI.

Fluid-attenuated inversion recovery (FLAIR) images obtained during the administration of supplemental oxygen demonstrate a hyperintense signal within the cerebrospinal fluid (CSF) that is likely caused by T1 changes induced by paramagnetic molecular oxygen. Previous studies demonstrated a linear relationship between the longitudinal relaxation rate (R1 = 1/T1) and oxygen content, which permits quantification of the CSF oxygen partial pressure (P(csf)O2). In the current study, CSF T1 was measured at 1.5 T in the lateral ventricles, third ventricle, cortical sulci, and basilar cisterns of eight normal subjects breathing room air or 100% oxygen. Phantom studies performed with artificial CSF enabled absolute P(csf)O2 quantitation. Regional P(csf)O2 differences on room air were observed, from 65 +/- 27 mmHg in the basilar cisterns to 130 +/- 49 mmHg in the third ventricle. During 100% oxygen, P(csf)O2 increases of 155 +/- 45 and 124 +/- 34 mmHg were measured in the basilar cisterns and cortical sulci, respectively, with no change observed in the lateral or third ventricles. P(csf)O2 measurements in humans breathing room air or 100% oxygen using a T1 method are comparable to results from invasive human and animal studies. Similar approaches could be applied to noninvasively monitor oxygenation in many acellular, low-protein body fluids.

Adult↗
PubMed2005

Mycorrhizas improve nitrogen nutrition of Trifolium repens after 8 yr of selection under elevated atmospheric CO2 partial pressure.

Altered environmental conditions may change populations of arbuscular mycorrhizal fungi and thereby affect mycorrhizal functioning. We investigated whether 8 yr of free-air CO2 enrichment has selected fungi that differently influence the nutrition and growth of host plants. In a controlled pot experiment, two sets of seven randomly picked single spore isolates, originating from field plots of elevated (60 Pa) or ambient CO2 partial pressure (pCO2), were inoculated on nodulated Trifolium repens (white clover) plants. Fungal isolates belonged to the Glomus claroideum or Glomus intraradices species complex, and host plants were clonal micropropagates derived from nine genets. Total nitrogen (N) concentration was increased in leaves of plants inoculated with fungal isolates from elevated-pCO2 plots. These isolates took up nearly twice as much N from the soil as isolates from ambient-pCO2 plots and showed much greater stimulation of biological N2 fixation. The morpho-species identity of isolates had a more pronounced effect on N2 fixation and on root length colonized than isolate identity. We conclude that rising atmospheric pCO2 may select for fungal strains that will help their host plants to meet increased N demands.

Atmosphere↗