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At least 19 recordsLinked to original sources
PubMed1997

[Intrahepatic pressure, oxygen partial pressure and pain in chronic pancreatitis].

We investigated the relationship between pain, intraductal and parenchymal pancreatic pressures and oxygen partial pressure in 39 patients who underwent surgery for chronic pancreatitis with intractable pain. Acute pain was correlated with parenchymal pressure; correlation between pain and oxygen pressure could not be found. Since no strong correlation exists between pain and parenchymal pressure, we hypothesise that pressure and parenchymal factors contribute to the pathogenesis of pain in chronic pancreatitis.

Abdomen, Acute↗
PubMed1985

Responsiveness of cerebral vessels to changes of blood pressure and partial pressure of carbon dioxide after a transient period of cardiac arrest in dogs.

Post-ischemic cerebral hypoperfusion supposedly due to constriction of cerebral vessels is considered to be one of the most important factors limiting the recovery of the brain after cerebral ischemia. An experimental study on dogs was carried out to determine the changes in the responsiveness of cerebral vessel to the dilating effects of increase of arterial pressure (AP) and of CO2 inhalation after 3-6 min of cardiac arrest. Responsiveness was measured by the ratio of change in intracranial pressure (ICP) to change in AP (delta ICP/delta AP) and to change in PCO2 (delta ICP/delta PCO2), since in a bony cranium the changes in cerebral vessel diameter are reflected by instantaneous ICP change. delta ICP/delta AP following the administration of intravenous epinephrine was 33%, 43%, 36%, 37% and 16% of pre-ischemic value 1 h, 2 h, 3 h, 4 h and 5 h after cerebral ischemia, respectively. delta ICP/delta PCO2 following 10% CO2 inhalation was 13%, 32%, 55%, 50%, 70% and 75% of pre-ischemic value 1/2 h, 1 h, 2 h, 3 h, 4 h and 5 h after cerebral ischemia, respectively. Normal delta ICP/central venous pressure (delta CVP) was observed during the post-ischemic period, although statistical analysis was not done. From this we concluded: After 3-6 min of cardiac arrest, cerebral arteries constricted for more than 5 h during post-ischemic period. These arteries did not respond well to the dilating effects of increased arterial pressure or CO2 inhalation, but after 3 h their responses to CO2 inhalation returned to their pre-ischemic levels. The intracranial pressure became more or less dependent on CVP during post-ischemic period.

Animals↗
PubMed2001

Partial pressure of oxygen and partial pressure of carbon dioxide of perfluorocarbon liquid during partial liquid ventilation: their regional difference and their dependence on tidal volume and positive end-expiratory pressure level.

OBJECTIVE: To investigate the regional partial pressure of oxygen (PO2) and partial pressure of carbon dioxide (PCO2) of the perfluorocarbon liquid (PpfcO2, PpfcCO2) during partial liquid ventilation (PLV). DESIGN: Prospective, controlled study. SETTING: A research laboratory at a university medical center. SUBJECTS: Thirteen Japanese white rabbits. INTERVENTIONS: After the tracheostomy, PLV was started with perflubron (15 ml/kg) following saline lung lavage. Fractional inspired oxygen (FIO2) was 1.0, respiratory rate was 30 bpm and tidal volume (VT) was 30 ml. Two epidural catheters (18 gauge) were inserted from the rubber diaphragm interposed in the respiratory circuit to sample perflubron. One catheter was inserted into the left lower lobe bronchus and placed at 5-6 cm distal from the carina (DISTAL). The other one was inserted at the tip of the endotracheal tube (PROXIMAL). Then the effect of the larger VT (50 ml) or positive end-expiratory pressure (PEEP; 10 cmH2O) to the gas tension in perflubron was examined. MEASUREMENTS AND MAIN RESULTS: (1) In the lower VT (30 ml) with 0 cmH20 PEEP, DISTAL PpfcO2 was significantly lower than PROXIMAL PpfcO2 (265 72 vs 386 +/- 47 mmHg, p < 0.0001), and DISTAL PpfcCO2 was significantly higher than PROXIMAL PpfcCO2 (51.1 +/- 14.4 vs 42.4 +/- 11.8 mmHg (p = 0.0007)), (2) the higher VT setting increased PpfcO2 (p = 0.0001) and decreased PpfcCO2 (p < 0.0001), although the gas tension gradient was significant, (3) 10 cmH2O PEEP increased PpfcO2 (p = 0.0004) and decreased PpfcCO2 (p = 0.0089) in the DISTAL sample. CONCLUSION: There was a difference in gas tension in perflubron between the central airway and the peripheral dependent lung region, and gas tension in perflubron was affected by the VT and the PEEP level.

Analysis of Variance↗
PubMed1991

Is the end-tidal partial pressure of isoflurane a good predictor of its arterial partial pressure?

End-tidal partial pressure of isoflurane (PE'iso) may be used as a measure of anaesthetic depth. During uptake, an arterial partial pressure (Paiso) which is considerably less than PE'iso (Paiso/PE'iso much less than 1) leads to underestimation of depth of anaesthesia and, during elimination, PE'iso/Paiso much less than 1 will lead to an overestimation of anaesthetic depth. We measured Paiso/PE'iso during a 60-min uptake period of 1% isoflurane and PE'iso/Paiso during the subsequent 60-min elimination period in 26 patients (age 13-88 yr, ASA I-III) undergoing various surgical procedures. After 15 min of isoflurane uptake, Paiso/PE'iso of 26 patients was mean 0.78 (SD 0.10) and this increased only marginally at 60 min (0.79 (0.09)), whereas during elimination, PE'iso/Paiso was in the range 0.79 (0.14)-0.83 (0.11). Predictability of Paiso in a given patient is hindered by the high SD of Paiso/PE'iso and PE'iso/Paiso, but it may be improved by taking into account age, ASA physical status category, vital capacity, inspired minus end-tidal isoflurane partial pressure and arterial minus end-tidal carbon dioxide partial pressure during uptake; and obesity, end-tidal isoflurane partial pressure and arterial minus end-tidal carbon dioxide partial pressure during elimination. However, even with multiple regression analysis (to account for the various possible variables), clinically useful prediction of Paiso/PE'iso and PE'iso/Paiso in a particular patient is not possible (residual SD 0.084 and 0.113, respectively).

Adolescent↗
PubMed2000

The effects of changing middle ear pressure and gas partial pressure on mucosal blood flow and vascular permeability in the chinchilla.

OBJECTIVE: To determine if middle ear (ME) gas composition and/or total pressure regulates local mucosal blood flow (MBF) and vascular permeability. The hypotheses tested are: (1) relatively high local CO2 tensions and/or low O2 tensions increase the ME MBF and vascular permeability; and (2) sub-atmospheric total ME pressure provokes similar effects. METHODS: The responses of ME MBF and vascular permeability parameters were measured during 60 min exposures of chinchilla MEs to one of two test gas mixtures (16.3% O2, 5.1% CO2, balance N2, or 5.3% O2, 15.6% CO2, balance N2) applied at different levels of underpressure (ref. ambient). In the first set of experiments (n = 19), mucosal perfusion parameters were recorded using a Laser Doppler Flowmeter for 60 min before and 60 min after exposure to the experimental conditions. In the second set of experiments (n = 19 chinchillas, 38 ears), the MEs were exposed to the gas mixtures and then maintained for 60 min at ambient pressure or at negative pressures of -200, -400, -600 mmH2O. Fifty minutes into the experiment, the animals were injected intravenously with 60 mg/kg of horseradish peroxidase (HRP). The animals were killed and existing effusion was aspirated, its volume recorded and then analyzed for total protein. From surface preparations of the ME mucosa, vascular leakage sites were measured as percent total surface area using an image analysis program with the threshold window set to discriminate HRP stain. RESULTS: Throughout the 120 min in the first set of experiments, the measured MBF parameters decreased in all exposure groups. Comparisons among groups for the absolute magnitude of the change from baseline showed that high local CO2 partial pressures decreased MBF and ME underpressures increased MBF, but the effects did not achieve statistical significance. The results of the second set of experiments demonstrated no effect of gas composition on any of the measured parameters of vascular permeability. All measures of permeability were linearly related to the magnitude of the underpressure. CONCLUSION: These data support a role for total ME pressure, but not CO2 partial pressure in regulating ME MBF and vascular permeability.

Animals↗
PubMed1990

Growth and product formation of actinomycetes cultivated at increased total pressure and oxygen partial pressure.

Influence of pressure (P) and oxygen partial pressure (PO2) on cultivation of various Streptomyces spp. and Micromonospora purpurea was examined in pressurized air-lift and stirred tank fermenters. The maximum PO2 was 2100 mbar. Growth and product formation of all cultures tested were markedly influenced by PO2 higher than 1000 mbar. There is evidence that wild strains are more oxygen tolerant than production strains. At a certain PO2 the metabolic activities of all cultures were inhibited. However, results obtained with S. aureofaciens and S. rimosus indicated an increase in specific product formation rate at elevated pressure. With increase in oxygen tension incorporation of oxygen into tetracycline molecules was enhanced. Since elevated oxygen tension can either show inhibiting effects or may be used for regulation of product formation and selectivity, the influence of PO2 should be determined in an appropriate experimental set-up for each process.

Aerobiosis↗
PubMed1995

Lack of general correlation between interstitial fluid pressure and oxygen partial pressure in solid tumors.

Several studies have shown a decrease in blood perfusion and oxygen partial pressure (pO2), and an increase in interstitial fluid pressure (IFP) with increasing tumor size. However, it is not evident if the elevated IFP is a key parameter responsible for the poor perfusion and oxygenation of solid tumors. To this end, IFP and pO2 were measured in nine human tumor xenografts in immunodeficient mice at a fixed tumor size (approximately 250 mm3). IFP and pO2 were also measured as a function of tumor volume in one human colon adenocarcinoma (LS174T) and in one human glioblastoma (HGL-9). In LS174T tumors IFP did not vary with size (P < .07); however, median pO2 decreased from approximately 35 mm Hg in 100-mm3 tumors to approximately 15 mm Hg in tumors of approximately 500 mm3 (P < 0.001). In HGL-9 tumors an inverse correlation between IFP and pO2 was found; IFP increased (P < 0.001) and pO2 decreased (P < 0.001) with increasing tumor size. At a fixed tumor size of 250 mm3 no correlation was found between mean IFP and median pO2 (P < 0.5) or between the mean IFP and the hypoxic fraction (pO2 < 2.5 mm Hg) (P < 0.7) in the nine tumors studied. The absence of a general relationship between IFP and pO2 could result in part from differences in vascular resistance between tumors. For example, a high geometric resistance to blood flow on the arterial side will lead to a low IFP and blood flow, whereas an elevation of the venous resistance will reduce blood flow and increase IFP.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Postmortem evaluation of rabbit aqueous humor partial pressure of carbon dioxide, total carbon dioxide, bicarbonate, partial pressure of oxygen and ionized calcium levels.

The aqueous humors of 100 freshly enucleated rabbit eyes were assessed within 10 min postmortem by taking samples in the last stage of corneal dissection following the Dikstein-Maurice procedure. Aqueous levels of partial pressure of carbon dioxide (pCO2) averaged 58.2 +/- 8.5 mm Hg to give calculated tCO2 and bicarbonate levels of 34.9 +/- 2.2 mEq/l and 30.0 +/- 3.4 mM/l, respectively. The pH and ionized Ca2+ levels averaged 7.39 and 1.50 mM while partial pressure of oxygen (pO2) values were variable (31.5 +/- 23.6 mm Hg). The pH showed an inverse correlation to pCO2 values, and Ca2+ increased as pCO2 increased. O2 levels tended to decrease as CO2 increased. The results suggest that significant hypercapnia and hypoxia of the eye fluids can occur even within 10 min postmortem for an enucleated globe at room temperature.

Animals↗
PubMed2006

Use of end-tidal partial pressure of carbon dioxide to predict arterial partial pressure of carbon dioxide in harp seals during isoflurane-induced anesthesia.

OBJECTIVE: To evaluate the relationship between end-tidal partial pressure of CO(2) (ETCO(2)) and PaCO(2) in isoflurane-anesthetized harp seals. ANIMALS: Three 5-month-old 25- to 47-kg harp seals (Phoca groenlandica). PROCEDURES: PaCO(2) was determined in serial arterial samples from isoflurane-anesthetized seals and compared with concomitant ETCO(2) measured with a side-stream microstream capnograph. Twenty-four paired samples were subjected to linear regression analysis and the Bland-Altman method for assessment of clinical suitability of the 2 methods (ie, PaCO(2) and ETCO(2) determinations). The influence of ventilation rate per minute (VR) on the ETCO(2) to PaCO(2) difference (P[ET-a] CO(2)) was examined graphically. RESULTS: The correlation coefficient between the 2 measurements was 0.94. The level of agreement between ETCO(2) and PaCO(2) varied considerably. Values of ETCO(2) obtained with a VR of < 5 underestimated PaCO(2) to a greater degree (mean bias, -4.01 mm Hg) and had wider limits of agreement of -13.10 to 5.07 mm Hg (-4.01 mm Hg +/- 1.96 SD), compared with a VR of > or = 5 (mean bias, -2.24 mm Hg; limits of agreement, -7.79 to 3.30 mm Hg). CONCLUSIONS AND CLINICAL RELEVANCE: These results indicate that a microstream sidestream capnograph provides a noninvasive, sufficiently accurate estimation of PaCO(2) with intermittent positive ventilation at a VR > or = 5 in anesthetized harp seals.

Anesthetics, Inhalation↗
PubMed1980

The independent effects of atmospheric pressure and oxygen partial pressure on gas exchange of the chicken embryo.

CO2 production and air cell PCO2 were continuously measured during late development in the chicken egg while acutely exposed from one to three hours to various O2 concentrations ranging from 11 to 39%. A small but significant increase in metabolism, ca. 8%, was found when O2 concentration was above normal values, while a reduction to 70% was observed when O2 concentrations were below normal, and fell to 50% when maintained for three hours. These values were also compared with metabolic rates reported by Lokhorst and Romijn (1965, 1967)) who incubated eggs continuously at reduced O2 concentrations as well as under reduced barometric pressure, and showed that at the same ambient PO2 the metabolism was significantly higher in the eggs at reduced barometric pressure. We attribute this difference to the increased diffusion coefficient of O2 which is inversely related to the barometric pressure. It illustrates that the ambient partial pressure of O2 and ambient atmospheric pressure exert an independent effect upon gas exchange of the avian embryo.

Animals↗
PubMed1980

End-tidal partial pressure of CO2 as an estimate of arterial partial pressure of CO2 during various ventilatory regimens in halothane-anesthetized dogs.

The correlation between end-tidal partial pressure of CO2 (PETCO2) and arterial PCO2 (PaCO2) was studied in six halothane-anesthetized dogs maintained under four different ventilatory regimens: (A) spontaneous breathing; (B) assisted positive-pressure ventilation; (C) intermittent manual inflation; and (D) ventilator-controlled breathing. For procedures A, B, and D together, there was a strong correlation between PETCO2 and PaCO2 (r = 0.8) that was highly significant at P less than 0.0001 for PETCO2 values between 31.3 and 61 mm of Hg. In spontaneous and controlled breathing, PETCO2 is representative of PaCO2 and provides a useful noninvasive tool for monitoring the patient maintained under general anesthesia. Furthermore, data suggest that any ventilatory support of the anesthetized patient markedly improves blood gas and acid-base status compared with that of the unsupported, spontaneously breathing animal.

Anesthesia, Inhalation↗
PubMed2000

[Redifferentiation of dedifferentiated joint cartilage cells in alginate culture. Effect of intermittent hydrostatic pressure and low oxygen partial pressure].

One of the goals in the field of tissue engineering is the development of artificial cartilage for the treatment of cartilage defects. Therefore autologous chondrocytes are seeded on different artificial matrices to test their possible use as implants (resorption, antigenicity, toxicity and their integration in the tissue). One of the main problems in these experiments is that usually the amount of available chondrocytes is too low for treating large-scale defects or for comparing different matrices. An in-vitro-multiplication of the cells is needed which causes the chondrocytes to dedifferentiate and become fibroblast-like. Therefore parameters which induce a redifferentiation are of great interest. The objective of this study was to determine the influence of intermittent hydrostatic pressure and low oxygen partial pressure on the redifferentiation of dedifferentiated bovine articular chondrocytes in monolayer and three-dimensional alginate bead culture. The redifferentiation process was monitored by immunocytochemical detection of newly synthesized collagen type II. The viability of the cells was determined by the trypanblue exclusion test. The chondrocytes were dedifferentiated by a two week culture in plastic flasks with an oxygen level of 20%. After this they were subcultured in monolayer or three-dimensional alginate culture and subjected to three different stimuli for three weeks in order to redifferentiate: 1.) 20% O2 (= 20.26 kPa PO2) + 5% CO2 + 75% N2; 2.) 5% O2 (= 5.07 kPa PO2) + 5% CO2 + 90% N2; 3.) 5% O2 (= 5.07 kPa PO2) + 5% CO2 + 90% N2 + 8 h/d of intermittent hydrostatic pressure (frequency: 3 bar absolute for 30 min and 1 bar absolute for 2 min). In the monolayer there was no detectable collagen type II found by immunocytochemistry under either of the three culture conditions. Therefore a redifferentiation of dedifferentiated chondrocytes was not possible in monolayer cultures with the tested parameters. In the three-dimensional alginate culture there was no immunocytochemical staining of collagen type II found in the beads cultured with 20% oxygen. With 5% oxygen we found a strong collagen type II-production by chondrocytes throughout the whole bead. The intermittent hydrostatic pressure combined with 5% oxygen lead to a decreased collagen type II-production compared to cells subjected to 5% oxygen only. Also chondrocytes closer to the edge of these beads were more often immunopositive and seemed to produce more immunoreactive collagen type II. The viability of the chondrocytes in the alginate culture was close to 90% after three weeks. Our experiments showed that oxygen partial pressure is an important parameter in the cultivation of articular chondrocytes. Reduced partial oxygen pressure promoted or induced the redifferentiation of dedifferentiated chondrocytes in alginate culture.

Alginates↗
PubMed1990

Effects of Partial O(2) Pressure, Partial CO(2) Pressure, and Agitation on Growth Kinetics of Azospirillum lipoferum under Fermentor Conditions.

Azospirillum lipoferum crt1 was grown in batch cultures under standard conditions at 85% saturation of dissolved oxygen (DO) and 30-g/liter glucose concentrations. Kinetic studies revealed nutritional limitations of growth and the presence of an initial lag phase prior to consumption of glucose. The influences of various gaseous environments and shear stress on growth, i.e., various conditions of agitation-aeration, were characterized. Faster growth in the first stages of the culture and shorter duration of the lag phase were observed at DO concentrations of <30% saturation. The possible influences of dissolved CO(2) concentration or shear stress or both were discounted, and we confirmed the detrimental effect of high DO levels (up to 80% saturation) and the favorable influence of low DO concentrations (lower than 30% saturation) on growth. It was concluded that the gaseous environment, i.e., the DO concentration, needs to be considered as an operating parameter and be accurately controlled to ensure optimal growth of Azospirillum cells.

Journal Article↗