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PubMed1992

[Development of continuous monitoring of spontaneous respiration in the postoperative phase. 2. Cutaneous oxygen and carbon dioxide partial pressures following i.v. bolus application of fentanyl, buprenorphine, naloxone and amiphenazole in healthy adult subjects].

METHODS: In an attempt to develop a noninvasive monitoring technique for patients in the early postoperative period, cutaneous O2 and CO2 pressures (pctO2, pctCO2) were monitored in ten healthy adult volunteers of both sexes (5 male, 5 female, age 29 +/- 5 years, weight 68 +/- 11 kg) who received, in several sessions after a 60-min equilibration period, i.v. bolus doses of fentanyl (3 micrograms/kg and, 60 min later, another 1.5 micrograms/kg), buprenorphine (3 and 1.5 micrograms/kg), naloxone (1.8 and 0.9 micrograms/kg), and the respiratory analeptic amiphenazole (2 and 1 mg/kg) as well as combinations of fentanyl/amiphenazole or buprenorphine/naloxone in the aforementioned dosages. Data were collected and stored by a personal computer using the TCM3 system with a combination electrode for simultaneous measuring of pctO2 and pctCO2 (TINA, Radiometer) at 30-s intervals. The overall observation period was 240 min. Means, standard deviations, and ranges were calculated for individual data and data pooled for 15-min intervals. Groups were compared by means of Student's t-test and analysis of variance. RESULTS: Following i.v. fentanyl 3 micrograms/kg, pctO2 decreased and pctCO2 increased rapidly and statistically significantly. The changes were of similar intensity after the first and second doses (1.5 micrograms/kg) and normalized about 60 min after each injection. In contrast, following i.v. buprenorphine (3 and 1.5 micrograms/kg) the cutaneous partial pressures changed continuously and progressively during the observation period and did not reach the control values after 240 min. Naloxone and amiphenazole injections had no obvious influence on the time course of the blood gas tensions. If opiates and antagonists were combined, neither the fentanyl/amiphenazole group nor the buprenorphine/naloxone group differed significantly from the respective opiate groups. DISCUSSION AND CONCLUSION: As was discussed in detail in a previous communication, monitoring of opiate-induced respiratory depression must be nonstimulant and, preferably, noninvasive. Whereas the precision and/or limitations of monitoring partial oxygen saturations by pulse oximetry is well documented in the literature, knowledge of the value of cutaneous partial pressure monitoring is still limited and controversial for the adult patient population. The present study was performed to define the usefulness of cutaneous blood gas analysis in healthy volunteers receiving opiate dosages well known in recovery room patients. It is concluded that continuous monitoring of pctO2 and pctCO2 can indeed detect opiate-induced respiratory depression in adults. The well-known difference in respiratory pattern for fentanyl and buprenorphine could easily be determined. It was confirmed that naloxone and amiphenazole in the dosage range studied do not influence spontaneous respiration in healthy adults. Thus, the authors are convinced that continuous monitoring of cutaneous partial pressures of oxygen and carbon dioxide is sensitive enough to be used, in combination with pulse oximetry, in a monitoring concept for patients recovering from surgery and anaesthesia. Results in patients undergoing conventional pain management or patient-controlled analgesia with relatively high opiate dosages will be presented in following papers. Concerning the controversy about clinically relevant interactions between fentanyl and amiphenazole or buprenorphine and naloxone, the present study did not confirm any useful antagonism. Whether this is due to limitations of cutaneous monitoring, the difference between volunteers and patients, or pharmacological reasons must be evaluated in further investigations.

Adult↗

PubMed1979

[Oxygen partial pressure, oxyhemoglobin saturation and the oxygen content of blood in endotoxic shock].

Our research showed in the endotoxic shock no fundamental and durable changes with reference to oxygen partial pressure and oxyhemoglobin saturation of the arterial blood within the first two hours. On the other hand the oxygen contents of the arterial blood decreased progressively in connection with the progressive decrease of hemoglobin. In detail the arterial oxygen partial pressure decreased within the first 30 minutes after the endotoxin injection and normalized itself by the sixtieth minute, afterwards it remained stationary. Statistically significant divergences of the oxyhemoglobin saturation were not existing during the whole examination. The oxygen contents of the blood decreased progressively in consequence of lower hemoglobin values.

Animals↗

PubMed1991

[Blood flow and blood oxygen partial pressure of the azygos vein in portal hypertension evaluated by the catheter method].

To evaluate the clinical significance of blood flow in the azygos vein and the oxygen partial pressure in azygos venous blood in portal hypertension, we examined 25 patients with liver cirrhosis, 4 with chronic hepatitis, 4 with idiopathic portal hypertension (IPH) and 16 controls by the continuous thermodilution method and azygos venous blood sampling. The azygos venous flow was significantly higher in the patients with chronic liver diseases than in the controls. There was a significant correlation between azygos venous flow and hepatic venous pressure gradient. In the patients with liver cirrhosis, about one half of the azygos venous flow was assumed to represent upward collateral flow, as the azygos venous flow was 3.4% of cardiac output in the controls, 6.3% in the liver cirrhosis patients, and 5.1% in the IPH patients. Oxygen partial pressure in azygos venous blood was higher in patients with portal hypertension, especially in the IPH patients, which indicates that part of splenic flow drains into the azygos vein.

Azygos Vein↗

PubMed1975

Measurement of partial pressure of gases in liquids by mass spectrometry.

The experimental setup of mass spectrometric determination of gas contents in liquids has been modified for continuous and discontinuous measurement of partial pressure of gases in liquids. The inlet system consists of a stainless steel capillary with slits covered by a silicone rubber membrane. Several gases can be measured simultaneously under static conditions and in flowing liquids. The measurement and calibration procedure is described. Results of the analysis of the test criteria, reproducibility, detection limit, response time, and depletion are presented. The difficulties in discontinuous measurement of oxygen in blood are explained by the complex permeation-diffusion process at the membrane and the form of the dissociation curve. With regard to solubility, physically dissolved gases can be determined without problems down to tensions of about 0.01 mm Hg. Continuous measurement of oxygen and carbon dioxide partial pressure in liquids, including blood, is possible with the described system.

Blood Gas Analysis↗

PubMed1992

ANP decreases arterial oxygen partial pressure by increasing shunt flow in pulmonary circulation.

This study was designed to clarify the decreased arterial oxygen partial pressure (PaO2) mechanism induced by atrial natriuretic peptide (ANP) infusion. In order to examine the effects of ANP on gas exchange across the normal lungs, ANP was infused to eight anesthetized dogs, ventilated with mixed gases of oxygen and nitrogen. PaO2 and venous oxygen partial pressure (PvO2), ventilation-perfusion ratio (VA/Q), shunt-total blood flow ratio (QS/QT) were measured before and during ANP infusion under ventilation with 10, 20, 30% oxygen. In this study ANP decreased PaO2 from 89.0 +/- 4.2 to 85.4 +/- 5.4 mmHg during 20% oxygen ventilation, and from 138.1 +/- 3.6 to 132.5 +/- 4.1 mmHg during 30% oxygen ventilation. ANP increased VA/Q and QS/QT. We conclude that the decrease in PaO2 caused by ANP infusion was mainly due to the increased venous admixture.

Animals↗

PubMed2000

Measurement of hepatic tissue hypoxia using near infrared spectroscopy: comparison with hepatic vein oxygen partial pressure.

Hepatic hypoxia occurs during liver surgery and transplantation. The critical level associated with irreversible hepatocellular damage is unknown. Measurement of hepatic tissue oxygenation and hepatic vein oxygen partial pressure (HVPO(2)) reflects oxygen supply and consumption. Near infrared spectroscopy (NIRS) can be used to monitor hepatic oxyhaemoglobin (HbO(2)), deoxyhaemoglobin (Hb) and cytochrome oxidase (Cyt Ox) oxidation. This study compared regional hepatic tissue oxygenation (HbO(2), Hb and Cyt Ox) using NIRS with HVPO(2). The use of tissue oxygenation measured by NIRS and HVPO(2) as indicators of hepatic tissue hypoxia was also investigated. Large Landrace pigs (n = 5) underwent laparotomy and liver exposure. Systemic and hepatic haemodynamics were monitored continuously. NIRS probes were placed on the liver to record continuously HbO(2), Hb and Cyt Ox. Graded hypoxaemia was achieved by stepwise reduction of the fraction of inspired oxygen (FiO(2)) from 30% (baseline) to 4%. A significant decrease in hepatic arterial blood flow and total hepatic blood flow was seen with severe hypoxaemia while there was no significant change to portal vein blood flow. Oxygen partial pressures in the hepatic artery, portal vein and hepatic vein decreased progressively with all grades of hypoxaemia. There was an immediate reduction of hepatic HbO(2) and simultaneous increase in hepatic Hb with all grades of hypoxaemia. Hepatic Cyt Ox was reduced significantly only with FiO(2) < or =10%. A significant correlation (p<0.001) was found between the changes in hepatic oxygenation parameters measured by NIRS and HVPO(2). HVPO(2) measurement did not predict the reduction in intracellular tissue oxygenation demonstrated by NIRS with a decrease of Cyt Ox oxidation. In conclusion there was a good correlation between the tissue oxygenation parameters measured by NIRS and HVPO(2). However, the reduction of intracellular oxygenation found with severe hypoxaemia was demonstrated only by NIRS.

Animals↗

PubMedDate not supplied

[Changes in the content of rat brain polyphosphoinositides after exposure to high partial pressures of helium and nitrogen].

Effect of the medium with high partial pressure of helium and nitrogen on the content of di- and triphosphinositides in the rat brain great hemispheres. The stay of the rats in helium-oxygen mixture under the pressure of 40 kg/cm2 for 1 h is accompanied by the true decrease in the content of the both components of polyphosphoinositides whose value does not depend on the decompression conditions. Nitrogen-oxygen mixture under the pressure of 15 and 25 kgf/cm2 also evokes a decrease of the content of di- and triphosphoinositides. The character of reduction of the content of the both components for 4 h after the stay of the rats under the pressure of 25 kgf/cm2 depends on the decompression conditions.

Animals↗

PubMedDate not supplied

Statistical modelling of human blood carbon dioxide partial pressure.

This paper deals with statistical modelling of blood carbon dioxide partial pressure pCO2. The clinical measurements were carried out in the Arab Centre for Heart and Special Surgery in Amman. The statistical analysis of the results obtained demonstrates that pCO2 for arterial, venous and capillary blood have histograms approaching normal ones. Moreover, the experimental data suggest that the blood pCO2 can be expressed by a linear regression model. Making use of this regression model, the blood pCO2 population can indirectly be obtained with accuracy fulfilling clinical requirements. Therefore, this approach will not only lead to less invasive methods but will also result in decreasing the cost of projected analyser for blood gas analysis. The implementation of this proposed regression equation ensures the effectiveness of the model as an indirect method for pCO2 measurements.

Arteries↗

PubMed1981

Energy metabolism in relation to oxygen partial pressure in human skeletal muscle during exercise.

1. The intramuscular oxygen partial pressure (pO2) in human gastrocnemius muscle was monitored during exercise and compared with metabolite concentrations reflecting the energy and the redox state in the tissue. Ten normal subjects and ten patients with peripheral vascular occlusive disease were investigated. 2. In normal subjects the pO2 at the end of exercise was related to the intensity of the exercise, expressed as effect (J/s) per contraction. 3. In both patients and normal subject the pO2 was related to the [ATP]/[ADP] ratio, the [lactate/[pyruvate] ratio and the phosphocreatine concentration in the muscle tissue at rest and during exercise. 4. At each pO2 value, a lower [lactate/[pyruvate] ratio was found in the muscle tissue of the patients compared with that of normal subjects. This was interpreted as a beneficial effect of the higher oxidative-enzyme capacity in the muscle of the patients. 5. The results show the importance of pO2 for the regulation of the energy and the redox state of the tissue. During exercise the changes induced in pO2 and thus the energy state will stimulate the respiratory rate. This might be an important link in triggering the oxidative-enzyme capacity in response to physical training as well as in peripheral vascular occlusive disease.

Energy Metabolism↗

PubMed1990

Oxygen partial pressure distribution within skeletal muscle: indicator of whole body oxygen delivery in patients?

Simultaneously with determination of cardiac output, the distribution of oxygen partial pressure within biceps muscle was measured during and after open heart surgery in 29 patients. During extracorporeal circulation (ECC) mean muscular oxygen partial pressure (MPO2m) decreased from 25 mmHg to 14 mmHg with an increase of MPO2 values below 5 mmHg from 4% to 20%. Sustained decrease of MPO2m (greater than 1h) did not occur after ECC. Before ECC and in the postoperative period, MPO2m was lineary correlated (r = 0.85) to whole body oxygen delivery (Ox. offer) suggesting that local oxygen delivery within biceps muscle was sufficiently indicated only by systemic parameters of oxygen transport which require determination of cardiac output. Particularly with regard to relative changes, MPO2m might be used for estimation of whole body oxygen offer clinically.

Adult↗

PubMed1984

Transcutaneous measurement of the oxygen partial pressure using argon to correct for the oxygen consumption of the probe.

The oxygen consumption of a transcutaneous probe creates an oxygen diffusion gradient between the skin capillaries and the probe, and this gradient causes the ratio between the oxygen partial pressure at the surface of the transcutaneous probe and the mean capillary pO2 to be less than 1. The ratio is usually increased towards unity by heating the skin to 43-45 degrees C, but this method introduces both practical and theoretical complications: the risk of skin burns and the increase in pO2 over the value in the blood at 37 degrees C. We present a new method to evaluate the ratio between the oxygen partial pressure at the surface of the transcutaneous probe and the mean capillary pO2. The method was used in measurements of the mean capillary pO2 in the skin of eight volunteers with a low-temperature probe (40 degrees C). The mean value of the ratio was 0.56 with a considerable variation from one person to another and from one skin location to another.

Argon↗

PubMed2003

Partial pressure of carbon dioxide in extremely low birth weight infants supported by nasal prongs continuous positive airway pressure.

OBJECTIVE: Traditionally, delivery room management of extremely low birth weight (ELBW) infants consisted of immediate intubation and mechanical ventilation. There have been recent reports of success using nasal prongs continuous positive airway pressure (NCPAP) in this population. Data on the partial pressure of carbon dioxide (PCO(2)) in spontaneously breathing ELBW infants is very limited. The objective of this study was to determine the trend of the average PCO(2) in the spontaneously breathing ELBW infants, while on NCPAP, during the first week of life and to determine whether a brief period of mechanical ventilation affects the PCO(2) levels after extubation. METHODS: This is a retrospective cohort study of infants who had birth weights <1000 g and were admitted to the neonatal intensive care unit at our institution. These ELBW infants were divided into groups on the basis of whether they were never intubated (group 1) or were intubated for <48 hours (group 2). Average daily PCO(2) levels while on NCPAP were compared between the 2 groups. Minimum and maximum PCO(2) levels were also compared with a third group of infants (group 3), who were intubated for >48 hours and treated mainly with mechanical ventilation during the first week of life. RESULTS: Sixty-two ELBW infants were included in this study: 24 infants in group 1, 19 infants in group 2, and 19 infants in group 3. There was no significant difference between the average PCO(2) levels of group 1 and group 2 during the first week of life. The daily PCO(2) level during the first week of life for infants who were breathing spontaneously on NCPAP had a mean value of 39.73 +/- 1.78 mm Hg. There was no difference between the daily average minimum PCO(2) levels among the 3 groups. Group 3, however, had significantly higher maximum PCO(2) levels compared with the first 2 groups during days 2 through 7 of life. CONCLUSIONS: Daily average PCO(2) levels in the spontaneously breathing ELBW infants during the first week of life remains at approximately 40 mm Hg. These levels seem to be unaffected by an initial brief period of mechanical ventilation. Infants who are treated with longer periods of mechanical ventilation have higher daily maximum PCO(2) levels during the first week of life. Additional studies are required to detect neurodevelopmental outcomes of these 3 groups.

Carbon Dioxide↗

PubMed2002

Effect of mild hypothermia on partial pressure of oxygen in brain tissue and brain temperature in patients with severe head injury.

OBJECTIVE: To study the changes of partial pressure of oxygen in brain tissue (P(bt)O(2)) and brain temperature (BT) in patient s in acute phase of severe head injury, and to study the effect of mild hypothermia on P(bt)O(2) and BT. METHODS: The P(bt)O(2) and the BT of 18 patients with severe head injury were monitored, and the patients were treated with mild hypothermia within 20 hours after injury. The rectal temperature (RT) of the patients was kept on 31.5-34.9 degrees C for 1-7 days (57.7 hours+/-28.4 hours averagely), simultaneously, the indexes of P(bt)O(2) and BT were monitored for 1-5 days (with an average of 54.8 hours+/-27.0 hours). According to Glasgow Outcome Scale (GOS), the prognosis of the patients was evaluated at 6 months after injury. RESULTS: Within 24 hours after severe head injury, the P(bt)O(2) was significantly lower (9.6 mm Hg+/-6.8 mm Hg, 1 mm Hg=0.133 kPa) than the normal value (16-40 mm Hg). After treatment of mild hypothermia, the mean P(bt)O(2) increased to 28.7 mm Hg+/-8.8 mm Hg during the first 24 hours, and the P(bt)O(2) was still maintained within the range of normal value at 3 days after injury. The BT was higher than the RT in the patients in acute phase of severe head injury, and the difference between the BT and the RT significantly increased after treatment of mild hypothermia. Hyperventilation (the partial pressure of carbon dioxide in artery (P(a)CO(2)) approximately 25 mm Hg) decreased the high intracranial pressure (ICP) and significantly decreased the P(bt)O(2). CONCLUSIONS: This study demonstrates that P(pt)O(2) and BT monitoring is a safe, reliable and sensitive diagnostic method to follow cerebral oxygenation. It might become an important tool in our treatment regime for patients in the acute phase of severe head injury requiring hypothermia and hyperventilation.

Adult↗

PubMed1981

In vivo evaluation of transcutaneous CO2 partial pressure monitoring.

Correlation between transcutaneous and arterial CO2 partial pressure (Ptcco2, and Paco2) under normal and hemorrhagic shock conditions was evaluated in rabbits. Under normal conditions the Paco2-to-Ptcco2 least-squares regression line had a slope of 1.03 an intercept of 4.57 Torr, and a root mean variance of +/- 3.79 Torr. Under hemorrhagic shock conditions the slope remained similar, but the intercept increased, producing a significant difference between arterial and transcutaneous values. The correlation line shifts to the left so that, for a given Paco2, the Ptcco2 value increases. The transcutaneous response time (90%) under conditions produced by breathing 10% CO2 lagged 2.8 +/- 1.4 min behind that of the breathing 10% CO2 lagged 2.8 +/- 1.4 min behind that of the Paco2. The difference between transcutaneous and arterial CO2 observed during hemorrhagic shock and the lag in transcutaneous response time can be altered by topical application of dimethyl sulfoxide, by altering both flow and permeability. These results indicate that good Ptcco2-to-Paco2 correlation exists under normal conditions and that hemorrhagic shock will produce tissue CO2 accumulation and therefore higher than arterial Ptcco2 values.

Animals↗

PubMed1999

Intramuscular oxygen partial pressure in the healthy during exercise.

The oxygen partial pressure (pO2) in the anterior tibial muscle was measured in n=12 (6 physically active and 6 sedentary) apparently healthy subjects. This was the first time a flexible micro catheter with an outer diameter of 0.45 mm was used during skeletal muscular activity in men. A two level tread mill test which is used in the diagnosis of peripheral arterial occlusive disease was chosen to induce physical stress. In the healthy volunteers a pO2 increase was noted at the beginning of exercise. This was followed by a pO2 decrease because of an increased O2 demand in the working muscle. The initial pO2 increase was thought to be due to the recruitment of capillaries and not the subsequently increased heart rate. At rest and during activity pO2 values were higher in physically active subjects than in the sedentary and the exercise induced decrease of pO2 values was slower and in addition to this the compensation to baseline values quicker.

Adult↗

PubMed1989

Biological nitrogen fixation under primordial Martian partial pressures of dinitrogen.

Early Earth and early Mars were similar enough such that past geochemical and climatic conditions on Mars may have also been favorable for the origin of life. However, one of the most striking differences between the two planets was the low partial pressure of dinitrogen (pN2) on early Mars (18 mb). On Earth, nitrogen is a key biological element and in many ecosystems the low availability of fixed nitrogen compounds is the main factor limiting growth. Biological fixation of dinitrogen on Earth is a crucial source of fixed nitrogen. Could the low availability of dinitrogen in the primordial Martian atmosphere have prevented the existence, or evolution of Martian microbiota? Azotobacter vinelandii and Azomonas agilis were grown in nitrogen free synthetic medium under various partial pressures of dinitrogen ranging from 780-0 mb (total atmosphere=1 bar). Below 400 mb the biomass, cell number, and growth rate decreased with decreasing pN2. Both microorganisms were capable of growth at a pN2 as low as 5 mb, but no growth was observed at a pN2 < or = 1 mb. The data appear to indicate that biological nitrogen fixation could have occurred on primordial Mars (pN2=18 mb) making it possible for a biotic system to have played a role in the Martian nitrogen cycle. It is possible that nitrogen may have played a key role in the early evolution of life on Mars, and that later a lack of available nitrogen on that planet (currently, pN2=0.2 mb) may have been involved in its subsequent extinction.

Atmosphere↗

PubMed1984

Dependency of blood flow velocity in the middle cerebral artery on end-tidal carbon dioxide partial pressure--a transcranial ultrasound Doppler study.

The end-tidal carbon dioxide partial pressure (PCO2) response curves for the flow velocity in the middle cerebral artery were studied in 31 normal subjects with transcranial Doppler techniques. An exponential curve with an exponent of 0.034 mm Hg-1 was found to be a good fit to the recorded data. By means of this relationship, recordings of flow velocity in cerebral arteries can be normalized to a standard value of PCO2. Physiological aspects of cerebrovascular reactivity to PCO2 and the clinical implications of the PCO2 response curve are discussed. The normal material provides a reference for assessing pathological responses.

Adolescent↗

PubMed1990

Mathematical model for the computation of alveolar partial pressure of carbon monoxide.

A mathematical model is formulated for computing alveolar partial pressure of carbon monoxide (PACO) from that in the atmospheric air. The model takes into account parameters like inspired/expired air flow rates, diffusion capacity of the lung, concentration of CO in the atmospheric air, blood flow rate and the non-linear CO dissociation curve. The effect due to the presence of O2 in the blood on CO dissociation curve is also incorporated. It is shown that for a given atmospheric CO concentration, PACO increases exponentialy with time and attains asymptotic value. Alveolar PCO increases further with the increase in the atmospheric CO concentration. The model can also be used to compute carboxyhaemoglobin levels in the blood as a function of exposure time and the results are comparable with the CFK equation and the values measured experimentally.

Carbon Monoxide↗