Mean pO2 Values Research Articles

Comparison of the effects of autologous and non-autologous blood transfusions on the advantages, disadvantages, extubation time and bleeding after coronary bypass

PurposeBlood transfusion; is considered an organ transplant. In coronary bypass surgery, large volumes of homologous blood transfusion may be required due to excessive bleeding. The large number of use of homologous blood transfusion in open heart surgery and the awareness of its various harmful effects have prompted researchers to conduct research on the use of autologous blood. With autologous transfusion, blood diseases, incompatibility, immunosuppression and organ damage can be prevented and the patient can be extubated earlier in the postoperative period. MethodsBetween January 2020 and January 2016, a total of 176 patients, 56 in the treatment group (with autologous blood transfusion) and 120 in the control group, whose information could be reached from hospital records were investigated retrospectively. ResultsNo statistical difference was found between the mean intubation SO2 and PO2 values of the groups. On the contrary, considering the mean intubation times in the intensive care unit of both groups, the patients who underwent autologous blood transfusion were extubated at a statistically significant earlier time. ConclusionAutologous blood transfusion is a safe method in selected patients as well. Thanks to this method, patients are protected from complications associated with homologous blood transfusion. It is believed that performing autologous blood transfusion in selected patients undergoing open-heart surgery can decrease the number of postoperative transfusions, frequency of transfusion-related complications (especially in the lungs), and mean intubation times.

The Race to Equilibrate

Background: While it is well documented that culture in hypoxic conditions produces superior outcomes, the mechanics of establishing such conditions within the embryo’s liquid environment is less clear. It is not uncommon for laboratories, while ‘culturing’ in low-oxygen, to equilibrate dishes in CO2 only environments prior to use, meaning embryos are exposed to high oxygen tension in their media even after placing into the hypoxic environment, but for how long is so far unclear. Aim: To assess the equilibration rate of oxygen within embryo culture media when exposed to hypoxic conditions. Method: A handheld blood gas analyser (EPOC system, ‘BGEM’ cartridges) was used to determine the pO2 of G1+ culture media after exposure to a reduced oxygen environment. Results: Culture media in atmospheric oxygen (with or without the presence of CO2) showed mean pO2 values of 150mmHg. Media fully equilibrated over 24 hours in 5% oxygen fell to approximately 70mmHg. This was well above the theoretically expected value but shown to be consistent across multiple measurements including various dish and incubator types. Initial equilibration to hypoxic conditions occurred relatively rapidly, with dishes undergoing 50% of the required oxygen reduction in only 30 minutes. Within 1.5 hours of exposure 5% O2, media achieved 83% of the required change, with full equilibration reached at approximately 2.5 hours. Pre-equilibration of dishes in 6% CO2 did not appear to affect the oxygen diffusion rate compared with non-equilibrated media. Oxygen exhibited similarly rapid diffusion into culture media when dishes equilibrated at 5% O2 were exposed to atmospheric conditions, with pO2 increasing by 1.46mmHg per minute. Conclusion: The diffusion rate of oxygen appears to be significantly faster than the more widely studied CO2, however, oxygen tension in media still requires greater than 2 hours to reach optimum levels, requiring us to consider oxygen in our equilibration practices.

Evaluation of arterial blood gases of patients with type 1-2 respiratory failure diagnosed in intensive care using the quantitative Stewart method

Introduction: Arterial blood gases are tests that provide reliable information about the metabolic and respiratory status of patients. In traditional methods, arterial blood gases are evaluated by calculating the bicarbonate concentration and anion gap in the plasma. Since ICU patients almost always have protein and electrolyte disorders, a different method has been suggested instead of the traditional method that neglects electrolyte and protein in the evaluation. In the mathematical model described by Stewart and modified by Figge et al., 4 types of respiratory failure were defined according to their pathophysiology: hypoxemic (type 1), hypercapnic (type 2), perioperative (type 3), and hypoperfusion-induced respiratory failure in shock patients (type 4). The study aims to evaluate the arterial blood gases of intensive care patients with type 1 and type 2 respiratory failure with the Stewart method and compare them with the traditional method.
 Material and Method: In the study, serum BUN (blood urea nitrogen), creatinine, glucose, sodium, chlorine, serum BUN (blood urea nitrogen) of 106 patients diagnosed with type 1-2 respiratory failure. Together with potassium, magnesium, albumin values, pH, pCO2, pO2, HCO3, base deficit, and lactate values studied in arterial blood gas sample were determined and evaluated according to the Stewart method.
 Results: The length of stay of the patients in the intensive care unit was determined as 17.48±10.58 (minimum 6-maximum 68) days. It was determined that 74 (69.8%) of the patients were discharged and 32 (30.2%) died. When the blood gases and laboratory values of the patients were compared according to the clinical outcomes of the patients, no statistically significant correlation was found between the patients’ mean pH, pCO2, HCO3, base deficit, pO2, albumin, lactate, creatinine, glucose, potassium, and chlorine values and the patients’ discharge or death. BUN values of patients who died were found to be higher than those who were discharged. A statistically significant difference was found between the development of hypoalbuminemia and the length of stay in the intensive care unit. It has been determined that the treatment costs of patients with severe hypoalbuminemia are higher than other patients. The length of stay in the intensive care unit of the patients who did not develop acidosis was found to be statistically significantly lower than the patients who developed metabolic and respiratory acidosis.
 Conclusion: While a significant relationship was found between albumin levels, which has an important place in the Stewart method, and the length of stay in the intensive care unit, no relationship was found between albumin levels or lactate levels and mortality. However, increased BUN values were associated with mortality. As the albumin value decreases in patients with hypoalbuminemia, treatment costs increase. There is a need for larger multicenter studies with a larger sample group that will evaluate metabolic status with the Stewart method and investigate its relationship with mortality.

Effect of iodinated contrast media on the oxygen tension in the renal cortico-medullary region of pigs.

Repeated injections of iodinated contrast media (CM) can lead to a deterioration of the renal blood flow, can redistribute blood from the renal cortex to other parts of the kidney and can cause small decreases of the blood flow in cortical capillaries, a significant reduction in blood flow in peritubular capillaries and a significant reduction in blood flow in the vasa recta. Therefore, a study in pigs was designed, to show whether the repeated injection of CM boli, alone, can cause a reduction of oxygenation in the cortico-medullar renal tissue - the region with the highest oxygen demand in the kidney - of pigs.While the mean pO2-value had only decreased by 0.3 mmHg from 29.9±4.3 mmHg to 29.6±4.3 mmHg (p = 0.8799) after the tenth Iodixanol bolus, it decreased by 5.9 mmHg from 34.0±4.3 mmHg to 28.1±4.3 mmHg after the tenth Iopromide bolus (p = 0.044). This revealed a remarkable difference in the influence of these CM on the oxygen partial pressure in the kidney.Repeated applications of CM had a significant influence on the renal oxygen partial pressure. In line with earlier studies showing a redistribution of blood from the cortex to other renal areas, this study revealed that Iodixanol - in contrast to Iopromide - induced no changes in the pO2 in the cortico-medullar region which confirms that Iodixanol did not hinder the flow of blood through the renal micro-vessels. These results are in favor of a hypothesis from Brezis that a microcirculatory disorder might be the basis for the development of CI-AKI.

Implantable microchip containing oxygen-sensing paramagnetic crystals for long-term, repeated, and multisite in vivo oximetry.

EPR oximetry is established as a viable method for measuring the tissue oxygen level (partial pressure of oxygen, pO2) in animal models; however, it has not yet been established for measurements in humans. EPR oximetry requires an oxygen-sensing paramagnetic probe (molecular or particulate) to be placed at the site/organ of measurement, which may pose logistical and safety concerns, including invasiveness of the probe-placement procedure as well as lack of temporal stability and sensitivity for long-term (repeated) measurements, and possible toxicity in the short- and long-term. In the past, we have developed an implantable oxygen-sensing probe, called OxyChip, which we have successfully established for oximetry in pre-clinical animal models (Hou et al. Biomed. Microdevices 20, 29, 2018). Currently, OxyChip is being evaluated in a limited clinical trial in cancer patients. A major limitation of OxyChip is that it is a large (1.4mm3) implant and hence not suitable for measuring oxygen heterogeneity that may be present in solid tumors, chronic wounds, etc. In this report, we describe the development of a substantially smaller version of OxyChip (0.07mm3 or 70 cubic micron), called mChip, that can be placed in the tissue of interest using a 23G syringe-needle with minimal invasiveness. Using in vitro and in vivo models, we have shown that the microchip provides adequate EPR sensitivity, stability, and biocompatibility and thus enables robust, repeated, and simultaneous measurement from multiple implants providing mean and median pO2 values in the implanted region. The mChips will be particularly useful for those applications that require repeated measurements of mean/median pO2 in superficial tissues and malignancies.

Effect of Graft Weight to Recipient Body Weight Ratio on Hemodynamic and Metabolic Parameters in Pediatric Liver Transplant: A Retrospective Analysis.

To analyze how graft-weight-to-bodyweight ratio in pediatric liver transplant affects intraoperative and early postoperative hemodynamic and metabolic parameters. We reviewed data from 130 children who underwent liver transplant between 2005 and 2015. Recipients were divided into 2 groups: those with a graft weight to body weight ratio > 4% (large for size) and those with a ratio ≤ 4% (normal for size). Data included demographics, preoperative laboratory findings, intraoperative metabolic and hemodynamic parameters, and intensive care follow-up parameters. Patients in the large-graft-for-size group (>4%) received more colloid solution (57.7 ± 20.1 mL/kg vs 45.1 ± 21.9 mL/kg; P = .08) and higher doses of furosemide (0.7 ± 0.6 mg/kg vs 0.4 ± 0.7 mg/kg; P = .018). They had lower mean pH (7.1 ± 0.1 vs 7.2 ± 0.1; P = .004) and PO2 (115.4 ± 44.6 mm Hg vs 147.6 ± 49.3 mm Hg; P = .004) values, higher blood glucose values (352.8 ± 96.9 mg/dL vs 262.8 ± 88.2 mg/dL; P < .001), and lower mean body temperature (34.8 ± 0.7°C vs 35.2 ± 0.6°C; P = .016) during the neohepatic phase. They received more blood transfusions during both the anhepatic (30.3 ± 24.3 mL/kg vs 18.8 ± 21.8 mL/kg; P = .013) and neohepatic (17.7 ± 20.4 mL/kg vs 10.3 ± 15.5 mL/kg; P = .031) phases and more fresh frozen plasma (13.6 ± 17.6 mL/kg vs 6.2 ± 10.2 mL/kg; P = .012) during the neohepatic phase. They also were more likely to be hypotensive (P < .05) and to receive norepinephrine infusion more often (44% vs 22%; P < .05) intraoperatively. More patients in this group were mechanically ventilated in the intensive care unit (56% vs 31%; P = .035). There were no significant differences between the groups in postoperative acute renal dysfunction, graft rejection or loss, infections, length of intensive care stay, and mortality (P > .05). High graft weight-to-body-weight ratio is associated with adverse metabolic and hemodynamic changes during the intraoperative and early postoperative periods. These results emphasize the importance of using an appropriately sized graft in liver transplant.

Partial Pressure of Oxygen in Capillary Blood Samples from the Fingertip

Many people with diabetes routinely measure their blood glucose (BG) on capillary blood samples from the fingertip. Beside other interfering factors, the blood samples’ partial pressure of oxygen (pO2) can affect BG measurements, particularly in systems based on glucose oxidase (GOx) enzyme reactions on test strips.1,2 Indeed, many of the available home-use systems for self-monitoring of blood glucose (SMBG) utilize the GOx enzyme reaction, which is prone to oxygen interference; however, in the literature, poor information is available concerning physiological pO2 values and possible variations in capillary blood from the fingertip in people with diabetes. In this investigation, the pO2 of capillary blood samples obtained from fingertips was determined in 110 subjects (55 female, 31 with type 1 diabetes mellitus, 69 with type 2 diabetes mellitus, 10 without diabetes; mean age 61 years, from 19 to 78 years); most of them were expected to perform SMBG regularly. The subjects had no acute serious diseases. They participate regularly in SMBG system evaluation studies at the Institute for Diabetes-Technology GmbH at Ulm University, Ulm, Germany. The study protocol was approved by the Ulm University Ethics Committee. Capillary blood samples were obtained by skin puncture, and the pO2 was analyzed on a blood gas analyzer (OPTI™ CCA-TS Analysator, OPTI Medical System Inc., Roswell, GA). Maintenance, handling, and quality control of the blood gas analyzer were performed according to the manufacturer’s labeling. Regular internal and external quality control measurements were performed, as required by German national guidelines. Sample collection and pO2 measurements were performed by trained clinical personnel. The 110 subjects showed a mean pO2 of 71.1 mmHg (standard deviation ± 6.9 mmHg), ranging from 49 to 86 mmHg. Female and male subjects showed similar mean pO2 values (72.5 and 69.8 mmHg, respectively). Ninety-four subjects (~85%) showed pO2 values between >60 and ≤80 mmHg, 6 subjects (~5%) showed pO2 values ≤60 mmHg, and 10 subjects (~9%) showed pO2 values >80 mmHg (Figure 1). Lowest pO2 values (53 and 49 mmHg) were found in two subjects with stable chronic respiratory disease. Figure 1. Relative number of subjects with pO2 values within the respective category. Our results indicate that a broad range of capillary pO2 values occur among a population of healthy people and people with diabetes without acute serious diseases. In a previous study using venous blood samples adjusted to different pO2 levels, we observed remarkable measurement deviations with some GOx systems. Particularly at pO2 ≤45 mmHg, we found considerably overestimated measurements.2 Decreased pO2 values can occur in patients with respiratory diseases, such as chronic obstructive pulmonary disease,3 which is described as being associated with type 2 diabetes.4 At high altitudes or also during long-distance flights, up to ~40% decreased pO2 is reported for arterial blood samples;5 a similar behavior can also be expected for capillary blood samples from the fingertip. In conditions with decreased pO2 values in capillary blood, measurements with oxygen-sensitive systems could be affected, and hypoglycemic events might not be detected adequately. Further investigations should be performed focusing on pO2 variations in capillary blood from fingertips in people with diabetes and the possible impact on glucose measurement results obtained with oxygen-sensitive systems.

3He pO2 mapping is limited by delayed‐ventilation and diffusion in chronic obstructive pulmonary disease

Lung pO2 mapping with (3)He MRI assumes that the sources of signal decay with time during a breath-hold are radiofrequency depolarization and oxygen-dependent T1 relaxation, but the method is sensitive to other sources of spatio-temporal signal change such as diffusion. The purpose of this work was to assess the use of (3)He pO2 mapping in patients with chronic obstructive pulmonary disease. Ten patients with moderate to severe chronic obstructive pulmonary disease were scanned with a 3D single breath-hold pO2 mapping sequence. Images showed signal increasing over time in some lung regions due to delayed ventilation during breath-hold. Regions of physically unrealistic negative pO2 values were seen in all patients, and regional mean pO2 values of -0.3 bar were measured in the two patients most affected by delayed ventilation (where mean time to signal onset was 3-4 s). Movement of gas within the lungs during breath-hold causes regional changes in signal over time that are not related to oxygen concentration, leading to erroneous pO2 measurements using the linear oxygen-dependent signal decay model. These spatio-temporal sources of signal change cannot be reliably separated at present, making pO2 mapping using this methodology unreliable in chronic obstructive pulmonary disease patients with significant bullous emphysema or delayed ventilation.

367 Post Resuscitative Factors Influencing Survival after In-Hospital Pediatric Cardiac Arrest

Background and AimsIn-hospital pediatric cardiac arrest (CA) achieves high return of spontaneous circulation (ROSC) rates but survival to hospital discharge is low. The aim of this study was to determine...

Radial oxygen gradients over rat cortex arterioles

We present the results of the visualisation of radial oxygen gradients in rats' cortices and their potential use in neurocritical management. PO₂ maps of the cortex of ten sedated, intubated and controlled ventilated Wistar rats were obtained with a camera (SensiMOD, PCO, Kelheim, Germany). Those pictures were analysed and edited by a custom-made software. A virtual matrix, designed to evaluate the cortical O₂ partial pressure, was placed vertically to the artery under investigation, and afterwards multiple regions of interest were measured (width 10 pixels, length 15-50 pixels). The results showed a map of the cerebral oxygenation, which allowed us to calculate radial oxygen gradients over arterioles. Three groups were defined according to the level of the arterial pO₂: PaO₂ < 80, PaO₂ 80-120 and PaO₂ > 120. Gradients were analysed from the middle of the vessel to its border (1), from the border into the parenchyma next to the vessel (2) and a combination of both (3). Gradient 1 showed significantly different cortical pO₂ values between the three different groups. The mean pO₂ values were 2.62, 5.29 and 5.82 mmHg/mm. Gradient 2 measured 0.56, 0.90 and 1.02 mmHg/mm respectively. Gradient 3 showed significant results between the groups with values of 3.18, 6.19 and 6.84 mmHg/mm. Using these gradients, it is possible to describe and compare the distribution of oxygen to the brain parenchyma. With the presented technique, it is possible to detect pO₂ changes in the oxygen supply of the brain cortex.

An Observational Study to Assess Changes in Arterial Blood Gas Values During Untreated Porcine Ventricular Fibrillation

Background. Cardiocerebral resuscitation (CCR) is reportedly superior to cardiopulmonary resuscitation (CPR) for out-of-hospital cardiac arrest (OHCA) even though active ventilation is not initially provided. Understandably, concerns have been raised regarding the withholding of positive pressure ventilation (PPV) during CCR because of the longstanding belief that respiratory gas exchange is a critical action during resuscitation. Objective. In this observational study, we sought to quantify the effect of prolonged untreated ventricular fibrillation (VF) on arterial pH, partial pressure of carbon dioxide (pCO2), and partial pressure of oxygen (pO2) values in a swine model of witnessed cardiac arrest to begin exploring the validity of these concerns. Methods. Both included studies were approved by the institutional animal care and use committee (IACUC). Eighty-three animals (25–35 kg) were instrumented under general anesthesia. Baseline characteristics were recorded. An arterial blood gas (ABG) sample was drawn from each animal via femoral catheter just prior to electrical induction of VF. After 8 minutes of untreated VF in one study (study 1 [n = 30]) and 10 minutes of untreated VF in the other study (study 2 [n = 53]), a second ABG sample was drawn. All samples were processed immediately using an i-STAT portable whole blood analyzer. Baseline characteristics of animals in the two studies were assessed using descriptive statistics. For the second ABG sample in each study, the mean pH, pCO2, and pO2 values, with 95% confidence intervals (95% CIs), were determined. The paired ABG results for each animal were then compared and the average pH, pCO2, and pO2 proportions, with 95% CIs, for each study were calculated. Results. The baseline characteristics of the animals in the two studies were similar. After 8 and 10 minutes of untreated VF cardiac arrest, the pH values were 7.35 (95% CI = 7.32, 7.37) and 7.37 (95% CI = 7.36, 7.38), the pCO2 increased to 44.1 mmHg (95% CI = 41.1, 47.1) and 52.7 mmHg (95% CI = 51.0, 54.4), and the pO2 decreased to 44.8 mmHg (95% CI = 42.2, 47.4) and 45.5 mmHg (95% CI = 43.3, 47.6), respectively. Conclusions. Using our swine model of witnessed cardiac arrest with prolonged untreated VF, the arterial pH remained essentially unchanged and the pCO2 increased to 1.42 times baseline after 10 minutes, while almost half of the initial O2 concentration in the blood at the beginning of resuscitation remained.

A short-breath-hold technique for lung pO2 mapping with 3He MRI.

A pulse-sequence strategy was developed for generating regional maps of alveolar oxygen partial pressure (pO2) in a single 6-sec breath hold, for use in human subjects with impaired lung function. Like previously described methods, pO2 values are obtained by measuring the oxygen-induced T1 relaxation of inhaled hyperpolarized 3He. Unlike other methods, only two 3He images are acquired: one with reverse-centric and the other with centric phase-encoding order. This phase-encoding arrangement minimizes the effects of regional flip-angle variations, so that an accurate map of instantaneous pO2 can be calculated from two images acquired a few seconds apart. By combining this phase-encoding strategy with variable flip angles, the vast majority of the hyperpolarized magnetization goes directly into the T1 measurement, minimizing noise in the resulting pO2 map. The short-breath-hold pulse sequence was tested in phantoms containing known O2 concentrations. The mean difference between measured and prepared pO2 values was 1 mm Hg. The method was also tested in four healthy volunteers and three lung-transplant patients. Maps of healthy subjects were largely uniform, whereas focal regions of abnormal pO2 were observed in diseased subjects. Mean pO2 values varied with inhaled O2 concentration. Mean pO2 was consistent with normal steady-state values in subjects who inhaled 3He diluted only with room air.

Measurements of Partial Oxygen Pressure (pO2) using the OxyLite System in R3327-AT Tumors under Isoflurane Anesthesia

The presence of oxygen-deficient tumor cells is a critical issue in cancer therapy. To identify tumor hypoxia, tissue partial oxygen pressure (pO2) can be measured directly. The OxyLite system allows determination of pO2 in tumors and permits continuous measurements of pO2 at a fixed point. In this study, this system was used to continuously measure pO2 in R3327-AT tumors in animals anesthetized with isoflurane. In addition, continuous pO2 measurement was performed in the muscle in non-tumor-bearing animals. In animals breathing isoflurane balanced by air, tumor pO2 at fixed positions decreased rapidly within 1-2 min of probe positioning but remained stable thereafter. In animals breathing isoflurane balanced by pure oxygen, tumor pO2 was higher and remained high. We also measured pO2 values at multiple positions in R3327-AT tumors of various sizes, with anesthetized animals breathing either air or pure oxygen. Our data showed that the frequency of pO2 measurements below 2.5 or 5.0 mmHg was significantly higher in animals breathing air than in animals breathing pure oxygen. Measurements in different-sized tumors showed that the mean pO2 value decreased as tumor volume increased, with the largest change occurring between tumor volumes of 100 and 200 mm3. Our data demonstrate that the OxyLite system, when used with isoflurane anesthesia, is a valuable tool in the study of tumor hypoxia.

Tumour oxygen dynamics measured simultaneously by near-infrared spectroscopy and 19F magnetic resonance imaging in rats**Presented in part at the 12th annual meeting of the International Society of Magnetic Resonance in Medicine, Kyoto, 2004.

Simultaneous near-infrared spectroscopy (NIRS) and magnetic resonance imaging (MRI) were used to investigate the correlation between tumour vascular oxygenation and tissue oxygen tension dynamics in rat breast 13762NF tumours with respect to hyperoxic gas breathing. NIRS directly detected global variations in the oxygenated haemoglobin concentration (Δ[HbO2]) within tumours and oxygen tension (pO2) maps were achieved using 19F MRI of the reporter molecule hexafluorobenzene. Multiple correlations were examined between rates and magnitudes of vascular (Δ[HbO2]) and tissue (pO2) responses. Significant correlations were found between response to oxygen and carbogen breathing using either modality. Comparison of results for the two methods showed a correlation between the vascular perfusion rate ratio and the mean pO2 values (R2 > 0.7). The initial rates of increase of Δ[HbO2] and the slope of dynamic pO2 response, d(pO2)/dt, of well-oxygenated voxels in response to hyperoxic challenge were also correlated. These results demonstrate the feasibility of simultaneous measurements using NIRS and MRI. As expected, the rate of pO2 response to oxygen is primarily dependent upon the well perfused rather than poorly perfused vasculature.

PO2 and pCO2 Increment in Post‐dialyzer Blood: The Role of Dialysate

Blood returning from a dialyzer during hemodialysis has a higher pO2 and pCO2 content than blood entering the dialyzer, and this has been attributed to the dialysate. The present study investigates this phenomenon. Acid-base and blood-gas parameters (pH, pO2, pCO2 and HCO3) were measured in three groups of stable chronic hemodialysis patients (A, B, and C) undergoing high-flux hemodialysis. In group A (n = 15), "arterial" (a) and "venous" (v) samples were withdrawn simultaneously before dialysis (samples A0), 5 min after circulation of the blood with the dialysate in the by-pass mode (samples A5), and 5 min after high-flux hemodialysis at a zero ultrafiltration rate (samples A10). In group B (n = 11) (a) and (v) samples were withdrawn simultaneously before dialysis (samples B0), 5 min after isolated-ultrafiltration with closed dialysate ports ("isolated-closed" ultrafiltration) (samples B5), and 5 min after high-flux hemodialysis at a zero ultrafiltration rate (samples B10). In group C (n = 14), after an initial arterial blood sample withdrawal before hemodialysis (sample C0), high-flux hemodialysis at a zero ultrafiltration rate was initiated. Five minutes later, blood and dialysate samples were withdrawn simultaneously from the hemodialysis lines (samples C5). In all cases blood and dialysate (bicarbonate) flow rates were set at 0.300 and 0.700 L/min, respectively. FLX-18 hemodialyzers (membrane PEPA 1.8 m2) were used in this study. Analysis of variance revealed significant changes only in venous samples. A comparison of arterial and venous samples revealed no differences between groups A and B before the initiation of dialysis (A0a vs. A0v and B0a vs. B0v, P = NS). The pO2 content was higher in A5v samples than in A5a samples (83.5 +/- 11.2 vs. 88.8 +/- 14.0 mm Hg, P < 0.02), while the level of HCO(3) was higher in A5a samples than in A5v samples (20.8 +/- 2.0 vs. 20.4 +/- 1.8 mEq/L, P < 0.05). A10a samples possessed a higher pH and lower levels of pO2, pCO2, and HCO3 in comparison to A10v samples (P < 0.001 for all). Mean pO2 and pCO2 values in A5v and A10v samples increased by 6.3% and 12.1% and by 1.29% and 52% in comparison to corresponding values of A5a and A10a samples, respectively. The pO2 level was the only parameter that differed significantly between B5a and B5v samples (B5a = 84.6 +/- 10.1 vs. B5v = 98.0 +/- 12.6 mm Hg, P < 0.005). B10a samples possessed a higher pH and lower levels of pCO2, pO2, and HCO3 in comparison to B10v samples (P < 0.0005 for all comparisons). Mean pO2 and pCO2 values in B5v and B10v samples increased by 16.2% and 16.3% and by -0.29% and 64.8% in comparison to corresponding values of B5a and B10a samples, respectively. C5a samples possessed a higher pH and lower levels of pCO2, pO2, and HCO3 in comparison to C5v samples (P < 0.001 for all). Mean pO2 and pCO2 values in C5v samples were, respectively, 16.0% and 65.0% higher than corresponding values of C5a samples. These results indicate that blood returning from the dialyzer after 5 min of high-flux hemodialysis has a higher pO2 and pCO2 than blood entering the dialyzer, and that this difference is due to O2 and CO2 transfer from the dialysate space into the blood.

The influence of vacuum extractor on fetal oxygenation and newborn status.

The aim of this study was to determine the effects of vacuum extractor assisted delivery on fetal oxygenation and acid-base balance. Sixty-one women were enrolled in the present study. The subjects were divided into two groups. Group A, consisting of 39 women, had normal vaginal deliveries. Group B, consisting of 22 women, underwent a vacuum extractor assisted vaginal delivery. Fetal arterial oxygen saturation (SpO2) monitoring was used in all women after full cervical dilatation. After delivery, umbilical artery pH, pCO2, pO2 and base deficit (BDecf) levels were determined in all neonates. The mean FSpO2 value in Group A was 51.53+/-5.87% and in Group B 48.03+/-6.39% (p<0.03). The mean cord pH value in fetuses of Group A was 7.26+/-0.05, and in Group B 7.17+/-0.09. There was also a significant difference between the two groups with regards to mean pO2, pCO2 and BDecf values. Vacuum assisted vaginal delivery was associated with lower fetal arterial oxygen saturation levels as well as lower cord blood pH values compared to those seen after unassisted vaginal delivery. Although decreased, however, the above parameters remained within normal ranges.

Brief Communication: EFFECTS OF QI-TRAINING (QIGONG) ON FOREARM BLOOD GAS CONCENTRATIONS

Using an ABA' design, the authors investigated the effects of Qi training on blood gas concentrations with a 20 min control rest period (A), 1 h of Qi-training (B), and a 20-min rest period (A'). The blood partial pressures of oxygen (PO2) and carbon dioxide (PCO2), and oxygen content, oxygen saturation, and pH were significantly altered. The mean PO2 value increased significantly during Qi training by 14 mmHg (about 24%, p < .01) compared with control A. During Qi-training, the mean decrease in PCO2 was 3 mmHg (about 10%). These results suggest that the practical application of Qi-training may exert a positive regulatory function on physiological status.

Oxygen gradients in the microcirculation.

As arterialized blood transits from the central circulation to the periphery, oxygen exits through the vessel walls driven by radial oxygen gradients that extend from the red blood cell column, through the plasma, the vessel wall, and the parenchymal tissue. This exit determines a longitudinal gradient of blood oxygen saturation whose extent is inversely related to the level of metabolic activity of the tissue, being small for the brain and considerable for skeletal muscle at rest where hemoglobin is only half-saturated with oxygen when blood arrives to the capillaries. Data obtained by a variety of methods show that the oxygen loss is too great to be explained by diffusion alone, and oxygen gradients measured in the arteriolar wall provide evidence that this structure in vivo is a very large oxygen sink, and suggests a rate of oxygen consumption two orders of magnitude greater than seen in in vitro studies. Longitudinal gradients in the capillary network and radial gradients in surrounding tissue also show a dependence on the metabolic rate of the tissue, being more pronounced in brain than in resting skeletal muscle and mesentery. Mean PO2 values increase from the postcapillary venules to the distal vessels of this network while radial gradients indicate additional oxygen loss. This circumstance may be due to pathways with higher flow having higher oxygen content than low flow pathways as well as possible oxygen uptake from adjacent arterioles. Taken together, these newer findings on oxygen gradients in the microcirculation require a reexamination of existing concepts of oxygen delivery to tissue and the role of the capillaries in this process.

Oxygenation of advanced head and neck cancer: prognostic marker for the response to primary radiochemotherapy.

Recent clinical studies suggest that the degree of tumor oxygenation may be predictive of the response of radiation therapy for cancer. In an exploratory investigation of cervical lymph node metastases in 27 patients with advanced squamous cell carcinoma of the oropharynx and hypopharynx, this relationship was investigated by means of oxygen measurements with an Eppendorf PO (2) histograph. The measurements were made before the start of radiation therapy and after the first week of therapy. Clinical response was evaluated 6 weeks after the completion of therapy. Before therapy, marked hypoxia was observed in the lymph node metastases, with a mean PO (2) value of 16.1 +/- 8.2 mm Hg and a hypoxic fraction (PO (2) < 10 mm Hg) of 56.4% +/- 20.0%. After the first week of radiation (9 Gy) there was a general reoxygenation (DeltaPO (2) = 5.0 +/- 10.1 mm Hg, P < 0.05; Deltahypoxic fraction = -11.3% +/- 31.3%, P = 0.11). A relationship between the degree of reoxygenation and tumor response was not observed. Patients without at least partial lymph node response (n = 8) showed poorer pretherapeutic oxygenation (PO (2) mean = 11.1 +/- 2.9 mm Hg) than those who responded to the therapy (n = 19, PO (2) mean = 18.2 +/- 8.8 mm Hg). In this investigation of a defined set of patients with advanced carcinoma of the oropharynx and hypopharynx, we found that pretherapeutic oxygenation data are predictive for the therapeutic response to radiation therapy or radiochemotherapy.

Cavernous oxygen tension in the patients with erectile dysfunction.

We designed a study consisting of 27 consecutive patients with erectile dysfunction in order to evaluate the role of cavernous oxygen tension. Patients were completely evaluated by history, physical examination, multiple blood analyses, serum testosterone level measurements, papaverine test, color duplex sonography and dynamic infusion cavernosometry-cavernosography. Blood gas samples were obtained from femoral artery and corpus cavernosum before drug injection and also from corpus cavernosum at 5, 10, 20, 30, 40 min following drug injection. Aetiologic classification of erectile dysfunction in our patients was as follows: psychogenic in 8, cavernosal failure in 14 and arterial disease in 5 cases. At flaccidity, no significant differences were found in the mean pO2, sO2, pCO2 and pH values of patient groups. After injection of intracavernous papaverine, results of the cavernous pO2 (P < 0.05), sO2 (P < 0.05) levels were found to be statistically significantly different between patients with vascular and psychogenic erectile dysfunction. Analysis of maximal cavernosal oxygen tension and PSV revealed statistically significant correlation (r = 0.66, P < 0.001). The results of this study suggest that changes in arterial and cavernosal pO2 and sO2 values may be contributing factors or co-factors in erectile failure.