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Abstract Background Arterial blood gas analysis (ABGA) plays a vital role in emergency and intensive care, which is affected by many factors, such as different instrumentation, temperature, and testing time. However, there are still no relevant reports on the difference in discarding different blood volumes on ABGA values. Methods We enrolled 54 patients who underwent thoracoscopic surgery and analysed differences in blood gas analysis results when different blood volumes were discarded from the front line of the arterial heparin blood collector. A paired t test was used to compare the results of the same patient with different volumes of blood discarded from the samples. The difference was corrected by Bonferroni correction. Results Our results demonstrated that the PaO2, PaCO2, and THbc were more stable in the 4th ml (PaO2 = 231.3600 ± 68.4878 mmHg, PaCO2 = 41.9232 ± 7.4490 mmHg) and 5th ml (PaO2 = 223.7600 ± 12.9895 mmHg, PaCO2 = 42.5679 ± 7.6410 mmHg) blood sample than in the 3rd ml (PaO2 = 234.1000 ± 99.7570 mmHg, PaCO2 = 40.6179 ± 7.2040 mmHg). Conclusion It may be more appropriate to discard the first 3 ml of blood sample in the analysis of blood gas results without wasting blood samples.

Background: Arterial blood gas analysis (ABGA) plays a vital role in emergency and intensive care, which is affected by many factors, such as different instrumentation, temperature, and testing time. However, there are still no relevant reports on the difference in discarding different blood volumes on ABGA values. Methods: We enrolled 54 patients who underwent thoracoscopic surgery and analysed differences in blood gas analysis results when different blood volumes were discarded from the front line of the arterial heparin blood collector. A paired t test was used to compare the results of the same patient with different volumes of blood discarded from the samples. The difference was corrected by Bonferroni correction. Results: Our results demonstrated that the PaO2, PaCO2, and THbc were more stable in the 4th ml (PaO2 = 231.3600 ± 68.4878 mmHg, PaCO2 = 41.9232 ± 7.4490 mmHg) and 5th ml (PaO2 = 223.7600 ± 12.9895 mmHg, PaCO2 = 42.5679 ± 7.6410 mmHg) blood sample than in the 3rd ml (PaO2 = 234.1000 ± 99.7570 mmHg, PaCO2 = 40.6179 ± 7.2040 mmHg). Conclusion: It may be more appropriate to discard the first 3 ml of blood sample in the analysis of blood gas results without wasting blood samples. [ABSTRACT FROM AUTHOR]

Preoxygenation is the administration of oxygen former to the induction of anesthesia, it permits a safety shield during stages of apnoea and hypoventilation and it also prolongs the time period of safe apnoea. During anesthesia, oxygenation chiefly depends on alveolar ventilation, distribution of ventilation/perfusion ratio, and consumption of O2. The highest preoxygenation is attained when the alveolar and arterial tissues and venous compartments are all occupied with oxygen. During induction of general anesthesia in patients, the usage of 100% oxygen has become standard practice, although preoxygenation was primarily proposed as an optional precautionary measure. Oxygenation techniques is a safe intubation technique for the majority of the surgical patients. Materials And Methods: The study was randomized control study with duration of 11 months. The study was conducted by the Department of Anesthesiology at Shadan Institute of Medical Sciences (SIMS), Hyderabad. The patients were explained regarding the study, the procedure and complications of arterial cannulation and the informed consent form was collected from all participating patients before the commencement of the study. 60 patients in the age group between 20-60 years of age and of either gender, belonging to ASA grade I-II scheduled for elective surgeries under general anesthesia, were included in the study and divided into two equal groups (Group a and Group b) of 30 each. ABG samples were obtained before and after preoxygenation. All patients were instructed regarding the procedure of preoxygenation and procedure for obtaining an arterial blood sample. Results: In group A (100% oxygen) the mean value for age (20-60yrs) is 1.50±0.82, and in group B (60% oxygen) it is found to be 1.52±0.80. In group A (100% oxygen) the mean value for gender is 1.45±0.45, and in group B (60% oxygen) it is found to be 1.43±0.50. BMI (mg/m2) was measured and in group A (100% oxygen) the mean value is 1.43±0.77 and in group B (60% oxygen), it is 1.37±0.76. Comparison of partial pressure of oxygen (PaO2) in the study groups was done, group A (100% oxygen) showed 99.03±6.10 at PaO2 (0 mins) and 100±0.00 at PaO2 (3 mins). Group B (60% oxygen) showed 99.05±5.67 at PaO2 (0 mins) and 100±0.00 at PaO2 (3 mins). Statistical significance (p<0.001*) was found between group A (100% oxygen) and group B (60% oxygen). Comparison of level of oxygen saturation (SpO2) in the study groups was done, group A (100% oxygen) showed 98.50±0.60 at SpO2 (0 mins) and 100±0.00 at SpO2 (3 mins). Group B (60% oxygen) showed 98.50±0.51 at SpO2 (0 mins) and 100±0.00 at SpO2 (3 mins). Conclusion: To be more apt, currently there is no clinical evidence claiming the increase in incidence of hypoxia and its complications with a lower FiO2. The findings of this current study performed over 60 patients could be reliable fundamental evidence for future references. Furthermore, the conclusions of our study could widen up the horizon for the anesthesiologists during times of oxygen scarcity. [ABSTRACT FROM AUTHOR]

Chronic obstructive pulmonary disease (COPD) and emphysema are characterized by functional and structural damage which increases the spaces for gaseous diffusion and impairs oxygen exchange. Here we explore the potential for hyperpolarized (HP) 3He MRI to characterize lung structure and function in a large-scale population-based study. Participants (n = 54) from the Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study, a nested case-control study of COPD among participants with 10+ packyears underwent HP 3He MRI measuring pAO2, apparent diffusion coefficient (ADC), and ventilation. HP MRI measures were compared to full-lung CT and pulmonary function testing. High ADC values (>0.4 cm2/s) correlated with emphysema and heterogeneity in pAO2 measurements. Strong correlations were found between the heterogeneity of global pAO2 as summarized by its standard deviation (SD) (p < 0.0002) and non-physiologic pAO2 values (p < 0.0001) with percent emphysema on CT. A regional study revealed a strong association between pAO2 SD and visual emphysema severity (p < 0.003) and an association with the paraseptal emphysema subtype (p < 0.04) after adjustment for demographics and smoking status. HP noble gas pAO2 heterogeneity and the fraction of non-physiological pAO2 results increase in mild to moderate COPD. Measurements of pAO2 are sensitive to regional emphysematous damage detected by CT and may be used to probe pulmonary emphysema subtypes. HP noble gas lung MRI provides non-invasive information about COPD severity and lung function without ionizing radiation.

Background and Objective: Retinopathy of Prematurity (ROP), as a retinal vasoproliferative disease, is affected by the incomplete development of the respiratory system of premature babies. Since premature babies suffering from ROP have a lower level of partial pressure of oxygen (PO2), the present study was conducted to investigate the effect of PO2 and venous oxygen saturation in treatment response of ROP patients. Methods: This retrospective cohort study (2010-2020) was conducted in the neonatal intensive care unit of Ayatollah Rouhani hospital in Babol among 502 premature babies (less than 34 weeks of pregnancy and with a birth weight of less than 2500 grams). ROP was diagnosed and determined by an ophthalmologist based on the ICROP index on the first day of birth. Data related to PO2 and venous oxygen saturation were collected from patients' files. After receiving standard treatment for ROP, patients were examined and compared in two groups of "completely cured" and "other patients" (including partial recovery, no change, and disease progression) in terms of the effect of PO2 and venous oxygen saturation on the decrease or increase in stage (I to IV) and zone (I, II, III). Findings: Of the 502 babies examined, 193 had stage I, 232 had stage II, 76 had stage III, 1 had stage IV, and 55 had zone I, 245 had zone II, and 202 had zone III involvement. The mean level of PO2 and oxygen saturation between the two groups of "completely cured" patients and "other patients" did not have a statistically significant difference. The mean level of PO2 and oxygen saturation between the three groups of patients with partial recovery, patients with no change and patients with disease progression did not show a statistically significant difference. Furthermore, the levels of PO2 and venous oxygen saturation were not related to the change of stage and zone in patients with ROP. Conclusion: The results of the study showed that lack of oxygen is effective in causing ROP and oxygen therapy has an effective role in the treatment of ROP patients, but the amount of oxygen at the beginning of ROP diagnosis is not related to the treatment process of ROP. [ABSTRACT FROM AUTHOR]

Background: Glucose oxidase (GOx)-based blood glucose monitors (BGMs) are influenced by the partial pressure of oxygen (Po 2 ) within the applied sample. Limited in-clinic data exists regarding the quantitative effect of Po 2 in unmanipulated capillary fingertip blood samples across physiologically representative glucose and Po 2 ranges., Method: Clinical accuracy data were collected as part of a BGM manufacturer's ongoing post-market surveillance program for a commercially available GOx-based BGM test-strip. The data set comprised 29 901 paired BGM-comparator readings and corresponding Po 2 values from 5 428 blood samples from a panel of 975 subjects., Results: A linear regression-calculated bias range of 5.22% (+0.72% [low Po 2 : 45 mm Hg] to -4.5% [high Po 2 : 105 mm Hg]); biases calculated as absolute at <100 mg/dL glucose was found. Below the nominal Po 2 of 75 mm Hg, a linear regression bias of +3.14% was calculated at low Po 2 , while negligible impact on bias (regression slope: +0.002%) was observed at higher than nominal levels (>75 mm Hg). When evaluating BGM performance under corner conditions of low (<70 mg/dL) and high (>180 mg/dL) glucose, combined with low and high Po 2 , linear regression biases ranged from +1.52% to -5.32% within this small group of subjects and with no readings recorded at <70 mg/dL glucose at low and high Po 2 ., Conclusions: Data from this large-scale clinical study, performed on unmanipulated fingertip capillary bloods from a diverse diabetes population, indicate Po 2 sensitivity of the BGM to be markedly lower than published studies, which are mainly laboratory-based, requiring artificial manipulation of oxygen levels in aliquots of venous blood., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: SS, SP, HC, and MG are employees of LifeScan Scotland, Ltd.

Endothelial PAS domain protein 1 gene (EPAS1) is a member of the HIF gene family. This gene encodes a transcription factor subunit that is involved in the induction of oxygen-regulated genes. Several studies have demonstrated that a mutation in EPAS1 could affect oxygen sensing, polycythemia, and hemoglobin level. However, whether EPAS1 mutation affects sheep oxygen metabolism is still unknown. Therefore, we explored the relationship between the variation of EPAS1 and oxygen metabolism in sheep. In this study, variations in ovine EPAS1 exon 15 were investigated in 332 Tibetan sheep and 339 Hu sheep by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis. In addition, we studied the effect of these variations on blood gas in 176 Tibetan sheep and 231 Hu sheep. Finally, the mRNA expression of EPAS1 in six tissues of Hu sheep and Tibetan sheep living at different altitudes (2500 m, 3500 m, and 4500 m) was analyzed by real-time quantitative PCR (RT-qPCR). Four alleles (A, B, C, and D) were detected, and their distributions highly differed between Tibetan sheep and Hu sheep. In Tibetan sheep, B was the dominant allele, and C and D alleles were rare, whereas all four alleles were common in Hu sheep. Six single nucleotide polymorphisms (SNPs) were identified between the four alleles and one of them was non-synonymous (p.F606L). While studying the blood gas levels in Tibetan sheep and Hu sheep, one variant region was found to be associated with an elevated pO2 and sO2, which suggested that variations in EPAS1 are associated with oxygen metabolism in sheep. RT-qPCR results showed that EPAS1 was expressed in the six tissues of Hu sheep and Tibetan sheep at different altitudes. In addition, the expression of EPAS1 in four tissues (heart, liver, spleen, and longissimus dorsi muscle) of Hu sheep was lower than that in Tibetan sheep from three different altitudes, and the expression of EPAS1 was positively correlated with the altitude. These results indicate that the variations and expression of EPAS1 is closely related to oxygen metabolism. [ABSTRACT FROM AUTHOR]

Chronic obstructive pulmonary disease (COPD) and emphysema are characterized by functional and structural damage which increases the spaces for gaseous diffusion and impairs oxygen exchange. Here we explore the potential for hyperpolarized (HP) 3He MRI to characterize lung structure and function in a large-scale population-based study. Participants (n = 54) from the Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study, a nested case-control study of COPD among participants with 10+ packyears underwent HP 3He MRI measuring pAO2, apparent diffusion coefficient (ADC), and ventilation. HP MRI measures were compared to full-lung CT and pulmonary function testing. High ADC values (>0.4 cm2/s) correlated with emphysema and heterogeneity in pAO2 measurements. Strong correlations were found between the heterogeneity of global pAO2 as summarized by its standard deviation (SD) (p < 0.0002) and non-physiologic pAO2 values (p < 0.0001) with percent emphysema on CT. A regional study revealed a strong association between pAO2 SD and visual emphysema severity (p < 0.003) and an association with the paraseptal emphysema subtype (p < 0.04) after adjustment for demographics and smoking status. HP noble gas pAO2 heterogeneity and the fraction of non-physiological pAO2 results increase in mild to moderate COPD. Measurements of pAO2 are sensitive to regional emphysematous damage detected by CT and may be used to probe pulmonary emphysema subtypes. HP noble gas lung MRI provides non-invasive information about COPD severity and lung function without ionizing radiation. [ABSTRACT FROM AUTHOR]

Background: Pulmonary embolism (PE) is extremely rare after shoulder arthroscopy. However, early identification of the situation deserves attention due to its potential risk of causing death. By now, it is still difficult to detect the PE without symptoms and clear sources during the perioperative period. Case presentation: We report here two cases of asymptomatic PE, both happening within 24 h after shoulder arthroscopy, without any detected deep venous thrombosis of extremities. It is suspected the cases were due to the abnormal decrease in partial pressures of oxygen and arterial oxygen saturation, and were confirmed by computed tomography pulmonary angiography. We also discuss the reason why the patients showed no related symptoms when PE occurred and perform a review of PE following shoulder arthroscopy. Conclusions: This report highlights that PE could occur in the early phase after shoulder arthroscopy. An unexplained decrease in partial pressure of oxygen or arterial oxygen saturation should be considered seriously. The symptoms of PE might be masked due to patients’ tolerance to hypoxia.

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Proning is the process of turning the patient from their supine (lying on their back) position to lying on their abdomen. It is a medically accepted position for improving oxygenation while breathing. Respiration in supine position, compresses the posterior surface of the lung preventing normal distension of the alveoli. This results in suboptimal oxygenation of the blood circulating in the lobes of the lung, particularly lower lobes. Lowered V/Q ratio from these regions of the lung contributes to the venous admixture. In the prone position, the heart with its pericardial chamber, occupies anterior dependent portion of the mediastinum, resulting in better expansion of the alveoli. This leads to improved V/Q ratio from these regions and lowers the physiological shunt effect on the oxygen saturation.

The variation in the conformations of hemoglobin heme and globin in response to different oxygen partial pressures (pO2) has been studied by Raman spectroscopy inside erythrocytes and in hemoglobin dissolved in incubation medium. The spectra of hemoglobin inside erythrocytes and in the medium show that several characteristic bands in the range from 1000 to 1700 cm–1 (stretching vibrations in the heme group) and in the high-frequency range from 2800 to 3000 cm–1 (stretching vibrations in globin amino acids) vary with pO2 levels. The curve of hemoglobin saturation with oxygen (sO2) obtained from the Raman-scattering data displays sigmoidal behavior only in hemoglobin inside erythrocytes. It has been shown that differences in heme conformation at different pO2 levels affect the ability of hemoglobin to form complexes with nitric oxide. As the pO2 level increases, the conformational changes of hemoglobin heme in the cell entail an increase in the contribution of vibrations of lateral –CH3 groups in pyrrole half-rings and group vibrations of bonds inside pyrrole half-rings, whereas the globin conformation is associated with a higher contribution of vibrations from H-methine groups and symmetrical terminal methylene groups in amino acids. [ABSTRACT FROM AUTHOR]

Patients admitted in the intensive care unit (ICU) are always managed with excessive high fraction of inspired oxygen and have hyperoxia for a significant period of time, which has potential harms. The guidelines for the management of patients in ICUs do not provide the target values for partial pressure of oxygen or arterial oxyhemoglobin saturations. The study was a before-after investigation comparing two time periods in which different oxygenation strategies were applied. Data of oxygen control, outcome measures, and mortality of a total of 273 patients (>18 years) admitted at least for 2 days in ICUs and received treatment for the sepsis were retrospectively collected and analyzed. Patients were received usual oxygen supplementation (targeted partial pressure of oxygen: 150 mmHg; a high fraction of inspired oxygen: 0.4; UOS cohort; n = 142) or conservative oxygen supplementation (targeted partial pressure of oxygen: 70–100 mmHg; a high fraction of inspired oxygen as low as possible; COS cohort; n = 131). Mechanical ventilation-free hours were significantly higher for patients of COS cohort than those of UOS cohort (77.99 ± 21.26 h/patient vs 70.01 ± 23.57 h/patient, p = 0.016). ICUs length of stays of patients of COS cohort was fewer than those of UOS cohort (7.05 ± 2.13 days/patient vs 7.69 ± 2.43 days/patients, p = 0.016). The probability of survival of patients was higher among patients of COS cohort than those of UOS cohort (p = 0.049). A higher number of patients from UOS cohort needed vasopressors than those from COS cohort (55 vs 35, p = 0.039). Conservative oxygen supplementation to maintain partial pressure of oxygen was improved outcome measures and decreases mortality as compared to that of usual oxygen supplementation. Level of Evidence: III. Technical Efficacy Stage: 4. [ABSTRACT FROM AUTHOR]

Background: Pulmonary embolism (PE) is extremely rare after shoulder arthroscopy. However, early identification of the situation deserves attention due to its potential risk of causing death. By now, it is still difficult to detect the PE without symptoms and clear sources during the perioperative period. Case presentation: We report here two cases of asymptomatic PE, both happening within 24 h after shoulder arthroscopy, without any detected deep venous thrombosis of extremities. It is suspected the cases were due to the abnormal decrease in partial pressures of oxygen and arterial oxygen saturation, and were confirmed by computed tomography pulmonary angiography. We also discuss the reason why the patients showed no related symptoms when PE occurred and perform a review of PE following shoulder arthroscopy. Conclusions: This report highlights that PE could occur in the early phase after shoulder arthroscopy. An unexplained decrease in partial pressure of oxygen or arterial oxygen saturation should be considered seriously. The symptoms of PE might be masked due to patients' tolerance to hypoxia. [ABSTRACT FROM AUTHOR]

Abstract Objective Exposure to hyperoxemia and hypoxemia is common in out-of-hospital cardiac arrest (OHCA) patients following return of spontaneous circulation (ROSC), but its effects on neurological outcome are uncertain, and study results are inconsistent. Methods Exploratory post hoc substudy of the Target Temperature Management (TTM) trial, including 939 patients after OHCA with return of spontaneous circulation (ROSC). The association between serial arterial partial pressures of oxygen (PaO2) during 37 h following ROSC and neurological outcome at 6 months, evaluated by Cerebral Performance Category (CPC), dichotomized to good (CPC 1–2) and poor (CPC 3–5), was investigated. In our analyses, we tested the association of hyperoxemia and hypoxemia, time-weighted mean PaO2, maximum PaO2 difference, and gradually increasing PaO2 levels (13.3–53.3 kPa) with poor neurological outcome. A subsequent analysis investigated the association between PaO2 and a biomarker of brain injury, peak serum Tau levels. Results Eight hundred sixty-nine patients were eligible for analysis. Three hundred patients (35%) were exposed to hyperoxemia or hypoxemia at some time point after ROSC. Our analyses did not reveal a significant association between hyperoxemia, hypoxemia, time-weighted mean PaO2 exposure or maximum PaO2 difference and poor neurological outcome at 6-month follow-up after correction for co-variates (all analyses p = 0.146–0.847). We were not able to define a PaO2 level significantly associated with the onset of poor neurological outcome. Peak serum Tau levels at either 48 or 72 h after ROSC were not associated with PaO2. Conclusion Hyperoxemia or hypoxemia exposure occurred in one third of the patients during the first 37 h of hospitalization and was not significantly associated with poor neurological outcome after 6 months or with the peak s-Tau levels at either 48 or 72 h after ROSC.

Introduction: Flap monitoring using partial pressure of oxygen (pO2) is a proven modality. Instruments needed are expensive and are not readily available to a clinician. Here, pO2 of flap has been determined using readily available and cheap methods, and a cut-off value is calculated which helps in predicting flap outcome. Methods and Results: Total 235 points on 84 skin flaps were studied. Capillary blood was collected from flap and fingertip using 1-ml syringes after at least 30 min of flap inset, and pO2 analysed using blood gas analyser. Fall/change of pO2 (difference of mean of pO2 [diff-pO2]) was also calculated by subtracting the flap pO2 from the finger pO2. Flap was monitored clinically in post-operative period and divided into two groups depending on its survival with Group 1 – dead points and Group 2 – alive points. pO2 and diff-pO2 amongst both the groups were compared and found to be statistically different (P = 0.0001). Cut-off value calculated for pO2 was found to be 68.503 mmHg of flap pO2 compared from finger pO2 was calculated as a cut-off with sensitivity of 94.12 and specificity of 79.60%. Conclusions: Flap areas having intra-operative pO2 value 68.5 mmHg, chances of those points getting necrosed in post-operative period are high.

We investigate theoretically the main aspects of the formation of cadmium oxide thin films (by metal evaporation) relative to non-stoichiometry and partial pressure of oxygen. As a matter of fact, mathematical relationships are obtained from that the Cd and CdO phases coexist when the corresponding chemical reaction begins. In fact, the Cd pressure (equal to the CdO one) is found to be proportional to the oxygen absolute temperature which, in turn, equals the Cd (or CdO) absolute temperature. Moreover, the electron drift-mobility in CdO is obtained as a function of the above temperature and as a function of the oxygen partial pressure. We emphasize that chemical kinetics is studied quantitatively by taking into account that a part of cadmium does not combine with oxygen, that is, stoichiometry vanishes. This means that, initially, CdO is still amorphous. This state occurs when the partial pressure of oxygen is smaller than the so-called optimum value of pressure which, by definition, is the value of the oxygen partial pressure at which the optical transmittance of CdO is maximum. These issues are investigated (by means of theoretical considerations) accurately in consistency with experimental data. [ABSTRACT FROM AUTHOR]

Background: It is essential to monitor the saturation of oxygen in newborns receiving supplemental oxygen to reduce the incidence of exposure to hyperoxemia and their potential hazardous effects of radical oxygen species. The oxygen saturation is measured by pulse oximeter which is a non-invasive tool. Arterial blood gas is used to determine the pH, PaCO2, PaO2 and the bicarbonate level. Aims and Objectives: This study aimed at searching the reliability of non-invasive pulse oximeter in knowing oxygen saturation (SpO2) in comparison with arterial blood PaO2 in neonates with respiratory distress. The primary objective was to correlate the values between partial pressure of oxygen (PaO2) and pulse oxygen saturation by pulse oximeter (SpO2).The secondary objectives were 1) To find out the efficacy of pulse oximeter in diagnosing hypoxia in comparison with PaO2. 2) To find out efficacy of pulse oximeter in diagnosing hyperoxemia in comparison with PaO2. Material and Method: Observational study was conducted on thirty neonates suffering from different causes of respiratory distress in NICU of Krishna Hospital, Karad during December 2017 to September 2019. The PaO2 measurements were obtained from the blood analyzer; simultaneous pulse oxygen saturation were recorded. Results: A significant correlation was observed between values of pulse oxygen saturation by pulse oximeter (SpO2) and partial pressure of oxygen (PaO2) by arterial blood sampling (r value -0.73, p<0.01) On ROC curve analysis, sensitivity and specificity of pulse oximetry in prediction of hypoxemia was 87.5% and 85.7% at cut-off of 90% and 91% each. The sensitivity and specificity of pulse oximetry in prediction of hyperoxemia was 100% and 71.4% at cuff-off of 94% while it was 88.9% and 76.2% at cut-off of 95% respectively. Conclusion: Pulse oximetry showed a good correlation with arterial blood PaO2. Oxygen saturation measured by pulse oximetry is a good diagnostic and prognostic tool for detecting hypoxemia and hyperoxemia. [ABSTRACT FROM AUTHOR]

Our understanding of how capillary blood flow and oxygen distribute across cortical layers to meet the local metabolic demand is incomplete. We addressed this question by using two-photon imaging of resting-state microvascular oxygen partial pressure (PO2) and flow in the whisker barrel cortex in awake mice. Our measurements in layers I-V show that the capillary red-blood-cell flux and oxygenation heterogeneity, and the intracapillary resistance to oxygen delivery, all decrease with depth, reaching a minimum around layer IV, while the depth-dependent oxygen extraction fraction is increased in layer IV, where oxygen demand is presumably the highest. Our findings suggest that more homogeneous distribution of the physiological observables relevant to oxygen transport to tissue is an important part of the microvascular network adaptation to local brain metabolism. These results will inform the biophysical models of layer-specific cerebral oxygen delivery and consumption and improve our understanding of the diseases that affect cerebral microcirculation.

Portable clinical analysers are gradually being involved in on-site assessment of haematic parameters in fish. The purpose of this study was to evaluate the i-STAT portable clinical analyser (i-STAT PCA) for accuracy and reliability of measuring blood pH, partial pressure of oxygen (pO2), haematocrit, haemoglobin, sodium, potassium and calcium in Atlantic cod (Gadus morhua). Haematological parameters detected with the i-STAT PCA were compared with conventional laboratory techniques (CLTs). Two types of disposable cartridges were used (CHEM8+ and CG4+) with the i-STAT PCA, and experiments were performed at two different temperature regimes (5 °C and 15 °C) and four different carbon dioxide (CO2) levels (0%, 0.1%, 0.5% and 1%). All blood parameters measured with the i-STAT PCA showed heterogeneous inaccuracy under the tested conditions, but the highest discrepancies were registered in blood pO2. The i-STAT PCA systematically overestimated the pO2 measurements. Our research suggests that i-STAT PCA is not an appropriate tool for pO2 measurements especially in coldwater fish species. The i-STAT PCA consistently underestimated the pH and haematocrit values especially at a lower temperature, although those parameters indicate significant high correlation at 15 °C. Furthermore, the analysed ions showed overestimation of sodium and underestimation of potassium and calcium. [ABSTRACT FROM AUTHOR]

Background: Chest physiotherapy (CPT) and positioning of neonates has been used in many developed countries around the world to improve airway clearance and avoid lung complications, but the combined effect of both techniques is less documented. The objective of the study was to compare the effectiveness of chest physiotherapy in prone position versus conventional chest physiotherapy in ventilated neonates on respiratory outcomes. Methods: The study design was randomized controlled pilot study. Participants: 12 ventilated neonates fitting in Inclusion Criteria. They were randomly divided into two groups (n=6 in each group) using simple random sampling i.e. Experimental group (4female and 2male) (Chest Physiotherapy and Prone Positioning) and the Control group (3 females and 3males) (Conventional Chest Physiotherapy). Primary outcome measures were SpO2 saturation, Partial Pressure of Arterial Oxygen (PaO2) & Peak Inspiratory Pressure (P.I.P.). Outcomes were recorded Pre & Post of every 120 minutes session of Intervention twice daily with a gap of 6 hours for consecutive three days for the experimental group while for the control group, parameters were measured at the same time of the day. Result: Total 10 participants completed the study protocol. On comparison of three parameters in two groups using the unpaired t-test, we found that there was a significant difference (p< 0.05) in SpO2 and PaO2 in both groups but no difference ( p >0.05) in P.I.P. levels. Conclusion: Chest physiotherapy in the prone position for ventilated neonate concluded with a higher oxygen saturation (SpO2) and partial pressure of oxygen in the arterial blood (PaO2) when compared to conventional chest physiotherapy.

Objective: Exposure to hyperoxemia and hypoxemia is common in out-of-hospital cardiac arrest (OHCA) patients following return of spontaneous circulation (ROSC), but its effects on neurological outcome are uncertain, and study results are inconsistent.Methods: Exploratory post hoc substudy of the Target Temperature Management (TTM) trial, including 939 patients after OHCA with return of spontaneous circulation (ROSC). The association between serial arterial partial pressures of oxygen (PaO2) during 37 h following ROSC and neurological outcome at 6 months, evaluated by Cerebral Performance Category (CPC), dichotomized to good (CPC 1-2) and poor (CPC 3-5), was investigated. In our analyses, we tested the association of hyperoxemia and hypoxemia, time-weighted mean PaO2, maximum PaO2 difference, and gradually increasing PaO2 levels (13.3-53.3 kPa) with poor neurological outcome. A subsequent analysis investigated the association between PaO2 and a biomarker of brain injury, peak serum Tau levels.Results: Eight hundred sixty-nine patients were eligible for analysis. Three hundred patients (35%) were exposed to hyperoxemia or hypoxemia at some time point after ROSC. Our analyses did not reveal a significant association between hyperoxemia, hypoxemia, time-weighted mean PaO2 exposure or maximum PaO2 difference and poor neurological outcome at 6-month follow-up after correction for co-variates (all analyses p = 0.146-0.847). We were not able to define a PaO2 level significantly associated with the onset of poor neurological outcome. Peak serum Tau levels at either 48 or 72 h after ROSC were not associated with PaO2.Conclusion: Hyperoxemia or hypoxemia exposure occurred in one third of the patients during the first 37 h of hospitalization and was not significantly associated with poor neurological outcome after 6 months or with the peak s-Tau levels at either 48 or 72 h after ROSC. [ABSTRACT FROM AUTHOR]

Introduction: Flap monitoring using partial pressure of oxygen (pO2) is a proven modality. Instruments needed are expensive and are not readily available to a clinician. Here, pO2 of flap has been determined using readily available and cheap methods, and a cut-off value is calculated which helps in predicting flap outcome. Methods and Results: Total 235 points on 84 skin flaps were studied. Capillary blood was collected from flap and fingertip using 1-ml syringes after at least 30 min of flap inset, and pO2 analysed using blood gas analyser. Fall/change of pO2 (difference of mean of pO2 [diff-pO2]) was also calculated by subtracting the flap pO2 from the finger pO2. Flap was monitored clinically in post-operative period and divided into two groups depending on its survival with Group 1 - dead points and Group 2 - alive points. pO2 and diff-pO2 amongst both the groups were compared and found to be statistically different (P = 0.0001). Cut-off value calculated for pO2 was found to be <86.3 mmHg with a sensitivity of 100% and specificity of 89.05%. The difference of >68.503 mmHg of flap pO2 compared from finger pO2 was calculated as a cut-off with sensitivity of 94.12 and specificity of 79.60%. Conclusions: Flap areas having intra-operative pO2 value <86.3 mmHG have higher chances (60.71%) of getting necrosis later. Similarly, if diff-pO2 compared to fingertip is >68.5 mmHg, chances of those points getting necrosed in post-operative period are high. [ABSTRACT FROM AUTHOR]

The partial pressure of oxygen (PO2) in the tumor microenvironment directly affects tumor sensitivity to chemotherapy. In the present study, a lithium phthalocyanine probe was implanted into MCF-7 human breast cancer cells, followed by transplant of the cells into nude mice. The present study used an electron paramagnetic resonance (EPR) oximetry measuring technique to dynamically monitor PO2 in the tumor microenvironment prior to and following chemotherapy, and aimed to determine the precise time window in which the microenvironmental PO2 peaked following chemotherapy. The results indicated that PO2 was significantly higher in breast cancer compared with control (P<0.05). Following four cycles of chemotherapy, the activity of NADH dehydrogenase, succinate-cytochrome c reductase and cytochrome c oxidase in the mitochondria of cells was significantly reduced when compared with their activity prior to chemotherapy (P<0.05). Regional blood flow in tumor tissues undergoing chemotherapy was significantly lower than that prior to chemotherapy (P<0.05). The rate of cellular apoptosis in the PO2 peak-based chemotherapy group was significantly greater than that in the conventional chemotherapy group after two and four cycles of chemotherapy (P<0.05). Tumor volume in the PO2 peak-based chemotherapy group was significantly reduced compared with that in the 0.9% NaCl solution control and the conventional chemotherapy groups after four cycles of chemotherapy (P<0.05). The tumor inhibitory rate of the experimental group was significantly higher than that of the conventional chemotherapy group (P<0.01). In conclusion, the present study may provide guidance for the development of effective strategies depending on tumor-maximal response to chemotherapy in an oxygen-rich environment. Additionally, the present study aimed to establish a foundation for a clinical noninvasive assessment intended to guide treatment and formulate individual regimens, in order to improve cancer therapeutics, sensitivity monitoring and curative effect estimation. [ABSTRACT FROM AUTHOR]

By considering the partial pressure of oxygen in the deposition process of cadmium oxide, we calculate the maximum transmittance of cadmium oxide in the visible range, which is achieved at the so-called optimum partial pressure of oxygen, this value of pressure being a key figure of merit. Our formulation agrees with experimental measurements and is consistent with the so-called plasma-optical effect. At this point, an exhaustive evaluation of previous experimental data is performed by doing a detailed comparison among the results from different authors and by performing numerical estimations (including estimations from experimental data) of relevant physical quantities. In fact, a comprehensive discussion relative to comparison between experimental measurements and our theoretical results is presented. [ABSTRACT FROM AUTHOR]

Simple and accurate expressions describing the PaO2-FiO2 relationship in mechanically ventilated patients are lacking. The current study aims to validate a novel mathematical expression for accurate prediction of the fraction of inspired oxygen that will result in a targeted arterial oxygen tension in non-smoking and smoking patients receiving mechanical ventilation following open heart surgeries. One hundred PaO2-FiO2 data pairs were obtained from 25 non-smoking patients mechanically ventilated following open heart surgeries. One data pair was collected at each of FiO2 of 40, 60, 80, and 100% while maintaining same mechanical ventilation support settings. Similarly, another 100 hundred PaO2-FiO2 data pairs were obtained from 25 smoking patients mechanically ventilated following open heart surgeries. The utility of the new mathematical expression in accurately describing the PaO2-FiO2 relationship in these patients was assessed by the regression and Bland-Altman analyses. Significant correlations were seen between the true and estimated FiO2 values in non-smoking (r2 = 0.9424; p < 0.05) and smoking (r2 = 0.9466; p < 0.05) patients. Tight biases between the true and estimated FiO2 values for non-smoking (3.1%) and smoking (4.1%) patients were observed. Also, significant correlations were seen between the true and estimated PaO2/FiO2 ratios in non-smoking (r2 = 0.9530; p < 0.05) and smoking (r2 = 0.9675; p < 0.05) patients. Tight biases between the true and estimated PaO2/FiO2 ratios for non-smoking (-18 mmHg) and smoking (-16 mmHg) patients were also observed. The new mathematical expression for the description of the PaO2-FiO2 relationship is valid and accurate in non-smoking and smoking patients who are receiving mechanical ventilation for post cardiac surgery. [ABSTRACT FROM AUTHOR]

Background: Apnea testing is an essential step in the clinical diagnosis of brain death. Current international guidelines recommend placement of an oxygen (O2) insufflation catheter into the endotracheal tube to prevent hypoxemia, but use of a continuous positive airway pressure (CPAP) valve may be more effective at limiting arterial partial pressure of O2 (PO2) reduction.Methods: We performed a multicenter study assessing consecutive apnea tests in 14 intensive care units (ICUs) in two cities utilizing differing protocols. In one city, O2 catheters are placed and arterial blood gases (ABGs) performed at intervals determined by the attending physician. In the other city, a resuscitation bag with CPAP valve is attached to the endotracheal tube, and ABGs performed every 3-5 min. We assessed arterial PO2, partial pressure of carbon dioxide (PCO2), pH, and blood pressure at the beginning and termination of each apnea test.Results: Thirty-six apnea tests were performed using an O2 catheter and 50 with a CPAP valve. One test per group was aborted because of physiological instability. There were no significant differences in the degree of PO2 reduction (-59 vs. -32 mmHg, p = 0.72), rate of PCO2 rise (3.2 vs. 3.9 mmHg per min, p = 0.22), or pH decline (-0.02 vs. -0.03 per min, p = 0.06). Performance of ABGs at regular intervals was associated with shorter test duration (10 vs. 7 min, p < 0.0001), smaller PCO2 rise (30 vs. 26 mmHg, p = 0.0007), and less pH reduction (-0.20 vs. -0.17, p = 0.0012). Lower pH at completion of the apnea test was associated with greater blood pressure decline (p = 0.006).Conclusion: Both methods of O2 supplementation are associated with similar changes in arterial PO2 and PCO2. Performance of ABGs at regular intervals shortens apnea test duration and may avoid excessive pH reduction and consequent hemodynamic effects. [ABSTRACT FROM AUTHOR]

Oxygen therapy is the main treatment method for acute respiratory failure in children. The method consisting in the administration of oxygen therapy by head box to infants is frequently used in pediatric practice. Objectives. To evaluate the effi ciency of oxygen therapy administered by head box to infants suffering from pneumogenic acute respiratory failure by comparing two methods for measuring hemoglobin oxygen saturation: in arterialized capillary blood and by pulse oximetry. Material and method. 30 infants suffering from pneumogenic acute respiratory failure were studied. We used a clinical appraisal score for acute respiratory failure, which appraises respiratory rate, nasal fl aring, recession, cyanosis, sensorial, before and after oxygen therapy. In arterialized capillary blood we measured partial pressure of oxygen and hemoglobin oxygen saturation, and we used an Automatic Blood Gas System analyzer. We also measured hemoglobin oxygen saturation using a pulse oximeter. Determinations were made before the initiation of oxygen therapy, and 30 minutes and 60 minutes after the initiation of oxygen therapy. Results. As compared to the baseline values, determined before the initiation of oxygen therapy, we recorded a statistically signifi cant improvement in the clinical score both after 30 minutes and 60 minutes from the initiation of oxygen therapy (p

The PalmLab glucometer is a newly designed plasma separation glucose oxidase (GO)-based glucometer. Past studies have shown that the accuracy of GO-based glucometers is compromised when measurements are taken in patients with high PO2 levels. We performed a two-arm study comparing the fitness of the PalmLab blood glucometer with that of a standard glucose analyzer in monitoring blood glucose levels in pediatric patients, especially when arterial partial pressure of oxygen (PO2) was high. Methods: In the first arm of the study, arterial blood samples from pediatric patients were measured by the PalmLab blood glucometer and the YSI 2302 Plus Glucose/Lactate analyzer. In the second arm of the study, venous blood samples from adult volunteers were spiked with glucose water to prepare three different levels of glucose (65, 150, and 300 mg/dL) and then oxygenated to six levels of PO2 (range, 40–400 mmHg). The biases of the PalmLab glucometer were calculated. Results: A total of 162 samples were collected in the first arm of the study. Results of linear regression showed that the coefficient of determination (R2) between PalmLab glucometer and standard glucose analyzer was 0.9864. Error grid analysis revealed that all the results were within Zone A (clinically accurate estimate zone). The biases between the two systems were low at different PO2 levels. In the second arm of the study, the results were also unaffected by changes in PO2. Conclusion: The PalmLab glucometer provides accurate results in samples with high PO2 and is suitable for measuring arterial glucose levels in pediatric patients.

The effect of hyperoxygenation with carbogen (95% O2 + 5% CO2) and 100% oxygen inhalation on partial pressure of oxygen (pO2) of radiation-induced fibrosarcoma (RIF-1) tumor was investigated. RIF-1 tumors were innoculated in C3H mice, and aggregates of oximetry probe, lithium phthalocyanine (LiPc), was implanted in each tumor. A baseline tumor pO2 was measured by electron paramagnetic resonance (EPR) oximetry for 20 minutes in anesthetized mice breathing 30% O2 and then the gas was switched to carbogen or 100 % oxygen for 60 minutes. These experiments were repeated for 10 days. RIF-1 tumors were hypoxic with a baseline tissue pO2 of 6.2-8.3 mmHg in mice breathing 30% O2. Carbogen and 100% oxygen significantly increased tumor pO2 on days 1 to 5, with a maximal increase at approximately 32-45 minutes on each day. However, the extent of increase in pO2 from the baseline declined significantly on day 5 and day 10. The results provide quantitative information on the effect of hyperoxic gas inhalation on tumor pO2 over the course of 10 days. EPR oximetry can be effectively used to repeatedly monitor tumor pO2 and test hyperoxic methods for potential clinical applications. [ABSTRACT FROM AUTHOR]

Introduction: Donor PO levels are used for assessing organs for lung transplantation (LTx), but survival implications of PO levels in adult cystic fibrosis (CF) patients receiving LTx are unclear. Methods: UNOS registry data spanning 2005-2013 were used to test for associations of donor PO with patient survival and bronchiolitis obliterans syndrome (BOS) in adult (age ≥ 18 years) first-time LTx recipients diagnosed with CF. Results: The analysis included 1587 patients, of whom 1420 had complete data for multivariable Cox models. No statistically significant differences among donor PO categories of ≤200, 201-300, 301-400, or >400 mmHg were found in univariate survival analysis (log-rank test p = 0.290). BOS onset did not significantly differ across donor PO categories (Chi-square p = 0.480). Multivariable Cox models of patient survival supported the lack of difference across donor PO categories. Interaction analysis found a modest difference in survival between the two top categories of donor PO when examining patients with body mass index (BMI) in the lowest decile (≤16.5 kg/m). Conclusions: Donor PO was not associated with survival or BOS onset in adult CF patients undergoing LTx. Notwithstanding statistically significant interactions between donor PO and BMI, there was no evidence of post-LTx survival risk associated with donor PO below conventional thresholds in any subgroup of adults with CF. [ABSTRACT FROM AUTHOR]

Abstract: We investigate diffusivity and conductivity in the context of electronic transport in crystalline cadmium oxide by knowing the electron concentration in CdO as a function of the partial pressure of oxygen in the deposition process of the material in question. From the chemical kinetics of the reaction by which CdO is formed, first we consider an approximate relationship for the electron concentration in terms of the above pressure. In fact, by taking into account this relationship and other issues, we determine the product diffusivityconductivity in crystalline CdO. This product can be considered as a significant figure of merit. [ABSTRACT FROM AUTHOR]

In this paper, the dependence on the partial pressure of oxygen of the shift in the energy band-gap of CdO thin films for the visible region is investigated from the theoretical point of view on an experimental basis. In our analysis, the role played by the dependence of the carrier density upon the above pressure is emphasized.

The partial pressure of oxygen during the deposition process of cadmium oxide is a crucial quantity whose influence on the electrical and optical properties of this material is really very significant (consider, for example, the experimental technique known as activated reactive evaporation). In fact, this paper is a theoretical formulation to evaluate the sensitivity changes of the aforementioned pressure of the electron drift-mobility and velocity in CdO. Indeed, as we will see later, given that the electron relaxation time depends upon the oxygen partial pressure, then the electron drift-mobility, mean free path and velocity also depend on this pressure. Relevant calculations involving the above physical quantities are carried out. [ABSTRACT FROM AUTHOR]

Transcutaneous polarography is one of the most objective noninvasive assessment of the capillary blood flow and microcirculation by controlling the oxygen partial pressure in the subcutaneous tissue. The outcome of research is influenced by such common factors as the oxygen content in the ambient air, the adequacy of the central hemodynamics of the patient, the presence of violations of the transport function of the blood, the pathology of the pulmonary system and local factors (disturbance of the local microcirculation, tissue edema, marked capillary spasm, etc.). For research purposes single-channel analyzers are generally used. Increasing the informative value of biomedical research is possible due to the use multi-channel raster array of oxygen sensors as a primary sensor. The use of such matrices will provide information about the in vivo distribution of the partial pressure of oxygen from the surface of the human skin, to more complete assess of its functional state and dynamics to control the impact of possible therapeutic interventions. The paper analyzes the influence of heat sources on the distribution of temperature field of multi-channel raster array of oxygen sensors as the main component of its operation and determines the optimum configuration of such sources. [ABSTRACT FROM AUTHOR]

Special features of carbooxidation of titanium in the process of saturation by a gas (gas-phase) method from powders are studied. The effects of various process factors, i.e., the temperature and time parameters of the saturation, the composition of the gas component of the saturating medium (the partial pressure of oxygen), its dynamics, the method of feeding into the reaction space of the furnace, and the composition and fineness of the powder carbon-containing component of the medium, are determined. [ABSTRACT FROM AUTHOR]

Purpose Lung pO2 mapping with 3He 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 3He pO2 mapping in patients with chronic obstructive pulmonary disease. Methods Ten patients with moderate to severe chronic obstructive pulmonary disease were scanned with a 3D single breath-hold pO2 mapping sequence. Results 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). Conclusions 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. Magn Reson Med 71:1172-1178, 2014. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Abstract: An innovative oxygen loading system which controls the partial pressure of oxygen (pO2) in a continuous inert gas stream in the range 10−4–10−7 bar is developed and successfully tested. It relies on adjusting the electro-chemical equilibrium in a metal oxide buffer via temperature control. The buffer consists of a mixture of small 1.5mm diameter spheres composed of Cu2O and CuO. The buffer system is integrated into a furnace and heated to the operational temperature range below 900°C. A continuous inert gas stream is guided through the buffer system while at operating temperature. The performance of the loading system is verified by comparing the pO2 values, which are deduced via the buffer temperature following the Ellingham diagrams with the readout of a conventional zirconia-based oxygen sensor. The measured curve follows the Ellingham diagram for this material system within the error margin. The system reveals a fast response time and allows for active control of the partial pressure of oxygen in a laminar streaming inert gas atmosphere with low complexity. [Copyright &y& Elsevier]

Abstract: Electrical conductivity of 10at.% manganese doped yttria (8mol%) stabilized zirconia (Mn-YSZ) has been investigated using electrochemical cell technique in 800–1000°C and 1–10−20 atm oxygen partial pressure range. The electrical conductivity increases according to power law with increasing in 1–10−5 atm range, remains independent in 10−5–10−15 atm range, and slightly decreases with decreasing in 10−15–10−20 atm range. The deviation from power law is attributed to the presence of multivalent state of manganese ions in 1–10−5 atm range. The electrical conductivity of Mn-YSZ is lower than that of yttria stabilized zirconia in reducing atmosphere. At lower oxygen partial pressures, lattice strain, defect association, and electron trapping results in decreased electrical conductivity. [Copyright &y& Elsevier]

Oxygen therapy is the main treatment method for acute respiratory failure in children. The method consisting in the administration of oxygen therapy by head box to infants is frequently used in pediatric practice. Objectives. To evaluate the efficiency of oxygen therapy administered by head box to infants suffering from pneumogenic acute respiratory failure by comparing two methods for measuring hemoglobin oxygen saturation: in arterialized capillary blood and by pulse oximetry. Material and method. 30 infants suffering from pneumogenic acute respiratory failure were studied. We used a clinical appraisal score for acute respiratory failure, which appraises respiratory rate, nasal flaring, recession, cyanosis, sensorial, before and after oxygen therapy. In arterialized capillary blood we measured partial pressure of oxygen and hemoglobin oxygen saturation, and we used an Automatic Blood Gas System analyzer. We also measured hemoglobin oxygen saturation using a pulse oximeter. Determinations were made before the initiation of oxygen therapy, and 30 minutes and 60 minutes after the initiation of oxygen therapy. Results. As compared to the baseline values, determined before the initiation of oxygen therapy, we recorded a statistically significant improvement in the clinical score both after 30 minutes and 60 minutes from the initiation of oxygen therapy (p<0.001). The improvement was greater after 60 minutes. The increase in the partial pressure of oxygen was statistically significant both at the 30 minute and 60 minute determination (p<0.001). Both methods of SaO2 measurement recorded statistically significant increases (p<0.001) in this variable after 30 and 60 minutes, respectively. Conclusions. Oxygen therapy administered by head box improves acute respiratory failure appraised by clinical score. The administration of oxygen therapy by head box to infants significantly increases the values of partial pressure of oxygen and hemoglobin oxygen saturation measured in capillary blood, as well as the values of hemoglobin oxygen saturation determined by pulse oximeter both after 30 minutes and after 60 minutes. The increases in the three parameters are larger after 60 minutes. There is statistically significant concordance between the values of hemoglobin oxygen saturation determined in capillary blood and by pulse oximetry at all determinations. [ABSTRACT FROM AUTHOR]