Search

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.

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., (© 2024. The Author(s).)

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 p O 2 and sO 2 , 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.

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: 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., (© 2021 The Authors. Orthopaedic Surgery published by Chinese Orthopaedic Association and John Wiley & Sons Australia, Ltd.)

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.

Some marine birds and mammals can perform dives of extraordinary duration and depth. Such dive performance is dependent on many factors, including total body oxygen (O 2 ) stores. For diving penguins, the respiratory system (air sacs and lungs) constitutes 30-50% of the total body O 2 store. To better understand the role and mechanism of parabronchial ventilation and O 2 utilization in penguins both on the surface and during the dive, we examined air sac partial pressures of O 2 ( P O 2 ) in emperor penguins ( Aptenodytes forsteri ) equipped with backpack P O 2  recorders. Cervical air sac P O 2  values at rest were lower than in other birds, while the cervical air sac to posterior thoracic air sac P O 2  difference was larger. Pre-dive cervical air sac P O 2  values were often greater than those at rest, but had a wide range and were not significantly different from those at rest. The maximum respiratory O 2 store and total body O 2 stores calculated with representative anterior and posterior air sac P O 2  data did not differ from prior estimates. The mean calculated anterior air sac O 2 depletion rate for dives up to 11 min was approximately one-tenth that of the posterior air sacs. Low cervical air sac P O 2  values at rest may be secondary to a low ratio of parabronchial ventilation to parabronchial blood O 2 extraction. During dives, overlap of simultaneously recorded cervical and posterior thoracic air sac P O 2  profiles supported the concept of maintenance of parabronchial ventilation during a dive by air movement through the lungs., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2021. Published by The Company of Biologists Ltd.)

Introduction: Low brain tissue oxygen tension (PbtO 2 ) has been shown to be an independent factor associated with unfavourable outcomes in traumatic brain injury (TBI). Although PbtO 2 provides clinicians with an understanding of ischaemic and non-ischaemic derangements of brain physiology, the value alone can be the result of several factors, including partial arterial oxygenation pressure (PaO 2 ), haemoglobin levels (Hb) and cerebral perfusion pressure (CPP)., Methods: This chapter presents a single-centre, retrospective cohort study of 70 adult patients with severe TBI who were admitted to the Neurocritical Care Unit (NCCU) at Addenbrooke's Hospital (Cambridge, UK) between October 2014 and December 2017. A total of 303 simultaneous measurements of different variables that included (but were not limited to) intracranial pressure (ICP), PaO 2 , PbtO 2 , CPP and the fraction of inspired oxygen (FiO 2 ) were considered in this work. We conducted a correlation analysis between all of the variables. We also implemented a longitudinal data analysis of the PbtO 2 and PaO 2 /FiO 2 ratio (PF ratio)., Results: There were strong and independent correlations between PbtO 2 and the PF ratio, and between PbtO 2 and PaO 2 , with adjusted p values of <0.001 for both correlations. After adjustment for ICP, age, sex and the Glasgow Coma Scale (GCS) score, a PF ≤ 330 was shown to be an independent risk factor for a compromised PbtO 2 value of <20, with an adjusted odds ratio of 1.94 (95% confidence interval 1.12-3.34) and a p value of 0.02., Conclusion: Brain and lung interactions in patients with TBI patients have complex interrelationships. Our results confirm the importance of employing lung-protective strategies to prevent brain hypoxia in patients with TBI.

Introduction Severe traumatic brain injury (TBI) is a leading cause of death and disability. Not all neuronal damage occurs at the time of primary injury, but rather TBI initiates a cascade of events that leads to secondary brain injury. Oxygenation is one crucial factor in maintaining brain tissue homeostasis post-injury. We performed a retrospective review of patients admitted to a single trauma center after TBI. Statistical analysis was performed to ascertain if the measured partial pressure of oxygen (PaO₂) affected overall outcome at the time of discharge from the hospital. Materials and Methods Statistical analysis was performed retrospectively on patients admitted with a Glasgow Coma Scale (GCS) < 8 and a diagnosis of TBI. GCS and Glasgow Outcome Scale (GOS) were calculated from physical examination findings at the time of hospital discharge or death. Patient data were separated into two groups: those with consistently higher average PaO₂ scores (≥ 150 mmHg; n = 7) and those with lower average PaO₂ scores (< 150 mmHg; n = 8). The minimum requirement to be categorized in the consistently higher group was to have an average hospital day 1 through 5 PaO₂ value of ≥ 150 mmHg. Results Patients with consistent hospital Day 1 through 5 PaO₂ scores of ≥ 150 mmHg had statistically significant higher GCS scores at the end of intensive care unit (ICU)-level care or hospital discharge (mean = 12, p = 0.01), compared to those in group 2 with lower PaO₂ levels (mean = 7.9). There was no statistically significant difference in GOS when comparing the two groups ( p = 0.055); however, the data did show a trend toward significance. Discussion and Conclusion In our study we analyzed patients diagnosed with TBI and stratified them into groups based on PaO₂ ≥ or < 150 mmHg. We demonstrate overall outcome improvement based on GCS with a trend toward improved GOS. The GCS showed statistical significance in patients with PaO₂ consistently ≥ 150 mmHg versus those in group 2 over the first five days of hospitalization., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2020, Wiginton et al.)

Background: thoracic trauma is one of the leading causes of death in all age groups and accounts for 25-50 % of all traumatic injuries. With the term lung injury in blunt chest trauma, we identified a spectrum of conditions: lung contusion, pneumothorax and haemothorax. The aim of this study was to evaluate the utility of arterial blood gas analysis parameters in predicting lung injury in blunt chest trauma., Methods: we included 51 patients presenting to the Emergency Department of "C.T.O." Hospital in Naples [Italy] for blunt chest trauma. The patients were assigned to the Lung Injury Group or to the Non-Lung Injury Group basing on CT scan findings. For each patient, we calculated the alveolar-arterial oxygen gradient [AaDO 2 ], the AaDO 2 augmentation, the arterial partial pressure of oxygen deficit [PaO 2 Deficit] and the ratio between arterial partial pressure of oxygen and fraction of inspired oxygen [P/F]. Areas under the curve [AUC] and receiver operating characteristic [ROC] curve were used to compare the performance of each different test in relation to the detection of lung injury in blunt chest trauma., Results: patients with lung injury had lower oxygen saturation, arterial partial pressure of oxygen, P/F and higher PaO 2 Deficit, AaDO 2 , AaDO 2 augmentation than patients without lung injury. PaO 2 Deficit, AaDO 2 and AaDO 2 augmentation showed a good accuracy to predict lung injury in blunt chest trauma., Conclusion: our study demonstrates that the combination of different arterial blood gas analysis variables may be a fast approach for identifying patients with lung injury in the setting of blunt chest trauma in the Emergency Department., Competing Interests: Declaration of Competing Interest None., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Background: Measurement results provided by blood glucose monitoring systems (BGMS) can be affected by various influencing factors. For some BGMS using glucose oxidase (GOx)-based test strips, one of these factors is the oxygen partial pressure (pO 2 ) of the applied blood sample. Because assessing the potential influence of pO 2 when measuring capillary blood samples is not straight-forward, we performed a proof of concept study., Method: Influence of pO 2 was investigated for two GOx-based BGMS (BGMS A and B). Measurement results of the GOx-based BGMS were compared with measurement results from a pO 2 -independent BGMS (BGMS C). A total of 119 samples from 60 subjects were measured, twice with BGMS C, then 6 times each with BGMS A and BGMS B or vice versa, and again twice with BGMS C. Immediately afterward, pO 2 was determined. Linear regression analysis based on relative differences between results from BGMS A or BGMS B and results from BGMS C was performed to estimate the degree of pO 2 influence., Results: The relative bias between the lowest and highest pO 2 values differed by 14.3% for BGMS A, indicating a pO 2 influence that might be clinically relevant, and by 9.7% for BGMS B, indicating that pO 2 influence may be too small to be reliably detected because of the BGMS' imprecision., Conclusions: This proof of concept study showed that with the procedures used, a potentially clinically relevant influence of pO 2 in capillary blood samples on GOx-based BGMS could be detected. Further larger-scale studies are needed to verify this influence.

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 (pO 2 ), 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 (CO 2 ) 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 pO 2 . The i-STAT PCA systematically overestimated the pO 2 measurements. Our research suggests that i-STAT PCA is not an appropriate tool for pO 2 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.

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 (PO 2 ) 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., Competing Interests: BL, TE, IS, KK, BF, MD, MM, SK, MY, FL, LØ, AD, DB, SV, SS No competing interests declared, (© 2019, Li et al.)

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 (PaO 2 ) 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 PaO 2 , maximum PaO 2 difference, and gradually increasing PaO 2 levels (13.3-53.3 kPa) with poor neurological outcome. A subsequent analysis investigated the association between PaO 2 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 PaO 2 exposure or maximum PaO 2 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 PaO 2 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 PaO 2 ., 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 (pO 2 ) is a proven modality. Instruments needed are expensive and are not readily available to a clinician. Here, pO 2 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 pO 2 analysed using blood gas analyser. Fall/change of pO 2 (difference of mean of pO 2 [diff-pO 2 ]) was also calculated by subtracting the flap pO 2 from the finger pO 2 . 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. pO 2 and diff-pO 2 amongst both the groups were compared and found to be statistically different ( P = 0.0001). Cut-off value calculated for pO 2 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 pO 2 compared from finger pO 2 was calculated as a cut-off with sensitivity of 94.12 and specificity of 79.60%., Conclusions: Flap areas having intra-operative pO 2 value <86.3 mmHG have higher chances (60.71%) of getting necrosis later. Similarly, if diff-pO 2 compared to fingertip is >68.5 mmHg, chances of those points getting necrosed in post-operative period are high., Competing Interests: There are no conflicts of interest.

The partial pressure of oxygen (PO 2 ) 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 PO 2 in the tumor microenvironment prior to and following chemotherapy, and aimed to determine the precise time window in which the microenvironmental PO 2 peaked following chemotherapy. The results indicated that PO 2 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 PO 2 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 PO 2 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.

Simple and accurate expressions describing the P a O 2 -F i O 2 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 P a O 2 -F i O 2 data pairs were obtained from 25 non-smoking patients mechanically ventilated following open heart surgeries. One data pair was collected at each of F i O 2 of 40, 60, 80, and 100% while maintaining same mechanical ventilation support settings. Similarly, another 100 hundred P a O 2 -F i O 2 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 P a O 2 -F i O 2 relationship in these patients was assessed by the regression and Bland-Altman analyses. Significant correlations were seen between the true and estimated F i O 2 values in non-smoking (r 2  = 0.9424; p < 0.05) and smoking (r 2  = 0.9466; p < 0.05) patients. Tight biases between the true and estimated F i O 2 values for non-smoking (3.1%) and smoking (4.1%) patients were observed. Also, significant correlations were seen between the true and estimated P a O 2 /F i O 2 ratios in non-smoking (r 2  = 0.9530; p < 0.05) and smoking (r 2  = 0.9675; p < 0.05) patients. Tight biases between the true and estimated P a O 2 /F i O 2 ratios for non-smoking (-18 mmHg) and smoking (-16 mmHg) patients were also observed. The new mathematical expression for the description of the P a O 2 -F i O 2 relationship is valid and accurate in non-smoking and smoking patients who are receiving mechanical ventilation for post cardiac surgery.

Background: Apnea testing is an essential step in the clinical diagnosis of brain death. Current international guidelines recommend placement of an oxygen (O 2 ) 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 O 2 (PO 2 ) 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, O 2 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 PO 2 , partial pressure of carbon dioxide (PCO 2 ), pH, and blood pressure at the beginning and termination of each apnea test., Results: Thirty-six apnea tests were performed using an O 2 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 PO 2 reduction (-59 vs. -32 mmHg, p = 0.72), rate of PCO 2 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 PCO 2 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 O 2 supplementation are associated with similar changes in arterial PO 2 and PCO 2 . Performance of ABGs at regular intervals shortens apnea test duration and may avoid excessive pH reduction and consequent hemodynamic effects.

The effect of hyperoxygenation with carbogen (95% O 2 + 5% CO 2 ) and 100% oxygen inhalation on partial pressure of oxygen (pO 2 ) 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 pO 2 was measured by electron paramagnetic resonance (EPR) oximetry for 20 minutes in anesthetized mice breathing 30% O 2 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 pO 2 of 6.2-8.3 mmHg in mice breathing 30% O 2 . Carbogen and 100% oxygen significantly increased tumor pO 2 on days 1 to 5, with a maximal increase at approximately 32-45 minutes on each day. However, the extent of increase in pO 2 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 pO 2 over the course of 10 days. EPR oximetry can be effectively used to repeatedly monitor tumor pO 2 and test hyperoxic methods for potential clinical applications., Competing Interests: The authors declare no conflicts of interest.

Introduction: Donor PaO2 levels are used for assessing organs for lung transplantation (LTx), but survival implications of PaO2 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 PaO2 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 PaO2 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 PaO2 categories (Chi-square p = 0.480). Multivariable Cox models of patient survival supported the lack of difference across donor PaO2 categories. Interaction analysis found a modest difference in survival between the two top categories of donor PaO2 when examining patients with body mass index (BMI) in the lowest decile (≤16.5 kg/m(2))., Conclusions: Donor PaO2 was not associated with survival or BOS onset in adult CF patients undergoing LTx. Notwithstanding statistically significant interactions between donor PaO2 and BMI, there was no evidence of post-LTx survival risk associated with donor PaO2 below conventional thresholds in any subgroup of adults with CF.

Objectives: Continuous flow in Fontan circulation results in impairment of pulmonary artery endothelial function, increased pulmonary vascular resistance, and, potentially, late failure of Fontan circulation. Bidirectional cavopulmonary shunt is the interim procedure in palliation of patients with single-ventricle physiology, but pulmonary arteriovenous malformations occur in many patients. In a porcine chronic model of cavopulmonary shunt, we studied pulmonary hemodynamics, pulmonary arteriovenous malformation occurrence, and gas exchange capabilities. We hypothesized that residual antegrade pulsatile pulmonary flow may attenuate the deleterious effects of nonpulsatile Fontan-type circulation., Methods: Thirty pigs underwent a sham procedure (n = 10, group I), a cavopulmonary shunt with right pulmonary artery ligation (n = 10, group II, nonpulsatile), or a cavopulmonary shunt with proximal right pulmonary artery partial ligation (n = 10, group III, micropulsatile). Three months later, in vivo hemodynamics, blood gas exchange, pulmonary arteriovenous malformation occurrence, and lung histology were assessed., Results: At 3 months, group II right lungs demonstrated significantly increased pulmonary artery pressure, pulmonary vascular resistance, and evidence of pulmonary arteriovenous malformations compared with groups I and III (all P < .001). Group III lungs also showed increased pulmonary artery pressure and pulmonary vascular resistance compared with the sham group, but significantly less than group II. Group III right lungs had the best gas exchange performance, with less histologic changes compared with group II., Conclusions: We developed a viable chronic large animal model of bidirectional cavopulmonary anastomosis. Residual antegrade pulsatile flow in the setting of a cavopulmonary shunt prevents pulmonary arteriovenous malformation formation and attenuates, but does not suppress, the development of pulmonary hypertension. From a clinical standpoint, these data would support keeping a small amount of antegrade pulsatile flow during creation of a cavopulmonary shunt., (Copyright © 2013 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.)