Arterial Blood Samples Research Articles

Bone Turnover in Patients with Chronic Kidney Disease Stage 5D and Healthy Controls - a Quantitative [18F]Fluoride PET Study.

Chronic kidney disease (CKD) is prevalent in the aging population and increases the risk of fracture 2-4 times. We compared optimized quantitative [18F]fluoride PET/CT methods to the reference standard with arterial input function (AIF) to identify a clinically accessible method for evaluation of bone turnover in patients with CKD. Ten patients on chronic hemodialysis treatment and ten control patients were recruited. A dynamic 60-min [18F]fluoride PET scan was obtained from the 5th lumbar vertebra to the proximal femur simultaneously with arterial blood sampling to achieve an AIF. Individual AIFs were time-shifted to compute a population curve (PDIF). Bone and vascular volumes-of-interest (VOIs) were drawn, and an image-derived-input-function (IDIF) was extracted. PDIF and IDIF were scaled to plasma. Bone turnover (Ki) was calculated with the AIF, PDIF, and IDIF and bone VOIs using a Gjedde-Patlak plot. Input methods were compared using correlations and precision errors. The calculated Ki from the five non-invasive methods all correlated to the Ki from the AIF method with the PDIF scaled to a single late plasma sample showing the highest correlations (r > 0.94), and the lowest precision error of 3-5%. Furthermore, the femoral bone VOI's correlated positively to p-PTH and showed significant differences between patients and controls. Dynamic 30 min [18F]fluoride PET/CT with a population based input curve scaled to a single venous plasma sample is a feasible and precise non-invasive diagnostic method for the assessment of bone turnover in patients with CKD. The method may potentially allow for earlier and more precise diagnosis and may be useful for assessment of treatment effects, which is crucial for development of future treatment strategies.

Spatiotemporal Learning of Dynamic Positron Emission Tomography Data Improves Diagnostic Accuracy in Breast Cancer

Positron emission tomography (PET) is a noninvasive imaging technology able to assess the metabolic or functional state of healthy and/or pathological tissues. In clinical practice, PET data are usually acquired statically and normalized for the evaluation of the standardized uptake value (SUV). In contrast, dynamic PET acquisitions provide information about radiotracer delivery to tissue, its interaction with the target and its physiological washout. The shape of the time activity curves (TACs) embeds tissue-specific biochemical properties. Conventionally, TACs are employed along with information about blood plasma activity concentration, i.e., the arterial input function, and tracer-specific compartmental models to obtain a full quantitative analysis of PET data. This method’s primary disadvantage is the requirement for invasive arterial blood sample collection throughout the whole PET scan. In this study, we employ a variety of deep learning models to illustrate the diagnostic potential of dynamic PET acquisitions of varying lengths for discriminating breast cancer lesions in the absence of arterial blood sampling compared to static PET only. Our findings demonstrate that the use of TACs, even in the absence of arterial blood sampling and even when using only a share of all timeframes available, outperforms the discriminative ability of conventional SUV analysis.

Utility of paediatric logistic organ dysfunction score in predicting mortality in children admitted to PICU at a tertiary care centre

Background: Critically ill children are typically characterized by multiple organ dysfunctions. The use of Paediatric logistic organ dysfunction-2 (PELOD-2) scoring systems has recently been replicated in the paediatric population for morbidity and mortality predictions. Objective of the study was to study the PELOD 2 score in predicting mortality in paediatric intensive care unit within 1 hour of admission. Methods: This was prospective observational study conducted at S Nijalingappa Medical College and Hanagal Shri Kumareshwar Hospital, Bagalkot for period of 16 months. Children aged from 1 month to 14 years admitted to PICU were included in the study and patients whose parents refuse to give consent, age less than 1 month or more than 14 years, those discharged against medical advice were excluded from the study. Venous blood sample were collected within one hour of admission and were analyzed for serum creatinine, serum lactate, total leukocyte count and platelet count and arterial blood sample were collected and paO2 and paCO2 were analysed. Results: Total sample size of study was 80, out of which 52 patients had PELOD 2 score of (<4), 14 patients had score of (5-9), 11 patients had score of (10-14) and 3 patients had score >15.Among total 80 patients 66 survived and 14 died (17.5%). Of the 14 deaths, 3 patients had PELOD 2 score of >15 and 9 had score of 10-14. Pelod-2 score >9 had requirement of mechanical ventilation in 68.4%. Conclusions: Higher the PELOD-2 score on day 1of admission has higher the mortality.

A graphical user interface for calculating the arterial input function during dynamic positron emission tomography

Purpose. Dynamic positron emission tomography (dPET) requires the acquisition of the arterial input function (AIF), conventionally obtained via invasive arterial blood sampling. To obtain the AIF non-invasively, our group developed and combined two novel solutions consisting of (1) a detector, placed on a patient’s wrist during the PET scans to measure the radiation leaving the wrist and (2) a Geant4-based Monte Carlo simulation software. The simulations require patient-specific wrist geometry. The aim of this study was to develop a graphical user interface (GUI) allowing the user to import 2D ultrasound scans of a patient’s wrist, and measure the wrist features needed to calculate the AIF. Methods. The GUI elements were implemented using Qt5 and VTK-8.2.0. The user imports a patient’s wrist ultrasound scans, measures the radial artery and veins’ surface and depth to model a wrist phantom, then specifies the radioactive source used during the dPET scan. The phantom, the source, and the number of decay events are imported into the Geant4-based Monte Carlo software to run a simulation. In this study, 100 million decays of 18F and 68Ga were simulated in a wrist phantom designed based on an ultrasound scan. The detector’s efficiency was calculated and the results were analyzed using a clinical data processing algorithm developed in a previous study. Results. The detector’s total efficiency decreased by 3.5% for 18F and by 51.7% for 68Ga when using a phantom based on ultrasound scans compared to a generic wrist phantom. Similarly, the data processing algorithm’s accuracy decreased when using the patient-specific phantom, giving errors greater than 1.0% for both radioisotopes. Conclusions. This toolkit enables the user to run Geant4-based Monte Carlo simulations for dPET detector development applications using a patient-specific wrist phantom. Leading to a more precise simulation of the developed detector during dPET and the calculation of a personalized AIF.

Cephalic and saphenous venous blood collected by continuous heating of the paws compared with arterial blood for measurement of blood gas values in well-perfused dogs.

"Arterialization" of the dorsal hand vein is well-established in human medicine, but not in veterinary medicine. To compare cephalic and saphenous venous blood collected by continuously heating the paws to 37°C ("arterialization"), with arterial blood (AB) for measurement of blood gas variables in well-perfused dogs. Eight healthy dogs. Experimental study. Fore and hind paws were continuously heated to 37°C to "arterialize" cephalic and saphenous venous blood. AB and "arterialized" cephalic and saphenous venous blood (ACV and ASV, respectively) were simultaneously collected from lightly anesthetized dogs with induced metabolic and respiratory acid-base disorders. The pH, partial pressures of carbon dioxide (PCO2 ) and oxygen (PO2 ), bicarbonate concentration [HCO3 - ], and base excess (BE) were measured once in each state. Systolic blood pressure was maintained above 100 mm Hg. The AB, ACV, and ASV values were compared. The pH, [HCO3 - ], and BE values had no significant difference and good agreement, the PCO2 values had a strong correlation (correlation coefficient of .91-1.00), and the PO2 values had a significant difference (P < .01) and poor agreement between AB and ACV, and between AB and ASV. The PCO2 values of ASV overestimated those of AB by ~3.0 mm Hg, which was considered within clinically allowable limits, while those of ACV were not within clinically allowable limits. Under experimental conditions, the ASV samples were more identical to the AB samples than the ACV samples for pH, PCO2 , [HCO3 - ], and BE values in well-perfused dogs. The saphenous vein is suitable for "arterialization."

Thiol/Disulfide Homeostasis and Ischemia-Modified Albumin Levels in 61 Patients with Hypercapnia: A Case-Control Study.

BACKGROUND Hypercapnia is abnormally high arterial partial pressure of carbon dioxide (CO₂). CO₂ can affect redox signaling mechanisms, leading to production of oxidative derivatives. Thiol is formed by attaching a sulfhydryl group to a carbon atom. Under oxidative stress, it forms covalent bonds called thiol disulphide bonds. Serum albumin is modified to ischemia-modified albumin (IMA) by exposure to free radicals. This case-control study aimed to evaluate thiol/disulphide homeostasis and IMA levels in 61 patients with hypercapnia. MATERIAL AND METHODS We studied 61 patients with hypercapnia and 61 normocapnic volunteers in the control group, between May 2018 and January 2019; 56 of these patients were diagnosed with chronic obstructive pulmonary disease and 5 of them were diagnosed with obstructive sleep apnea syndrome. Arterial blood samples analyzed by using the Ellman reagent for thiol/disulphide data. A colorometric assay was used for detection of IMA levels. RESULTS Native thiol and total thiol values in the hypercapnic group were significantly lower than in the control group (P=0.024, P=0.006 respectively), as IMA values were significantly higher (P<0.001). There was no statistically significant difference between the hypercapnic and control groups in terms of disulphide, disulphide/native thiol, disulphide/total thiol, and native thiol/total thiol values (P>0.05). CONCLUSIONS In hypercapnic patients, there are changes in thiol/disulphide homeostasis and IMA levels. All significant differences in this study support that changes in thiol disulphide homeostasis and IMA in hypercapnic patients are indicators of oxidative stress.

Prolonged Anesthesia Induction to Delivery Time Did Not Influence Plasma Remifentanil Concentration in Neonates.

Remifentanil, in combination with etomidate and sevoflurane, is commonly used in clinics for general anesthesia induction in cesarean section (CS). This study aimed to evaluate the correlation between the induction to delivery (I-D) time and neonatal plasma drug concentration and anesthesia, as well as its effects on neonates. Fifty-two parturients in whom general anesthesia was induced for CS were divided into group A (I-D<8 min) and group B (I-D≥8 min). Maternal arterial (MA), umbilical venous (UV), and umbilical arterial (UA) blood samples were collected at delivery to analyze the remifentanil and etomidate concentrations using liquid chromatography-tandem mass spectrometry. There were no statistically significant differences between the two groups in terms of plasma concentrations of remifentanil in the MA, UA, and UV blood (P > 0.05). The plasma concentration of etomidate in MA and UV was higher in group A than that in group B (P<0.05), whereas the UA/UV ratio of etomidate was higher in group B than that in group A (P<0.05). The Spearman rank correlation test showed no correlation between the I-D time and plasma remifentanil concentration in the MA, UA, and UV plasma (P>0.05). The concentrations of etomidate in the MA and UV were negatively correlated with the I-D time (P < 0.05). Prolonged I-D time did not significantly influence the maternal or neonatal plasma concentration of remifentanil. It is safe to administer remifentanil target-controlled infusion in combination with etomidate and sevoflurane for general anesthesia induction during CS.

Generation of Whole-Body FDG Parametric Ki Images from Static PET Images Using Deep Learning.

FDG parametric Ki images show great advantage over static SUV images, due to the higher contrast and better accuracy in tracer uptake rate estimation. In this study, we explored the feasibility of generating synthetic Ki images from static SUV ratio (SUVR) images using three configurations of U-Nets with different sets of input and output image patches, which were the U-Nets with single input and single output (SISO), multiple inputs and single output (MISO), and single input and multiple outputs (SIMO). SUVR images were generated by averaging three 5-min dynamic SUV frames starting at 60 minutes post-injection, and then normalized by the mean SUV values in the blood pool. The corresponding ground truth Ki images were derived using Patlak graphical analysis with input functions from measurement of arterial blood samples. Even though the synthetic Ki values were not quantitatively accurate compared with ground truth, the linear regression analysis of joint histograms in the voxels of body regions showed that the mean R2 values were higher between U-Net prediction and ground truth (0.596, 0.580, 0.576 in SISO, MISO and SIMO), than that between SUVR and ground truth Ki (0.571). In terms of similarity metrics, the synthetic Ki images were closer to the ground truth Ki images (mean SSIM = 0.729, 0.704, 0.704 in SISO, MISO and MISO) than the input SUVR images (mean SSIM = 0.691). Therefore, it is feasible to use deep learning networks to estimate surrogate map of parametric Ki images from static SUVR images.

Population pharmacokinetic and safety analysis of ropivacaine used for erector spinae plane blocks

IntroductionErector spinae plane blocks have become popular for thoracic surgery. Despite a theoretically favorable safety profile, intercostal spread occurs and systemic toxicity is possible. Pharmacokinetic data are needed to guide...

Cardiac output affects the response to pulsed inhaled nitric oxide in mechanically ventilated anesthetized ponies determined by CT angiography of the lung.

To measure changes in regional lung perfusion using CT angiography in mechanically ventilated, anesthetized ponies administered pulsed inhaled nitric oxide (PiNO) during hypotension and normotension. 6 ponies for anesthetic 1 and 5 ponies for anesthetic 2. Ponies were anesthetized on 2 separate occasions, mechanically ventilated, and placed in dorsal recumbency within the CT gantry. Pulmonary arterial, right atrial, and facial arterial catheters were placed. During both anesthetics, PiNO was delivered for 60 minutes and then discontinued. Anesthetic 1: hypotension (mean arterial pressure < 70 mmHg) was treated using dobutamine after 30 minutes of PiNO delivery. Following the discontinuation of PiNO, dobutamine administration was discontinued in 3 ponies and was continued in 3 ponies. The lung was imaged at 30, 60, and 105 minutes. Anesthetic 2: hypotension persisted throughout anesthesia. The lung was imaged at 30, 60, and 90 minutes. At all time points, arterial and mixed venous blood samples were analyzed and cardiac output (Q˙t) was measured. Pulmonary perfusion was calculated from CT image analysis. During PiNO delivery, perfusion to well-ventilated lungs increased if ponies were normotensive, leading to increased arterial oxygenation, reduced alveolar dead space, and reduced alveolar to arterial oxygen tension gradient. When PiNO was stopped and dobutamine administration continued, alveolar dead space and venous admixture increased, in contrast to when dobutamine and PiNO were both discontinued. If PiNO is administered to mechanically ventilated, anesthetized ponies with concurrent hypotension and low Q˙t, this must be supported to achieve favorable redistribution of pulmonary perfusion to improve pulmonary gas exchange.

Study of Correlation of Arterial Blood Gas Measurements with Peripheral Venous Blood Gas Values in Adult Patients Admitted in ICU in Tertiary Care Hospital in Central India – A Cross-Sectional Study

Objectives: Arterial blood gas (ABG) analysis is an essential investigation for assessment of ventilation, oxygenation and acid–base status in critically ill patients. Arterial puncture to obtain arterial blood is more invasive procedure than venous and has more potential complications. The present study was undertaken to find out the correlation between arterial and peripheral venous blood gas (VBG) values for PO2 (Partial pressure of oxygen), PCO2 (Partial pressure of carbon dioxide), pH (Potential of hydrogen) and HCO3 (bicarbonates). Material and Methods: A total of 131 consecutive patients admitted to intensive care unit (ICU) requiring ABG analysis to determine their acid–base status or ventilatory status were included in the study. Arterial and venous blood samples were obtained with a heparinised syringe within &lt;15 min, after performing modified Allen’s test and were analysed using blood gas analysis machine. The mean of pH, pCO2, HCO3, and PO2, values in arterial and venous samples was determined, along with peripheral arterial oxygen saturation (SpO2) of patients. Results: ABG and VBG analysis correlated well for pH, pCO2 and HCO3, as their correlation coefficient (r) were 0.976, 0.992 and 0.984, respectively, whereas PO2 has correlation coefficient of 0.010 which suggests that there was poor correlation in PO2. For each unit increase in pCO2, pH and HCO3 of VBG, all these ABG changes by 0.9831 units, 0.914 units and 0.992 units, respectively. Peripheral O2 saturation (SpO2) correlates well with arterial O2 saturation, however, does not correlate with venous O2 saturation. Conclusion: The results show that VBG analysis can be a substitute for ABG for evaluation of ventilatory function and acid–base imbalance for pH, pCO2 and HCO3 in patients of ICU setup in many clinical contexts.

Lipidomics, Acute Ischemic Stroke, Symptoms, and Outcomes: Observational Study Protocol.

Acute ischemic stroke is one of the leading causes of death and disability globally. Recent advances in omics methodology enable lipidomic profiling, which may provide knowledge of the underlying pathology of acute ischemic stroke and its associated outcomes. This study aims to examine the longer-term relationships between symptoms and outcomes following acute ischemic stroke and the underlying lipidomic signatures over 6 months during recovery between acute ischemic stroke patients who received reperfusion therapies and those who did not. This prospective cohort study will enroll 104 participants post-acute ischemic stroke in two groups based on their receipt of reperfusion therapy (Group 1) or not (Group 2; n = 52/group). Peripheral plasma samples will be collected from both groups for lipidomic analysis over 6 months. Arterial blood samples will be collected during the procedure for those receiving reperfusion. Self-reported symptoms and outcome data will be collected from both groups. We will compare and examine the associations among plasma lipidomic biomarkers and symptoms and cognitive, functional, and health-related quality of life outcomes over 6 months between acute ischemic stroke patients who did and did not receive reperfusion intervention.

Clearance of Piperacillin-Tazobactam and Vancomycin During Continuous Renal Replacement With Regional Citrate Anticoagulation.

The use of regional citrate anticoagulation during continuous venovenous hemodiafiltration (CVVHDF) has increased worldwide. However, data on its effect on the pharmacokinetics of antibiotics are limited. In this study, the authors aimed to measure the clearance of piperacillin-tazobactam and vancomycin in patients receiving CVVHDF with regional citrate anticoagulation. This study measured piperacillin-tazobactam and vancomycin concentrations in patients receiving CVVHDF with regional citrate anticoagulation. Dosing regimens were independently selected by intensivists. Arterial blood and effluent fluid samples were obtained over a single dosing interval and analyzed using ultra-high-performance liquid chromatography with tandem mass spectrometry. Seventeen sampling intervals in 15 patients (9 receiving piperacillin-tazobactam only, 4 receiving vancomycin only, and 2 receiving both) were used. The median overall clearance for piperacillin was 35.2 mL/min [interquartile range (IQR): 32.2-38.6], 70 mL/min (IQR: 62.7-76.2) for tazobactam, and 29.5 mL/min (IQR: 26.2-32) for vancomycin. This is the first study to quantify the pharmacokinetics of vancomycin and piperacillin-tazobactam in patients receiving CVVHDF with regional citrate anticoagulation. These results indicate high clearance and provide key information to guide optimal dosing.

Measurement of Cerebral Perfusion Indices from the Early Phase of [18F]MK6240 Dynamic Tau PET Imaging.

6-(fluoro-18F)-3-(1H-pyrrolo[2,3-c]pyridin-1-yl)isoquinolin-5-amine ([18F]MK6240) has high affinity and selectivity for hyperphosphorylated tau and readily crosses the blood-brain barrier. This study investigated whether the early phase of [18F]MK6240 can be used to provide a surrogate index of cerebral perfusion. Methods: Forty-nine subjects who were cognitively normal (CN), had mild cognitive impairment (MCI), or had Alzheimer's disease (AD) underwent paired dynamic [18F]MK6240 and [11C]Pittsburgh compound B (PiB) PET, as well as structural MRI to obtain anatomic information. Arterial blood samples were collected in a subset of 24 subjects for [18F]MK6240 scans to derive metabolite-corrected arterial input functions. Regional time-activity curves were extracted using atlases available in the Montreal Neurologic Institute template space and using FreeSurfer. The early phase of brain time-activity curves was analyzed using a 1-tissue-compartment model to obtain a robust estimate of the rate of transfer from plasma to brain tissue, K 1 (mL⋅cm-3⋅min-1), and the simplified reference tissue model 2 was investigated for noninvasive estimation of the relative delivery rate, R 1 (unitless). A head-to-head comparison with R 1 derived from [11C]PiB scans was performed. Grouped differences in R 1 were evaluated among CN, MCI, and AD subjects. Results: Regional K 1 values suggested a relatively high extraction fraction. R 1 estimated noninvasively from simplified reference tissue model 2 agreed well with R 1 calculated indirectly from the blood-based compartment modeling (r = 0.99; mean difference, 0.024 ± 0.027), suggesting that robust estimates were obtained. R 1 measurements obtained with [18F]MK6240 correlated strongly and overall agreed well with those obtained from [11C]PiB (r = 0.93; mean difference, -0.001 ± 0.068). Statistically significant differences were observed in regional R 1 measurements among CN, MCI, and AD subjects, notably in the temporal and parietal cortices. Conclusion: Our results provide evidence that the early phase of [18F]MK6240 images may be used to derive a useful index of cerebral perfusion. The early and late phases of a [18F]MK6240 dynamic acquisition may thus offer complementary information about the pathophysiologic mechanisms of the disease.

Comparison of cardiac image-derived input functions for quantitative whole body [18F]FDG imaging with arterial blood sampling.

Introduction: Dynamic positron emission tomography (PET) and the application of kinetic models can provide important quantitative information based on its temporal information. This however requires arterial blood sampling, which can be challenging to acquire. Nowadays, state-of-the-art PET/CT systems offer fully automated, whole-body (WB) kinetic modelling protocols using image-derived input functions (IDIF) to replace arterial blood sampling. Here, we compared the validity of an automatic WB kinetic model protocol to the reference standard arterial input function (AIF) for both clinical and research settings. Methods: Sixteen healthy participants underwent dynamic WB [18F]FDG scans using a continuous bed motion PET/CT system with simultaneous arterial blood sampling. Multiple processing pipelines that included automatic and manually generated IDIFs derived from the aorta and left ventricle, with and without motion correction were compared to the AIF. Subsequently generated quantitative images of glucose metabolism were compared to evaluate performance of the different input functions. Results: We observed moderate to high correlations between IDIFs and the AIF regarding area under the curve (r = 0.49-0.89) as well as for the cerebral metabolic rate of glucose (CMRGlu) (r = 0.68-0.95). Manual placing of IDIFs and motion correction further improved their similarity to the AIF. Discussion: In general, the automatic vendor protocol is a feasible approach for the quantification of CMRGlu for both, clinical and research settings where expertise or time is not available. However, we advise on a rigorous inspection of the placement of the volume of interest, the resulting IDIF, and the quantitative values to ensure valid interpretations. In protocols requiring longer scan times or where cohorts are prone to involuntary movement, manual IDIF definition with additional motion correction is recommended, as this has greater accuracy and reliability.

Effects of routine procedures on salivary cortisol in mechanically ventilated neonates

Even though the stress secondary to invasive procedures has been investigated, less attention has been paid to the stimulation or pain caused by routine procedures on neonates. The changes in salivary cortisol concentration in mechanically ventilated NICU patients during routine procedures were monitored to provide reference and guidance for pain management. 80 mechanically ventilated neonates in the hospital from Sep 2021 to Mar 2022 were selected. The salivary cortisol levels of the neonates were monitored during nursing procedures and were categorized by their risk levels to the following groups: high-risk (endotracheal suctioning and arterial blood sampling), moderate-risk (gastric tube insertion, venipuncture), and low-risk (bedside bathing and diaper changes). The changes in heart rate were also recorded and compared. The concentration of cortisol in the saliva of the neonates was 1.5 ± 0.8 nmol/L during the sleeping state, 6.2 ± 1.3 nmol/L during endotracheal suctioning, 6.4 ± 1.4 nmol/L during arterial blood sampling, 6.1 ± 1.2 nmol/L during venipuncture, 4.4 ± 1.1 nmol/L during gastric tube insertion, 3.5 ± 0.8 nmol/L during bedside bathing, and 3.3 ± 0.9 nmol/L during a diaper change. The results revealed a statistically significant effect between routine procedures on salivary cortisol levels. Compared with the neonates in the control sleep state, there was a significant (P < 0.05) change in salivary cortisol concentration of infants undergoing high and moderate-risk nursing procedures. There was a small but significant (P < 0.05) change in salivary cortisol levels in infants who underwent low-risk procedures compared to infants in the control sleep state. Further, the fluctuation of salivary cortisol levels in routine procedures was more frequent compared with routine handling at night. The fluctuations of salivary cortisol concentration in high-risk procedures were larger than that of infants who underwent low-risk procedures, with the difference being statistically significant (P < 0.05). It was also determined that the top four influencing factors on the infants’ heart rate were arterial blood sampling venipuncture, intubation, endotracheal suctioning, and gastric tube insertion (P < 0.05). Monitoring the saliva cortisol concentration index and heart rates can reflect the impact of different routine procedures on newborns and can be used to manage neonatal pain in the future.

Performance and reliability of two frequently used point-of-care blood gas analyzers at 423 and 4,559 m

Background and ObjectivesBlood gas analyzers (BGA) aid medical decision-making. Their specified performance criteria are based on sea level conditions. However, millions of people are living at high altitude (HA) where the performance of BGAs is poorly characterized. We investigated the effect of exposure to 4,559 m on the reliability and robustness of two BGAs widely used at HA. MethodsIn this prospective study arterial blood samples from 13 volunteers (2 female) with susceptibility to the development of high-altitude pulmonary edema were collected once near sea level at 423 m (nSL423) and three times at high altitude (HA4,559). Samples were measured in triplicate with the cartridge BGAs Rapidpoint 500 (SIE; Siemens Healthcare) and the ABL90 (RAD; Radiometer) to calculate coefficients of variation (CV) and intraclass correlation coefficients (ICC) within a mixed model. ResultsAt nSL423 and HA4,559, 3% and 17% of all data were not reported with SIE, mainly due to clotting of the sample caused by delays because of the frequent automated calibration routines. No data were missing with RAD. ICCs were not significantly lower (mean (min–max) 0.87 (0.68–0.98) vs. 0.94 (0.84–1.00); p = 0.217) with SIE at nSL423, but significantly lower at HA4,559 (0.87 (0.49–1.00) vs. 0.99 (0.96–1.00); p = 0.025). All CVs, except that for arterial oxygen saturation at HA4,559,were higher with SIE . ConclusionIn this study, the reliability of RAD was superior to SIE at nSL423 and HA4,559. In contrast to RAD, the performance of SIE declined at HA4,559. SIE was more prone to not reporting all variables, especially at HA4559.

THE EFFECTIVENESS OF PASSIVE EXERCISES ON ARTERIAL BLOOD GASES IN MECHANICALLY VENTILATED SUBJECTS FROM INTENSIVE CARE UNITS

ABSTRACT. Introduction: Mechanically ventilated critically ill subjects are often given strict bed rest and sometimes completely immobilized because of the severity of their illness and the administration of drugs such as sedatives. Active mobilization is not possible in subjects under deep sedation and unable to follow commands. In this scenario, passive therapy is an interesting alternative. Objective: This study aimed to evaluate the effectiveness of passive exercises on arterial blood gases in mechanically ventilated subjects from intensive care units. Methods: Five mechanically ventilated subjects participated in the study. The subjects were assigned to one study group, which received passive exercises for one daily session, including ten repetitions in three series per articulation. Arterial Blood Gases were assessed by arterial blood sample analysis with the Stat Profile Prime Plus device. Results: The results revealed a marked improvement in arterial blood gas exchange as compared to baseline reflecting an increase in FIO2- the inspiratory fraction of oxygen, pO2- partial pressure of oxygen, and pO2/FIO2- the ratio between the partial pressure of oxygen and the inspiratory fraction of oxygen and a decrease in CO2- carbon dioxide. Conclusions: The passive exercise showed a slight trend of beneficial changes at the cellular level in mechanically ventilated subjects since the first day after admission, which may indicate a reduction in the inspiratory fraction of oxygen and at the end extubation of subjects.

Non-invasive regional cerebral blood flow quantification in the 123I-IMP autoradiography using artificial neural network.

Regional cerebral blood flow (rCBF) quantification using 123I-N-isopropyl-p-iodoamphetamine (123I-IMP) requires an invasive, one-time-only arterial blood sampling for measuring the 123I-IMP arterial blood radioactivity concentration (Ca10). The purpose of this study was to estimate Ca10 by machine learning (ML) using artificial neural network (ANN) regression analysis and consequently calculating rCBF and cerebral vascular reactivity (CVR) in the dual-table autoradiography (DTARG) method. This retrospective study included 294 patients who underwent rCBF measurements through the 123I-IMP DTARG. In the ML, the objective variable was defined by the measured Ca10, whereas the explanatory variables included 28 numeric parameters, such as patient characteristic values, total injection 123I-IMP radiation dose, cross-calibration factor, and the distribution of 123I-IMP count in the first scan. ML was performed with training (n = 235) and testing (n = 59) sets. Ca10 was estimated in testing set by our proposing model. Alternatively, the estimated Ca10 was also calculated via the conventional method. Subsequently, rCBF and CVR were calculated using estimated Ca10. Pearson's correlation coefficient (r-value) for the goodness of fit and the Bland-Altman analysis for assessing the potential agreement and bias were performed between the measured and estimated values. The r-value of Ca10 estimated by our proposed model was higher compared with the conventional method (0.81 and 0.66, respectively). In the Bland-Altman analysis, mean differences of 4.7 (95% limits of agreement (LoA): -18-27) and 4.1 (95% LoA: -35-43) were observed using proposed model and the conventional method, respectively. The r-values of rCBF at rest, rCBF after the acetazolamide challenge, and CVR calculated using the Ca10 estimated by our proposed model were 0.83, 0.80 and 0.95, respectively. Our proposed ANN-based model could accurately estimate the Ca10, rCBF, and CVR in DTARG. These results would enable non-invasive rCBF quantification in DTARG.

Image-derived input functions from dynamic 15O–water PET scans using penalised reconstruction

BackgroundQuantitative positron emission tomography (PET) scans of the brain typically require arterial blood sampling but this is complicated and logistically challenging. One solution to remove the need for arterial blood sampling is the use of image-derived input functions (IDIFs). Obtaining accurate IDIFs, however, has proved to be challenging, mainly due to the limited resolution of PET. Here, we employ penalised reconstruction alongside iterative thresholding methods and simple partial volume correction methods to produce IDIFs from a single PET scan, and subsequently, compare these to blood-sampled input curves (BSIFs) as ground truth. Retrospectively we used data from sixteen subjects with two dynamic 15O-labelled water PET scans and continuous arterial blood sampling: one baseline scan and another post-administration of acetazolamide.ResultsIDIFs and BSIFs agreed well in terms of the area under the curve of input curves when comparing peaks, tails and peak-to-tail ratios with R2 values of 0.95, 0.70 and 0.76, respectively. Grey matter cerebral blood flow (CBF) values showed good agreement with an average difference between the BSIF and IDIF CBF values of 2% ± and a coefficient of variation (CoV) of 7.3%.ConclusionOur results show promising results that a robust IDIF can be produced for dynamic 15O–water PET scans using only the dynamic PET scan images with no need for a corresponding MRI or complex analytical techniques and thereby making routine clinical use of quantitative CBF measurements with 15O–water feasible.