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Objective: To assess the quality of SpO2 and PCO2 recordings via transcutaneous monitoring in children with neurological conditions. Methods: Overnight transcutaneous SpO2 and PCO2 were analyzed. T...

Background The relationship of PaO2 and PaCO2 levels with outcome after cardiac arrest (CA) is controversial. Few studies have analysed both PaO2 and PaCO2 in this setting and the overall exposure to different PaO2 and PaCO2 levels has not been taken into account. Methods We reviewed blood gas data obtained within the first 24 h from all comatose adult patients who were admitted to the intensive care unit after successful resuscitation from CA. Exposure times to different PaO2 and PaCO2 thresholds were reported as areas under the curve (AUC) and the time above these thresholds was then calculated. The primary outcome measure was neurological outcome assessed using the Cerebral Performance Category (CPC) score at 3 months. An unfavourable outcome was defined as a CPC of 3–5 and a favourable outcome as a CPC of 1–2. Results A total of 356 patients were studied, with a median number of 9 [6–11] blood gas measurements within the first 24 h after admission. The highest and lowest PaO2 and PaCO2 were similar in patients with unfavourable and favourable neurological outcomes. There were no differences in the AUCs or times over different thresholds of PaO2 and PaCO2 in the two groups. In a multivariable analysis, high blood lactate concentrations on admission, presence of shock and a non-shockable initial rhythm were significantly associated with unfavourable outcome. Conclusions There was no association between exposure to various levels of PaO2 and PaCO2 and neurological outcome after cardiac arrest.

Background Within- and/or between-instrument variation may falsely indicate patient trends or obscure real trends. We employ a methodology that transforms sequential intra-patient results into estimates of biologic and analytic variation. We previously derived realistic biologic variation (s b ) of blood gas (BG) and hematology analytes. We extend this methodology to derive the imprecision of two GEM 4000 BG analyzers. Methods A laboratory data repository provided arterial BG, electrolyte and metabolite results generated by two GEM 4000s on ICU patients in 2012–2013. We tabulated consecutive pairs of intra-patient results separated by increasing time interval between consecutive tests. The average between pair variations were regressed against time with the y-intercept representing the sum of the biologic variation and short term analytic variation: y o 2 = s b 2 + s a 2 . Using an equivalent equation for the Radiometer ABL, the imprecision of the two GEMs was calculated: s aGEM = (y oGEM 2 − y oABL 2 + s aABL 2 ) 1/2 . This analysis was performed for nearly all measurements, regardless of time as well for values obtained over two 12 h mutually exclusive periods, starting either at 2 am or 2 pm. Results Regression graphs were derived from 1800 patients' blood gas results with least 10,000 data pairs grouped into 2 h intervals. The calculated s aGEM exceed the directly measured s aABL with many GEM sigma ratios of biologic variation/analytic variation being close to unity. All of the afternoon s aGEM exceeded their morning counterparts with pH, pCO 2 , K and bicarbonate being statistically significant. Conclusion For many analytes, the average analytical variation of tandem GEMs approximates the biologic variation, indicating impaired clinical usefulness of tandem sequential measurements. A significant component of this variation is due to increased variation of the GEMs between 2 pm and 2 am.

Objective: Chloride is the major plasma anion. There are several methods available for the determination of serum chloride levels. Unfortunately these methods are sometimes not available in the urgent setting where values are needed. Here we describe a formula for estimating plasma chloride levels. Methods: Fifty-two consecutive patients were enrolled for which serum chloride levels were estimated using the formula CL- = (Na+ + 10 –TBB), and also measured directly through the colorimetric method. Correlation between the two values was analyzed using Pearson correlation coefficient and agreement was shown in the Bland-Altman plot. Results: Comparing the values achieved through estimation and laboratory determination of plasma chloride revealed a significant correlation (r = 0.97). Consistent agreement was described within -4.8 and +6.6 on the Bland-Altman plot throughout the measurements. Conclusion: The formula presented here may be a reliable alternative to direct measurement of serum chloride when direct results are not available.

Introduction and objective NICE (2016)1Motor Neurone Disease (MND) guideline recommends respiratory assessment should be undertaken by exploring symptoms and pulmonary function tests which includes measuring oxygen saturation using SpO2 and performing blood gas measurements. Smith et al., (2018)2 demonstrated that the NICE screening method risks missing half of the patients who have developed ventilatory failure. Our centre does not currently undertake blood gas analysis routinely if SpO2 is above the NICE recommendation. We wanted to know whether patients die without being offered NIV by following NICE recommendation. Methods MND patients referred to our centre between April 2013 to March 2018 were retrospectively evaluated using clinical records. Results 171 patients were evaluated from the registry. Among them, 94 (55%) patients had a trial or started Non-invasive Ventilation (NIV) and 76/94 (81%) managed NIV in the long term. 31 (18%) patients refused NIV and 46 (27%) patients were never offered NIV. Among the 46 patients, 15 patients are currently alive without an indication for NIV. 31 patients died without ever being offered NIV. These have been categorised in figure 1. Among these, 25 patients had no indication for NIV based on NICE guidance. 4 of these patients underwent blood gas analysis and had pCO2 of Conclusion This review demonstrates that there is a cohort of MND patients who were not offered NIV based on NICE screening guidelines and who died shortly after review. More detailed work should be undertaken to understand why patients with MND, who do not appear to need NIV die before being offered this life prolonging treatment. References NICE. ( 2016) Motor neurone disease: assessment and management. Smith, et al. ( 2018) S124 Symptoms and daytime pulse oximetry: an unreliable screen for ventilatory failure in motor neurone disease.

Background: Variability could be present between different manufacturers due to using different algorithms or other factors. Aim: Investigate the variance in bias and differences in oxygen saturation (SPO2) between Masimo and Nonin oximeters during 6 minute walk test (6MWT) Method: Data was retrospectively analysed comparing contemporaneous measurements of SPO2 between forehead sensors during 6MWT in 72 patients. Two way repeated measures analysis of variance (ANOVA) was performed to compare SPO2 values. Bland-Altman analysis was performed to compare the agreement between the two sensors for resting SPO2 and lowest SPO2. Results: ANOVA results demonstrated a difference (p Conclusion: Varabality in bias in a proportion of the population between different sensors was demonstrated. Clinicians should consider using the same manufacturer of oximeter when performing serial 6MWT9s. Future studies should compare SPO2 values with blood gas measurements.

Background: Correct measurement of PO2 and PCO2 is essential to establish appropriate therapy such as long-term oxygen therapy (LTOT) in patients suffering from respiratory failure. Objectives: We aimed to compare common invasive and noninvasive methods for assessing blood gas components for spot check analysis. Methods: Arterial (PaO2, PaCO2) and capillary blood gas (PCBGO2, PCBGCO2) measurements were taken consecutively in a randomized order and were compared with noninvasive measurements obtained from the transcutaneous monitoring of PO2 and PCO2 (PtcO2, PtcCO2, sensor-temperature 44°C). Capillary samples were taken from both arterialized earlobes, where samples of right earlobes were defined as a reference value. Pain assessment of all measurements was evaluated by each subject using the 100-mm visual analogue scale. Results: 83 patients and 17 healthy subjects were included. The mean difference between PaO2 and PtcO2 was 11.9 ± 15.0 mm Hg, with lower limits of agreement (LLA) of -17.4 mm Hg (95% confidence interval (CI) -22.5 to -12.3 mm Hg), and upper limits of agreement (ULA) of 41.1 mm Hg (95% CI 36.0-46.2 mm Hg). The comparison of PaO2 with PCBGO2 showed a mean difference of 5.6 ± 7.2 mm Hg (LLA -11.0; ULA 19.6 mm Hg). The mean difference between PaCO2 and PtcCO2 was 1.1 ± 4.9 mm Hg (LLA -8.6; ULA 10.8 mm Hg) and that between PaCO2 and PCBGCO2 was 0.7 ± 2.0 mm Hg (LLA -3.3; ULA 4.8 mm Hg). The analysis of capillary blood gases (36.2 ± 22.3 mm) was rated as more painful than the analysis of arterial blood gases (26.1 ± 20.6 mm), while transcutaneous measurement was rated as the least painful method (1.9 ± 7.4 mm; all p < 0.0001). Conclusions: The comparison of different methods for blood gas measurements showed substantial differences between capillary and arterial PO2 and between transcutaneous and arterial PO2. Therefore, arterial PO2 analysis is the essential method evaluating indication for LTOT. Nevertheless, comparative analysis further indicated capillary PCO2 as an adequate surrogate for arterial PCO2.

Background: Capnography provides a continuous, non-invasive monitoring of the CO 2 to assess adequacy of ventilation and provide added safety features in mechanically ventilated patients by allowing for quick identification of unplanned extubation. These monitors may allow for decreased utilization of blood gases. The objective was to determine if implementation of continuous capnography monitoring decreases the utilization of blood gases resulting in decreased charges. Methods: This is a retrospective review of a quality improvement project that compares the utilization of blood gases before and after the implementation of standard continuous capnography. The time period of April 2010 to September 2010 was compared to April 2011 to September 2011. Parameters collected included total number of blood gases analyzed, cost of blood gas analysis, ventilator and patient days. Results: The total number of blood gases after the institution of end tidal CO 2 monitoring decreased from 12,937 in 2009 and 13,171 in 2010 to 8,070 in 2011. The average number of blood gases per encounter decreased from 20.8 in 2009 and 21.6 in 2010 to 13.8 post intervention. The blood gases per ventilator day decreased from 4.94 in 2009 and 4.76 in 2010 to 3.30 post intervention. The total charge savings over a 6-month period was $880,496. Conclusions: Continuous capnography resulted in a significant savings over a 6-month period by decreasing the utilization of blood gas measurements. J Clin Med Res. 2015;7(2):71-75 doi: http://dx.doi.org/10.14740/jocmr1997w

Objective: We compared transcutaneous and intra-arterial blood gas measurements following pediatric cardiac surgery in this study. Material and Methods: A total of 150 pediatric patients who underwent surgery for congenital cardiac disease between June 2014 and November 2015 were included in the study. The efficacy of a transcutaneous non-invasive device in measuring oxygen and carbon dioxide pressures was evaluated in pediatric patients who underwent cardiovascular surgery for congenital diseases. Simultaneous transcutaneous and conventional arterial blood gases, as well as partial oxygen and carbon dioxide pressure levels were measured in 150 pediatric patients. Results: The mean age and weight of the patients were 3.7±3.1 years (range, 1 month to 16 years) and 11.7±15.1 kg (range 3.5 to 55 kg), respectively. The differences in the mean partial oxygen and carbon dioxide pressure levels were 8 mmHg (range, 3 to 20 mmHg) and 12 mmHg (range, 7 to 25 mmHg), respectively (p 0.05). This was due to the fact that transcutaneous measurements dependent on skin perfusion yielded more accurate and reliable results in optimal conditions, such as a relatively normal cardiovascular function. Conclusion: Although transcutaneous measurements were less accurate than the invasive method in the present study, its use in intensive care units where optimal conditions are provided could decrease the number of invasive arterial interventions and contact with blood, while also allowing continuous monitoring and the evaluation of ventilation efficacy.

Introduction Hypoxic challenge test consisting of breathing 15% FiO2 for 20 min with blood gas measurements is recommended by BTS guidelines for the assessment of the requirement for in-flight oxygen. FEV1 and SpO2 have been demonstrated to be poor predictors of desaturation with no established reliable upper limit of PaO2, above which patients will not desaturate. We investigated whether there were lower-limit thresholds, beyond which oxygen is always required and hence HCT can be avoided. Methods Retrospective analysis of all hypoxic challenge tests conducted at our centre between 2010 and 2017 was undertaken. Baseline demographics, diagnosis and contemporaneous lung function data was recorded. HCT was performed as per BTS guidance and included baseline resting blood gas followed by a repeat after 20 min inspiring 15% FiO2. If PaO2 was Results HCT was performed on 170 occasions during the study period. COPD was the underlying diagnosis in 110 (64.7%) of tests, ILD in 40 (23.5%) and CF (13, 11.8%). Average age (median [range]) was 67.5 years [49.1–83.8]COPD, 67 [52.3–83.3]ILD, 32.5 [19.1–66.8]CF. Lung function (FEV1%pred) was 49.7[21–115]COPD, 71.6 [31–124]ILD, 36.5[23–65]CF. Following HCT, in-flight oxygen was recommended in 99 (58.2%) patients all of whom were recommended 2 l/min. A threshold of Conclusion HCT is a useful tool for assessing the need for in-flight oxygen in lung diseases but is a resource heavy test and requires multiple blood samples taken from patients. Our data suggests that there are lower-limit thresholds for resting PaO2 beyond which HCT can be avoided in a significant proportion of patients.

Blood gas measurements provide vital clinical information in critical care. The current "gold standard" for blood gas measurements involves obtaining blood samples, which can be painful and can lead to bleeding, thrombus formation, or infection. Mass transfer equilibrium-based transcutaneous blood gas monitors have been used since the 1970s, but they require heating the skin to ≥42 °C to speed up the transcutaneous gas diffusion. Thus, these devices have a potential risk for skin burns. Here we report a new generation of noninvasive device for respiratory status assessment. Instead of waiting for mass transfer equilibrium, the blood gas levels are monitored by measuring the transcutaneous diffusion rate, which is proportional to blood gas concentration. The startup time of this device is almost independent of skin temperature, so the measurement can be made at any body temperature. The test results show that this device can track the blood gas levels quickly even at normal body temperature.

Aim We studied the diagnostic accuracy of blood gas determination as a novel method for the estimation of arteriovenous fistula (AVF) recirculation (RC). Methods In 25 patients on chronic haemodialysis, with failure of a previously well functioning native AVF (mean two-needle urea-based RC: 41 ± 10%), arterial line (AL) as well as a peripheral vein (PV) blood samples drawn by the end of a 4 h haemodialysis session, before and after the surgical repair of their AVF. Results Compared to PV samples, patients with RC had significantly higher AL blood pCO2 and pO2 values (P 40 mmHg was shown to have the best sensitivity and AL pH 5.5) making it a powerful diagnostic as well as screening tool. Conclusion We propose the regular AL blood gas measurement as a novel method of AVF function surveillance and RC diagnosis. AL blood pH 40 mmHg and RC index > 5.5, escorted by rather high pO2 and low K+ by the end of dialysis session, but probably earlier as well, signify an important RC (>20%) and warrant further investigation of AVF patency.

Introduction: Different blood gas criteria have been used in the diagnosis of hepatopulmonary syndrome (HPS). Patients and methods: Arterial blood gases were prospectively evaluated in 194 cirrhotic candidates for liver transplantation (LT) in the supine and seated position. Three blood gas criteria were analyzed: classic (partial pressure of oxygen [PaO2] < 70 mmHg and/or alveolar-arterial gradient of oxygen [A-a PO2] ≥ 20 mmHg), modern (A-a PO2 ≥ 15 mmHg or ≥ 20 mmHg in patients over 64) and the A-a PO2 ≥ threshold value adjusted for age. Results: The prevalence of HPS in the supine and seated position was 27.8% and 23.2% (classic), 34% and 25.3% (modern) and 22.2% and 19% (adjusted for age), respectively. The proportion of severe and very severe cases increased in a seated position (11/49 [22.4%] vs 5/66 [7.6%], p = 0.02). No difference was observed in the pre-LT, post-LT and overall mortality in patients with HPS, regardless of the criteria used. Conclusion: Obtaining blood gas measurements in the supine position and the use of modern criteria are more sensitive for the diagnosis of HPS. Blood gas analysis with the patient seated detects a greater number of severe and very severe cases. The presence of HPS was not associated with an increase in mortality regardless of blood gas criterion used.

We present the case of a critically ill woman whose dialysis line was noted to be circulating bright red blood. Located in the right internal jugular vein, the line had previously been working normally with the change occurring shortly after the patient was liberated from positive pressure mechanical ventilation. An arterial malposition was ruled out and subsequent investigations revealed the presence of a left-sided partial anomalous pulmonary venous connection (PAPVC) that had been previously undiagnosed. The identification of a left-sided PAPVC from blood gas measurements taken from a right internal jugular vein dialysis catheter in this case provides an informative opportunity to consider the intricate physiological relationship between the respiratory and cardiovascular systems in critically ill patients requiring invasive procedures and treatments.

Most of the time, blood samples must be taken by syringe from radial, humeral or femoral artery in order to measure the arterial blood gas. These blood tests can be also carried out directly through an arterial catheter. The correct way to do a reliable blood test for measuring blood gas is now well established (5, 10), and must be respected if we are to have trustworthy results. Choosing the right equipment is one of the main pre-analytical criteria.In this work, the blood gasometry results obtained by 3 types of syringes were compared with a sample of 27 patients.In this study, the practicalities and the safety aspects of the 3 syringes were the same. There were statistically different values for blood gas measurements between the 3 syringes.For the electrolytes Na+ and K+, Bayer heparin saturated and Bayer heparin reduced syringes seemed to be more reliable. This was not the case for Ca2+ although many publications (2, 11, 12,) have shown the sensitivity of this ion to anticoagulants.The Becton...

To demonstrate that in comparison to implantable O(2) microelectrodes, capillary blood gas measurements represent a reliable, accessible, and easy method of identifying failing free flaps.Groin fasciocutaneous flaps were elevated in 10 rats and following venous occlusion, O(2) microelectrode measurements (pO(2) and flow), and capillary blood gas measurements (pO(2), pCO(2), pH, HCO(3)) were obtained at 10-minute intervals.Measurements with capillary blood gas paralleled measurements with O(2) microelectrodes. Average capillary blood gas pO(2) fell from 42.71 to 31.57 mm Hg at 10 minutes and then to 28.67 mm Hg at 20 minutes. Average pH fell from 7.38 to 7.33 at 10 minutes and to 7.30 at 20 minutes. Results were statistically significant with both the paired Student's t test and the Wilcoxon signed rank test.While providing users an ability to simultaneously monitor accepted modalities of flap surveillance, pH and pO(2), capillary blood gas is a reliable, accessible, and reproducible marker of flap health.

In 10 Skoliose-patients undergoing Harringtons-Operation, measurements of the oszillatory impedance and arterial blood gases were made intraoperatively. The resistance was elevated from the beginning without any change during the operation. The phase was in the inductive range with a further deviation during increasing extension. The possible reasons are the maximal rigidity of thorax and/or parenchyma or change in tracheobronchial "arborisation". Increase in dead space or changes in ventilation-perfusion ratio are suggested by the blood gas measurements. Further investigations will be necessary to determine, if the impedance of the lung is of value in determining the amount of intraoperative extension or postoperative lung function.

Introduction Setting ventilator pressures in critically ill patients requires consideration of the effects on both lung mechanics and gas exchange. Increasing positive end-expiratory pressure (PEEP) recruits collapsed lung compartments improving gas exchange, however, high pressures can also cause ventilator associated lung injury (VALI). Many studies have analysed these effects independently, using blood gas measurements, dynamic compliance and static pressure volume curves to discuss optimal PEEP settings. However, recent studies have highlighted the need to consider the combined effects of PEEP changes on lung mechanics and gas exchange. This study investigates the effects of changes in PEEP on both gas exchange, using a model of oxygen transport in the lungs, and lung mechanics, using methods of measuring the static pressure-volume (PV) curve and the dynamic compliance (Cdyn).

Intraoperative monitoring of tissue oxygen saturation (StO2 ) has potentially important applications in procedures such as organ transplantation or colorectal surgery, where successful reperfusion affects the viability and integrity of repaired tissues. In this paper a liquid crystal tuneable filter-based multispectral imaging (MSI) laparoscope is described. Motion-induced image misalignments are reduced, using feature-based registration, before regression of the tissue reflectance spectra to calculate relative quantities of oxy- and deoxyhaemoglobin. The laparoscope was validated in vivo, during porcine abdominal surgery, by making parallel MSI and blood gas measurements of the small bowel vasculature. Ischaemic conditions were induced by local occlusion of the mesenteric arcade and monitored using the system. The MSI laparoscope was capable of measuring StO2 over a wide range (30-100%) with a temporal error of ± 7.5%. The imager showed sensitivity to spatial changes in StO2 during dynamic local occlusions, as well as tracking the recovery of tissues post-occlusion.

British Thoracic Society guidance on air travel in patients with respiratory disease advises that a hypoxic challenge test (HCT) can be used to determine the need for in-flight oxygen in patients at high risk of medical complications. Evidence to inform the clinician as to which patients are high-risk, particularly disease-specific evidence, is lacking. We present a case series of 40 patients with motor neurone disease (MND) referred for hypoxic challenge testing. We aimed to identify parameters that might predict the outcome of an HCT in patients with MND to aid clinicians undertaking pre-flight assessments. An HCT was performed and capillary blood gas measurements, spirometric data and sinus nasal inspiratory pressure measurements were obtained. Data from those patients requiring in-flight oxygen according to the HCT was compared to data obtained from patients who did not and results are summarised below. According to our data, baseline paCO2 was the only independent predictor of hypoxaemia following an HCT. Our data also suggests that inability to perform spirometry and need for home non-invasive ventilation reflect disease severe enough to warrant an HCT as part of a pre-flight assessment.

Background: Nasal Highflow has a growing importance in clinical practice. Unfortunately there exist only few small studies. Effectiveness and mode of action of this new non-invasive ventilatory support device is unclear. Aims: We want to prove the hypothesis that Nasal Highflow works through a wash-out effect. Methods: We used a self-constructed lung model. CO2 was introduced in the „lung" and measured continuously. We ventilated the „lung" with a tidal volume of 400 ml and a breathing frequency of 20/ min. After achievement of stable CO2 values we added NHF with 20 l/ min. Results: The concentration of CO2 decreased of 7,7 %Vol by application of 20 l/ min. Discussion: Increasing flow results in a wash-out of CO2 in a lung model. This result shows a good correlation with blood gas measurements in patients with COPD (pCO2 -9,9%) and IPF (-6,1%). This observation supports the hypothesis of a wash-out effect of NHF as main mechanism.

Whole body plethysmography using unrestrained animals is a common technique for assessing the respiratory risk of new drugs in safety pharmacology studies in rats. However, wide variations in experimental technique make cross laboratory comparison of data difficult and raise concerns that non-appropriate conditions may mask the deleterious effects of test compounds - in particular with suspected respiratory depressants. Therefore, the objective of this study was to evaluate the robustness of arterial blood gas analysis as an alternative to plethysmography in rats. We sought to do this by assessing the effect of different vehicles and times post-surgical catheterization on blood gas measurements, in addition to determining sensitivity to multiple opioids. Furthermore, we determined intra-lab variability from multiple datasets utilizing morphine and generated within a single lab and lastly, inter-lab variability was measured by comparing datasets generated in two separate labs. Overall, our data show that arterial blood gas analysis is a measure that is both flexible in terms of experimental conditions and highly sensitive to respiratory depressants, two key limitations when using plethysmography. As such, our data strongly advocate the adoption of arterial blood gas analysis as an investigative approach to reliably examine the respiratory depressant effects of opioids.

The pain and risk of infection associated with invasive blood sampling for blood gas measurements necessitate the search for reliable noninvasive techniques. In this work we developed a novel rate-based noninvasive method for a safe and fast assessment of respiratory status. A small sampler was built to collect the gases diffusing out of the skin. It was connected to a CO2 sensor through gas-impermeable tubing. During a measurement, the CO2 initially present in the sampler was first removed by purging it with nitrogen. The gases in the system were then recirculated between the sampler and the CO2 sensor, and the CO2 diffusion rate into the sampler was measured. Because the measurement is based on the initial transcutaneous diffusion rate, reaching mass transfer equilibrium and heating the skin is no longer required, thus, making it much faster and safer than traditional method. A series of designed experiments were performed to analyze the effect of the measurement parameters such as sampler size, measurement location, subject positions, and movement. After the factor analysis tests, the prototype was sent to a level IV NICU for clinical trial. The results show that the measured initial rate of increase in CO2 partial pressure is linearly correlated with the corresponding arterial blood gas measurements. The new approach can be used as a trending tool, making frequent blood sampling unnecessary for respiratory status monitoring.

Summary Objectives To assess the correlation and agreement between measurements of P O 2 , P CO 2 , H + and HCO 3 − in arterial and capillary blood in patients with acute exacerbations of COPD. To assess the repeatability of capillary measurements. Design Method comparison study. Setting Accident and emergency department in a university teaching hospital. Main outcome measures Measurements of P O 2 , P CO 2 , H + and HCO 3 − in one arterial and two capillary samples taken from consecutive patients with acute exacerbations of COPD. Results The agreement between measurements of P CO 2 , H + and HCO 3 − in arterial and capillary blood was good with mean differences of 0.087kPa, 1.044nmol/l and 0.513mmol/l, respectively. The corresponding 95% limits of agreement were narrow. The agreement between measurements of P O 2 was poor with a mean difference of 1.256kPa and wide 95% limits of agreement. There was good repeatability between capillary samples with mean differences of 0.094kPa, 0.674nmol/l and 0.028mmol/l for measurements of P CO 2 , H + and HCO 3 respectively and narrow coefficients of repeatability. Conclusions Capillary blood gas measurements provide an accurate assessment of P CO 2 , H + and HCO 3 − and can be used to reliably measure the ventilatory status of patients. Combined with continuous pulse oximetry they can be used as an alternative to arterial blood gas measurements in patients with acute exacerbations of COPD.

SOPAVent ( S imulation o f P atients under A rtificial Vent ilation) is a blood gas model for ventilated patients in intensive care units. In this paper, a continuously updated blood gas model based on SOPAVent is developed and extended to simulate patients' states from a stable to an unstable status. The changes in the patient's physiological state are simulated by updating the shunt and relative dead space in the patient model. The model was validated against blood gas measurements from real patients during a 7-hour period and with changes to the ventilator settings. Results show that, with a selector based on a time criterion, the autonomous model can represent the real patient with a changing physiological state and give good blood gas predictions.

Pressure ulcers cause great pain and suffering to patients as well as unnecessary strain on nursing staff. Their treatment is both costly and time consuming. Every effort therefore should be directed towards their prevention. Understanding of the aetiology of pressure ulcers is still incomplete and assessment of devices aimed at prevention is difficult. Over the years, numerous parameters, including interface pressure and transcutaneous blood gas measurements, have been used to evaluate mattresses and cushions. However, the quality of the data gathered is variable and its clinical interpretation remains unsatisfactory. It could be said that the science of evaluation of support surfaces is still at a formative stage, as clinical validation of many of the approaches has yet to be carried out.

Precise measurements of blood gases and pH are of pivotal importance to respiratory physiology. However, the traditional electrodes that could be calibrated and maintained at the same temperature as the experimental animal are increasingly being replaced by new automated blood gas analyzers. These are typically designed for clinical use and automatically heat the blood sample to 37°C for measurements. While most blood gas analyzers allow for temperature corrections of the measurements, the underlying algorithms are based on temperature-effects for human blood, and any discrepancies in the temperature dependency between the blood sample from a given species and human samples will bias measurements. In this study we review the effects of temperature on blood gases and pH and evaluate the performance of an automated blood gas analyzer (GEM Premier 3500). Whole blood obtained from pythons and freshwater turtles was equilibrated in rotating Eschweiler tonometers to a variety of known P(O2)'s and P(CO2)'s in gas mixtures prepared by Wosthoff gas mixing pumps and blood samples were measured immediately on the GEM Premier 3500. The pH measurements were compared to measurements using a Radiometer BMS glass capillary pH electrode kept and calibrated at the experimental temperature. We show that while the blood gas analyzer provides reliable temperature-corrections for P(CO2) and pH, P(O2) measurements were substantially biased. This was in agreement with the theoretical considerations and emphasizes the need for critical calibrations/corrections when using automated blood gas analyzers.

Introduction The introduction of a new method or new analyser is a common occurrence in clinical biochemistry laboratory. Blood gas measurements and electrolytes are often performed in Point-of-Care (POC) settings. When a new POC analyser is obtained, the performance of the analyser should be evaluated by comparison to the measurements with the reference analyser in the laboratory. Objectives Evaluation of method performance of pH, PCO2, PO2, Na(+), K(+) of cobas b121 ABG analyser. Materials & methods The evaluation of method performance of pH, PO2, PCO2, Na(+), K(+) of cobas b121 ABG analyser was done by comparing the results of 50 patient samples run on cobas b121 with the results obtained from Rapid lab values (reference analyser). Correlation coefficient was calculated from the results obtained from both the analysers. Precision was calculated by running biorad ABG control samples. Results The correlation coefficient values obtained for parameters were close to 1.0 indicating good correlation. The CV obtained for all the parameters were less than 5 indicating good precision. Conclusion The new ABG analyser, Cobas b121 correlated well with the reference ABG analyser (Rapid Lab) and could be used to run on patient samples.

Monitoring of blood gas measurements is an important part of the assessment of patients with chronic lung disease. Increasingly, this is being done in the patients' homes by specialist nurses. This makes it important to know the effect of time delay and storage temperature on the reliability of capillary blood gas analysis results.In this study, the effect of a delay of 1 and 2 h and of storage at both room temperature and in ice, on blood stored in glass capillary tubes was investigated. Samples, initially taken from the earlobes, were transferred to glass capillary tubes and used to provide duplicate initial samples for immediate analysis, and then single samples at 1 and 2 h stored at room temperature or in ice.The duplicate baseline measurements showed good reproducibility. There was a small, but statistically significant, increase in PCO2 when samples were stored in capillaries at room temperature, or in ice, both at 1 and 2 h. Small changes in PO2 were not statistically significant, either in ice or at room temperature. None of the changes was considered to be sufficient to be of clinical significance, thus supporting the use of capillary blood sampling even when there might be a delay of 1–2 h and transport is at room temperature, as might be the case when taking domiciliary samples.

Blood gas measurements were collected on healthy lifetime nonsmokers at sea level (n = 96) and at an altitude of 1,400 meters (n = 243) to establish reference equations. At each study site, arterial blood samples were analyzed in duplicate on two separate blood gas analyzers and CO-oximeters. Arterial blood gas variables included Pa(O(2)), Pa(CO(2)), pH, and calculated alveolar-arterial PO(2) difference (AaPO(2)). CO-oximeter variables were Hb, COHb, MetHb, and Sa(O(2)). Subjects were 18 to 81 yr of age with 166 male and 173 female. Outlier data were excluded from multiple regression analysis, and reference equations were fitted to the data in two ways: (1) best fit using linear, squared, and cross-product terms; (2) simple equations, including only the variables that explained at least 3% of the variance. Two sets of equations were created: (1) using only the sea level data and (2) using the combined data with barometric pressure as an independent variable. Comparisons with earlier studies revealed small but significant differences; the decline in Pa(O(2)) with age at each altitude was consistent with most previous studies. At sea level, the equation that included barometric pressure predicted Pa(O(2)) slightly better than the sea level specific equation. The inclusion of barometric pressure in the equations allows better prediction of blood gas reference values at sea level and at altitudes as high as 1,400 meters.

Objective We conducted a study to determine whether the pH and base excess of umbilical artery blood samples are significantly different when taken from a double-clamped segment of umbilical cord as compared with a nonisolated segment of umbilical cord. Study Design A prospective study with 43 singleton pregnancies was conducted. Matched pair samples of umbilical arterial blood were compared from double-clamped and nonisolated segments. The means for pH and base excess were compared and a paired t test was used to determine significance. Result The means for pH and base excess were not significantly different ( P = .70) between the 2 groups. Conclusion Double clamping the umbilical cord before obtaining an umbilical artery sample is not necessary for accurate blood gas results.

In vitro blood gas analysers inherently limit the frequency of serial blood gas measurements because of blood loss and cost. In vivo blood gas monitors eliminate an inherent cost and blood loss associated with measurement. Optode microsensing is a technology that can be readily adapted to in vivo measurement of pH, PCO2, and PO2. Optode-based intra-arterial devices that display continuous values have been developed that are practical for routine use but consistent performance remains a problem; an extra-arterial device that provides intermittent values has been shown to be consistent but is not yet available for routine use. The transfer of blood gas measurements from laboratory analysers to the combination of point-of-care analysers and monitors should have as profound an impact on acute respiratory care as did the introduction of laboratory-based blood gas analysers over 30 years ago. However, we must be sure these devices are reliable, consistent and cost beneficial in order to avoid widespread adoption of yet another technology that provides more data, more cost, and questionable patient benefit.

To evaluate activin A as a potential, early marker of perinatal hypoxia and to analyze factors, other than hypoxia, which influence on activin A concentration.Umbilical cord blood samples were collected from 86 newborns with gestational age 30-41. Of the 86 newborns, 26 were regarded as hypoxic. Activin A concentrations were measured by means of specific two-site enzyme immunoassays. Activin A concentrations were correlated with newborns' gender, week gestation, mode of delivery and blood gas measurements.Activin A levels were significantly higher in hypoxic than nonhypoxic newborns (medians, minimum and maximum values: 1.516; 0.149 -1.974 versus 0.368; 0.054 - 1.041 ng/mL, p = 0.0452). Activin A concentration was significantly higher in male newborns (p = 0.0074). Activin A levels were lower in term than preterm babies but the differences were not statistically significant (p = 0.2368 in hypoxic, p = 0.2487 nonhypoxic). Mode of delivery did not influence on activin A concentration (p = 0.8293 hypoxic, p = 0.9458 nonhypoxic). The differences of occurrence of intraventricular hemorrhage (IVH) in both group was not statistically significant (p = 0.61).Umbilical artery activin A combined with other markers of hypoxia could be a useful marker of perinatal hypoxia. Concentration of activin A is significantly higher in male newborns. The mode and time of delivery have no influence on activin A concentration.

In children, laser acupuncture is used more often than needle acupuncture in Western countries, due to their aversion to needles. When applying laser acupuncture to premature babies and neonates, firstly the degree of the thermal increase to the skin has to be evaluated so as to guarantee safe application. The patients were premature neonates before their discharge from hospital. The measurements were carried out by means of a polygraphy while they were asleep shortly. The large intestine 4 acupoint (LI4,Hegu) was stimulated by a microlaser needle (10 mW, 685 nm) twice (5 and 10 min). Local thermographic pictures were taken with a thermal camera (Flir i5, Flir Systems Inc., Portland, USA), and the warmest point was determined and subsequently compared. The study included 10 premature neonates (7 male, 3 female). The measurements were carried out on the 33rd day of life (weight 2030 g, gestational age36+3weeks of pregnancy). In comparison to the initial temperature (32.9C°), after 5 minutes of stimulation (33.9°C) (P=0.025) and also after 10 minutes of stimulation (34.0°C) (P=0.01), there was found to be a significant increase in the skin temperature. The singular maximum value of 37.9°C bears a potential danger; however, compared to the local temperatures reached in transcutaneous blood gas measurements it appears not to entail any risks.

This paper is concerned with the prediction of the occurrence of Periventricular Leukomalacia (PVL) that occurs in neonates after heart surgery. The data which is collected over a period of 12 hours after the cardiac surgery contains vital measurements as well as blood gas measurements with different resolutions. The decision tree classification technique has been selected as a tool for prediction of the PVL because of its capacity for discovering rules and novel associations in the data. Vital data measured using near-inferred spectroscopy (NIRS) at the sampling rate of 0.25 Hz and blood gas measurement up to 12 times with irregular time intervals for 35 patients collected from Children's Hospital of Philadelphia (CHOP) are used for this study. Vital data contain heart rate (HR), mean arterial pressure (MAP), right atrium pressure (RAP), blood hemoglobin (Hb), hemoglobin oxygen content (HbO2), oxygen saturation (SpO2) and relative cerebral blood flow (rCBF). Features derived from the data include statistical moments (mean, variance, skewness and kurtosis), trend and min and max of the vital data and rate of change, time weighted mean and a custom defined out of range index (ORI) for the blood gas data. A decision tree is developed for the vital data in order to identify the most important vital measurements. In addition, a decision tree is developed for blood gas data to find important factors for the prediction of PVL occurrence. Results show that in blood gas data, maximum rate of change in the concentration of bicarbonate ions in blood (HCO3) and minimum rate of change in the partial pressure of dissolved CO2 in the blood (PaCO2) are the most important factors for prediction of the PVL. Among vital features the kurtosis of HR and Hb are the most important parameters.

Blood gas measurements performed at the central laboratory and at a satellite laboratory of Brigham and Women's Hospital were studied to determine the differences in quality, turnaround time (TAT), and cost. The quality in both laboratories, as determined by results on proficiency and quality control samples, satisfactorily met current standards for patient care. The central laboratory receives specimens for blood gas measurements through a pneumatic tube system and broadcasts results to computer terminals at the originating site, with a mean TAT of 6 minutes. The satellite laboratory, which is within the neonatal intensive care unit that it serves, has a mean TAT of 4.5 minutes. The difference is attributable to transit time in the pneumatic tube and accessioning time in the central laboratory. The total cost per reportable result was substantially higher for the satellite laboratory than for the central laboratory. The minor difference in TAT can be considered in a cost-benefit analysis that weighs medical utility criteria against cost.

SUMMARY Alfentanil (50 μg/kg) was administered intravenously, over 1 minute, to 6 healthy cats. Blood samples were collected from a preplaced arterial catheter at 0.625, 1.25, 2.5, 5, 10, 15, 20, 30, 45, 60, 90, 120, 180, 240, 360, and 480 minutes after the end of the alfentanil injection. A radio-immunoassay technique was used to measure alfentanil concentrations in plasma obtained from these samples. Arterial blood pressure was measured at 0.625, 1.25, 2.5, 5, 10, 15, 20, and 30 minutes and pH and blood gas measurements were carried out at 5, 10 and 30 minutes after the alfentanil. Analgesia, tested by placing a clamp on the base of the tail for 5 seconds, was assessed at each blood sampling time until analgesia was absent. The cats were observed for behavioural changes at each sample time. Alfentanil caused a transient increase in blood pressure and respiratory and metabolic acidosis. Following alfentanil all cats became excited and showed pupillary dilation. Analgesia was present for 21.7 ± 14 minutes. The plasma concentration-time data for 5 cats were best described by a 3 compartment open model with the curve fitting the equation: C to = 162.6e −0.2062t + 60.le −0.041t + 13.2e −0.0062t The harmonic means for the half lives of the rapid distribution, the slow distribution and the elimination phases were 4.12, 18.8, 119.2 minutes respectively.

Background: Most estimates of biologic variation (sb) are based on periodically acquiring and storing specimens, followed by analysis within a single analytic run. We demonstrate for many intensive care unit (ICU) tests, only patient results need be statistically analyzed to provide reliable estimates of sb. Methods: Over 11 months, approximately 28,000 blood gas measurements (including electrolyte panels and glucose) were performed on one of two Radiometer ABL800 FLEX analyzers (Radiometer, Copenhagen, Denmark) from 1676 ICU patients. We tabulated the measurements of paired intra-patient blood samples drawn within 24 h of each other. After removal of outliers, we calculated the standard deviations of duplicates (SDD) of the intra-patient pairs grouped in 2-h intervals: 0–2 h, 2–4 h, 4–6 h, … 20–22 h and 22–24 h. The SDDs were then regressed against the time intervals of 2–14 h; extrapolation to zero time represents the sum of sb and short-term analytic variation (sa). Results: Substitution of experimentally derived analytic error permitted the calculation of coefficient of variation (biologic) (CVb) (100 sb/mean): pH, 0.3%; pCO2, 5.7%; pO2, 13%; Na+, 0.6%; K+, 4.8%; Cl–, 0.8%; HCO3 –, 3.2%; iCa++, 2.4%; and glucose, 10.3%. The CVb of the electrolytes very closely matches the lowest estimates obtained in the usual manner. Conclusions: Derivation of the ratio of biologic to analytic variation indicates that the ABL800 is extremely suitable for ICU testing. This analysis should be extended to other point of care instrument systems. Clin Chem Lab Med 2010;48:1447–54.

Background: Portable blood gas analyzer and monitor devices are increasingly being used to direct ventilator therapy. The purpose of this study was to evaluate the "measure of treatment agreement" between portable and laboratory blood gas measurements used in guiding protocol-driven ventilator management. Materials and Methods: Using National Institutes of Health Acute Respiratory Distress Syndrome network ventilator management guidelines to manage patient care, measurements taken from the Nonin 8500 M pulse oximeter (SpO 2 ), the Novametrix-610 end-tidal CO 2 (ETCO 2 ) detector, and the i-STAT 1 (SaO 2 , PO 2 , pH, PCO 2 ) were compared with the recommended treatment from paired laboratory ABL-725 (SaCO 2 , PO 2 , pH, PCO 2 ) measurements. Results: Four hundred forty-six intubated adult intensive care unit patients were studied prospectively. Except for the ETCO 2 (R 2 = 0.460), correlation coefficients between portable and laboratory measurements were high (R 2 ≥ 0.755). Testing for equivalence, the Nonin-SpO 2 , iSTAT-PO 2 , iSTAT-pH, and iSTAT-PCO 2 were deemed "equivalent" surrogates to paired ABL measurements. Testing for the limits of agreement found only the iSTAT-PCO 2 to be an acceptable surrogate measurement The measure of treatment agreement between the portable and paired laboratory blood gas measurements were Nonin-SpO 2 (68%), iSTAT-SaO 2 (73%), iSTAT-PO2 (97%), iSTAT-pH (88%), iSTAT-PCO 2 (95%), and Novametrix-ETCO 2 (60%). Only the iSTAT-PO 2 and the iSTAT-PCO 2 achieved the ≥95% treatment agreement threshold to be considered as acceptable surrogates to laboratory measurements. Conclusions: The iSTAT-PO 2 and -PCO 2 were portable device measurements acceptable as surrogates to standard clinical laboratory blood gas measurements in guiding protocol-directed ventilator management. The "measure of treatment agreement," based on standardized decisions and measurement thresholds of a protocol, provides a simple method for assessing clinical validity of surrogate measurements.

The following topics are covered: respiration; blood gas measurements; the lung; inspired and expired gases; blood pH; muscle tone; the heart; measurement of cardiac output; blood pressure; intracranial pressure; control of pain.

This paper presents the use of an ISFET sensor during extracoporeal circulation (ECC). Initially, the ISFET time response and stability were measured. The flow rate dependency was also determined. The sensor gave a correct response in a few milliseconds which, compared with presently available sensors, is very good. Stability provided to be as good as with Ingold pH sensors (glass electrode). The sensitivity of the sensor used for the experiment was then evaluated precisely, before installation in the ECC arterial line. An Ag/AgCl reference was used. An Ingold sensor was used simultaneously in order to provide comparative measurements. ECC was then performed on a sheep for 6 h. Flow rate stabilized at approximately 31/min and blood temperature was set and regulated to 37°C. Standard laboratory blood gas measurements were performed every 15 min for the first hour and every 30 min thereafter so as to obtain a good control. The results show that standard measurement, Ingold probe and ISFET sensor values vary in the same way and experimentation is continuing.

Therapeutic decisions in the Operating Room (OR) are often made based solely upon results obtained from arterial blood gas machines. We evaluated how precise and accurate the results obtained from Bayer Rapid Point 405 (RP405) were vis-à-vis those of our blood gas laboratory and if they met the standards of the members of the anesthesia department.About 3 ml of blood from an indwelling arterial catheter were drawn into a heparinized syringe (FIMS Portex Inc.) from each of 90 patients and immediately analyzed by two RP405 and the hospital's main blood gas machines (Instrumentation Laboratories GEM 3000). The remaining 2.8 ml of blood was used to measure Hematocrit and sent to the hospital's main biochemistry laboratory for electrolyte measurement using an indirect ion selective method (Roche Diagnostics Modular ISE Module). A survey was distributed to each of the 19 anesthesiologists at the Sir Mortimer B Davis Jewish General Hospital (JGH). Their opinions for accuracy and treatment thresholds for each of the 12 variables measured by the RP405 were sought.For all measured variables, including pH, pCO2, pO2, potassium and Hematocrit, the correlation between the measurements from the RP405 and the gold standard were all above 95.5% with a p0.001. The survey results demonstrate that the machine gives results that are accurate within the acceptability frame expected by our staff anesthesiologists.Anesthesiologists must be confident that the information they receive is accurate in the context of rapidly changing clinical status. Our results show that the RP405 analyzers produce reliable measurements.

It is believed that a chronic state of corporal oxygen desaturation or hypoxemia secondary to the loss of nocturnal erections is a fundamental pathophysiological cause of erectile dysfunction (ED). Limited invasive blood gas measurements in human models have shown decreased oxygen tension in vasculogenic impotence. Normative data on flaccid and erect oxygen saturation (StO(2)) levels are lacking due to the invasive nature of blood gas determinations. Our objective was to determine StO(2) in the flaccid and erect penis in men with and without ED using a tissue oximeter. This FDA-approved instrument provides instantaneous, noninvasive, painless local tissue StO(2) measurements, which highly correlate to blood gas data. The study population included 171 men (18-90 years) who presented to one andrologist. They completed the Sexual Health Inventory for Men (SHIM) based on pharmacologically unassisted erectile function and had penile StO(2) measurements taken. 64 of these men had repeat measurements after PGE-1 induced erections. There are significant differences (P

Blood gas measurement-monitoring is essential to monitor gas exchange in critically ill patients in the intensive care units, and “standard of care” monitoring to deliver general anesthesia. It is a cornerstone in the diagnosis and management of the patient's oxygenation and acid-base disorders. Moreover, it may indicate the onset or culmination of cardiopulmonary problems, and may help in evaluating the effectiveness of the applied therapy. Numerous studies and reports have shown the significance of utilizing blood gas analyses in preventing serious oxygenation and acid-base problems. This article gives a summarized explanation of the common methods and instruments used nowadays in blood gas measurements in clinical medicine. This explanation includes a brief history of the development of these methods and instruments, the principles of their operation, a general description of their designs, and some of their clinical uses, hazards, risks, limitations, and finally the direction in the future to improve these instruments or to invent new ones. Keywords: invasive blood gas measurements; noninvasive blood gas measurements; blood gas electrodes; blood gas physiology; oximetry; TCM

Theoretical modelling predicts that the concentrating effect of nitrous oxide (N 2 O) uptake on alveolar oxygenation is a persisting phenomenon at typical levels of ventilation - perfusion (V/Q) inhomogeneity under anaesthesia. We sought clinical confirmation of this in 20 anaesthetised patients. Artenal oxygen pressure (P a o 2 ) was measured after a minimum of 30 min of relaxant general anaesthesia with an inspired oxygen (F 1 o 2 ) of 30%. Patients were randomly allocated to two groups. The intervention group had N 2 O introduced following baseline blood gas measurements, and the control group continued breathing an identical F 1 o 2 in nitrogen (N 2 ). The primary outcome variable was change in P a o 2 . Mean (SD) in P a o 2 was increased by 1.80 (1.80) kPa after receiving a mean of 47.5 min of N 2 O compared with baseline conditions breathing O 2 /N 2 (p = 0.01). This change was significantly greater (p = 0.03) than that in the control group: + 0.09 (1.37) kPa, p = 0.83 and confirms the presence of significant persisting concentrating and second gas effects.