Blood Gas Samples Research Articles

Oxygen reserve index vs. peripheral oxygen saturation for the prediction of hypoxemia in morbidly obese patients: a prospective observational study

BackgroundPulse oximetry is a standart of anesthesia for perioperative monitoring. Due to the principles of Hb oxygen dissociation curve, peripheral oxygen saturation has an approximate sensitivity and specificity of 90% for the detection of hypoxemia.ObjectivesThe primary outcome of the study was to evaluate ORiⓇ as an early parameter to determine hypoxia in morbidly obese patients. The secondary outcome was to compare the effectiveness of ORiⓇ with SpO2 in non-obese patients.DesignProspective, observational study.SettingDepartment of elective operating room at tertiary hospital.Patients and methodsObservational study included written informed consent from 51 patients with 19 < BMI < 25 kg/m2 and 51 patients with BMI > 40 kg/m2 undergoing an elective surgery requiring tracheal intubation. In addition to standard monitors, an ORi sensor was placed and baseline values were recorded. The patients were preoxygenated until end tidal expiratory oxygen concentration is reached to 90%. After anesthesia induction and tracheal intubation, the breathing circuit was not connected tracheal tube until the SpO2 decreased to 95%. Shapiro-Wilk, Pearson Chi-square, t-test, and Mann Whitney U test were used for the study.Main outcome measuresTimes of tolerable apnea, ORiⓇ and SpO2 values at the end of preoxygenation, beginning of intubation, beginning of the ORi alarm, when SpO2 reached 95%, and when ORi reaches a plateau.Sample size102 patients.ResultsThe alert period: time to reach ORiⓇ from 0.24 to a value of 95% SpO2 was observed as 32 s in morbidly obese patients and 94 s in patients with a normal body mass index. The SpO2 alert period was determined as time difference between 97% and 95% SpO2. The data were recorded as 15 s and 36 s, respectively. It was observed that tolerable apnea, ORiⓇ, SpO2 and added alert times were longer in patients with normal BMI compared to morbidly obese patients.ConclusionsAs a result, ORiⓇ can provide an early warning to prevent unexpected hypoxia before saturation begins to decrease in morbidly obese patients.LimitationsInability to perform arterial blood gas sampling in the time periods when we looked at the parameters to determine the relationship between ORiⓇ and PaO2.Clinical trials. gov identifierNCT05480748 registered 2022-07-29.

A-127 Stability of Ionized Calcium in Blood Gas Specimens

Abstract Background Ionized calcium monitoring is crucial for monitoring critically ill patients as well as patients undergoing apheresis. According to CLSI C31-A2:2001, the acceptable stability time for all tests to be run on blood gas analyzers in heparinized syringes is thirty minutes from collection. We sought to determine whether the stability of ionized calcium in blood gas samples can be extended to accommodate prolonged transport times. Methods Sixty whole blood samples were collected into 1CC syringes containing 23 IU of heparin (Vital Signs, Inc.) and sent to the laboratory for ionized calcium and pH analysis on the Siemens RAPIDLab 1265. If the remaining sample was sufficient, it was set aside for additional testing 40, 60 and 90 minutes after receipt in the laboratory. All samples were kept at room temperature during all timepoints. The three timepoints were compared to the initial reported baseline result and the average percent bias and standard deviation was determined. Results When compared to the baseline result, samples analyzed at the 40-, 60-, and 90-minute timepoints showed negligible bias for both pH and ionized calcium. The absolute bias was within +/- 0.6 and +/-0.4 for ionized calcium and pH, respectively. Conclusions This study showed that accurate measurements of both ionized calcium and pH can be obtained from blood gas samples collected in heparinized syringes at least till 90 minutes after collection.

A-362 Hemolysis Detection and Flagging of Potassium Results on GEM Premier 7000 with iQM3

Abstract Background Blood gas analyzers that report whole blood potassium (K+) are vulnerable to inaccurate results due to in vitro hemolysis. GEM Premier 7000 with iQM3 (GEM 7000) automatically detects hemolysis (plasma free hemoglobin) and flags impacted K+ results. Here, we report the hemolysis impact on K+ measurements and the flagging approach used in the GEM 7000 system. Methods Hemolysis interference was assessed according to CLSI EP07c at low (3.8 mmol/L) and high (5.3 mmol/L) K+ levels. Ultrasonically-lysed whole blood was used to generate a high test pool (100% = 1000 mg/dL hemoglobin). This was mixed volumetrically with a low pool (0% = native blood) to create additional test pools (25%, 50%, and 75%) and analyzed on three (3) GEM 7000 systems. K+ bias at each test pool was calculated from the low pool to generate hemolysis interferograms. Linear regression was performed to determine the hemolysis level that exceeds the interference limit of 7%. Results Hemolysis exceeding the interference limit was ≥ 116 mg/dL for the low K+ and ≥ 147 mg/dL for the high K+ level. These correspond to an elevation of 0.27 mmol/L and 0.37 mmol/L of K+, respectively. Based on this study, the GEM 7000 triggers a hemolysis flag when the detected hemolysis exceeds 115 mg/dL. By default, GEM 7000 hemolysis flags are categorized into mild (116 -300 mg/dL), moderate (301 - 400 mg/dL), and gross (≥401 mg/dL) hemolysis. Conclusions The magnitude of the observed increase in K+ (0.277 - 0.295 mmol/L for every 100 mg/dL of hemoglobin) on the GEM 7000 due to in vitro hemolysis is consistent with previously published reports in the literature. Automated hemolysis detection and flagging of K+ results in GEM 7000 overcome the limitation of the inability to detect hemolysis in blood gas samples.

A-333 Comparison between measured total carbon dioxide and calculated bicarbonate in hospitalized patients

Abstract Background Bicarbonate (HCO3-) is a key indicator of anion excess or deficit and important clinically for assessing acid-base balance. For patient care, HCO3- may be reported as a calculated value from blood gas analysis or measured on automated chemistry analyzers. When measured, the final result includes HCO3-, carbonate (CO32-) and carbamino compounds and thus is reported as total CO2 (TCO2). Anecdotally, some patients have discrepancies between HCO3- and TCO2. However, there is limited data in the published literature assessing agreement between the two methods. Our study aims to compare the calculated HCO3- values with measured TCO2 obtained from simultaneously collected clinical specimens. Methods This study included all results from physician ordered HCO3- and TCO2 between 01/2019 to 12/2020 retrospectively retrieved from the laboratory information system (Cerner). Specimens were collected by nursing staff within 5 minutes of each other. TCO2 was assessed on a Roche cobas 702 (CV = 4.2%) according to the manufacturer’s instructions using an enzymatic phosphoenolpyruvate carboxylase method in lithium heparin tubes. HCO3- was calculated using a Radiometer ABL800 blood gas analyzer from arterial or venous blood gas samples according to the manufacturer’s instructions. Briefly, HCO3- is calculated using the Henderson-hasselbalch equation and the measurement of PCO2 (CV= 1.75%), and pH (CV = 0.06%). Deming regression was performed. The CLIA total allowable error of 4 mmol/L and a reference change value (RCV, Cv Individual = 4%) of -13 and + 14 for TCO2 was used to assess agreement. All data was analyzed in R. Results There were 101,895 paired HCO3- and TCO2 results during the study period. The values ranged from 4 to 56 mmol/L and the mean was 25.7. The mean difference between the calculated HCO3- and measured TCO2 was 1.33 mmol/L. Relative to HCO3-, there were 2,119 (2.1%) TCO2 results with a negative bias exceeding 4 mmol/L and 427 (0.4%)[FC1] with a positive bias exceeding 4 mmol/L. Twenty-two samples exceeded the positive RCV of 14% and 22 samples exceeded the negative RCV. Deming regression revealed a slope of 1.09 (95% CI: 1.087-1.092) an intercept of -2.19 (-2.18 to -2.06), and a Pearson correlation of 0.960 (0.959 to 0.960). We also analyzed differences between HCO3- and TCO2 in arterial and venous samples. The Pearson r for venous samples was 0.956 (0.955 to 0.957) and for arterial samples was 0.966 (0.966-0.966). Deming regression revealed a slope of 1.099 (0.195 to 1.104) and 1.071 (1.068 to 1.074) for venous and arterial samples respectively. The intercept for venous samples was -1.441 (-1.559 to -1.324) and for arterial was -2.005 (-2.072 to -1.938). Conclusions There is bias between HCO3- calculations and TCO2 measurements in simultaneously drawn samples. A small proportion of samples (2.5%) exceed the CLIA total allowable error between the results but very few exceed the RCV. This may due to differences in matrices, with different correlations and slopes observed between arterial and venous specimens. Further studies are required to distinguish the causes of the observed differences between HCO3- and TCO2.

A-343 Novel In-Line Hemolysis Detection on a Blood Gas Analyzer for Capillary Samples

Abstract Background Point-of-care (POC) blood gas and electrolyte analyzers utilizing whole blood as the predominant sample type are blinded by the presence of hemolysis until today. Moreover, capillary samples are particularly vulnerable to in-vitro hemolysis due to excessive force applied during sample collection. Here, we introduce the GEM Premier 7000 with iQM3 (GEM 7000) which incorporates automatic, in-line hemolysis detection in capillary blood gas samples without a need for additional sample volume or reagents. Methods The hemolysis detection module which is integrated into the disposable GEM cartridge uses acoustophoretic technology and photometric measurements to detect hemolysis in whole blood. In GEM 7000, hemolysis of ≥ 116 mg/dL was found to have significant interference with potassium results. A hemolysis flag is presented as the degree of hemolysis: none (0 - 50 and 51 - 115), mild (116 - 200 and 201 - 300), moderate (301 - 400), and gross (≥401). Due to volume limitations with native capillary samples and challenges in assessing hemolysis levels with a comparator assay, venous blood spiked volumetrically with hemolysate and transferred to capillary devices was used to verify the hemolysis flag performance. An agreement analysis was performed using the Roche cobas hemolysis value. The device's (GEM 7000) ability to flag hemolyzed capillary samples is demonstrated in a simulated clinical setting using native and contrived fingerstick capillary samples. Results Hemolysis verification with transferred capillary samples demonstrated that 98.2% (274/279) of samples were correctly flagged based on the cobas hemolysis value of spiked hemoglobin. Hemolysis in the native capillary samples (N = 235) was primarily distributed in the 0-50 mg/dL range. Additionally, native capillary samples altered using vigorous flea mixing (&amp;gt; 1 minute) showed hemolysis distribution over a wide hemolysis degree (none to gross), and their potassium results were flagged accordingly. Conclusions By providing integrated hemolysis detection in capillary blood sample measurements, the GEM Premier 7000 with iQM3 system can provide quality and confidence in the clinical interpretation of critical results such as potassium.

Comparative analysis of Glasgow Coma Scale, quick Sepsis-related Organ Failure Assessment, base excess, and lactate for mortality prediction in critically ill emergency department patients

Abstract OBJECTIVES: It is crucial to promptly identify high-mortality patients in emergency departments and initiate their treatment as soon as possible. Although many parameters have been studied to select patients with high mortality, no comprehensive evaluation exists in previous literature on these parameters in critically ill patients, regardless of patient groups. The aim of this study is to evaluate the Glasgow Coma Scale (GCS), quick Sepsis-related Organ Failure Assessment (qSOFA), blood gas base excess (BE), and blood gas lactate in predicting mortality in critically ill patients admitted to the emergency department. METHODS: This prospective observational cohort study included adult patients with Emergency Severity Index 1–2 (critically ill) admitted to the emergency department. All patients were evaluated by the physician within 10 min, and blood gas samples were taken. The data collection forms recorded the patients’ GCS and qSOFA scores at the time of first evaluation by the physician. The qSOFA score assessment was performed in all patients with ESI levels 1 and 2, regardless of whether infective pathology was suspected. Blood gas BE and lactate values were also from laboratory test results. Patients or their relatives were contacted by phone at the end of the 1st month to obtain information about the clinical condition (survival or mortality). RESULTS: A total of 868 patients were included, with 163 deaths observed within 30 days. GCS score, qSOFA score, and lactate value were significant in predicting mortality within 30 days. While the BE value was significant for predicting 30-day mortality for values equal to or below the lower limit of −1.5 (P &lt; 0.001), it was not significant for values equal to or above the upper limit of +3 (P &gt; 0.05). The most successful prediction model for predicting 30-day mortality was found to be qSOFA with a cutoff value of ≥1. CONCLUSION: In emergency departments, each of the GCS, qSOFA scores, BE, and lactate values can be used independently as a practical mortality prediction model in critically ill patients. Among these four models, qSOFA is the most successful practical mortality prediction model in critically ill patients.

Association between early metabolic acidosis and bronchopulmonary dysplasia/death in preterm infants born at less than 28 weeks’ gestation: an observational cohort study

BackgroundMetabolic acidosis occurs frequently during the first postnatal days in extremely preterm infants and is mainly attributed to renal immaturity. Recent studies suggested a link between metabolic acidosis and the development of BPD. The aim of this study was to systematically investigate the association between severe metabolic acidosis during the first two weeks of life and bronchopulmonary dysplasia (BPD) / mortality among preterm infants born before 28 weeks’ gestation.MethodsMonocentric observational cohort study including 1748 blood gas samples of 138 extremely preterm infants born 2020–2022. Metabolic acidosis was defined as pH < 7.2 with base excess (BE) < -10 mmol/L or standard bicarbonate (SBC) < 12 mmol/L. Primary outcome was BPD and/or death at 36 weeks postmenstrual age.ResultsFifty-six (40.6%) infants had BPD/death. Metabolic acidosis occurred in 50.0% of infants with BPD/death, compared to 22.0% of BPD-free survivors (p = 0.001) during the first 14 postnatal days. Minimum pH (median 7.12 vs. 7.19, p < 0.001), BE (median -10.9 vs. -9.5 mmol/L, p = 0.005), SBC (median 14.7 vs. 16.1 mmol/L, p < 0.001) were different between the two groups. After adjusting for confounders, pH (postnatal days 2–6), BE (postnatal day 3) and SBC (postnatal days 2–4) were significantly lower in infants with BPD/death. Metabolic acidosis on postnatal days 1–7 was associated with higher odds of BPD (adjusted Odds Ratio (aOR) 3.461, 95% CI 1.325–9.042) and BPD/death (aOR 3.087, 95% CI 1.225–7.778).ConclusionsMetabolic acidosis during the first week of life was associated with higher odds of BPD/death in extremely preterm infants.

Can end-tidal CO2 measurement replace arterial partial CO2 in emergency department respiratory distress management?

ObjectiveTo assess the feasibility of using end-tidal carbon dioxide (EtCO2) as a non-invasive substitute for partial pressure of arterial carbon dioxide (PaCO2) in emergency department (ED) triage and follow-up, and to explore the potential of partial pressure of venous carbon dioxide (PvCO2) as an alternative to PaCO2. DesignProspective cross-sectional study. SettingTertiary university hospital. Patients or participants97 patients presenting with acute respiratory distress to the ED. InterventionsEtCO2, arterial blood gases, and venous blood gases measured at admission (0 min), 60 min, and 120 min. Main variables of interestCO2 levels. ResultsAmong 97 patients (mean age: 70.93 ± 9.6 years; 60.8% male), EtCO2 > 45 mmHg at admission showed strong positive correlations with PaCO2 and PvCO2 (r = 0.844, r = 0.803; p < 0.001, respectively). Significant positive correlation was observed between 60-min EtCO2 and PaCO2 (r = 0.729; p < 0.001). Strong correlation between PaCO2 and PvCO2 at 120 min when EtCO2 > 45 mmHg (r = 0.870; p < 0.001). EtCO2 was higher in hospitalized patients compared to discharged ones. ConclusionsEtCO2 appears promising as a substitute for PaCO2 in ED patients with acute respiratory distress within the initial two hours of treatment. Venous blood gas sampling offers a less invasive alternative to arterial sampling, facilitating simultaneous blood tests.

Effect of Deep Hypothermia (18°C) on Dioxygen Metabolism During Pulmonary Thromboendarterectomy Surgery

Objectives: The aim of this physiological pilot study was to investigate the effect of deep hypothermia on oxygen extraction (OE) and consumption (VO2) in normothermic conditions (36-37°C) then at different stages of cooling: 30°C, 25°C and 18°C. Design: For three months, we conduct a prospective study on patients that underwent pulmonary thromboendarterectomy. Settings: This is a single center study done in a university teaching hospital. ParticipantsPatients that underwent pulmonary thromboendarterectomy during the inclusion period. InterventionsHemodynamic and biological data were recorded from arterial and venous blood gas samples withdrawn first at normothermia, then at 30°C, 25°C and 18°C.. Measurements and Main Results24 patients were included in the final analysis. Indexed VO2 decreased from 65.9 ml to 25.1 ml of O2/min/m2 between 36°C and 18°C (p<0.001). The OE decreased from 18% to 9% between 36°C and 18°C (p<0.001). At normal temperature and at 18°C, the median venoarterial difference of O2 bound to hemoglobin was 2.22 [1.68-2.58] and 0.03 [0.01-0.07] ml of O2/100 ml of blood, respectively (p<0.001). Whereas the median venoarterial difference of dissolved O2 was 0.78 [0.66-0.92] and 1.09 [1.03-1.32] ml of O2/100 ml of blood, respectively (p=0.0013). Conclusion: There is a VO2 and OE decrease of more than half of their baseline value at 18°C. Seeing that the metabolic needs are essentially supplied from dissolved O2 during cooling from 30°C to 18°C, we suggest that PaO2 should be increased during the period of cooling and/or of deep hypothermia to prevent hypoxia.

Interpretation of acid-base metabolism on arterial blood gas samples via machine learning algorithms.

Arterial blood gas evaluation is crucial for critically ill patients, as it provides essential information about acid-base metabolism and respiratory balance, but evaluation can be complex and time-consuming. Artificial intelligence can perform tasks that require human intelligence, and it is revolutionizing healthcare through technological advancements. This study aims to assess arterial blood gas evaluation using artificial intelligence algorithms. The study included 21.541 retrospective arterial blood gas samples, categorized into 15 different classes by experts for evaluating acid-base metabolism status. Six machine learning algorithms were utilized; accuracy, balanced accuracy, sensitivity, specificity, precision, and F1 values of the models were determined; and ROC curves were drawn to assess areas under the curve for each class. Evaluation of which sample was estimated in which class was conducted using the confusion matrices of the models. The bagging classifier (BC) model achieved the highest balanced accuracy with 99.24%, whereas the XGBoost model reached the highest accuracy with 99.66%. The BC model shows 100% sensitivity for nine classes and 100% specificity for 10 classes, and the model correctly predicted 6438 of 6463 test samples and achieved an accuracy of 99.61%, with an area under the curve > 0.9 in all classes on a class basis. The machine learning models developed exhibited remarkable accuracy, sensitivity, and specificity in predicting the status of acid-base metabolism. However, implementing these models can aid clinicians, freeing up their time for more intricate tasks.

Evaluation of Hyponatremia in Infants on Vasopressin Therapy.

Vasopressin has systemic vasoconstrictive yet pulmonary vasodilatory effects, making it an ideal agent for hypotension management in infants with congenital diaphragmatic hernia (CDH)-associated pulmonary hypertension. The side effects of vasopressin in this population, such as hyponatremia, are understudied. This study aims to characterize the effect of vasopressin on sodium concentrations in infants with and without CDH. This was a retrospective review of patients who received vasopressin while admitted to a level IV neonatal intensive care unit. The primary outcome was the incidence of hyponatremia (blood sodium <135 mmol/L) during vasopressin therapy. Secondary outcomes included time to hyponatremia, dose and duration of vasopressin, incidence of severe hyponatremia (blood sodium <125 mmol/L), and hypertonic saline use. Both blood serum and blood gas sample sodium concentrations were used to compare CDH vs non-CDH patients. The average difference between baseline and lowest blood sodium was significant for both CDH and non-CDH patients for all samples (p < 0.001). There was no significant difference in the primary outcome, nor in the secondary outcomes of time to hyponatremia or duration of vasopressin infusion. The average dose of vasopressin was higher in the CDH vs non-CDH group (p = 0.018). The incidences of severe hyponatremia and hypertonic saline use were greater in the CDH vs non-CDH group for patients who had blood serum sodium samples collected (p = 0.049 and p = 0.033, respectively). This study showed that severe hyponatremia occurred more frequently in CDH vs non-CDH patients. Extreme caution is necessary when managing total body sodium in patients with CDH.

Australian and New Zealand Society of Respiratory Science position statement for arterial blood gas sampling.

The assessment of gas exchange under varying ambient and metabolic conditions is an important and fundamental investigation of respiratory function. The gold standard is an arterial blood gas (ABG) sample; however, the procedure is not universally performed by medical scientists, is not standardised, and is typically taught by a subjective Halsted 'see one, do one' approach. The Australian and New Zealand Society of Respiratory Science recognised the need to create an ABG position statement that includes the required pre-requisite education, an evidence-based procedure and the minimum reporting and competency assessment requirements. This position statement aims to minimise patient discomfort, to improve puncture success rate and reduce the potential for sample handling and analysis error. Importantly, this position statement translates to all relevant health professionals, including medical officers, scientists, nursing staff and allied health.

Performance of a Wearable Ring in Controlled Hypoxia: A Prospective Observational Study.

Over recent years, technological advances in wearables have allowed for continuous home monitoring of heart rate and oxygen saturation. These devices have primarily been used for sports and general wellness and may not be suitable for medical decision-making, especially in saturations below 90% and in patients with dark skin color. Wearable clinical-grade saturation of peripheral oxygen (SpO2) monitoring can be of great value to patients with chronic diseases, enabling them and their clinicians to better manage their condition with reliable real-time and trend data. This study aimed to determine the SpO2 accuracy of a wearable ring pulse oximeter compared with arterial oxygen saturation (SaO2) in a controlled hypoxia study based on the International Organization for Standardization (ISO) 80601-2-61:2019 standard over the range of 70%-100% SaO2 in volunteers with a broad range of skin color (Fitzpatrick I to VI) during nonmotion conditions. In parallel, accuracy was compared with a calibrated clinical-grade reference pulse oximeter (Masimo Radical-7). Acceptable medical device accuracy was defined as a maximum of 4% root mean square error (RMSE) per the ISO 80601-2-61 standard and a maximum of 3.5% RMSE per the US Food and Drug Administration guidance. We performed a single-center, blinded hypoxia study of the test device in 11 healthy volunteers at the Hypoxia Research Laboratory, University of California at San Francisco, under the direction of Philip Bickler, MD, PhD, and John Feiner, MD. Each volunteer was connected to a breathing apparatus for the administration of a hypoxic gas mixture. To facilitate frequent blood gas sampling, a radial arterial cannula was placed on either wrist of each participant. One test device was placed on the index finger and another test device was placed on the fingertip. SaO2 analysis was performed using an ABL-90 multi-wavelength oximeter. For the 11 participants included in the analysis, there were 236, 258, and 313 SaO2-SpO2 data pairs for the test device placed on the finger, the test device placed on the fingertip, and the reference device, respectively. The RMSE of the test device for all participants was 2.1% for either finger or fingertip placement, while the Masimo Radical-7 reference pulse oximeter RMSE was 2.8%, exceeding the standard (4% or less) and the Food and Drug Administration guidance (3.5% or less). Accuracy of SaO2-SpO2 paired data from the 4 participants with dark skin in the study was separately analyzed for both test device placements and the reference device. The test and reference devices exceeded the minimum accuracy requirements for a medical device with RMSE at 1.8% (finger) and 1.6% (fingertip) and for the reference device at 2.9%. The wearable ring meets an acceptable standard of accuracy for clinical-grade SpO2 under nonmotion conditions without regard to skin color. ClinicalTrials.gov NCT05920278; https://clinicaltrials.gov/study/NCT05920278.

Assessment of Autoregulation of the Cerebral Circulation during Acute Lung Injury in a Neonatal Porcine Model.

In neonates with acute lung injury (ALI), targeting lower oxygenation saturations is suggested to limit oxygen toxicity while maintaining vital organ function. Although thresholds for cerebral autoregulation are studied for the management of premature infants, the impact of hypoxia on hemodynamics, tissue oxygen consumption and extraction is not well understood in term infants with ALI. We examined hemodynamics, cerebral autoregulation and fractional oxygen extraction, as measured by near-infrared spectroscopy (NIRS) and blood gases, in a neonatal porcine oleic acid injury model of moderate ALI. We hypothesized that in ALI animals, cerebral oxygen extraction would be increased to a greater degree than kidney or gut oxygen extraction as indicative of the brain's adaptive efforts to increase cerebral oxygen extraction at the expense of splanchnic end organs. Fifteen anesthetized, ventilated 5-day-old neonatal piglets were divided into moderate lung injury by treatment with oleic acid or control (sham injection). The degree of lung injury was quantified at baseline and after establishment of ALI by blood gases, ventilation parameters and calculated oxygenation deficit, hemodynamic indices by echocardiography and lung injury score by ultrasound. PaCO2 was maintained constant during ventilation. Cerebral, renal and gut oxygenation was determined by NIRS during stepwise decreases in inspired oxygen from 50% to 21%, correlated with PaO2 and PvO2; changes in fractional oxygen extraction (ΔFOE) were calculated from NIRS and from regional blood gas samples. The proportion of cerebral autoregulation impairment attributable to blood pressure, and to hypoxemia, was calculated from autoregulation nomograms. ALI manifested as hypoxemia with increasing intrapulmonary shunt fraction, decreased lung compliance and increased resistance, and marked increase in lung ultrasound score. Brain, gut and renal NIRS, obtained from probes placed over the anterior skull, central abdomen and flank, respectively, correlated with concurrent SVC (brain) or IVC (gut, renal) PvO2 and SvO2. Cerebral autoregulation was impaired after ALI as a function of blood pressure at all FiO2 steps, but predominantly by hypoxemia at FiO2 < 40%. Cerebral ΔFOE was higher in ALI animals at all FiO2 steps. We conclude that in an animal model of neonatal ALI, cerebrovascular blood flow regulation is primarily dependent on oxygenation. There is not a defined oxygenation threshold below which cerebral autoregulation is impaired in ALI. Cerebral oxygen extraction is enhanced in ALI, reflecting compensation for exhausted cerebral autoregulation due to the degree of hypoxemia and/or hypotension, thereby protecting against tissue hypoxia.

Effect of nitrate supplementation on diurnal emission of enteric methane and nitrous oxide

The objective of this study was to investigate the effect of nitrate supplementation on diurnal enteric methane (CH4) and nitrous oxide (N2O) emissions in dairy cows. Four Danish Holstein dairy cows fitted with ruminal cannulas were used in a 2 × 2 crossover design with 2 periods of 14 d duration. Cows were fed ad libitum with 2 experimental diets based on either urea or nitrate (8.6 g NO3−/kgofDM) supplementation. Samples of ruminal fluid, blood, and rumen headspace gas samples were collected. Gas exchange was measured in respiration chambers during a 96-h period. N2O emission was calculated from the ratio between CH4 and N2O in the rumen head space and the measured CH4 emission. Nitrate supplementation resulted in a lower daily CH4 production (g/d), CH4 yield (g/kg of DMI), a lower CH4 per kg of FPCM, a tendency of lower CH4 intensity (g/kg ECM), and higher daily hydrogen (H2) production, H2 yield, and daily N2O production compared with urea supplementation. The only difference in ruminal volatile fatty acid composition was a higher valerate proportion in cows receiving nitrate compared with urea supplementation. In conclusion, nitrate compared with urea supplementation reduced CH4 production, mainly just after feeding, but also increased N2O production.

Introduction of Safe-PICO syringes to minimize the rate of aborted blood gas samples in MICU

Introduction of Safe-PICO syringes to minimize the rate of aborted blood gas samples in MICU

Can end-tidal CO2 measurement replace arterial partial CO2 in emergency department respiratory distress management?

ObjectiveTo assess the feasibility of using end-tidal carbon dioxide (EtCO2) as a non-invasive substitute for partial pressure of arterial carbon dioxide (PaCO2) in emergency department (ED) triage and follow-up, and to explore the potential of partial pressure of venous carbon dioxide (PvCO2) as an alternative to PaCO2. DesignProspective cross-sectional study. SettingTertiary university hospital. Patients or participants97 patients presenting with acute respiratory distress to the ED. InterventionsEtCO2, arterial blood gases, and venous blood gases measured at admission (0 min), 60 min, and 120 min. Main variables of interestCO2 levels. ResultsAmong 97 patients (mean age: 70.93 ± 9.6 years; 60.8% male), EtCO2 > 45 mmHg at admission showed strong positive correlations with PaCO2 and PvCO2 (r = 0.844, r = 0.803; p < 0.001, respectively). Significant positive correlation was observed between 60-min EtCO2 and PaCO2 (r = 0.729; p < 0.001). Strong correlation between PaCO2 and PvCO2 at 120 min when EtCO2 > 45 mmHg (r = 0.870; p < 0.001). EtCO2 was higher in hospitalized patients compared to discharged ones. ConclusionsEtCO2 appears promising as a substitute for PaCO2 in ED patients with acute respiratory distress within the initial two hours of treatment. Venous blood gas sampling offers a less invasive alternative to arterial sampling, facilitating simultaneous blood tests.

Managing established bronchopulmonary dysplasia without using routine blood gas measurements

ObjectiveRoutine blood gas measurements are common in infants with severe bronchopulmonary dysplasia (sBPD) and are a noxious stimulus. We developed a guideline-driven approach to evaluate the care of infants with sBPD without routine blood gas sampling in the chronic phase of NICU care (after diagnosis at 36 weeks PMA).Study designWe examined blood gas utilization and outcomes in our sBPD inpatient care unit using data collected between 2014 and 2020.Results485 sBPD infants met inclusion criteria, and 303 (62%) never had a blood gas obtained after 36 weeks PMA. In infants who had blood gas measurements, the median number of total blood gases per patient was only 4 (IQR 1–10). We did not identify adverse effects on hospital outcomes in patients without routine blood gas measurements.ConclusionsWe found that patients with established BPD could be managed without routine blood gas analyses after 36 weeks PMA.

Quantitative Computed Tomography and Response to Pronation in COVID-19 ARDS.

The use of prone position (PP) has been widespread during the COVID-19 pandemic. Whereas it has demonstrated benefits, including improved oxygenation and lung aeration, the factors influencing the response in terms of gas exchange to PP remain unclear. In particular, the association between baseline quantitative computed tomography (CT) scan results and gas exchange response to PP in invasively ventilated subjects with COVID-19 ARDS is unknown. The present study aimed to compare baseline quantitative CT results between subjects responding to PP in terms of oxygenation or CO2 clearance and those who did not. This was a single-center, retrospective observational study including critically ill, invasively ventilated subjects with COVID-19-related ARDS admitted to the ICUs of Niguarda Hospital between March 2020-November 2021. Blood gas samples were collected before and after PP. Subjects in whom the PaO2 /FIO2 increase was ≥ 20 mm Hg after PP were defined as oxygen responders. CO2 responders were defined when the ventilatory ratio (VR) decreased during PP. Automated quantitative CT analyses were performed to obtain tissue mass and density of the lungs. One hundred twenty-five subjects were enrolled, of which 116 (93%) were O2 responders and 51 (41%) CO2 responders. No difference in quantitative CT characteristics and oxygen were observed between responders and non-responders (tissue mass 1,532 ± 396 g vs 1,654 ± 304 g, P = .28; density -544 ± 109 HU vs -562 ± 58 HU P = .42). Similar findings were observed when dividing the population according to CO2 response (tissue mass 1,551 ± 412 g vs 1,534 ± 377 g, P = .89; density -545 ± 123 HU vs -546 ± 94 HU, P = .99). Most subjects with COVID-19-related ARDS improved their oxygenation at the first pronation cycle. The study suggests that baseline quantitative CT scan data were not associated with the response to PP in oxygenation or CO2 in mechanically ventilated subjects with COVID-19-related ARDS.

Impaired muscle oxygenation despite normal pulmonary function in type 2 diabetes without complications.

Long-term hyperglycemia in individuals with type 2 diabetes (T2D) can detrimentally impact pulmonary function and muscle oxygenation. As a result, these factors can impede the body's adaptation to physical exertion. We aimed to evaluate the oxygen pathway during maximal exercise among overweight/obese individuals with type 2 diabetes free from complications, in comparison with a group of matched overweight/obese individuals without diabetes, specifically concentrating on the effects on pulmonary function and muscle oxygenation. Fifteen overweight/obese adults with type 2 diabetes [glycated hemoglobin (HbA1c) = 8.3 ± 1.2%] and 15 matched overweight/obese adults without diabetes underwent pre- and post exercise lung function assessment. A maximal incremental exercise test was conducted, monitoring muscle oxygenation using near-infrared spectroscopy and collecting arterial blood gas samples. Both groups exhibited normal lung volumes at rest and after exercise. Spirometric lung function did not significantly differ pre- and post exercise in either group. During maximal exercise, the type 2 diabetes group showed significantly lower augmentation in total hemoglobin and deoxygenated hemoglobin compared with the control group. Despite comparable usual physical activity levels and comparable heart rates at exhaustion, the type 2 diabetes group had a lower peak oxygen consumption than controls. No significant differences were found in arterial blood gas analyses ([Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]) between the groups. Individuals with type 2 diabetes free from complications displayed normal pulmonary function at rest and post exercise. However, impaired skeletal muscle oxygenation during exercise, resulting from reduced limb blood volume and altered muscle deoxygenation, may contribute to the lower V̇o2peak observed in this population.NEW & NOTEWORTHY Individuals with type 2 diabetes free from micro- and macrovascular complications have normal resting pulmonary function, but their V̇o2peak is impaired due to poor skeletal muscle oxygenation during exercise. Tailoring exercise regimes for this population should prioritize interventions aimed at enhancing muscle oxygenation and blood flow improvement.