Arterial Blood Gas Measurements Research Articles

Responses to exercise in systemicsclerosis-associated interstitial lung disease.

Pulmonary complications in systemic sclerosis (SSc) significantly increase morbidity and mortality. Our aim was to determine the factors limiting exercise capacity in SSc patients with and without interstitial lung disease (ILD), and to identify and quantify abnormalities during exercise that might assist in clinical assessment of this complication. Fifteen patients with SSc and ILD(SSc-ILD) were compared with 10 patients with SSc without ILD and 9age- and sex-matched normal volunteers. Subjects performed symptom-limited incremental treadmill exercise with online measurement of respiratory gas exchange, arterial blood gas sampling and measurement of neurohormones in venous blood. Patients with SSc-ILD had lower exercise capacity than SSc patients without ILD or normal subjects (peak oxygen consumption (PV̇O2 ) (17.1 [4.2] vs. 22.0 [4.7] and 23.0 [5.4] ml kg-1 min-1 , respectively, mean [SD], p < 0.01 ANOVA), but PV̇O2 did not correlate with static pulmonary function measurements. Ventilatory equivalent for CO2 (V̇E/V̇CO2 ; nadir) was higher in SSc-ILD patients than the other two groups (36.6 [8.0] vs. 29.9 [4.4] and 30.0 [2.5], p < 0.005) as were peak exercise dead-space tidal volume ratio (0.44 [0.06] vs. 0.26 [0.09] and 0.26 [0.05], p < 0.001) and peak exercise alveolar-arterial difference (28.9 [16.9] vs. 18.8 [14.0] and 11.5 [6.9] mmHg, p < 0.05). Atrial natriuretic peptide was elevated in both SSc patient groups. SSc-ILD results in lower exercise capacity than SSc without ILD, and abnormalities of gas exchange are seen. The possible use of cardiopulmonary exercise testing to identify disease and quantify impairment in SSc-ILD merits further study.

Donation after circulatory death heart transplantation using normothermic regional perfusion:The NYU Protocol.

This study aimed to evaluate the impact of cardiopulmonary bypass for thoraco-abdominal normothermic regional perfusion on the metabolic milieu of donation after cardiac death organ donors before transplantation. Local donation after cardiac death donor offers are assessed for suitability and willingness to participate. Withdrawal of life-sustaining therapy is performed in the operating room. After declaration of circulatory death and a 5-minute observation period, the cardiac team performs a median sternotomy, ligation of the aortic arch vessels, and initiation of thoraco-abdominal normothermic regional perfusion via central cardiopulmonary bypass at 37 °C. Three sodium chloride zero balance ultrafiltration bags containing 50 mEq sodium bicarbonate and 0.5g calcium carbonate are infused. Arterial blood gas measurements are obtained every 15 minutes after every zero balance ultrafiltration bag is infused, and blood is transfused as needed to maintain hemoglobin greater than 8 mg/dL. Cardiopulmonary bypass is weaned with concurrent hemodynamic and transesophageal echocardiogram evaluation of the donor heart. The remainder of the procurement, including the abdominal organs, proceeds in a similar controlled fashion as is performed for a standard donation after brain death donor. Between January 2020 and May 2022, 18 donation after cardiac death transplants using the thoraco-abdominal normothermic regional perfusion protocol were performed at our institution. The median donor age was 42.5 years (range, 20-51 years), and 88.9% (16/18) were male. The mean total donor cardiopulmonary bypass time was 88.8 ± 51.8 minutes. At the beginning of cardiopulmonary bypass, the average donor lactate was 9.4 ± 1.5 mmol/L compared with an average final lactate of 5.3 ± 2.7 mmol/L (P<.0001). The average beginning potassium was 6.5 ± 1.8 mmol/L compared with an average end potassium of 4.2 ± 0.4 mmol/L (P<.0001) . The average beginning hemoglobin was 6.8 ± 0.7 g/dL, and the average end hemoglobin was 8.2 ± 1.3 g/dL (P<.001) . On average, donation after cardiac death donors received transfusions of 2.3 ± 1.5 units of packed red blood cells. Of the 18 donors who underwent normothermic regional perfusion, all hearts were deemed suitable for recovery and successfully transplanted, a yield of 100%. Other organs successfully recovered and transplanted include kidneys (80.6% yield), livers (66.7% yield), and bilateral lungs (27.8% yield). The use of cardiopulmonary bypass for thoraco-abdominal normothermic regional perfusion is a burgeoning option for improving the quality of organs from donation after cardiac death donors. Meticulous intraoperative management of donation after cardiac death donors with a specific focus on improving their metabolic milieu may lead to improved graft function in transplant recipients.

Agreement between arterial and venous blood gas measurements in patients with sepsis and septic shock

&lt;p&gt;Background and Objective: Acid&amp;ndash;base status is mandatory for clinical assessment of patients with septic shock and severe sepsis. Generally, venous blood gas sample collection is easier, however, the data regarding this approach are lesser defined in our population as a substitute for arterial blood gas (ABG) sample. The present study aimed to determine and compare the pH, pCO2, and bicarbonate levels in VBG and ABG samples in patients with sepsis and septic shock.&lt;/p&gt;&#x0D; &lt;p&gt;Method: A cross sectional comparative study was conducted on 350 patients with sepsis and/or septic shock admitted to the medical emergency of Jinnah Hospital, Lahore, Pakistan. Both ABG and VBG samples were collected and pH, pCO2, and bicarbonate levels were determined by standard methods. Data were analyzed using Pearson correlation and the Bland&amp;ndash;Altman method for bias.&lt;/p&gt;&#x0D; &lt;p&gt;Results: An interclass correlation (r = 0.995, r = 0.929 and r = 0.946) was found for pH, pCO2, and bicarbonate between ABG and VBG samples, respectively. The Bland&amp;ndash;Altman method showed a high degree of agreement for two sets of measurements; pH (bias &amp;plusmn; SD, 0.089 &amp;plusmn; 0.00472) and pCO2 (bias &amp;plusmn; SD, -1.1096 &amp;plusmn; 1.0089) with a clinically acceptable difference whereas the difference in bicarbonate measurement was found slightly higher (bias &amp;plusmn; SD, 1.124 &amp;plusmn; 0.674) revealing, however, a good degree of agreement with clinically acceptable bias.&lt;/p&gt;&#x0D; &lt;p&gt;Conclusion: Use of a venous blood sample in patients with sepsis or septic shock is a clinically acceptable substituent for ABG measurement in evaluating acid-base status of these patients for further management.&lt;/p&gt;

Assessment of Statin Treatment for Pulmonary Alveolar Proteinosis without Hypercholesterolemia: A 12-Month Prospective, Longitudinal, and Observational Study

Pulmonary alveolar proteinosis (PAP) is a rare disorder which is characterized by the accumulation of excessive surfactant lipids and proteins in alveolar macrophages and alveoli. Oral statin therapy has been reported to be a novel therapy for PAP with hypercholesterolemia. We aimed to evaluate the safety and efficacy of oral statin therapy for PAP without hypercholesterolemia. In a prospective real-world observational study, 47 PAP patients without hypercholesterolemia were screened. Oral statin was initiated as therapy for these PAP patients with 12 months of follow-up. Forty PAP patients completed the study. 26 (65%) of 40 PAP patients responded to statin therapy according to the study criteria. Partial pressure of arterial oxygen (PaO2) and percentage of diffusion capacity predicted (DLCO%) significantly increased while disease severity score (DSS) and radiographic abnormalities decreased after 12 months of statin therapy (all p < 0.05). The factors associated with response were higher levels of granulocyte-macrophage colony-stimulating factor (GM-CSF) antibody and baseline total cholesterol/high-density lipoprotein cholesterol (TC/HDL) (p = 0.015 and p = 0.035, respectively). The area under the receiver operating characteristic curve (AUROC) of dose of atorvastatin for predicting the response to statin therapy for PAP was 0.859 (95% CI: 0.738-0.979, p < 0.001). The cutoff dose of atorvastatin was 67.5 mg daily with their corresponding specificity (64.3%) and sensitivity (96.2%). No severe side effects were observed during the study. In PAP patients without hypercholesterolemia, statin therapy resulted in improvements in arterial blood gas (ABG) measurement, pulmonary function, and radiographic assessment.

Small, short-term, point-of-care creatinine changes as predictors of acute kidney injury in critically ill patients.

To assess short-term creatinine changes as predictors of acute kidney injury (AKI) when used alone and in combination with AKI risk factors. In this prospective cohort study, we identified all creatinine measurements from frequent point-of-care arterial blood gas measurements from ICU admission until AKI. We evaluated the predictive value of small changes between these creatinine measurements for AKI development, alone and with AKI risk factors. Of 377 patients with 3235 creatinine measurements, generating 15,075 creatinine change episodes, 215 (57%) patients developed AKI, and 68 (18%) developed stage 2 or 3 AKI. In isolation, a creatinine increase over 4.1-7.3 h had a 0.65 area under the curve for predicting stage 2 or 3 AKI within 3-37.7 h. Combining creatinine increases of ≥1 μmol/L/h (≥0.0113 mg/dL/h) over 4-5.8 h with three AKI risk factors (cardiac surgery, use of vasopressors, chronic liver disease) had 83% sensitivity, 79% specificity and 0.87 area under the curve for stage 2 or 3 AKI occurring 8.7-25.6 h later. In combination with key risk factors, frequent point-of-care creatinine assessment on arterial blood gases to detect small, short-term creatinine changes provides a robust, novel, low-cost, and rapid method for predicting AKI in critically ill patients.

Akut solunum yetmezliğinde optik sinir kılıf çapının prognostik önemi

Purpose: The primary aim of this study was to determine the role of the optic nerve sheath diameter (ONSD) measured using ultrasonography in the differentiation of hypoxemic respiratory failure and hypercarbic respiratory failure. The secondary aim was to determine the value of ONSD in predicting the clinical outcome in hypercarbic patients.&#x0D; Materials and Methods: Non-traumatic adult patients presenting with dyspnea were included in this study. Arterial blood gas and concurrent ONSD measurements were obtained from all patients included in the study during presentation and at the second hour of treatment. The patients were divided into two groups - hypoxic and hypercarbic respiratory failure. An equivalent number of healthy volunteers were enrolled as the control group. &#x0D; Result: Mean ONSD values were 3.8±0.2 mm in the 24 patients with type 1 respiratory failure, 5.2 ± 0.5 mm in the 25 patients with type 2 respiratory failure, and 3.9±0.3 mm in the healthy controls. The ONSD of the hypercarbic patients was statistically significantly greater than that of the hypoxic patients and healthy volunteers. The ONSD of the hypercarbic patients was 5.2±0.5mm at baseline and 4.4±0.6 mm after treatment, the difference being statistically significant. However, the difference in ONSD was not statistically significant in predicting hospitalization and mortality. &#x0D; Conclusion: Sonographically measured ONSD may be an effective parameter in the differential diagnosis of type 1 and 2 respiratory failure. ONSD values changed significantly with treatment in patients with type 2 respiratory failure.

211.7: Is Pulse Oximetry a Good Screening Test for Hepatopulmonary Syndrome in Liver Transplant Candidates?

Background: Pulse oximetry with oxygen saturation (SpO2) ≤96% is recommended as a screening test to identify patients (pts) with severe hepatopulmonary syndrome (HPS) to be eligible for MELD exceptions. However, diagnosis of milder forms requires contrast-enhanced echocardiography (CE-TTE) and arterial blood gas (ABG). Goals: 1) To investigate the prevalence of intrapulmonary vascular dilatations (IPVD) and HPS in pts with cirrhosis evaluated for liver transplantation (OLT) and 2) To compare the results of SpO2 with ABG measurements. Methods: The study included 972 consecutive pts (2013-2021) who completed pre-OLT evaluation including CE-TTE, SpO2 and ABG. IPVD was defined as the appearance of microbubbles in the left heart within 3-5 cardiac cycles and HPS by an alveolar arterial O2 gradient ≥ 15 mm Hg or ≥ 20 if age > 64 and absence of pulmonary chronic diseases. HPS was considered as mild, moderate or severe according to PaO2 (>80, 60-80 and <60 respectively). Results: The prevalence of IPVD was 15.4% (150/972) and of HPS 7.8% (76/972). Age of pts with HPS was 47±3 years (57% males) and MELD-Na 17± 1.HCV, alcoholism and autoimmune hepatitis were the most frequent etiologies of cirrhosis (22% each). Among pts with HPS 59 (78%) were mild (PaO2 108 ±22), 13 (17%) moderate (73 ±4) and 4 severe (55.5±3). SpO2 was ≤96% in 26% (20/76), 15% in mild (9/59), 54% in moderate (8/13) and 100% in severe (4/4) HPS. Unexpectedly, of 20 pts with Spo2 ≤96% only 4 had PaO2 <60 mmHg. Conclusions: Universal testing with CE-TTE followed by ABG in patients with cirrhosis evaluated for OLT resulted in a lower prevalence than reported of HPS, most likely due to the preponderance of mild clinical forms with normal SpO2. Using the recommended cut-off value of Spo2 ≤96% we found a poor correlation between pulse oximetry and ABG measurement.

AARC Clinical Practice Guidelines: Capillary Blood Gas Sampling for Neonatal and Pediatric Patients.

In the absence of an indwelling arterial catheter, capillary blood gas sampling may be used to evaluate the acid/base and ventilation status of neonatal and pediatric patients with cardiorespiratory conditions. These guidelines were developed from a comprehensive review of the literature to provide guidance for the collection, handling, and interpretation of blood obtained from an arterialized capillary sample. Capillary and venous blood gas measurements are a useful alternative to arterial blood gas measurements for neonatal and pediatric patients who do not require close monitoring of [Formula: see text] In the presence of alterations in body temperature, blood pressure, or peripheral perfusion, agreement between a capillary blood gas with an arterial sample is recommended to determine whether changes in these physiologic conditions reduce reliability. Perfusion to the sample site should be assessed and preference given to blood sampling from a well perfused site, and blood should be analyzed within 15 min of sampling to minimize the propensity for pre-analytical errors. Clinicians should consider re-collecting a blood sample, obtained from an artery, vein, or capillary, when the blood gas or analyte result interpretation does not align with the patient's clinical presentation. A pneumatic tube system can be reliably used to transport blood gas samples collected in a syringe and capillary tube to a clinical laboratory for analysis. To reduce the cumulative pain effect and risk of complications, the capillary puncture procedure should be minimized when possible. Non-pharmacologic interventions should be used to reduce pain associated with capillary blood gas sampling. Automatic lancets are preferred to puncture the skin for capillary blood gas collection.

The Effect of Mild Hypocapnia on Postoperative Ecchymosis in Rhinoplasty.

Ecchymosis and edema are the most common complications in patients following rhinoplasty in the early postoperative period. Vasoconstriction created by hypocarbia may have a positive effect on postoperative ecchymosis. The aim of this study was to evaluate the effect of mild hypocapnia induced in rhinoplasty on the severity of periorbital ecchymosis. The study was carried out retrospectively in the digital photographs (control group and study group) of 31 participants who underwent open technical rhinoplasty between January and March 2019. During the operation, partial carbon dioxide pressure in the study group was kept in the range of 32 to 38 mmHg and in the control group between 42 and 46 mmHg and this was confirmed by arterial blood gas measurements taken during the operation. Measuring the brightness and shadows of digital photos Digital color meter was used in MacOS X as a computer software. The mean ratio of periorbital ecchymosis to forehead brightness was 0.84 ± 0.05 in the study group and 0.81 ± 0.03 in the control group. There was no significant difference between the study and control groups (P > .05). This study investigates the potential role of hypocapnia on postoperative ecchymosis during rhinoplasty. The severity of ecchymosis was less in the patients with induced mild hypocapnia regarding both subjective and objective evaluations, but this difference didn't reach statistical significance compared to the normocapnic control group.

Polycythemia in dogs with chronic hypoxic pulmonary disease.

BackgroundProlonged tissue hypoxia caused by chronic pulmonary disease is commonly regarded as an important mechanism in the development of secondary polycythemia, but little clinical data are available to support this hypothesis.ObjectiveTo study the prevalence and severity of erythrocytosis accompanying chronic hypoxic pulmonary disease in dogs.AnimalsForty‐seven dogs with hypoxic chronic pulmonary disease, 27 dogs with nonhypoxic chronic pulmonary disease, and 60 healthy controls.MethodsDogs with chronic pulmonary disease and chronic hypoxemia (partial pressure of arterial oxygen [PaO2] < 80 mm Hg on at least 2 arterial blood gas measurements a minimum of 1 month apart) were identified retrospectively from patient records. Association between arterial oxygen and red blood cell parameters was analyzed using Pearson's correlation coefficients and multivariable linear regression analysis.ResultsRed blood cell parameters measured at the end of the hypoxemia period were within the laboratory reference range in most dogs. In chronically hypoxemic dogs, hematocrit (Hct) was increased in 4/47 (8.5%; 95% confidence interval [CI], 0‐17) dogs, erythrocyte count (Erytr) was increased in 12/47 (26%; 95%CI, 13‐38) dogs and hemoglobin concentration (Hb) was increased in 3/47 (6.4%; 95%CI, 0‐14) dogs. No marked polycythemia (Hct ≥65%) was noted in any of the dogs. Red blood cell parameters were not associated with the severity of hypoxemia (correlation to PaO2: Erytr, r = −.14; Hb, r = −.21; Hct, r = −.14; P > .05 for all).Conclusions and Clinical ImportancePolycythemia is uncommon, and usually mild if present, in dogs with chronic hypoxia caused by pulmonary disease.

Capnography and Pulse Oximetry Improve Fast Track Extubation in Patients Undergoing Coronary Artery Bypass Graft Surgery: A Randomized Clinical Trial.

BackgroundUse of capnography as a non-invasive method during the weaning process for fast track extubation (FTE) is controversial. We conducted the present study to determine whether pulse oximetry and capnography could be utilized as alternatives to arterial blood gas (ABG) measurements in patients under mechanical ventilation (MV) following coronary artery bypass graft (CABG) surgery.MethodsIn this randomized clinical trial, 70 patients, who were candidates for CABG surgery, were randomly assigned into two equal groups (n = 35), intervention and control group. In the intervention group, the ventilator management and weaning from MV was done using Etco2 from capnography and SpO2 from pulse oximetry. Meanwhile, in the control group, weaning was done based on ABG analysis. The length of intensive care unit (ICU) stay, time to extubation, number of manual ventilators setting changes, and alarms were compared between the groups.ResultsThe end-tidal carbon dioxide (ETCO2) levels in the intervention group were completely similar to the partial pressure of carbon dioxide (PaCo2) in the control group (39.5 ± 3.1 vs. 39.4 ± 4.32, p > 0.05). The mean extubation times were significantly shorter in the intervention group compared to those in the control patients (212.2 ± 80.6 vs. 342.7 ± 110.7, p < 0.001). Moreover, the number of changes in the manual ventilator setting and the number of alarms were significantly lower in the intervention group. However, the differences in the length of stay in ICU between the two groups were not significant (p = 0.219).ConclusionOur results suggests that capnography can be used as an alternative to ABG. Furthermore, it is a safe and valuable monitor that could be a good alternative for ABG in this population. Further studies with larger sample sizes and on different disease states and populations are required to assess the accuracy of our findings.Clinical Trial RegistrationCurrent Controlled Trials, IRCT, IRCT201701016778N6, Registered 3 March 2017, https://www.irct.ir/trial/7192.

Peripartum Severe COVID-19 Pneumonia: Fetal and Neonatal Implications.

Peripartum Severe COVID-19 Pneumonia: Fetal and Neonatal Implications.

This Month in Anesthesiology

This Month in Anesthesiology

Invasive And Non-invasive Assessment Of Arterial Blood Oxygen Saturation In Patients With Continuous Flow LVADs: Is There A Correlation?

<h3>Background</h3> Patients with continuous flow left ventricular assist devices (CF-LVAD) typically have a narrow pulse pressure. This may pose a challenge for transcutaneous automated pulse oximeter devices to accurately measure arterial blood saturation. This study aimed to assess their accuracy in a CF-LVAD population by comparing pulse oximetry readings to invasive arterial blood gas (ABG) measurements. <h3>Methods</h3> A total of eighteen patients with a CF-LVAD were identified using chart review at the University of Minnesota and Minneapolis Heart Institute. All, except one patient were implanted with a HeartMate III device (Abbott Laboratories, Minneapolis, MN). Non-invasively assessed oxygen saturation was compared to simultaneously obtained arterial blood oxygen saturation. Two patients were receiving mechanical ventilation, one received BiPAP support, and 15 patients were either breathing room air or receiving supplemental oxygen by nasal cannula. <h3>Results</h3> A non-invasive pulse oximeter read was obtained on every patient. There was a moderate correlation between the invasively and non-invasively obtained oxygen saturation values as shown in Figure 1 (R²=0.624). Waveform quality, as assessed by the treating physician, qualified as good or acceptable in 16 cases and as poor for 2 patients. Data points for these 2 patients are marked in red in Figure 1. <h3>Conclusion</h3> Despite a narrow pulse pressure in patients with CF-LVAD, non-invasive pulse oximetry provided a reliable assessment of arterial blood saturation when compared to the gold standard ABG measurement. This finding presents an opportunity to conduct future studies in this patient population in which continuous monitoring of oxygen saturation may be necessary, such as evaluation for obstructive sleep apnea.

The Corevent 2020: An Open-source, Rapid Design-build-Test Emergency Ventilator Developed for Covid-19

In the first quarter of 2020, SARs-CoV-2 (COVID-19) infections began to grow at an alarming rate despite drastic measures to reduce infection rates. Severe COVID-19 cases required mechanical ventilation, resulting in ventilator shortages worldwide. To address the ventilator shortages, the authors developed the CoreVent 2020, an emergency-use ventilator for adult patients that was designed, built, and tested in ten days. The CoreVent 2020 is a pressure-cycled, time-limited ventilator with a breath-assist mode that operates on standard pressurized oxygen and medical air. It provides adjustable peak inspiratory pressure (PIP) and positive end-expiratory pressure (PEEP). A medical-grade commercially available breathing circuit is used to minimize non-medical component requirements. The CoreVent 2020 was fabricated in-house at Stony Brook University Hospital and tested on three mechanical lung simulators in which the operating modes and alarm features were demonstrated. Animal studies were also performed in both normal breathing mode and breath-assisted modes. Arterial blood gas measurements confirmed that the ventilator provided satisfactory ventilation for the test subjects. The COVID-19 pandemic presented unique constraints on the design and innovation process not normally encountered in typical practice. Design decisions such as component choice, delivery time, and ease of high-volume, rapid manufacturing influenced all aspects of the design process. This aspect of the design/innovation process is also discussed, as well as an introductory discussion on how training and simulations can be developed so that innovation can occur efficiently in future crises situations.

Efficacy and safety testing of a COVID-19 era emergency ventilator in a healthy rabbit lung model

BackgroundThe COVID-19 pandemic revealed a substantial and unmet need for low-cost, easily accessible mechanical ventilation strategies for use in medical resource-challenged areas. Internationally, several groups developed non-conventional COVID-19 era emergency ventilator strategies as a stopgap measure when conventional ventilators were unavailable. Here, we compared our FALCON emergency ventilator in a rabbit model and compared its safety and functionality to conventional mechanical ventilation.MethodsNew Zealand white rabbits (n = 5) received mechanical ventilation from both the FALCON and a conventional mechanical ventilator (Engström Carestation™) for 1 h each. Airflow and pressure, blood O2 saturation, end tidal CO2, and arterial blood gas measurements were measured. Additionally, gross and histological lung samples were compared to spontaneously breathing rabbits (n = 3) to assess signs of ventilator induced lung injury.ResultsAll rabbits were successfully ventilated with the FALCON. At identical ventilator settings, tidal volumes, pressures, and respiratory rates were similar between both ventilators, but the inspiratory to expiratory ratio was lower using the FALCON. End tidal CO2 was significantly higher on the FALCON, and arterial blood gas measurements demonstrated lower arterial partial pressure of O2 at 30 min and higher arterial partial pressure of CO2 at 30 and 60 min using the FALCON. However, when ventilated at higher respiratory rates, we observed a stepwise decrease in end tidal CO2. Poincaré plot analysis demonstrated small but significant increases in short-term and long-term variation of peak inspiratory pressure generation from the FALCON. Wet to dry lung weight and lung injury scoring between the mechanically ventilated and spontaneously breathing rabbits were similar.ConclusionsAlthough conventional ventilators are always preferable outside of emergency use, the FALCON ventilator safely and effectively ventilated healthy rabbits without lung injury. Emergency ventilation using accessible and inexpensive strategies like the FALCON may be useful for communities with low access to medical resources and as a backup form of emergency ventilation.

Outcomes and Predictors of Severe Hyperoxemia in Patients Receiving Mechanical Ventilation: A Single-Center Cohort Study.

Rationale: Supplemental oxygen is among the most commonly administered therapies in intensive care units (ICUs). High supplemental oxygen exposure has been associated with harm in observational human studies and animal models, yet no consensus exists regarding which dose and duration of high oxygen constitutes harmful hyperoxemia, and little is known regarding the clinical factors that predict potentially injurious exposure. Objectives: To determine the dose and duration of the arterial partial pressure of oxygen (PaO2) associated with mortality among mechanically ventilated patients and to identify the clinical factors that predict this exposure. Methods: We performed a retrospective cohort study of patients who received invasive mechanical ventilation at a single academic institution in 2017 and 2018. We used a generalized additive model to visualize the relationship between the measured PaO2 via arterial blood gas measurements and 30-day mortality. We used multivariable logistic regression to identify patient- and hospital-level factors that predict exposure to harmful hyperoxemia. Results: We analyzed 2,133 patients with 33,310 arterial blood gas measurements obtained during mechanical ventilation. We identified a U-shaped relationship between PaO2 and mortality, in which PaO2 was positively correlated with mortality above a threshold of 200 mm Hg. A total of 1,184 patients (55.5%) had at least one PaO2 measurement above this threshold. If patients spent an entire day exposed to PaO2 > 200 mm Hg, they had 2.19 (95% confidence interval [CI], 1.33-3.60; P = 0.002) greater odds of 30-day mortality in an adjusted analysis. Any exposure to severe hyperoxemia (PaO2 > 200 mm Hg) was associated with mortality (odds ratio, 1.29; 95% CI, 1.04-1.59; P = 0.021). The strongest clinical predictor of severe hyperoxemia exposure was the identity of the ICU in which mechanical ventilation was delivered. Conclusions: Exposure to high arterial oxygen concentrations is common among mechanically ventilated patients, and the dose and duration of PaO2 ⩾ 200 mm Hg is associated with mortality. Severe hyperoxemia is highly variable across ICUs and is far more common in clinical practice than in recent randomized trials of oxygen-targeting strategies. Efforts to minimize this common and injurious exposure are needed.

Accuracy of a Novel Transcutaneous PCO2 and PO2 Sensor with Optical PO2 Measurement in Neonatal Intensive Care: A Single-Centre Prospective Clinical Trial

Background and Objectives: Transcutaneous PCO2 and PO2 measurement systems offer non-invasive blood gas trend monitoring. The aim of this prospective study was to assess bias and precision of a transcutaneous PCO2 and PO2 measurement system incorporating a novel pO2 sensor (Sentec OxiVenT™) in neonates ≥34 weeks of gestational age (GA) admitted to intensive care. Methods: Transcutaneous PCO2 and PO2 were compared to arterial and capillary blood gas measurements. Bias and precision were calculated by fitting linear mixed models to account for repeated measurements, and influence of clinical covariates on bias and precision was assessed. Results: We obtained 611 paired transcutaneous and blood gas measurements in 110 patients (median GA 38.3 [interquartile range 36.1–39.7] weeks; age 9 [4–15] days; weight 3,000 [2,500–3,500] g). Transcutaneous PCO2 showed significant bias to arterial PCO2 (+0.61; 95% confidence interval 0.46, 0.76 kPa), but not to capillary PCO2 (−0.23; −0.46, 0.002 kPa). Bias of transcutaneous PO2 was significant to arterial PO2 (−2.50; −2.94, −2.06 kPa), while no significant bias compared to capillary PO2 was observed (+0.17; −0.30, 0.64 kPa). Precision intervals were ±1.8/2.0 kPa for arterial versus capillary PCO2 and ±4.9/3.3 kPa for arterial versus capillary PO2 comparisons, respectively. Further, sensor operating temperature (43°C vs. 42°C), soft tissue oedema, vasoactive drugs, weight, and GA significantly altered bias (p < 0.05). Conclusions: The tested transcutaneous blood gas measurement system showed no significant bias compared to capillary PCO2 and PO2, acceptable bias to arterial PCO2, and limited agreement with arterial PO2. Precision intervals were wide for all comparisons.

Pseudohypoxemia From Leukocyte Larceny in a Patient With Chronic Myelogenous Leukemia

Arterial blood gas (ABG) analysis is a generally reliable and frequently employed test for evaluating blood oxygen content. False readings of low oxygen content are rare but can be expected in specific clinical scenarios such as leukemia patients with marked leukocytosis who can develop “leukocyte larceny,” a phenomenon of excess oxygen consumption by leukocytes. Awareness of this phenomenon may lead to early recognition and avoidance of unnecessary diagnostic and therapeutic interventions. This case report presents a patient with marked leukocytosis from chronic myelogenous leukemia whose extubation was briefly delayed due to pseudohypoxemia on ABG measurements.

Unmasking Hypoxia in Cirrhosis Patients: Six-Minute Walk Test as a Screening Tool for Hepatopulmonary Syndrome.

Background:Hepatopulmonary syndrome (HPS) is one of the complications of advanced cirrhosis which has a serious impact on prognosis of patient. Finding arterial deoxygenation early and initiating higher-level treatment is one of the most critical strategies in the therapy of HPS. In this study, we aimed to assess the utility of six-minute walk test (6MWT) in the diagnosis of HPS.Materials and Methods:We have enrolled 100 consecutive cirrhosis patients referred to the Liver Clinic of a tertiary care centre of India for >1 year. The Child-Pugh score and the MELD score were used to determine the severity of cirrhosis. All the patients underwent transthoracic contrast echocardiography, arterial blood gas measurements on room air, 6MWT, and chest imaging.Results:A total of 100 patients were included in the study after fulfilling the inclusion criteria. HPS was present in 21 out of 100 patients (21%). Median (twenty fifth to seventy fifth percentile) MELD score in patients with HPS was 29 (26–33), which was significantly higher as compared to patients without HPS 22 (14.5–26); P <.0001. The 6MWT was positive in 20 (95.23%) HPS patients, while only 1 patient (4.77%) of HPS had negative 6MWT. If 6MWT is positive, then there was 76.92% probability of HPS and if 6MWT is negative, then 98.65% chances of no HPS.Conclusion:The 6MWT is a simple and effective screening test for HPS, it helps in identifying the patients early who have a potential to deteriorate. This simple intervention would help in prioritizing patients for liver transplantation as liver transplant is the only effective treatment for HPS.