Comparison of CDHSG model and PCO2 in predicting mortality risk in patients with congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is one of the illnesses with high mortality and morbidity rates. The study aims to compare the Congenital Diaphragmatic Hernia Study Group (CDHSG) model and PCO₂ in determining the mortality risk of CDH in the early postnatal period in neonates. The data of 35 patients who were treated CDH were analyzed retrospectively. The sex, gestational age, birth weight, delivery method, presence of chromosomal anomaly, congenital cardiac and other anomalies, pulmonary hypertension, the 5-min Apgar score, PCO₂ values of blood gas in the first 24 h, mode of ventilation were recorded. According to the CDHSG model, the mortality risk of CDH was divided into three categories: as low, moderate, high risk. Based on the blood gases in the first 24 h after delivery, the CDH mortality risk was considered in two categories as low and high. Based on the CDHSG model, the risk of CDH mortality was low in 11.4%, moderate in 20%, and high in 68.6%. Mortality rates were 0%, 42.8%, and 83.3%, respectively. Based on the PaCO₂ , the risk of CDH mortality was low in 37.1% of patients and high in 62.8%. The mortality rate was 86.3% in high-severity patients and 30.7% in low-risk patients. No significant difference was found between the area under the curve values of the CDHSG model and PCO₂ . Especially in developing countries, in cases where opportunities are limited, the severity of the disease, the need for more aggressive treatment, and the need for higher-level intensive care can be determined with the easily accessible and low-cost blood gas PCO₂ at the bedside.

Mathematical Arterialization of Capillary Blood for Blood Gas Analysis in Critically Ill Patients

BACKGROUND

In clinical practice, capillary blood taken from hyperemized earlobes (CBGE) or fingertips (CBGF) is frequently used as substitute for arterial blood (ABG) for blood gas analysis. While there is a close agreement between ABG and CBGE/CBGF regarding pH and pCO2, pO2 is often underestimated by CBG. Recently, a software tool (v-TAC®; Roche Diagnostics, Risch-Rotkreuz, Switzerland) has been developed to calculate ABG values based on a peripheral venous blood gas analysis supplemented with peripheral oxygen saturation.

OBJECTIVE

Here we investigate whether v-TAC can also be used to calculate ABG values from capillary blood samples.

METHODS

Patients (n = 85) with an indwelling arterial line were included in the study. A reference ABG sample (ABG1) was obtained, followed by CBGE, CBGF, and finally a second ABG (ABG2). Results of CBGE/CBGF before and after mathematical arterialization by v-TAC (aCBGE/aCBGF) were compared to ABG1.

RESULTS

After mathematical arterialization by v-TAC, the mean bias in pO2 between ABG1 and CBGE went down from 5.24 mm Hg (95% limit of agreement [95% LoA]: -14.19 to 24.67) to 0.18 mm Hg (95% LoA: -11.84 to 12.20) and was in a similar range as the mean bias between ABG1 and ABG2 (0.39 mm Hg [95% LoA: -13.46 to 14.24]). Differences in pH and pCO2 between arterial and capillary samples were small before and after mathematical arterialization. Very similar results were obtained when using fingertip instead of earlobe capillary blood.

CONCLUSION

In summary, v-TAC can be used for mathematical arterialization of capillary blood samples for blood gas analysis resulting in increased diagnostic accuracy for pO2.

Treatment-emergent central sleep apnoea after surgery for obstructive sleep apnoea

Central sleep apnoea (CSA) is a lack of drive to breathe during sleep, which can occur in physiologic as well as in pathologic conditions. A particular type of CSA, defined treatment-emergent CSA (TECSA), may occur after the treatment of obstructive sleep apnoea syndrome (OSAS), either with CPAP or surgery. TECSA is transitory and seems to be related to the severity of OSAS. We describe a 51-year-old man affected by severe OSAS who developed severe, transient CSA immediately after upper airways surgery. We believe that CSA was triggered by the sudden variation in nocturnal arterial PCO₂, which decreased from 52.3 mmHg before surgery to 42.0 mmHg after surgery. It is conceivable that, due to long-lasting severe OSAS, our patient lowered his chemosensitivity to PCO₂. Consequently, the resolution of obstructive apnoeas and the restoration of normal nocturnal values of PCO₂ may have reduced the nocturnal PCO₂ to the point of being inadequate to stimulate ventilation.

Intraspecific variation in physiological performance of a benthic elasmobranch challenged by ocean acidification and warming

Elucidating the combined effects of increasing temperature and ocean acidification on performance of fishes is central to our understanding of how species will respond to global climate change. Measuring the metabolic costs associated with intense and short activities, such as those required to escape predators, is key to quantifying changes in performance and estimating the potential effects of environmental stressors on survival. In this study, juvenile little skate Leucoraja erinacea from two neighboring locations (Gulf of Maine, or northern location, and Georges Bank, or southern location) were developmentally acclimatized and reared at current and projected temperatures (15, 18 or 20°C) and acidification conditions (pH 8.1 or 7.7), and their escape performance was tested by employing a chasing protocol. The results from this study suggest countergradient variation in growth between skates from the two locations, while the optimum for escape performance was at a lower temperature in individuals from the northern latitudes, which could be related to adaptation to the local thermal environment. Aerobic performance and scope declined in skates from the northern latitudes under simulated ocean warming and acidification conditions. Overall, the southern skates showed lower sensitivity to these climatic stressors. This study demonstrates that even mobile organisms from neighboring locations can exhibit substantial differences in energetic costs of exercise and that skates from the northern part of the geographic range may be more sensitive to the directional increase in temperature and acidification expected by the end of the century.

Ocean acidification causes structural deformities in juvenile coral skeletons

Rising atmospheric CO2 is causing the oceans to both warm and acidify, which could reduce the calcification rates of corals globally. Successful coral recruitment and high rates of juvenile calcification are critical to the replenishment and ultimate viability of coral reef ecosystems. Although elevated Pco2 (partial pressure of CO2) has been shown to reduce the skeletal weight of coral recruits, the structural changes caused by acidification during initial skeletal deposition are unknown. We show, using high-resolution three-dimensional x-ray microscopy, that ocean acidification (Pco2 ~900 μatm, pH ~7.7) not only causes reduced overall mineral deposition but also a deformed and porous skeletal structure in newly settled coral recruits. In contrast, elevated temperature (+3°C) had little effect on skeletal formation except to partially mitigate the effects of elevated Pco2. The striking structural deformities we observed show that new recruits are at significant risk, being unable to effectively build their skeletons in the Pco2 conditions predicted to occur for open ocean surface waters under a "business-as-usual" emissions scenario [RCP (representative concentration pathway) 8.5] by the year 2100.

Diffusion capacity of the lung for carbon monoxide - A potential marker of impaired gas exchange or of systemic deconditioning in chronic obstructive lung disease?

Gas exchange impairment is primarily caused by ventilation-perfusion mismatch in chronic obstructive pulmonary disease (COPD), where diffusing capacity of the lungs for carbon monoxide (DLCO) remains the clinical measure. This study investigates whether DLCO: (1) can predict respiratory impairment in COPD, that is, changes in oxygen and carbon dioxide (CO2); (2) is associated with combined risk assessment score for COPD (Global Initiative for Chronic Obstructive Lung Disease (GOLD) score); and (3) is associated with blood glucose and body mass index (BMI). Fifty patients were included retrospectively. DLCO; arterial blood gas at inspired oxygen (FiO2) = 0.21; oxygen saturation (SpO2) at FiO2 = 0.21 (SpO2 (21)) and FiO2 = 0.15 (SpO2 (15)) were registered. Difference between arterial and end-tidal CO2 (ΔCO2) was calculated. COPD severity was stratified according to GOLD score. The association between DLCO, SpO2, ΔCO2, GOLD score, blood glucose, and BMI was investigated. Multiple regression showed association between DLCO and GOLD score, BMI, and glucose level (R (2) = 0.6, p < 0.0001). Linear and multiple regression showed an association between DLCO and SpO2 (21) (R (2) = 0.3, p = 0.001 and p = 0.03, respectively) without contribution from SpO2 (15) or ΔCO2. A stronger association between DLCO and GOLD score than between DLCO and SpO2 could indicate that DLCO is more descriptive of systemic deconditioning than gas exchange in COPD patients. However, further larger studies are needed. A weaker association is seen between DLCO and SpO2 (21) without contribution from SpO2 (15) and ΔCO2. This could indicate that DLCO is more descriptive of systemic deconditioning than gas exchange in COPD patients. However, further larger studies are needed.

A new equation to estimate temperature-corrected PaCO2 from PET CO2 during exercise in normoxia and hypoxia

End-tidal PCO2 (PET CO2 ) has been used to estimate arterial pressure CO2 (Pa CO2 ). However, the influence of blood temperature on the Pa CO2 has not been taken into account. Moreover, there is no equation validated to predict Pa CO2 during exercise in severe acute hypoxia. To develop a new equation to predict temperature-corrected Pa CO2 values during exercise in normoxia and severe acute hypoxia, 11 volunteers (21.2 ± 2.1 years) performed incremental exercise to exhaustion in normoxia (Nox, PI O2 : 143 mmHg) and hypoxia (Hyp, PI O2 : 73 mmHg), while arterial blood gases and temperature (ABT) were simultaneously measured together with end-tidal PCO2 (PET CO2 ). The Jones et al. equation tended to underestimate the temperature corrected (tc) Pa CO2 during exercise in hypoxia, with greater deviation the lower the Pa CO2 tc (r = 0.39, P < 0.05). The new equation has been developed using a random-effects regression analysis model, which allows predicting Pa CO2 tc both in normoxia and hypoxia: Pa CO2 tc = 8.607 + 0.716 × PET CO2 [R(2)  = 0.91; intercept SE = 1.022 (P < 0.001) and slope SE = 0.027 (P < 0.001)]. This equation may prove useful in noninvasive studies of brain hemodynamics, where an accurate estimation of Pa CO2 is needed to calculate the end-tidal-to-arterial PCO2 difference, which can be used as an index of pulmonary gas exchange efficiency.

Hypercapnia and low pH induce neuroepithelial cell proliferation and emersion behaviour in the amphibious fish Kryptolebias marmoratus

Aquatic hypercapnia may have helped to drive ancestral vertebrate invasion of land. We tested the hypothesis that amphibious fishes sense and respond to elevated aquatic PCO2 by behavioural avoidance mechanisms, and by morphological changes at the chemoreceptor level. Mangrove rivulus (Kryptolebias marmoratus) were exposed to 1 week of normocapnic control water (pH 8), air, hypercapnia (5% CO2, pH 6.8) or isocapnic acidosis (pH 6.8). We found that the density of CO2/H(+) chemoreceptive neuroepithelial cells (NECs) was increased in hypercapnia or isocapnic acidosis-exposed fish. Projection area (a measure of cell size) was unchanged. Acute exposure to progressive hypercapnia induced the fish to emerse (leave water) at water pH values ∼6.1, whereas addition of HCl to water caused a more variable response with a lower pH threshold (∼pH 5.5). These results support our hypothesis and suggest that aquatic hypercapnia provides an adequate stimulus for extant amphibious fishes to temporarily transition from aquatic to terrestrial habitats.

Energy metabolism and cellular homeostasis trade-offs provide the basis for a new type of sensitivity to ocean acidification in a marine polychaete at a high-CO2 vent: adenylate and phosphagen energy pools versus carbonic anhydrase

Species distributions and ecology can often be explained by their physiological sensitivity to environmental conditions. Whilst we have a relatively good understanding of how these are shaped by temperature, for other emerging drivers, such as PCO2  we know relatively little. The marine polychaete Sabella spallanzanii increases its metabolic rate when exposed to high PCO2  conditions and remains absent from the CO2 vent of Ischia. To understand new possible pathways of sensitivity to CO2 in marine ectotherms, we examined the metabolic plasticity of S. spallanzanii exposed in situ to elevated PCO2  by measuring fundamental metabolite and carbonic anhydrase concentrations. We show that whilst this species can survive elevated PCO2  conditions in the short term, and exhibits an increase in energy metabolism, this is accompanied by a significant decrease in carbonic anhydrase concentration. These homeostatic changes are unlikely to be sustainable in the longer term, indicating S. spallanzanii may struggle with future high PCO2  conditions.

Evaluation of a transcutaneous blood gas monitoring system in critically ill dogs

OBJECTIVES

To describe the use of a transcutaneous blood gas monitoring system in critically ill dogs, determine if transcutaneous and arterial blood gas values have good agreement, and verify if clinical or laboratory variables are correlated with differences between transcutaneous and arterial blood gas measurements.

DESIGN

Prospective observational study.

SETTING

University teaching hospital ICU.

ANIMALS

Twenty-three client-owned dogs.

INTERVENTIONS

In critically ill dogs undergoing arterial blood gas monitoring, a transcutaneous blood gas monitor was used to measure transcutaneous partial pressure of carbon dioxide (PtcCO2 ) and transcutaneous partial pressure of oxygen (PtcO2 ) values 30 minutes after sensor placement, which were compared to PaCO2 and PaO2 values measured simultaneously. Clinical and laboratory variables were concurrently recorded to determine if they were correlated with the difference between transcutaneous and arterial blood gas measurements.

MEASUREMENTS AND MAIN RESULTS

Bland-Altman analysis revealed a mean bias of 4.6 ± 26.3 mm Hg (limits of agreement [LOA]: -46.9/+56.1 mm Hg) between PtcO2 and PaO2 and a mean bias of 9.3 ± 8.5 mm Hg (LOA: -7.5/+26.0 mm Hg) between PtcCO2 and PaCO2 . The difference between PtcCO2 -PaCO2 was strongly negatively correlated with HCO3 (-) (r(2) = 0.52, P < 0.001) and PaCO2 (r(2) = 0.58, P < 0.001) and weakly positively correlated with diastolic blood pressure (r(2) = 0.21, P = 0.044), whereas the difference between PtcCO2 -PaCO2 was moderately negatively correlated with diastolic blood pressure (r(2) = 0.33, P = 0.008).

CONCLUSIONS

Agreement between transcutaneous and arterial PO2 and PCO2 measurements in these critically ill dogs was inferior to that reported in similar adult and pediatric human studies. The transcutaneous monitor consistently over-estimated PaO2 and PaCO2 and should not be used to replace arterial blood gas measurements in critically ill dogs requiring blood gas interpretation.