CO2 Tension Research Articles

Dynamics of indicators of the acid-base state of the blood in different seasons

At high latitudes, seasonal changes in the environment have a significant impact on the dynamics of physiological processes. The purpose of the study: to identify the content of carbon dioxide in the atmospheric air and the features of the acid-base state of the blood in different seasons of the year. Methods and scope of research. The surveyed contingent consisted of: group 1 - 58 healthy male students of a medical institute, aged 18-20 years, group 2 - young men, residents of rural areas, aged 17-19 years. The study of the parameters of the acid-base state of the blood was carried out according to standard methods in different seasons of the year. Results. It was found that the values of carbon dioxide tension in the capillary blood of the subjects are lower in winter, and the level of CO2 in the atmospheric air is lower in summer. At the same time, an inverse correlation was found between the values of CO2 voltage in capillary blood and the level of CO2 in the atmospheric air: the pair correlation coefficient was r=-0.4. In winter (December), when the level of CO2 in the atmospheric air is high, the CO2 tension in the capillary blood of those examined is lower than in summer (June), when the content of carbon dioxide in the atmospheric air falls. Regardless of the season, all the subjects showed a decrease in pH to the acid side, especially in winter. At the same time, there was a tendency to decrease the level of buffer bases, which indicates compensated gaseous acidosis. The conducted studies indicate the presence of a close relationship between the content of CO2 and the tension of this gas in capillary blood.

Automatic air volume control system for ventilation of two patients using a single ventilator: a large animal model study

The COVID-19 pandemic outbreak led to a global ventilator shortage. Hence, various strategies for using a single ventilator to support multiple patients have been considered. A device called Ventil previously validated for independent lung ventilation was used in this study to evaluate its usability for shared ventilation. We performed experiments with a total number of 16 animals. Eight pairs of pigs were ventilated by a ventilator or anesthetic machine and by Ventil for up to 27 h. In one experiment, 200 ml of saline was introduced to one subject’s lungs to reduce their compliance. The experiments were analyzed in terms of arterial blood gases and respiratory parameters. In addition to the animal study, we performed a series of laboratory experiments with artificial lungs (ALs). The resistance and compliance of one AL (affected) were altered, while the tidal volume (TV) and peak pressure (Ppeak) in the second (unaffected) AL were analyzed. In addition, to assess the risk of transmission of pathogens between AL respiratory tracts, laboratory tests were performed using phantoms of virus particles. The physiological level of analyzed parameters in ventilated animals was maintained, except for CO2 tension, for which a permissive hypercapnia was indicated. Experiments did not lead to injuries in the animal’s lungs except for one subject, as indicated by CT scan analysis. In laboratory experiments, changes in TV and Ppeak in the unaffected AL were less than 11%, except for 2 cases where the TV change was 20%. No cross-contamination was found in simulations of pathogen transmission. We conclude that ventilation using Ventil can be considered safe in patients undergoing deep sedation without spontaneous breathing efforts.

Interfacial tension of carbon dioxide - water under conditions of CO2 geological storage and enhanced geothermal systems: A molecular dynamics study on the effect of temperature

In recent years, CO2 injection into geological formations under a wide range of temperature conditions, including super-hot geothermal reservoirs, has attracted much attention (i.e., higher than 500 K). Despite the importance, however, no study has been reported on the interfacial tension (IFT) of CO2 - water systems at temperatures higher than 478 K. In this study, we performed molecular dynamics (MD) simulations to estimate the CO2 - water IFT from 278 to 573 K at 8 to 50 MPa. Our results show the IFT at 10 MPa and 573 K is approximately 80% lower than that at a typical reservoir condition for CO2 geological storage. This indicates that the effect of the capillary pressure on the flow of CO2 and water in the geological formation is expected to be significantly reduced in such a super-hot geothermal reservoir.We discuss a possible mechanism for the IFT variation against temperature, including the maxima around 373 K at 8 to 12 MPa, which is reproduced and tackled by MD simulations for the first time. On the basis of the Gibbs-Duhem relation, the temperature dependence is directly related to the interfacial excess molar entropy. Our analyses show (1) the IFT increase is attributed to the substantial variation of the entropy and density of the bulk CO2 phase near the critical point, and (2) this variation is characterized by the distinct behavior of the molecular ordering and the mobility of CO2 at the interface, consistent with the close relationship between the disorder in molecular arrangement and configurational entropy.

The history of chemical concepts and field studies of CO2 in seawater: A tribute to Kurt Buch (1881–1967)

This review of the research on the marine CO2 system spans the time between the mid-19th century and the first years after World War II. It covers the period from the first attempts to determine the amount of CO2 dissolved in seawater to the first complete physico-chemical characterization of the marine CO2 system. The development of the latter was significantly influenced by the theoretical and experimental work of the Finnish chemical oceanographer Kurt Buch (1881–1967) during the first half of the 20th century. To acknowledge his outstanding achievements in Chemical Oceanography, this review is dedicated to him.The first part of our discussion is organized along the characteristic variables of the marine CO2 system. The analytical procedures that led successively to the definition of total CO2, alkalinity (“neutral carbonate”), the CO2 partial pressure (“CO2 tension”) and pH are briefly described. We trace the attempts to connect these variables quantitatively through the mass action law. After several failed attempts, CO2 dissociation constants were finally determined with the support of the International Council for the Exploration of the Sea (1931). Their results constituted the basis of the marine CO2 studies conducted after World War II.The second focus of our review refers to the various field studies, including early measurements of total CO2 and alkalinity during Norwegian (1878) and Danish expeditions (1895/96) in the North Atlantic and Arctic Ocean and the first measurements of surface water pCO2 in the North Atlantic, in 1902. Furthermore, we acknowledge the achievements of the German Atlantic expedition (1925–1927) for the characterization of the vertical and horizontal distribution of pH, pCO2 and CaCO3 saturation in the Atlantic Ocean. Among Buch's field studies of the CO2 system, we consider the Finnish monitoring program, in which pH and alkalinity were measured at over 70 stations in the northern Baltic Sea.Whenever it is appropriate, we show the connection between past scientific ideas, concepts and knowledge with current efforts and developments concerning the understanding of the marine carbon cycle and its response to increasing atmospheric CO2.

Cerebral vascular function following the acute consumption of caffeinated artificially- and sugar sweetened soft drinks in healthy adults.

Chronic consumption of sugar- and artificially-sweetened beverages (SSB and ASB) are associated with an increased risk of stroke but it is unclear how acute consumption influences cerebral vascular function. Purpose: We hypothesized that: (1) acute consumption of SSB and ASB would augment dynamic cerebral autoregulation (dCA) and attenuate cerebral vascular reactivity to hypercapnia (CVRCO2) compared to water; and (2) dCA and CVRCO2 would be attenuated with SSB compared to ASB and water. Methods: Twelve healthy adults (age: 23 ± 2 years, four females) completed three randomized trials where they drank 500 ml of water, SSB (Mountain Dew®), or ASB (Diet Mountain Dew®). We measured mean arterial pressure (MAP), middle and posterior cerebral artery blood velocities (MCAv and PCAv), and end-tidal CO2 tension (PETCO2). Cerebral vascular conductance was calculated as cerebral artery blood velocity/MAP (MCAc and PCAc). Twenty min after consumption, participants completed a 5 min baseline, and in a counterbalanced order, a CVRCO2 test (3%, 5%, and 7% CO2 in 3 min stages) and a dCA test (squat-stand tests at 0.10 Hz and 0.05 Hz for 5 min each) separated by 10 min. CVRCO2 was calculated as the slope of the linear regression lines of MCAv and PCAv vs. PETCO2. dCA was assessed in the MCA using transfer function analysis. Coherence, gain, and phase were determined in the low frequency (LF; 0.07-0.2 Hz) and very low frequency (VLF; 0.02-0.07 Hz). Results: MCAv and MCAc were lower after SSB (54.11 ± 12.28 cm/s, 0.58 ± 0.15 cm/s/mmHg) and ASB (51.07 ± 9.35 cm/s, 0.52 ± 1.0 cm/s/mmHg) vs. water (62.73 ± 12.96 cm/s, 0.67 ± 0.11 cm/s/mmHg; all P < 0.035), respectively. PCAc was also lower with the ASB compared to water (P = 0.007). MCA CVRCO2 was lower following ASB (1.55 ± 0.38 cm/s/mmHg) vs. water (2.00 ± 0.57 cm/s/mmHg; P = 0.011) but not after SSB (1.90 ± 0.67 cm/s/mmHg; P = 0.593). PCA CVRCO2 did not differ between beverages (P > 0.853). There were no differences between beverages for coherence (P ≥ 0.295), gain (P ≥ 0.058), or phase (P ≥ 0.084) for either frequency. Discussion: Acute consumption of caffeinated SSB and ASB resulted in lower intracranial artery blood velocity and conductance but had a minimal effect on cerebral vascular function as only MCA CVRCO2 was altered with the ASB compared to water.

Measurement and modelling of the interfacial tensions of CO2 + decane-iododecane mixtures at high pressures and temperatures

Experimentally determined interfacial tensions (IFTs) of CO2 and decane-iododecane mixtures are reported, with iododecane mass fractions of 0%, 50%, 70%, 90% and 100% over the temperature range of 298 K to 353 K and at pressures from 1 MPa up to the mixture critical point pressure. Measurements were carried out in a thermostatic high-pressure view cell by means of the pendant drop method. It was observed that the volume of a fresh drop of hydrocarbon initially increased, while the IFT decreased, before reaching equilibrium values. These observations correspond to two key mechanisms of CO2 flooding: oil swelling and IFT reduction. The equilibrium IFTs decrease with increasing pressure isothermally until the mixture critical point pressure is reached. The IFTs also increase with increasing mass fraction of iododecane. An empirical model was developed that is able to represent the experimental results with an overall average absolute deviation of 0.2 mN∙m−1.The IFT data were modeled with the square gradient theory coupled with the volume-translated Peng-Robinson equation of state. The temperature-independent influence parameters of decane and iododecane were regressed from their surface tensions, while the influence parameter of CO2 was taken from literature. The theoretical predictions are in good agreement with the experimental results with an average absolute deviation of 0.4 mN∙m−1. Finally, we extend a group-contribution approach for the binary interaction parameters in the Peng-Robinson equation of state to encompass the CH2I functional group, thereby facilitating application of the modelling approach to other systems comprising CO2 or N2 with iodoalkanes.

Multi‐center study reveals impairment of cortical tissue oxygenation during rising blood CO2 tension in MCI and AD patients

AbstractBackgroundAn ongoing multi‐center study of a consortium of Alzheimer’s Disease Centers in Los Angeles (USC), Dallas (UT‐SWMC) and Kansas City (KUMC) has explored quantitatively the dynamics of the homeostatic mechanism that maintains adequate cortical tissue oxygenation during a rise in blood CO2 tension. The results from cognitively normal subjects and MCI/AD patients were compared to assess differences in the dynamics of this important homeostatic mechanism.MethodQuantification of the dynamics of cortical tissue oxygenation was achieved through extraction of predictive models from five‐minute data‐records of spontaneous fluctuations in cortical tissue oxygenation (CTO), measured non‐invasively via near infrared spectroscopy at the prefrontal cortex, and the associated fluctuations in arterial blood pressure (ABP) and end‐tidal CO2 (etCO2). Using a novel kernel‐based modeling methodology, we analyzed the time‐series data from 25 MCI patients, 7 AD patients and 45 age‐matched cognitively normal controls (NC) and obtained predictive models of the dynamic effects of ABP and etCO2 (viewed as a proxy for blood CO2 tension) upon CTO. These predictive models were used to quantify the dynamics of cortical CO2 reactivity (CCR) in each participant, as the time‐average of the model‐predicted CTO response to unit‐step etCO2 change over the first 30 sec. The obtained CCR indices were used to evaluate the differences between NC and MCI/AD patients.ResultThe obtained CCR indices were significantly different for the 32 patients (MCI and AD lumped together due to small number of AD) vs. 45 age‐matched controls (p= 0.0083), with respective mean (SD): 0.014 (0.108) vs ‐0.059 (0.119). This is illustrated in Figure 1, where the average model‐predicted CTO responses to a unit‐step change of etCO2 are shown for 32 MCI/AD patients (red line) and 45 controls (blue line). Note the negative values of the average CTO response for patients (red line) to unit‐step increase of etCO2 that indicates polarity reversal of the normal CO2 vasomotor reactivity (blue line).ConclusionQuantitative analysis of cortical oxygenation dynamics under resting spontaneous conditions in 32 MCI/AD patients relative to 45 age‐matched controls revealed a significant impairment of the homeostatic mechanism that maintains adequate oxygenation of cortical tissue during a rise in blood CO2 tension.

Dynamic effects of cholinergic blockade upon cerebral blood flow autoregulation in healthy adults.

Background: Cerebral flow autoregulation (CFA) is a homeostatic mechanism critical for survival. The autonomic nervous system (ANS) plays a key role in maintaining proper CFA function. More quantitative studies of how the ANS influences CFA are desirable. Objective: To discover and quantify the dynamic effects of cholinergic blockade upon CFA in response to changes of arterial blood pressure and blood CO2 tension in healthy adults. Methods: We analyzed time-series data of spontaneous beat-to-beat mean arterial blood pressure (ABP) and cerebral blood flow velocity in the middle cerebral arteries (CFV), as well as breath-to-breath end-tidal CO2 (CO2), collected in 9 adults before and after cholinergic blockade, in order to obtain subject-specific predictive input-output models of the dynamic effects of changes in ABP and CO2 (inputs) upon CFV (output). These models are defined in convolutional form using "kernel" functions (or, equivalently, Transfer Functions in the frequency domain) that are estimated via the robust method of Laguerre expansions. Results: Cholinergic blockade caused statistically significant changes in the obtained kernel estimates (and the corresponding Transfer Functions) that define the linear dynamics of the ABP-to-CFV and CO2-to-CFV causal relations. The kernel changes due to cholinergic blockade reflect the effects of the cholinergic mechanism and exhibited, in the frequency domain, resonant peaks at 0.22 Hz and 0.06Hz for the ABP-to-CFV and CO2-to-CFV dynamics, respectively. Conclusion: Quantitative estimates of the dynamics of the cholinergic component in CFA are found as average changes of the ABP-to-CFV and CO2-to-CFV kernels, and corresponding Transfer Functions, before and after cholinergic blockade.

Cool Head-out Water Immersion Augments Cerebral Artery Blood Velocity In Healthy Young Adults

Adequate cerebral blood flow (CBF) is critical for brain function. Thermoneutral head-out water immersion (HOWI) may be a useful modality to increase CBF but it is unclear whether a colder water temperature influences the cerebrovascular responses. PURPOSE: We tested the hypothesis that middle cerebral artery blood velocity (MCAv) and cerebrovascular reactivity to hypercapnia (CVRCO2) would be higher during an acute bout of thermoneutral (TN; 35 °C) vs. cool (COOL; 25 °C) HOWI. METHODS: Ten healthy participants (age: 23 ± 3 y; BMI: 23 ± 3 kg/m2; 4 females) completed two randomized 45-minute HOWI visits. Core temperature (Tcore) was recorded every five minutes via an ingested telemetry pill. Right mean MCAv, end-tidal CO2 tension (PETCO2), and mean arterial pressure (MAP) were continuously recorded. CVRCO2 was assessed using a fixed inspired stepped hypercapnia protocol before (PRE), at 30 minutes of HOWI (HOWI), and 45 minutes after cessation of HOWI (POST). CVRCO2 was calculated as the slope of the linear regression line between MCAv and PETCO2. Values are reported as a change from PRE (mean ± SD). RESULTS: There were no differences between conditions at PRE (all P ≥ 0.09). During HOWI, the change in Tcore, MCAv, PETCO2, MAP, CVRCO2 were not different between TN and COOL (all P ≥ 0.22). Tcore did not change during TN (-0.10 ± 0.14 °C; P = 0.55) or COOL (-0.00 ± 0.22 °C; P > 0.99). MCAv did not increase during TN (4 ± 5 cm/s; P = 0.06) but increased during COOL (7 ± 6 cm/s; P < 0.01). PETCO2 did not change during TN (1 ± 2 mmHg; P = 0.20) or COOL (1 ± 2 mmHg; P = 0.16). MAP increased during TN (11 ± 7 mmHg; P < 0.01) and COOL (16 ± 4 mmHg; P < 0.01). At POST, the change in Tcore, MCAv, and PETCO2 was greater in COOL vs. TN (all P < 0.01). Tcore did not change in TN (P > 0.99), but decreased in COOL (P = 0.04) at POST. MCAv did not change in TN (1 ± 7 cm/s; P > 0.99) but increased in COOL (9 ± 5 cm/s; P < 0.01) at POST. PETCO2 did not change in TN (-1 ± 2 mmHg; P = 0.42) or COOL (1 ± 1 mmHg; P = 0.06) at POST. MAP did not increase in TN (5 ± 8 mmHg; P = 0.06) but increased in COOL (11 ± 10 mmHg; P < 0.01) at POST. CVRCO2 did not change over time (P ≥ 0.11) or between conditions (P ≥ 0.32). CONCLUSION: Cool water augmented MCAv during immersion and MCAv was greater following COOL HOWI vs. TN at 45 minutes post. However, neither condition altered CVRCO2 in healthy young adults. Supported by ONR N00014-17-1-2878

Correlation of central venous-to-arterial carbon dioxide difference to arterial-central venous oxygen difference ratio to lactate clearance and prognosis in patients with septic shock: A prospective observational cohort study.

To assess the relationship between the ratio of difference of venoarterial CO2 tension (P (v-a) CO2) and difference of arterio-venous oxygen content (C (a-cv) O2), i.e., ΔPCO2/ΔCaO2 with lactate clearance (LC) at 8 and 24 h, to define a cutoff for the ratio to identify LC >10% and >20% at 8 and 24 h, respectively, and its association with prognosis in septic shock. Adult patients with septic shock were included in this prospective, observational cohort study. Blood samples for arterial lactate, arterial, and central venous oxygen and carbon dioxide were drawn simultaneously at time zero (T0), 8 h (T8), and 24 h (T24). At T8, patients were divided into Group 8A (LC ≥10%) and Group 8B (LC <10%). At T24, patients were divided into Group 24A (LC ≥20%) and Group 24B (LC <20%). Ninty-eight patients were included. The area under the curve of ΔPCO2/ΔCaO2 at T8 (0.596) and T24 (0.823) was the highest when compared to P(v-a) CO2 and C(a-v) O2. The best cutoff of P(v-a) CO2/C (a-v) O2 as predictor of LC >10% was 1.31 (sensitivity 70.6% and specificity 53.3%) and for LC >20% was 1.37 (sensitivity 100% and specificity 50%). At both T8 and T24, P(v-a) CO2/C (a-v) O2 showed a significant negative correlation with LC. Groups 8A and 24A showed lower intensive care unit mortality than 8B and 24B, respectively. Values of P(v-a) CO2/C (a-v) O2 at T8 were comparable, but at T24, there was a significant difference between the survivors and nonsurvivors (P < 0.001). ΔPCO2/ΔCaO2 predicts lactate clearance, and its 24 h value appears superior to the 8-h value in predicting LC and mortality in septic shock patients.

An implementation of apneustic anesthesia ventilation in the horse: comparison with conventional mechanical ventilation

ObjectiveTo compare the cardiopulmonary effects of apneustic anesthesia ventilation (AAV) and conventional mechanical ventilation (CMV) in dorsally recumbent anesthetized horses. Study designRandomized, crossover design. AnimalsA total of 10 healthy adult horses from a university-owned herd. MethodsFollowing xylazine, midazolam and ketamine administration, horses were orotracheally intubated and positioned in dorsal recumbency. Anesthesia was maintained with isoflurane in oxygen [inspired oxygen fraction (FiO2) = 0.3 initially, with subsequent titration to maintain PaO2 ≥ 85 mmHg (11.3 kPa)]. Horses were instrumented and ventilated with AAV or CMV for 1 hour according to predefined criteria [10 mL kg–1 tidal volume (VT), PaCO2 of 40–45 mmHg (5.3–6.0 kPa) during CMV and <60 mmHg (8.0 kPa) during AAV]. Dobutamine was administered to maintain mean arterial pressure (MAP) >65 mmHg. Cardiopulmonary data were collected at baseline, 30 and 60 minutes. The effects of ventilation mode and time were analyzed using repeated-measures anova with significance defined as p < 0.05. ResultsData from nine horses were analyzed. A significant effect of mode at one or more time points was found for respiratory rate, arterial and end-tidal CO2 tensions, arterial pH, mean airway pressure (Paw), respiratory system dynamic compliance index (CrsI), venous admixture (Q˙s/Q˙t), mean pulmonary artery pressure and systemic vascular resistance. No significant differences between modes were found for VT, FiO2, PaO2, arterial hemoglobin saturation, alveolar dead space, heart rate, MAP, cardiac index, stroke volume index, oxygen delivery index, oxygen extraction ratio and dobutamine administration. Conclusions and clinical relevanceIn dorsally recumbent anesthetized horses, both ventilation modes supported adequate oxygenation with minimal supplemental oxygen. Compared with CMV, AAV resulted in higher CrsI and lower Q˙s/Q˙t. Despite higher mean Paw with AAV, the cardiovascular effects of each mode were not different. Further trials of AAV in anesthetized horses are warranted.

How to avoid rapid carbon dioxide changes at the start of veno-venous extracorporeal membrane oxygenation: Role of end-tidal CO2 monitoring.

Background: Venovenous ECMO is a lifesaving technique for patients with severe respiratory failure. Management of carbon dioxide (CO2) levels at ECMO start is crucial, as recent studies found an association between rapid CO2 shifts and increased incidence of neurological complications.Purpose: To describe the role of end tidal CO2 (etCO2) monitoring at the ECMO start to minimize carbon dioxide shifts.Research design: Retrospective cohort study.Methods: We performed a retrospective analysis of patients who started venovenous ECMO support at our institution between 2011 and 2021. We analysed the minute-by-minute variations of etCO2, ventilatory parameters and arterial blood gas before and after the ECMO start.Results: 36 patients with a complete dataset of parameters were included. After the ECMO start, minute ventilation was progressively reduced from 10.8±;3.3 to 2.9±1.2 L/min (p<0.001). etCO2 did not vary significantly (baseline 37±10 vs 35±9 mmHg 20 minutes after ECMO start, p = 0.36). Despite a stable etCO2 level, a mild drop of arterial CO2 tension (9.5 mmHg, corresponding to a 18% change) was recorded at the first ABG sampled after the ECMO start. No patient developed neurological complications after the ECMO commencement.Conclusion: etCO2 monitoring during ECMO start is feasible and allows to adjust gas flow and ventilator settings to limit changes in arterial CO2 levels.

Measurement and Modelling of the Interfacial Tensions of Co2 + Decane-Iododecane Mixtures at High Pressures and Temperatures

Measurement and Modelling of the Interfacial Tensions of Co2 + Decane-Iododecane Mixtures at High Pressures and Temperatures

Viable Allogeneic Mitochondria Transplantation Improves Gas Exchange and Alveolar-Capillary Permeability in Rats with Endotoxin-Induced Acute Lung Injuries.

Background: Acute lung injuries (ALI) cause disruption of the alveolar-capillary barrier and is the leading cause of death in critically ill patients. This study tested the hypothesis that the administration of freshly isolated viable allogeneic mitochondria can prevent alveolar-capillary barrier injuries at the endothelial level, as mitochondrial dysfunction of the pulmonary endothelium is a critical aspect of ALI progression.Methods: ALI was induced by intratracheal lipopolysaccharide instillation (LPS, 1mg/kg) in anesthetized rats. Mitochondria (100 µg) were isolated from the freshly harvested soleus muscles of naïve rats and stained with a green fluorescence MitoTracker™ dyne. A mitochondria or placebo solution was randomly administered into the jugular veins of the rats at 2 h and 4 h after ALI induction. An arterial blood gas analysis was done 20 h later. The animals were then sacrificed and lung tissues were harvested for analysis.Results: An IVIS Spectrum imaging system was used to obtain ex vivo heart-lung block images and track the enhancement of MitoTracker™ fluorescence in the lungs. Mitochondria transplantation significantly improved arterial oxygen contents (PaO2 and SaO2) and reduced CO2 tension in rats with ALI. Animals with mitochondrial transplants had significantly higher ATP concentrations in their lung tissues. Allogeneic mitochondria transplantation preserved alveolar-capillary barrier function, as shown by a reduction in protein levels in the bronchoalveolar lavage fluid and decreased extravasated Evans blue dyne and hemoglobin content in lung tissues. In addition, relaxation responses to acetylcholine and eNOS expression were potentiated in injured pulmonary arteries and inflammatory cells infiltration into lung tissue was reduced following mitochondrial transplantation.Conclusions: Transplantation of viable mitochondria protects the integrity of endothelial lining of the alveolar-capillary barrier, thereby improving gas exchange during the acute stages of endotoxin-induced ALI. However, the long-term effects of mitochondrial transplantation on pulmonary function recovery after ALI requires further investigation.

Respiratory Changes under Spinal Anaesthesia for Laparoscopic Gynaecological Procedures- a comparison with General Anaesthesia

Background: Laparoscopic surgery has become a frequently applied technique for a wide field ofindications. The procedure has become the gold standard for many procedures, with some of the mostcommon being gynecological procedures and appendectomy. Laparoscopic procedures that are widelyused in gynecological surgery are commonly applied under general anesthesia (GA). Now a days spinalanaesthesia (SAB) has become a routine technique for healthy patients. It is currently presumed thatspinal anaesthesia can compromise respiratory muscle function during carbon dioxide (CO2)pneumoperitoneum and causes some respiratory changes. Objective: This study was designed to compare the respiratory effects of CO2 pneumoperitoneumunder spinal anaesthesia with general anaesthesia for short duration (&lt;1hr) laparoscopicgynaecological procedures. Methods: A total number of sixty female patients, thirty in each group of ASA grade I &amp; II wereenrolled for the study. Group I patients received lumber SAB with 15 mg heavy bupivacaine and 25mcg fentanyl. Group II patients received standard general anaesthesia with propofol, halothane andfentanyl. Baseline heart rate, blood pressure, respiratory rate, ETCO2 &amp; SPO2 were noted in allpatients. Arterial blood gas analysis was done at time 0, 20 and 40 min after initiation ofpneumoperitoneum. Continuous ECG, pulse oximetry, noninvasive blood pressure, and ETCO2 weremonitored during the procedure. Any per operative and post-operative side effects were recorded andmanaged. Results: There were no observed changes in the respiratory rate. In group I, ETCO2 increased in astepwise manner over the first 10 min and reached a plateau between 15th and 30th min and declinedafter deflation of pneumoperitoneum. Arterial CO2 tension also increased at 20 min with significantchanges (p=0.000) in arterial to end tidal carbon dioxide tension. ETCO2 and arterial carbon dioxidetension changes were almost similar in both groups. Conclusion: Arterial and end-tidal CO2 tension changes during lower abdominal laparoscopicsurgery under SAB remain within physiological limits and comparable to the CO2 tension under GA.SAB may be adopted in ASA physical status I and II patients with proper preoperative counseling.Hence it is a safe alternative to GA with minimum respiratory alterations. JBSA 2021; 34 (2) : 10-15

On the Evaluation of Interfacial Tension (IFT) of CO2–Paraffin System for Enhanced Oil Recovery Process: Comparison of Empirical Correlations, Soft Computing Approaches, and Parachor Model

Carbon dioxide-based enhanced oil-recovery (CO2-EOR) processes have gained considerable interest among other EOR methods. In this paper, based on the molecular weight of paraffins (n-alkanes), pressure, and temperature, the magnitude of CO2–n-alkanes interfacial tension (IFT) was determined by utilizing soft computing and mathematical modeling approaches, namely: (i) radial basis function (RBF) neural network (optimized by genetic algorithm (GA), gravitational search algorithm (GSA), imperialist competitive algorithm (ICA), particle swarm optimization (PSO), and ant colony optimization (ACO)), (ii) multilayer perception (MLP) neural network (optimized by Levenberg-Marquardt (LM)), and (iii) group method of data handling (GMDH). To do so, a broad range of laboratory data consisting of 879 data points collected from the literature was employed to develop the models. The proposed RBF-ICA model, with an average absolute percent relative error (AAPRE) of 4.42%, led to the most reliable predictions. Furthermore, the Parachor approach with different scaling exponents (n) in combination with seven equations of state (EOSs) was applied for IFT predictions of the CO2–n-heptane and CO2–n-decane systems. It was found that n = 4 was the optimum value to obtain precise IFT estimations; and combinations of the Parachor model with three-parameter Peng–Robinson and Soave–Redlich–Kwong EOSs could better estimate the IFT of the CO2–n-alkane systems, compared to other used EOSs.

Ratio of venous-to-arterial PCO2 to arteriovenous oxygen content difference during regional ischemic or hypoxic hypoxia

The purpose of the study was to evaluate the behavior of the venous-to-arterial CO2 tension difference (ΔPCO2) over the arterial-to-venous oxygen content difference (ΔO2) ratio (ΔPCO2/ΔO2) and the difference between venous-to-arterial CO2 content calculated with the Douglas’ equation (ΔCCO2D) over ΔO2 ratio (ΔCCO2D/ΔO2) and their abilities to reflect the occurrence of anaerobic metabolism in two experimental models of tissue hypoxia: ischemic hypoxia (IH) and hypoxic hypoxia (HH). We also aimed to assess the influence of metabolic acidosis and Haldane effects on the PCO2/CO2 content relationship. In a vascularly isolated, innervated dog hindlimb perfused with a pump-membrane oxygenator system, the oxygen delivery (DO2) was lowered in a stepwise manner to decrease it beyond critical DO2 (DO2crit) by lowering either arterial PO2 (HH-model) or flow (IH-model). Twelve anesthetized and mechanically ventilated dogs were studied, 6 in each model. Limb DO2, oxygen consumption ({dot{text{V}}text{O}}_{2}), ΔPCO2/ΔO2, and ΔCCO2D/ΔO2 were obtained every 15 min. Beyond DO2crit, {dot{text{V}}text{O}}_{2} decreased, indicating dysoxia. ΔPCO2/ΔO2, and ΔCCO2D/ΔO2 increased significantly only after reaching DO2crit in both models. At DO2crit, ΔPCO2/ΔO2 was significantly higher in the HH-model than in the IH-model (1.82 ± 0.09 vs. 1.39 ± 0.06, p = 0.002). At DO2crit, ΔCCO2D/ΔO2 was not significantly different between the two groups (0.87 ± 0.05 for IH vs. 1.01 ± 0.06 for HH, p = 0.09). Below DO2crit, we observed a discrepancy between the behavior of the two indices. In both models, ΔPCO2/ΔO2 continued to increase significantly (higher in the HH-model), whereas ΔCCO2D/ΔO2 tended to decrease to become not significantly different from its baseline in the IH-model. Metabolic acidosis significantly influenced the PCO2/CO2 content relationship, but not the Haldane effect. ΔPCO2/ΔO2 was able to depict the occurrence of anaerobic metabolism in both tissue hypoxia models. However, at very low DO2 values, ΔPCO2/ΔO2 did not only reflect the ongoing anaerobic metabolism; it was confounded by the effects of metabolic acidosis on the CO2–hemoglobin dissociation curve, and then it should be interpreted with caution.

Dynamic Cerebral Autoregulation following the Acute Consumption of Soft‐drinks in Healthy Adults

Chronic consumption of high-fructose corn syrup (HFCS) and artificially sweetened beverages (ASB) are associated with an increased risk of stroke. An attenuation in dynamic cerebral autoregulation (dCA), a measure cerebral vascular function during changes in arterial blood pressure, may indicate cerebral vascular dysfunction. Thus, understanding the acute effects that HFCS and ASB consumption has on dCA may help understand the increased risk of stroke associated with the chronic consumption of these beverages. Purpose We tested the hypothesis that dynamic cerebral autoregulation (dCA) is attenuated following the acute consumption of HFCS and ASB soft-drinks compared to Water. Methods Twelve healthy adults (age: 23±2 y, 4 females) completed three randomized, double-blind trials. Participants drank 500 mL of Water, HFCS (Mountain Dew) or ASB (Diet Mountain Dew). We continuously measured blood pressure (MAP), mean middle cerebral artery blood velocity (MCAv), and end-tidal CO2 tension (PETCO2). Cerebral vascular conductance (CVC) was calculated as mean MCAv/MAP. Twenty minutes after experimental beverage consumption participants completed a 5 minute seated baseline, followed by an oscillatory blood pressure challenge. The oscillatory blood pressure challenge consisted of squat-to-stand intervals at two different frequencies (0.10 Hz and 0.05 Hz) for 5 minutes each separated by 5 minutes of seated rest. dCA was assessed in the MCA using transfer function analysis. Coherence, gain and phase are reported in in predefined frequency domains: low frequency (LF; 0.07-0.2 Hz) and very low frequency (VLF; 0.01-0.07 Hz) for the 0.10 Hz and 0.05 Hz, respectively. Values are reported as mean±SD. Results At baseline, MCAv (HFCS: 53.7±11.5 and ASB: 52.2±10.3 vs. Water: 61.4±10.8 cm/s; p<0.01) and MCA CVC (HFCS: 0.6±0.2 and ASB: 0.5±0.1 vs. Water: 0.7±1 cm/s/mmHg; p<0.02) were lower following HFCS and ASB vs. Water. During the 0.10 Hz squat-to-stand, there were no differences between beverages for coherenceLF (p=0.30) or phaseLF (p=0.68). GainLF was lower following ASB (0.81±0.21 cm/s/mmHg) compared to Water (0.95±0.27 cm/s/mmHg; p=0.01) but there was no difference in gainLF between HFCS (0.92±0.23 cm/s/mmHg) and Water (p=0.53). During the 0.05 Hz squat-to-stand, there were no differences between beverages for coherenceVLF (p=0.83) or gainVLF (p=0.28). PhaseVLF was higher following ASB (45.4±8.5 degrees) compared to Water (39.8±8 degrees; p=0.06) but there was no difference in phaseVLF between HFCS (43.8±10.3 degrees) and Water (p=0.31). Conclusions Our data indicate that acute consumption of an ASB did not consistently alter dCA in both frequency bands. Additionally, dCA was not altered following a HFCS soft-drink. However, future research is warranted to determine the effects of chronic consumption of HFCS and ASB soft-drinks on cerebral vascular function and the increased the risk of stroke.

ISOLATION AND IDENTIFICATION OF ORNITHOBACTERIOSIS FROM BROILER CHICKENS IN NEW VALLEY AND ASSIUT GOVERNORATES

ABSTRACT Respiratory infections are the most dangerous diseases facing poultry industry. Ornithobacteriosis is a respiratory disease in chicken broiler farms, it causes severe economic losses (high condemnation rate at slaughter, high treatment costs). Scientific research papers should be focused on the causative agent in order to make a plan for the ideal steps for its isolation and identification, in addition to prevention and control of this infection. The present work was conducted to isolate and identify Ornithobacteriumrhinotracheale (ORT) in chicken broilers.A total of 195 samples (trachea, lungs and air sacs) were collected from dead and sacrificed broiler chickens aged (20 - 42 days old) from different broiler chickens farms in Assiut and New Valley Governorates for possible recovery of ORT. Samples were cultured on blood agar plates under 7.5 – 10 % CO2 tension at 37oC for 48 hours. Bacteriological examination used for isolation and identification of the ORT bacteria (cellular and colonial morphology, biochemical reactions, API 20 NE and growth on MacConkey's agar) showed 32 suspected isolates at percentage of 16.4%. Results of isolation by conventional method were confirmed by molecular identification using Polymerase Chain reaction technique (PCR); which revealed the positive detection of only 5 strains of ORT and produced the predicated 625 bp amplification product. Serotyping of the isolates by using agar gel precipitation test proved that all isolates belonged to serotype A. Challenge of broilers aged 14 days old with ORT strain alone or combined with live ND vaccine by spraying method caused mild respiratory manifestations with tracheitis, pneumonia and mild airsaculitis. While Infection of chicks with ORT via spray combined with prior administration of ND vaccine (stress factor) caused a moderate respiratory signs and more severe lesions. From the results obtained in this work, we can conclude that: The prevalence of ORT infection in broiler chickens in Assiut and New Valley governorates was 2.56% from living and scarified birds. The current investigation revealed that the isolates of ORT bacteria belonged to serotype A. Post mortem lesions especially yogurt like exudate in the abdominal air sac considered very pathognomonic in the tentative diagnosis of ORT infection. While PCR technique was proved to be more sensitive and specific for detection of ORT pathogen.

Respiratory parameters on diagnostic sleep studies predict survival in patients with amyotrophic lateral sclerosis

ObjectiveIn amyotrophic lateral sclerosis (ALS), respiratory muscle involvement and sleep-disordered breathing relate to worse prognosis. The present study investigated whether respiratory outcomes on first-ever sleep studies predict survival in patients with ALS, specifically taking into account subsequent initiation of non-invasive ventilation (NIV).MethodsFrom patients with ALS, baseline sleep study records, transcutaneous capnometry, early morning blood gas analysis, survival data and clinical disease characteristics were retrospectively analyzed. Patients were stratified according to whether enduring NIV was consecutively established (“NIV(+)”) or not (“NIV(–)”).ResultsAmong the study cohort (n = 158, 72 female, 51 with bulbar onset ALS, 105 deceased) sleep-disordered breathing was present at baseline evaluation in 97 patients. Early morning base excess (EMBE) > 2 mmol/l predicted nocturnal hypercapnia. Ninety-five patients were NIV(+) and 63 were NIV(–). Survival from baseline sleep studies was significantly reduced in NIV(–) but not in NIV(+) patients with nocturnal CO2 tension ≥ 50 mmHg, apnea hypopnea index ≥ 5/h, and EMBE > 2 mmol/l. Hazard ratio for EMBE > 2 mmol/l was increased in NIV(–) patients only, and EMBE independently predicted survival in both NIV(–) and NIV(+) patients. Furthermore, EMBE on baseline sleep studies was the only predictor for survival from symptom onset, and hazard ratio for shorter survival was markedly higher in the NIV(–) than the NIV(+) group (2.85, p = 0.005, vs. 1.71, p = 0.042).Interpretation: In patients with ALS, EMBE > 2 mmol/l predicts nocturnal hypercapnia and shorter survival. Negative effects of sleep-disordered breathing on survival are statistically abolished by sustained NIV.