A Simple Method for Measuring Carbon Dioxide in Soils

Continuous determination of the cerebrovascular changes induced by bicuculline and kainic acid in unanaesthetized spontaneously breathing rats

Blood flow compensates oxygen demand in the vulnerable ca3 region of the hippocampus during kainate-induced seizures

Arterial blood gases, oxygen, carbon dioxide, and the potential of hydrogen are the key indicators of respiratory status and should be continuously monitored for patients whose respiratory vital signs may alter frequently and rapidly. The arterial partial pressure of oxygen and carbon dioxide can be estimated with transcutaneous monitoring, which measures the partial pressure of oxygen and carbon dioxide diffusing from the skin. However, requiring a heating element and a large, expensive bedside monitor are the limitations of the traditional transcutaneous blood gas monitors preventing continuous monitoring outside a clinical setting. Therefore, we propose a miniaturized fluorescent thin film-based prototype, envisioned as a first-of-its-kind continuous transcutaneous carbon dioxide monitoring wearable device. The computation principle relies on measuring the fluorescence intensity of a carbon dioxide-sensitive thin film. The prototype monitor estimates the partial pressure of carbon dioxide ranging from 0 to 75 mmHg, covering the clinically significant range, 35–45 mmHg for healthy humans. The prototype is designed with a small form factor on a 60 mm×55 mm printed circuit board and consumes 64.33 mW, suitable to be translated into a wearable device in further design stages.

Pathological changes in bone have been related to a preceding impediment of the arterial or venous bone circulation and hypoxia. In this study, we analyzed the feasibility of mass spectrometry in measuring intraosseous oxygen and carbon dioxide. The partial pressures were also measured in intraosseous blood samples, and blood flow in bone was measured with the radioactive microspheres technique. The average partial pressure of oxygen in the lateral femoral condyle was 34 +/- 1.6 mm Hg when measured in intraosseous blood samples and 36.3 +/- 2.3 mm Hg when measured with the on-line mass spectrometer, with significant correlation between the methods. The absolute value of the partial pressure of carbon dioxide measured in situ with mass spectrometry was correlated with the value in the withdrawn blood. There was no significant difference in partial pressures of oxygen and carbon dioxide between the two sides or between repetitive measurements. Arterial occlusion resulted in severe hypoxia, whereas more moderate changes followed venous occlusion.

Objective To evaluate the accuracy of continuous noninvasive partial pressure of carbon dioxide monitoring in the old diabetic patients undergoing general anesthesia. Methods Sixty-six old diabetic patients of both sexes, aged 65-76 yr, weighing 49-95 kg, of American Society of Anesthesiologists physical status Ⅰ or Ⅱ, undergoing elective surgery under general anesthesia, were included in this study.Transcutaneous partial pressure of carbon dioxide(TcPCO2)was monitored by a noninvasive transcutaneous carbon dioxide monitor.Arterial blood samples were collected at 30 and 60 min after endotracheal intubation, partial pressure of arterial carbon dioxide(PaCO2)was monitored, and TcPCO2 and end-tidal pressure of carbon dioxide(PETCO2)were recorded.Bland-Altman analysis was used to measure the agreement. Results At 30 min after intubation, the results of Bland-Altman analysis showed that the mean difference between PaCO2 and TcPCO2 was 1.3, 95% confidence interval(CI)was 1.0-1.6, and the limit of agreement was -1.1-3.7; the mean difference between PaCO2 and PETCO2 was -3.2, 95%CI: -3.6--2.8, and the limit of agreement was -6.6-0.2.At 60 min after intubation, the results of Bland-Altman analysis showed that the mean difference between PaCO2 and TcPCO2 was 1.4, 95% CI was 1.1-1.7, and the limit of agreement was -1.0-3.4; the mean difference between PaCO2 and PETCO2 was -3.1, 95%CI was -3.5--2.7, and the limit of agreement was -6.7-0.5.The repeatability coefficients of PaCO2, TcPCO2 and PETCO2 were 2.1, 2.3 and 2.3, respectively, at 30 and 60 min after intubation. Conclusion Continuous noninvasive partial pressure of carbon dioxide monitoring provides good accuracy and can be used as an alternative to PaCO2 monitoring, and the accuracy is higher than that of PETCO2 for the old diabetic patients undergoing general anesthesia. Key words: Carbon dioxide; Monitoring, physiologic; Diabetes mellitus; Anesthesia, general

This study compares two noninvasive techniques for monitoring the partial pressure of carbon dioxide (PCO2) in 24 anesthetized adult patients. End-tidal PCO2 (PetCO2) and transcutaneous PCO2 (PtcCO2) were simultaneously monitored and compared with arterial PCO2 (PaCO2) determined by intermittent analysis of arterial blood samples. PETCO2 and PtcCO2 values were compared with PaCO2 values corrected to patient body temperature (PaCO2T) and PaCO2 values determined at a temperature of 37 degrees C (PaCO2). Linear regression was performed along with calculations of the correlation coefficient (r), bias, and precision of the four paired variables: PETCO2 versus PaCO2 and PaCO2T (n = 211), and PtcCO2 versus PaCO2 and PaCO2T (n = 233). Bias is defined as the mean difference between paired values, whereas precision is the standard deviation of the difference. The following values were found for r, bias, and +/- precision, respectively. PETCO2 versus PaCO2: 0.67, -7.8 mm Hg, +/- 6.1 mm Hg; PETCO2 versus PaCO2T: 0.73, -5.8 mm Hg, +/- 5.9 mm Hg; PtcCO2 versus PaCO2: 0.87, -1.6 mm Hg, +/- 4.3 mm Hg; PtcCO2 versus PaCO2T: 0.84, +0.7 mm Hg, +/- 4.8 mm Hg. Although each of these PCO2 variables is physiologically different, there is a significant correlation (P less than 0.001) between the noninvasively monitored values and the blood gas values. Temperature correction of the arterial values (PaCO2T) slightly improved the correlation, with respect to PETCO2, but it had the opposite effect for PtcCO2. In this study, the chief distinction between these two noninvasive monitors was that PETCO2 had a large negative bias, whereas PtcCO2 had a small bias. We conclude from these data that PtcCO2 may be used to estimate PaCO2 with an accuracy similar to that of PETCO2 in anesthetized patients.

BackgroundContinuous monitoring of partial pressure of arterial blood carbon dioxide (PaCO2) is important in preterm babies during the first 36 h after birth to avoid episodes of hypo/hypercarbia. There is...

We developed an acoustic capnometer to estimate the partial pressures of arterial carbon dioxide from expired air in the pulmonary rehabilitation devices for patients with respiratory failure. Because partial pressures of carbon dioxide reduce the velocity of sound propagating through expired air, we developed an acoustic capnometer. The present study proposes a unique method based on the measurement of acoustic velocity in expired air, thus eliminating the use of a specific carbon dioxide sensor. The current method can fabricate the capnometer at an appreciably low cost, enabling the device to be used for various rehabilitation purposes. The acoustic capnometer comprises a cylindrical small sample cavity, an ultrasonic transmitter-receiver system, electronic circuits for velocity determination, and a microprocessor for data processing. To validate the device, 12 patients with pulmonary disease were enrolled, and end-tidal partial pressures of carbon dioxide obtained from the current device were compared to the carbon dioxide tension measured by conventional arterial blood gas analysis. The results show a linear relationship in the region of interest (40–60 torr). Therefore, the proposed device facilitates the estimation arterial carbon dioxide partial pressures without sampling blood.

Sensitivity of an infrared gas analyzer used in the differential mode, to partial gas pressures of carbon dioxide and water vapor in the bulk air

Hypercapnia has been reported to play an active role in protection against organ injury. The aim of this study was to determine whether a higher level of partial pressure of arterial carbon dioxide (PaCO2) within the normal range in pediatric patients undergoing cardiac surgery had a similar organ-protective effect. From May 2017 to May 2018, 83 consecutive infant patients undergoing ventricular septal defect (VSD) repair with cardiopulmonary bypass were retrospectively enrolled. We recorded the end-expiratory tidal partial pressure of carbon dioxide (Pet-CO2) as an indirect and continuous way to reflect the PaCO2. The patients were divided into a low PaCO2 group (LPG; 30mmHg < Pet-CO2 < 40mmHg) and a high PaCO2 group (HPG; 40mmHg < Pet-CO2 < 50mmHg). The regional cerebral oxygen saturation (rScO2), cerebral blood flow velocity (CBFV), and hemodynamics at five time points throughout the operation, and perioperative data were recorded and analyzed for the two groups. In total, 34 LPG and 49 HPG patients were included. Demographics and perioperative clinical data showed no significant difference between the groups. Compared with LPG, the HPG produced lower postoperative creatine kinase isoenzyme-MB (40.88 versus 50.34ng/mL, P = 0.038). The postoperative C-reactive protein of HPG trended lower than in LPG (61.09 versus 73.4mg/L, P = 0.056). The rScO2 and mean CBFV of HPG were significantly higher compared with LPG (P < 0.05) except at the end of cardiopulmonary bypass. Hemodynamic data showed no significant difference between the groups. As a convenient and safe approach, higher-normal PaCO2 could attenuate brain injury, heart injury, and inflammatory response in infant patients undergoing VSD repair.

Objective To observe the effects of lateral position plus jacknife position on difference of partial pressure of carbon dioxide in artery and end-tidal pressure of carbon dioxide[P(a-ET）CO2].Methods Thirty-six patients undergoing elective surgery under total intravenous anesthesia were involved.Patients were divided into two groups (n=18):control group (group C) and experimental group (group L).Patients undergoing abdominal surgery were at supine position in group C.Patients undergoing nephrectomy,ureterolithotomy surgery or adrenal cyst resection were at lateral position plus jacknife position.Patients were endotracheal intubation and mechanical ventilation,respiratory rate was 15 rpm,inspiratory/expiratory ratio was 1∶1.5.End-tidal pressure of carbon dioxide(PETCO2) was stable between 30 mmHg-35 mmHg (1 mm Hg=0.133 kPa).Blood gas analysis was done at 15 (T1),35 min (T2) and PETCO2 was stable (T0)(the fluctuation was less than 1 mmHg).The ventilator parameters were not been constant during T0-T2 At T1,patients' position were changed from supine position to lateral position plus jacknife position in group L,and patients' position remained supine position in group C.Intraoperative monitoring consisted of electrocardiogram,invasive arterial pressure,heart rate,pulse oxygen saturation,tidal volume,minute ventilation,peak of airway pressure,end-tidal pressure of carbon dioxide(PETCO2),and so on.Results PETCO2,partial pressure of carbon dioxide in artery(PaCO2) and P(a-ET)CO2 were respectively (28.4±2.3),(35.7±3.3),(7.2±3.0) mmHg at T2 in group L.In group L,those items were(32.2± 1.8),(34.2±2.0),(2.6±2.8) mmHg at T1 respectively(P＜O.05).P(a-ET)CO2 were(2.6±2.5) and (3.1 ±1.5) mmHg at T1 and T2 respectively in group C.Compared with group L,P (aET)CO2 were significantly lower (P＜0.05).Conclusions P (a-ET)CO2 was significantly increases at lateral position plus jacknife position.So the ventilator parameters should be adjusted according PETCO2. Key words: Lateral position; Jackknife position; End-tidal pressure of carbon dioxide ; Hemodynamics; Blood gas analysis

High-flow nasal cannula oxygen therapy reduces the arterial partial pressure of carbon dioxide and acute exacerbation but does not increase exercise capacity or decrease hospitalisation or mortality. The study aimed to test the hypothesis that in chronic obstructive pulmonary disease patients, the use of high-flow nasal cannula decreases arterial partial pressure of carbon dioxide and increases the partial pressure of oxygen and 6-min walking distance. PubMed, Embase and the Cochrane library were searched for eligible studies published from database inception to November 2020 (Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist). The primary outcomes were partial pressure of carbon dioxide and partial pressure of oxygen, and the secondary outcomes were transcutaneous partial pressure of carbon dioxide and 6-min walking distance. Nine studies (680 patients) were included. high-flow nasal cannula did not decrease partial pressure of carbon dioxide compared with the control interventions (mean difference=-0.81, 95% confidence interval: -2.68 to 1.06, p=.395; I2 =42.9%, pheterogeneity =.105). high-flow nasal cannula decreased partial pressure of carbon dioxide compared with long-term oxygen therapy (mean difference=-3.25, 95% confidence interval: -5.65 to -0.85, p=.008; I2 =0%, pheterogeneity =.375); no difference was observed for the control modalities. high-flow nasal cannula resulted in better partial pressure of carbon dioxide compared with control interventions in hypoxemic patients (mean difference=-2.59, 95% confidence interval: -4.82 to -0.35, p=.023; I2 =32.5%, pheterogeneity =.224), but not in other types of patients. high-flow nasal cannula did not increase partial pressure of oxygen compared with the control interventions (mean difference=1.17, 95% confidence interval: -1.50 to 3.83, p=.390; I2 =0%, pheterogeneity =.660). high-flow nasal cannula decreased transcutaneous carbon dioxide tension (transcutaneous partial pressure of carbon dioxide) compared with the control interventions (mean difference=2.37, 95% confidence interval: 0.07-4.68, p=.044; I2 =8.7%, pheterogeneity =.295). high-flow nasal cannula increased 6-min walking distance compared with the control interventions (mean difference=18.22, 95% confidence interval: 0.86-,35.57, p=.040; I2 =0%, pheterogeneity =.918). The sensitivity analyses showed that the results were robust. High-flow nasal cannula did not significantly decrease partial pressure of carbon dioxide or increase partial pressure of oxygen in chronic obstructive pulmonary disease patients, which is different from the previous meta-analysis, but it decreases transcutaneous partial pressure of carbon dioxide and increased 6-min walking distance. This meta-analysis shows that in patients with chronic obstructive pulmonary disease, high-flow nasal cannula improves both transcutaneous partial pressure of carbon dioxide and 6-min walking distance, suggesting the high-flow nasal cannula has benefits in the management of chronic obstructive pulmonary disease. Considering that the literature suggests no impact of high-flow nasal cannula on hospitalisation and mortality, the benefits of high-flow nasal cannula might be limited to the patients who survive the chronic obstructive pulmonary disease events. Still, the global impact of high-flow nasal cannula on the quality of life of patients with chronic obstructive pulmonary disease should be examined.

Roles of oxygen and carbon dioxide on methane oxidative coupling over CaO and Sm2O3 catalysts

Puncture of the radial artery is the preferred method of obtaining an arterial blood sample for blood gas analysis. The chief indication for blood gas analysis is the need to obtain values for the partial pressures of oxygen and carbon dioxide and for arterial pH. This information is needed in assessing a patient with acute, severe respiratory distress. Measurements of arterial pH and the partial pressures of carbon dioxide and oxygen provide accurate information on the status of acid–base balance and gas exchange. Another indication for arterial blood gas sampling is the need to perform CO-oximetry in order to assess for methemoglobinemia and carboxyhemoglobinemia. Contraindications Radial arterial puncture is contraindicated in the presence of a known deficiency of collateral circulation to the distal upper extremity. A modified Allen test can be performed to assess the adequacy of the collateral circulation of the radial artery by the ulnar artery (Fig. 1). To perform the test, occlude both the ulnar and radial arteries. Instruct the patient to make a fist to drain the blood from the hand; this should be done for approximately 30 seconds. Instruct the patient to unclench the fist. The patient’s palm should appear blanched or pale. Now, release pressure only from the ulnar artery. Adequate collateral circulation is indicated by the return of normal color within 10 seconds. 1 There is no agreement as to whether the Allen test can accurately predict the risk of rare ischemic complications. 2 On the basis of current evidence, its use can be neither refuted nor supported. Alternative techniques to measure collateral circulation of the forearm include color Doppler studies of flow, plethysmography, and magnetic resonance imaging. 3 These methods are more often used in assessing the radial artery for more invasive procedures, such as arterial harvesting for coronary bypass. Radial arterial puncture should not be performed in patients with an overlying skin infection. In patients who are taking anticoagulants or in those with coagulopathies, it should be performed only if absolutely necessary, because of the increased risk of bleeding and hematoma formation. Preparation Standard kits for sampling arterial blood gas are readily available and should contain a syringe, a small 23-to-25-gauge needle (either with a rubber stopper used to remove the needle from the syringe or with an attached safety cap), and a syringe cap containing dry lithium heparin or sodium heparin. The concentration of hepa

Objective. To study the impact of compression on velocity of venous and arterial main blood flow of the lower extremity, as well as cutaneous microcirculation in the back part of the foot in healthy individuals and patients with decompensated forms of varicose disease and postthrombophlebitis syndrome. Materials and methods. In the investigation 56 individuals took part and divided into three groups: Group I – 20 healthy persons; Group II – 15 patients with varicose disease in decompensated stage; Group III– 21 patients with decompensated stage of postthrombophlebitis syndrome. In all participants of the investigation the index of ankle–brachial pressure, deep–femoro–popliteal index, the regional perfusion index, transcutaneous partial pressure of oxygen and partial pressure of carbon dioxide, the arterial blood flow velocity in femoral artery and of venous blood flow distally from sapheno–femoral junction were measured before and after application of elastic medical knitwear of various Class of compression or the cuff pressure. Results. In the Class III compression in patients of Group III the transcutaneously registered indices crossing have occurred between partial pressure of oxygen and carbon dioxide, accompanied by domination of the carbon dioxide partial pressure over the oxygen partial pressure while further enhancement of the compression Class. In patients of Group II this tendency was observed while application of Class IV compression only. At the investigation beginning the values of partial pressure of carbon dioxide registered were higher in the Group III patients, than in the patients of Group II (p=0.0001). Conclusion. While application of the Class III compression the velocity of the hip venous blood flow, comparing with its initial values, have lowered at average by 78% in patients of Group II and at average in 7.4 times in the patients of |Group III (p=0.0001). It is affordable in patients, suffering decompensated postthrombophlebitic syndrome, to apply the elastic compression of Classes I–II, while in those, having varicose disease in decompensated stage, – the elastic compression of Classes III and iV as well.