Archaean palaeosols and Archaean air

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

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

Partial pressures of oxygen and carbon dioxide in bone and their correlation with bone‐blood flow: Effect of decreased arterial supply and venous congestion on intraosseous oxygen and carbon dioxide in an animal model

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.

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

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

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.

In an appendix to a paper on the static diffusion of gases, communicated to the Society in 1900, it was shown that when a current of air containing a constant proportion of carbon dioxide is caused to move in a turbulent stream over the free surface of a solution of caustic alkali, the rate of absorption of that gas increases with the velocity of the air-current up to a certain optimal speed, beyond which no further increase in the speed of the current influences the rate of absorption. It was further shown that when the optimal velocity of the air-current has been reached, and the temperature is maintained practically constant, the rate of absorption then varies directly as the partial pressure of the carbon dioxide in the air. In other words, if under the above conditions the rate of absorption per unit of area of the liquid surface is a for a partial pressure of carbon dioxide represented by and is for a partial pressure of p' , then at similar temperatures, a / p = a' / p' . A suggestion was also made that this principle might be found applicable to a determination of the carbon dioxide in air, and that if the method were found to be a practical one it would have the manifest advantage of not requiring any measurement of the air from which the gas was absorbed.

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.

Impact of sodium chloride and carbon dioxide on conidial germination and radial growth of Penicillium camemberti

Modeling the CO2 dynamics in the Laptev Sea, Arctic Ocean: Part II. Sensitivity of fluxes to changes in the forcing

We confirm the finding of Behnke,et al.(1935) that air at 8·6 atm. pressure has a somewhat intoxicating effect on human beings, and that this effect is due to nitrogen. The nitrogen effect reaches its maximum after about 3 min. There was no reduction of manual dexterity in the test used by us, but a considerable effect on performance of arithmetic, and on most practical activities. At 10 atm. these effects were somewhat enhanced, and manual dexterity was lowered in some cases. When helium or hydrogen was substituted for nitrogen there was no intoxication.3–4% of carbon dioxide at atmospheric pressure caused no deterioration in manual or arithmetical skill, and in the two subjects tested, 6% of carbon dioxide caused no deterioration.When air containing about 0·4% of carbon dioxide, and therefore with a partial pressure of about 4%, was breathed at 10 atm., there was a marked deterioration in manual dexterity, and a good deal of confusion. When breathing carbon dioxide at partial pressures of 6·6–9·7% at 10. atm., eight subjects lost consciousness in 1–5 min., but some could tolerate partial pressures of over 8% for 5 min. or more. With half an hour's exposure to a partial pressure of 6–7% of carbon dioxide, one subject lost consciousness after 7 min. at 10 atm. pressure, and another nearly did so.We consider that the percentage of carbon dioxide in air at 10 atm. pressure should be kept below 0·3%. Exposure to high partial pressures of carbon dioxide at 10 atm. does not increase the liability to ‘bends’ or other symptoms due to rapid decompression.Immersion in water below 40° F. did not enhance the effects of high-pressure air, or of carbon dioxide at atmospheric pressure, but somewhat enhanced those of high pressure and carbon dioxide together.In certain breathing apparatus the resistance became so great at 10 atm. as to be intolerable.Few subjects experienced serious trouble during compression, or during or after decompression. But one developed a unilateral pneumothorax.

Oxidative metabolism is essential for our cellular life. Although tissues such as skeletal muscle can operate for short periods anaerobically, human life does not continue for long in the absence of a ready supply of oxygen. Adequate oxygen delivery to tissues is essential for aerobic metabolism and disorders of delivery ultimately become life-threatening. The factors contributing to oxygen delivery are summarised in the oxygen flux equation: OXYGEN FLUX = CARDIAC OUTPUT × ARTERIAL OXYGEN CONTENT The cardiac output is the product of heart rate and stroke volume and amounts to about 5 litres per minute. The arterial oxygen content is the product of the blood’s haemoglobin concentration multiplied by the haemoglobin’s % saturation. The latter is determined by the partial pressure of oxygen in the blood. This is higher in arterial than in venous blood. A small, additional amount of oxygen is carried dissolved in the blood, the amount again determined by the oxygen partial pressure. The five litres of arterial blood delivered to the tissues each minute contain about 1000ml of oxygen. Only a quarter of this (250ml) is needed to support resting metabolism. There is therefore a large safety factor in oxygen delivery. This can be utilized, in concert with adaptive changes to cardiac output, vascular resistance and pulmonary ventilation, in situations such as muscular exercise, where oxygen demand increases dramatically, or at high altitude where inspired oxygen is low. Oxygen delivery depends on the cardiovascular system, respiratory system and the blood. In the lungs, blood in the alveoli is brought into close proximity with alveolar air so that oxygen can diffuse easily into the blood and carbon dioxide, a major waste product of metabolism, can diffuse into the alveolar air. Alveolar air is kept refreshed with atmospheric air by pulmonary ventilation which keeps the partial pressures of oxygen and carbon dioxide in alveolar air and pulmonary capillary blood in a constant equilibrium. This process ensures that pulmonary venous blood and systemic arterial blood have high oxygen and low carbon dioxide partial pressures. Once in the blood, almost all of the oxygen combines with haemoglobin and is transported by the cardiovascular system to the tissues.

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...

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.