Search

High intensity exercise can lead to depletion of CO2 from the body (hypocapnia). This disturbance becomes more noticeable during recovery or between seasons of intermittent exercise, putting the subject in a neural fatigue state. Objectives: A possible hypothesis to address this condition would be to provide high CO2 mixtures (hypercapnic) during the recovery period from exercise in order to relieve hypocapnia. Methods: Eight men (23.8 ± 1.2 yrs, VO2max = 45 ± 1.9 ml▪kg-1▪min-1) performed cycling exercise at 80%VO2max for 6-7 min. During recovery (23 min) they inhaled hypercapnic air (EXP-21%O2, 3%CO2, and 76%N2) or normal air (CON-21%O2, 0.003%CO2, and 79%N2). Respiratory parameters were collected with open spirometry and heart rate was measured. Results: Exercise caused mild hypocapnia {9.9 mmHg drop of CO2 end-expiratory partial pressure (PETCO2)} in CON condition after exercise (p < .005). PETCO2 elevated close to the rest values during the three hypercapnic phases in EXP condition (main effect of condition p < .001 between EXP and CON), but after hypercapnic breathing it returned to hypocapnia similarly with CON. The ventilatory response (VE▪PETCO2-1) and the exhaled volume of CO2 (VCO2) progressively increased during and also after ventilatory manipulations in EXP compared to CON condition (VE▪PETCO2-1: post hoc p < .001, VCO2: pVCO2: p < .05-.001), and VO2 became lower after the end of second hypercapnic manipulation (p < .05 between EXP and CON). Conclusion: It seems that hypercapnic breathing after exercise is not a good strategy to reverse exercise hypocapnia, because of great hyperventilation caused by CO2 and exercise mechanisms during the recovery period leading to increased CO2 removal from body. This intervention may also decrease O2 supply and muscles blood flow. [ABSTRACT FROM AUTHOR]

The ventilatory anaerobic threshold (VAT) occurs when there is an isolated increase in the slope for ventilatory equivalent for oxygen consumption (VE/VO2) with no change in the slope for ventilatory equivalent for carbon dioxide production (VE/VCO2) when both are plotted against time. The concept of anaerobic threshold remains controversial. However, it is a clinically useful tool in evaluating the exercise capacity of children. This paper will review the history, biochemistry, and methodology involved in determining the anaerobic threshold, as well as the ventilatory anaerobic threshold, in children. [ABSTRACT FROM AUTHOR]

Background: Traditional desks require students to sit; however, recently schools have provided students with nontraditional standing desks. The purpose of this study was to investigate differences in caloric expenditure of young adults while sitting at a standard classroom desk and standing at a nontraditional standing classroom desk. Methods: Twenty (10 male/10 female) young (22.8 ± 1.9 y), healthy participants reported to the laboratory between the hours of 7:00 AM and 2:00 PM following a 12-h fast and 48-h break in exercise. Participants were randomly assigned to perform a series of mathematical problems either sitting at a normal classroom desk or standing at a nontraditional standing desk. Inspired and expired gases were collected for 45-min for the determination of oxygen consumption (VO2), carbon dioxide production (VCO2), and minute ventilation (VE) using a metabolic gas system. Results: There were significant increases from sitting to standing in VO2 (0.22 ± 0.05 vs. 0.28 ± 0.05 L⋅min-1, P ≤ .0001), VCO2 (0.18 ± 0.05 vs. 0.24 ± 0.050 L⋅min-1, P ≤ .0001), VE (7.72 ± 0.67 vs. 9.41 ± 1.20 L⋅min-1, P ≤ .0001), and kilocalories expended per minute (1.36 ± 0.20 kcal/min, P ≤ .0001 vs. 1.02 ± 0.22 kcal/min, P ≤ .0001). Conclusions: Results indicate a significant increase in caloric expenditure in subjects that were standing at a standing classroom desk compared with sitting at a standard classroom desk. [ABSTRACT FROM AUTHOR]

Abstract Lower ventilation rates and higher occupant density lead to accumulation of carbon dioxide (CO 2) accompanied by human bioeffluents inside built environments. Research had been conducted to evaluate the effect of CO 2 and bioeffluents using physiological measurements and correlated with reduced cognitive performance. However, no study has reported the underlying mechanism for the reduction in cognitive performance when exposed to elevated CO 2 concentration with bioeffluents. It is suggested that the reduction in cognitive performance is due to CO 2 retention in human, caused by the reduced gas transfer in lungs. The aim of the study was to obtain the lung performance functions at varying CO 2 concentrations with bioeffluents and to investigate their influence on the gas exchange mechanism. A spirometric analysis was made with eight healthy male volunteers at four different exposure conditions—ambient, 1000 ppm, 2000 ppm, and 3000 ppm—for a 3-h duration. The important parameters such as forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) showed reduced value, whereas FEV1/FVC showed a stable value across exposure conditions. Evidences for a restrictive lung behavior were reported, indicating a reduced gas transfer in the lung region. The partial pressure of CO 2 in lungs was derived from a literature experimental database and found to be increasing during elevated CO 2 concentration with bioeffluents. The underlying mechanism for the CO 2 retention in humans is elaborated. Graphical abstract Spirometry flow-volume loop diagram. Image 1 Highlights • A non-invasive study to assess the lung function under elevated CO 2 concentration. • Study of physiological variation in occupants exposed to indoor CO 2 with bioeffluents. • Prediction of variation in partial pressures of CO 2 and O 2 in lung region. • Evidence of restrictive lung behavior on exposure to elevated CO 2 concentration. • Estimation of CO 2 retention in human blood and its effects. [ABSTRACT FROM AUTHOR]

We explored a novel doubly labelled water (DLW) method based on breath water (BW-DLW) in mice to determine whole body CO2 production and energy expenditure noninvasively. The BW-DLW method was compared to the DLW based on blood plasma. Mice (n = 11, 43.5 ± 4.6 g body mass (BM)) were administered orally a single bolus of doubly labelled water (1.2 g H218O kg BM−1 and 0.4 g 2H2O kg BM−1, 99 atom% (AP) 18O or 2H). To sample breath water, the mice were placed into a respiration vessel. The exhaled water vapour was condensed in a cold-trap. The isotope enrichments of breath water were compared with plasma samples. The 2H/1H and 18O/16O isotope ratios were measured by means of isotope ratio mass spectrometry. The CO2 production (RCO2) was calculated from the 2H and 18O enrichments in breath water and plasma over 5 days. The isotope enrichments of breath water vs. plasma were correlated (R2 = 0.89 for 2H and 0.95 for 18O) linearly. The RCO2 determined based on breath water and plasma was not different (113.2 ± 12.7 vs. 111.4 ± 11.0 mmol d-1), respectively. In conclusion, the novel BW-DLW method is appropriate to obtain reliable estimates of RCO2 avoiding blood sampling. [ABSTRACT FROM AUTHOR]

Background and Aims: Not many studies have explored the correlation between arterial carbon dioxide tension (PaCO2) and end-tidal carbon dioxide tension (ETCO2) in surgeries requiring pneumoperitoneum of more than 1 hour duration with the patient in non-supine position. The aim of our study was to evaluate the correlation of ETCO2 with PaCO2 in patients undergoing laparoscopic nephrectomy under general anaesthesia. Methods: A descriptive study was performed in thirty patients undergoing laparoscopic nephrectomy from September 2014 to August 2015. The haemodynamic parameters, minute ventilation, PaCO2 and ETCO2 measured at three predetermined points during the procedure were analysed. Correlation was checked using Pearson's Correlation Coefficient Test. P <0.05 was considered statistically significant. Results: Statistical analysis of the values showed a positive correlation between ETCO2 and PaCO2 (P < 0.05). Following carbon dioxide insufflation, both ETCO2 and PaCO2 increased by 5.4 and 6.63 mmHg, respectively, at the end of the 1st hour. The PaCO2-ETCO2 gradient was found to increase during the 1st hour following insufflation (4.07 ± 2.05 mmHg); it returned to the pre-insufflation values in another hour (2.93 ± 1.43 mmHg). Conclusion: Continuous ETCO2 monitoring is a reliable indicator of the trend in arterial CO2 fluctuations in the American Society of Anesthesiologists Grades 1 and 2 patients undergoing laparoscopic nephrectomy under general anaesthesia. [ABSTRACT FROM AUTHOR]

This review examines the control of gas exchange in insects, specifically examining what mechanisms could explain the emergence of discontinuous gas exchange cycles (DGCs). DGCs are gas exchange patterns consisting of alternating breath-hold periods and bouts of gas exchange. While all insects are capable of displaying a continuous pattern of gas exchange, this episodic pattern is known to occur within only some groups of insects and then only sporadically or during certain phases of their life cycle. Investigations into DGCs have tended to emphasise the role of chemosensory thresholds in triggering spiracle opening as critical for producing these gas exchange patterns. However, a chemosensory basis for episodic breathing also requires an as-of-yet unidentified hysteresis between internal respiratory stimuli, chemoreceptors, and the spiracles. What has been less appreciated is the role that the insect’s central nervous system (CNS) might play in generating episodic patterns of ventilation. The active ventilation displayed by many insects during DGCs suggests that this pattern could be the product of directed control by the CNS rather than arising passively as a result of self-sustaining oscillations in internal oxygen and carbon dioxide levels. This paper attempts to summarise what is currently known about insect gas exchange regulation, examining the location and control of ventilatory pattern generators in the CNS, the influence of chemoreceptor feedback in the form of O2 and CO2/pH fluctuations in the haemolymph, and the role of state-dependent changes in CNS activity on ventilatory control. This information is placed in the context of what is currently known regarding the production of discontinuous gas exchange patterns. [ABSTRACT FROM AUTHOR]

An editorial on the usage of extracorporeal life support (ELS) methods following a thoracic surgery, lung transplantation, and cardiorespiratory failure is presented. The authors talks about how ELS can provide short to mid-term extracorporeal mechanical support by helping in carbon dioxide (CO2) clearance, aiding oxygen (O2) enrichment and providing cardiocirculatory support. The authors also discuss the usage of Novalung lung assist device and Pumpless interventional lung assist device.

Understanding the evolution of a new metabolic capability in full mechanistic detail is challenging, as causative mutations may be masked by non-essential "hitchhiking" mutations accumulated during the evolutionary trajectory. We have previously used adaptive laboratory evolution of a rationally engineered ancestor to generate an Escherichia coli strain able to utilize CO2 fixation for sugar synthesis. Here, we reveal the genetic basis underlying this metabolic transition. Five mutations are sufficient to enable robust growth when a non-native Calvin-Benson-Bassham cycle provides all the sugar-derived metabolic building blocks. These mutations are found either in enzymes that affect the efflux of intermediates from the autocatalytic CO2 fixation cycle toward biomass (prs, serA, and pgi), or in key regulators of carbon metabolism (crp and ppsR). Using suppressor analysis, we show that a decrease in catalytic capacity is a common feature of all mutations found in enzymes. These findings highlight the enzymatic constraints that are essential to the metabolic stability of autocatalytic cycles and are relevant to future efforts in constructing non-native carbon fixation pathways. [ABSTRACT FROM AUTHOR]

The article discusses research on arterial to end-tidal carbon dioxide difference in children undergoing mechanical ventilation of the lungs during general anesthesia with tracheal lung intubation and insertion of in-dwelling arterial cannula for blood gas analysis. The study analyzed arterial to end-tidal carbon dioxide differences in using spirometry and side-stream capnography and determined patients' age, weight, physical status, cardiac abnormalities, cardiovascular and pulmonary diseases.

Objective: There are conflicting data regarding the use of end-tidal carbon dioxide (PetCO2) measurement in preterm infants. The aim of this study was to evaluate the effects of different dead space to tidal volume ratios (VD/VT) on the correlation between PetCO2 and arterial carbon dioxide pressure (PaCO2) in ventilated preterm infants with respiratory distress syndrome (RDS). Methods: We enrolled ventilated preterm infants (with assist control mode or synchronous intermittent mandatory mode) with RDS who were treated with surfactant in this prospective study. Simultaneous PetCO2 and PaCO2 data pairs were obtained from ventilated neonates monitored using mainstream capnography. Data obtained before and after surfactant treatment were also analyzed. Results: One-hundred and one PetCO2 and PaCO2 pairs from 34 neonates were analyzed. There was a moderate correlation between PetCO2 and PaCO2 values (r = 0.603, P < 0.01). The correlation was higher in the post-surfactant treatment group (r = 0.786, P < 0.01) than the pre-surfactant treatment group (r = 0.235). The values of PaCO2 and PetCO2 obtained based on the treatment stage of surfactant therapy were 42.4 ± 8.6 mmHg and 32.6 ± 7.2 mmHg, respectively, in pre-surfactant treatment group, and 37.8 ± 10.3 mmHg and 33.7 ± 9.3 mmHg, respectively, in the post-surfactant treatment group. Furthermore, we found a significant decrease in VD/VT in the post-surfactant treatment group when compared to the pre-surfactant treatment group (P = 0.003). Conclusions: VD/VT decreased significantly after surfactant therapy and the correlation between PetCO2 and PaCO2 was higher after surfactant therapy in preterm infants with RDS. [ABSTRACT FROM AUTHOR]

Background Intraoperative hypercapnia and acidosis are risk factors during thoracoscopy in neonates and infants. Methods In a prospective pilot study, we evaluated the effects of thoracoscopy in neonates and infants on cerebral microcirculation, oxygen saturation, and oxygen consumption. Regional cerebral oxygen saturation and blood flow were measured noninvasively using a new device combining laser Doppler flowmetry and white light spectrometry. Additionally, cerebral fractional tissue oxygen extraction and approximated oxygen consumption were calculated. Fifteen neonates and infants undergoing thoracoscopy were studied using the above-mentioned method. The chest was insufflated with carbon dioxide with a pressure of 2-6 mm Hg. Single lung ventilation was not used. As control group served 15 neonates and infants undergoing abdominal surgery. Results Data are presented as median and range. The 95% confidence intervals for differences of means (95% CI) are given for the mean difference from baseline values. We observed a correlation between intrathoracic pressure exceeding 4 mm Hg and transient decrease in regional cerebral oxygen saturation of 12.7% (95% CI: 9.7-17.2, P<.001). Peripheral oxygen saturation was normal at the same time. Intraoperative increase in arterial pa CO2 (median maximum value: 48.8 mm Hg, range: [36.5-65.4]; 95% CI: −16.0 to −3.0, P=.002) and decrease in arterial pH (median minimum value: 7.3, range: [7.2-7.4]; 95% CI: 0.04-0.12, P=.008) were observed during thoracoscopy with both parameters recovering at the end of the procedure. Periods of regional cerebral oxygen saturation below 20% from baseline were significantly more frequent during thoracoscopy as compared to the control group (median maximum value: 1.3%min/h, range: [0.0-66.2] vs median maximum value: 0.0%min/h, range: [0.0-4.0]; 95% CI: −16.6 to −1.1, P=.028). Conclusion We suggest that thoracoscopic surgery in neonates and infants, although generally safe, may be associated with a decrease in regional cerebral oxygen saturation correlating with the applied intrathoracic pressure. According to our data an inflation pressure >4 mm Hg should be avoided during thoracoscopic surgery. [ABSTRACT FROM AUTHOR]

Background and Aim: Monitoring carbon dioxide (CO2) is of utmost importance in neurosurgical patients. It is measured by partial pressure of arterial CO2 (PaCO2) and end-tidal CO2 (ETCO2). We aimed to study the correlation between PaCO2 and ETCO2 in neurosurgical patients in the intraoperative and postoperative period on mechanical ventilation in Postanesthesia Care Unit (PACU). Methodology: This was prospective observational study done at tertiary care teaching public hospital over a period of 1 year. We studied 30 patients undergoing elective craniotomy intraoperatively and in the postoperative period on mechanical ventilation for 24 h. Serial measurement of ETCO2 and PaCO2 at baseline, hourly intraoperatively and every 6 hourly in the PACU were studied. Data analysis was done using SPSS software version 20. Results: The mean PaCO2-ETCO2 gradient intraoperatively over 4 h is 3.331 ± 2.856 and postoperatively over 24 h is 2.779 ± 2.932 and lies in 95% confidence interval. There was statistically significant correlation between PaCO2 and ETCO2 intraoperatively baseline, 1 h, 2 h, 3 h, and 4 h with Pearson's correlation coefficients of 0.799, 0.522, 0582, 0.439, and 0.547, respectively (P < 0.05). In PACU at baseline, 6 h, 12 h, 18 h, and 24 h Pearson's correlation coefficients were. 534, -0.032, 0.522, 0.242, 0.592, and 0.547, respectively, which are highly significant at three instances (P < 0.01). Conclusion: ETCO2 correlates PaCO2 with acceptable accuracy in neurosurgical patients in the intraoperative and postoperative period on mechanical ventilation in Intensive Care Unit. Thus, continuous and noninvasive ETCO2 can be used as a reliable guide to estimate arterial PCO2 during neurosurgical procedures and in PACU. [ABSTRACT FROM AUTHOR]

CONTEXT: Although the technical feasibility of laparoscopic donor nephrectomy (LDN) has been established, concerns have been raised about the impaired renal function resulting from pneumoperitoneum and its short- and long-term effects. AIMS: We used urinary biomarkers of acute kidney injury including urinary neutrophil gelatinase-associated lipocalin (uNGAL) and urinary N-acetyl-beta-D-glucosaminidase (uNAG) to study the injury caused to the donor's retained kidney by pneumoperitoneum. SETTINGS AND DESIGN: This was a prospective cohort study of thirty consecutive patients who underwent LDN at our hospital. SUBJECTS AND METHODS: We measured urinary creatinine, uNAG and uNGAL at the time of induction of anaesthesia, at 1 h after starting surgery, at 5 min after clamping the ureter, at the time of skin closure and then at 4, 8 and 24 h after the surgery. RESULTS: The uNAG level showed a gradual increase from the start of the surgery and reached the peak at the time of the closure. Thereafter, there was a gradual fall in the level and reached to pre-operative level at 24 h post-surgery. Similarly, the uNGAL also showed a similar trend although it did not reach pre-operative value by 24 h. CONCLUSIONS: We objectively confirm that although there is acute injury to the retained kidney in the donor after LDN due to the CO2 pneumoperitoneum, the renal function improves and reaches close to the preoperative level within 24 h after surgery. [ABSTRACT FROM AUTHOR]

The respiratory effort in hyperbaric conditions is of particular nature, leading to an increase of the respiratory flow of the diver and to the change of their pulmonary volumes. There are important criteria in the selection process of the most suitable divers. Some of these criteria are related to the respiratory function. In order to evaluate the divers respiratory function an examination of the pulmonary volumes is performed in regards to their variations measured by spirometry, of the increased oxygen consumption in hyperbaric conditions and of the production of carbon dioxide during the unitary dive at the depth of work using air as a respiratory mixture. The physical and physiological phenomena invol ved in the hyperbaric respiration have been studied in cooperation with "Ovidius" University of Constanta, Faculty of Medicine. A specific medical method of evaluation of the pulmonary ventilation, spirometry, the measurement of forced expiratory volume in the first second of a forced expiration, Tiffneau index, have been adapted to the under pressure breathing environment. The parameters have been studied as experimental determinations on diver groups, during simulated diving, using air as a respiratory mixture, at 50 [mH2O] in the Hyperbaric Complex of the Diving Centre. [ABSTRACT FROM AUTHOR]

Copyright of Jornal de Pediatria is the property of Sociedade Brasileira de Pediatria and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Shoulder pain and pain in the upper abdomen are common complaints after laparoscopy, sometimes surpassing the pain at incision sites. The incidence of shoulder pain ranges from 35 to 80%. Post-laparoscopic pain is caused by retention of carbon dioxide in the abdomen, which irritates the phrenic nerve and diaphragm, causing referred pain in the shoulder and in the upper abdomen. A promising strategy to reduce this post-laparoscopic pain is the pulmonary recruitment maneuver, which indirectly increases intraperitoneal pressure and thereby facilitates removal of residual carbon dioxide. An alternative strategy is the infusion of intraperitoneal normal saline. With normal saline infusion, carbon dioxide rises and escapes through the port sites. In addition, normal saline offers a physiologic buffer system to dissolve excess carbon dioxide.Methods/design: This multicenter randomized controlled trial is conducted in two teaching hospitals in the Netherlands. Women between 18 and 65 years of age, with an ASA classification of I-II who are scheduled to undergo an elective laparoscopic procedure with benign gynecologic indication can participate. Following informed consent, participants are randomly allocated into two groups at the end of the surgical procedure. In the intervention group, the upper abdomen is filled with normal saline infusion with the patient in the Trendelenburg position. Then the anesthesiologist performs a standardized pulmonary recruitment maneuver with a pressure of 40 cm H2O. The trocar sleeve valves will be left open, so carbon dioxide can escape the abdominal cavity. With the patient in a neutral position the instruments are removed from the abdomen. In the control group, carbon dioxide is removed from the abdominal cavity at the end of surgery, with gentle abdominal pressure and passive exsufflation through the port sites, with open sleeve valves. The primary outcomes are the incidence and intensity of post-laparoscopic pain in the shoulder, upper abdomen and at the operation sites, at 8, 24 and 48 h after surgery. Secondary outcomes are postoperative use of analgesics, nausea, vomiting and pulmonary complications.Discussion: This study may reduce post-laparoscopic pain in women undergoing laparoscopy.Trial Registration: Dutch trial register, number NTR4812 . [ABSTRACT FROM AUTHOR]

Objective: The ability to ventilate babies with tidal volumes (VTs) below dead space has been demonstrated both in vivo and in vitro, though it appears to violate classical respiratory physiology. We hypothesised that this phenomenon is made possible by rapid flow of gas that penetrates the dead space allowing fresh gas to reach the lungs and that the magnitude of this phenomenon is affected by flow rate or how rapidly air flows through the endotracheal tube.Methods: We conducted two bench experiments. First, we measured the time needed for complete CO2 washout from a test lung to assess how fixed VT but different inflation flow rates affect ventilation. For the second experiment, we infused carbon dioxide at a low rate into the test lung, varied the inflation flow rate and adjusted the VT to maintain stable end tidal carbon dioxide (ETCO2).Results: At all tested VTs, lower flow rate increased the time it took for CO2 to washout from the test lung. The effect was most pronounced for VTs below dead space. The CO2 steady-state experiment showed that ETCO2 increased when the flow rate decreased. Ventilating with a slower flow rate required a nearly 20% increase in VT for the same effective alveolar ventilation.Conclusions: Inflation flow rate affects the efficiency of CO2 removal with low VT. Our results are relevant for providers using volume-controlled ventilation or other modes that use low inflation flow rates because the VT required for normocapnia will be higher than published values that were generated using pressure-limited ventilation modes with high inflation flows. [ABSTRACT FROM AUTHOR]

Purposes: Thoracoscopic anatomical lung resection is a minimally invasive technique, but intraoperative massive bleeding is a critical complication. We investigated the hemostatic efficacy and safety of intrapleural carbon dioxide (CO) insufflation in thoracoscopic surgery in a swine vessel injury model. Methods: Swines were assigned to one of four groups subjected to thoracoscopic surgery under target intrathoracic pressures of 0, 5, 10, or 15 mmHg CO insufflation, respectively. A pin-hole injury of the right cranial lobe pulmonary vein was inflicted thoracoscopically and we compared the blood loss and hemodynamic changes in each group. Results: There were no signs or echographic findings of air embolus. Both the blood loss per minute and total blood loss during the experiment were significantly lower in the 10 and 15 mmHg groups than in the 0 mmHg group ( p > 0.05, respectively). The hemodynamic signs, including heart rate, mean arterial pressure, and peripheral oxygen saturation, were not significantly different in the 0 and 10 mmHg groups at most times, although they were significantly correlated with the insufflation pressure during the experiments ( p < 0.05). Conclusions: CO insufflation in thoracoscopic major lung resection appears to be safe, even in the short term, and can help to control vessel injury. [ABSTRACT FROM AUTHOR]

Severe sepsis and septic shock are life-threatening conditions with mortality rates exceeding 31% (Levy et al., 2012) [1]. Septicemia was the most expensive US hospital condition in 2011 (Torio and Andrews, 2006) [2]. Urinary carbon dioxide may provide rapid, clinically useful information about a patient’s status, empowering physicians to intervene earlier and improve septic shock mortality. The objective of this paper is to validate a protocol with a Severinghaus-type CO 2 probe for the measurement of urinary CO 2 of septic shock patients. This protocol includes (i) sampling urine from a Foley catheter in an intensive care unit setting, (ii) storing samples until analysis at a separate facility, (iii) calibration of the Severinghaus-type CO 2 sensor, and (iv) measuring urinary CO 2 levels. We discuss the preparation and stability of standard solutions, storage of urine samples, and the performance characteristics of the Severinghaus type CO 2 sensor in relation to mock urine samples, urine quality control standards, and urine samples from healthy volunteers as well as patients in severe sepsis or septic shock. We report the influence of the sample pH, temperature, and ionic strength on the precision and accuracy of the measurements of urinary CO 2 levels and show that the protocol developed for the quantitative assessment of urinary CO 2 levels is adequate for the analysis of urine samples collected from a Foley catheter. [ABSTRACT FROM AUTHOR]

Background: Isocapnic hyperventilation (IHV) is a method that fastens weaning from inhalation anaesthesia by increasing airway concentration of carbon dioxide (CO2 ) during hyperventilation (HV). In an animal model, we evaluated a technique of adding CO2 directly to the breathing circuit of a standard anaesthesia apparatus.Methods: Eight anaesthetised pigs weighing 28 ± 2 kg were intubated and mechanically ventilated. From a baseline ventilation of 5 l/min, HV was achieved by doubling minute volume and fresh gas flow. Respiratory rate was increased from 15 to 22/min. The CO2 absorber was disconnected and CO2 was delivered (DCO2 ) to the inspiratory limb of a standard breathing circuit via a mixing box. Time required to decrease end-tidal sevoflurane concentration from 2.7% to 0.2% was defined as washout time. Respiration and haemodynamics were monitored by blood gas analysis, spirometry, electric impedance tomography and pulse contour analysis.Results: A DCO2 of 261 ± 19 ml/min was necessary to achieve isocapnia during HV. The corresponding FICO2 -level remained stable at 3.1 ± 0.3%. During IHV, washout of sevoflurane was three times faster, 433 ± 135 s vs. 1387 ± 204 s (P < 0.001). Arterial CO2 tension and end-tidal CO2 , was 5.2 ± 0.4 kPa and 5.6 ± 0.4%, respectively, before IHV and 5.1 ± 0.3 kPa and 5.7 ± 0.3%, respectively, during IHV.Conclusions: In this experimental in vivo model of isocapnic hyperventilation, the washout time of sevoflurane anaesthesia was one-third compared to normal ventilation. The method for isocapnic hyperventilation described can potentially be transferred to a clinical setting with the intention to decrease emergence time from inhalation anaesthesia. [ABSTRACT FROM AUTHOR]

Dead space fraction (V d/V t) measurement performed using volumetric capnography requires arterial blood gas (ABG) sampling to estimate the partial pressure of carbon dioxide (PaCO2). In recent years, transcutaneous capnography (PtcCO2) has emerged as a noninvasive method of estimating PaCO2. We hypothesized that PtcCO2 can be used as a substitute for PaCO2 in the calculation of V d/V t. In this prospective pilot comparison study, 30 consecutive postcardiac surgery mechanically ventilated patients had V d/V t calculated separately using volumetric capnography by substituting PtcCO2 for PaCO2. The mean V d/V t calculated using PaCO2 and PtcCO2 was 0.48 ± 0.09 and 0.53 ± 0.08, respectively, with a strong positive correlation between the two methods of calculation (Pearson's correlation = 0.87, p < 0.05). Bland-Altman analysis showed a mean difference of -0.05 (95% CI: -0.01 to -0.09) between the two methods. PtcCO2 measurements can provide a noninvasive means to measure V d/V t, thus accessing important physiologic information and prognostic assessment in patients receiving mechanical ventilation. [ABSTRACT FROM AUTHOR]

During colonoscopy, air insufflation to distend the lumen and facilitate careful inspection and scope insertion can induce pain and cause discomfort. Carbon dioxide (CO2) insufflation can decrease abdominal pain and discomfort during and after colonoscopy. The advantage of CO2 insufflation is the rapid absorption of the gas across the intestine. Another painless option is water-assisted colonoscopy. Two methods for water-assisted colonoscopy are available: water immersion and water exchange. In a recent direct comparison, the water exchange method was superior to water immersion, CO2 insufflation, and air insufflation with respect to pain during colonoscopy, although it still had the disadvantage of being a time-consuming procedure. Cap-assisted colonoscopy is a simple technique involving the use of a small transparent cap attached to the tip of the scope. Three studies showed an advantage of this technique in terms of reduced patient discomfort compared with the conventional method. Three robotic colonoscopy systems (Endotics System [Era Endoscopy], NeoGuide [NeoGuide Systems Inc.], and Invendoscope [Invendo Medical]) have been introduced to evaluate pain reduction during colonoscopy, but none has been widely adopted and used in practice. In this review, clinical trials of several techniques and new devices for painless colonoscopy are described and summarized. [ABSTRACT FROM AUTHOR]

Purpose: The availability of difficult airway management (DAM) resources and the extent of capnometry use in Japanese intensive care units (ICUs) remained unclear. The purpose of this study was to clarify whether: (1) DAM resources were adequate, and (2) capnometry was routinely applied in Japanese ICUs. Methods: This nationwide cross-sectional study was conducted from September 2015 to February 2016. All ICUs received a mailed questionnaire about their DAM resources and use of capnometry. Outcome measures were availability of: (1) 24-h in-house backup coverage; (2) a supraglottic airway device (SGA); (3) a dedicated DAM cart; and (4) surgical airway devices, and (5) routine use of capnometry to verify tube placement and for continuous monitoring of ventilator-dependent patients. The association between these outcomes and ICU type (academic, high-volume, closed, surgical) was also analyzed. Results: Of the 289 ICUs, 196 (67.8 %) returned completed questionnaires. In-house backup coverage and surgical airway devices were highly available (89.3 and 95.9 %), but SGAs and dedicated DAM carts were not (60.2 and 60.7 %). The routine use of capnometry to confirm tube placement was reported by 55.6 % of the ICUs and was highest in closed ICUs (67.2 %, p = 0.03). The rate of continuous capnography monitoring was also 55.6 % and was highest in academic ICUs (64.5 %, p = 0.04). Conclusion: In Japanese ICUs, SGAs and dedicated DAM carts were less available, and capnometry was not universally applied either to confirm tube placement, or for continuous monitoring of ventilated patients. Our study revealed areas in need of improvement. [ABSTRACT FROM AUTHOR]

New Findings What is the topic of this review? This review highlights the transcriptional consequences for decreased cellular O2 levels (hypoxia) and increased cellular CO2 levels (hypercapnia)., What advances does it highlight? We discuss recent advances in our understanding of the cellular response to hypoxia and consider the potential cross-talk between O2- and CO2-dependent transcriptional regulation., Oxygen and carbon dioxide are the substrate and product of aerobic metabolism, respectively. Thus, the levels of these physiological gases are inextricably linked in physiological and pathophysiological conditions. Increased mitochondrial consumption of O2 (to produce ATP) will produce more CO2. Furthermore, in lung pathologies such as chronic obstructive pulmonary disease, sleep apnoea and central hypoventilation syndrome, hypoxia and hypercapnia are co-incident. Acute responses to hypoxia involve carotid body-mediated changes in the rate and depth of breathing. Chronic adaptation to hypoxia involves a multitude of changes on a transcriptional level, which simultaneously increases oxygen utilization (via hypoxia-inducible factor and others), while suppressing superfluous energy-demanding processes. Acute responses to CO2 affect breathing primarily via central chemoreceptors. The nature of hypercapnia-dependent transcriptional regulation is an emerging area of research, but at present the mechanisms underpinning this response are not fully characterized and understood. Thus, given the juxtaposition of hypoxia and hypercapnia in health and disease, this manuscript reviews the current evidence for transcriptional responses to hypoxia and hypercapnia. Finally, we discuss the potential cross-talk between hypoxia and hypercapnia on a transcriptional level. [ABSTRACT FROM AUTHOR]

Background: Isocapnic hyperventilation (IHV) has the potential to increase the elimination rate of anaesthetic gases and has been shown to shorten time to wake-up and post-operative recovery time after inhalation anaesthesia. In this bench test, we describe a technique to achieve isocapnia during hyperventilation (HV) by adding carbon dioxide (CO2) directly to the breathing circuit of a standard anaesthesia apparatus with standard monitoring equipment.Methods: Into a mechanical lung model, carbon dioxide was added to simulate a CO2 production (V(CO2)) of 175, 200 and 225 ml/min. Dead space (V(D)) volume could be set at 44, 92 and 134 ml. From baseline ventilation (BLV), HV was achieved by doubling the minute ventilation and fresh gas flow for each level of V(CO2), and dead space. During HV, CO2 was delivered (D(CO2)) by a precision flow meter via a mixing box to the inspiratory limb of the anaesthesia circuit to achieve isocapnia.Results: During HV, the alveolar ventilation increased by 113 ± 6%. Tidal volume increased by 20 ± 0.1% during IHV irrespective of V(D) and V(CO2) level. D(CO2) varied between 147 ± 8 and 325 ± 13 ml/min. Low V(CO2) and large V(D) demanded a greater D(CO2) administration to achieve isocapnia. The FICO2 level during IHV varied between 2.3% and 3.3%.Conclusion: It is possible to maintain isocapnia during HV by delivering carbon dioxide through a standard anaesthesia circuit equipped with modern monitoring capacities. From alveolar ventilation, CO2 production and dead space, the amount of carbon dioxide that is needed to achieve IHV can be estimated. [ABSTRACT FROM AUTHOR]

The present paper shows, by means of single-cell recordings, responses of antennal sensory neurons of the damselfly Ischnura elegans when stimulated by air streams at different CO 2 concentrations. Unlike most insects, but similarly to termites, centipedes and ticks, Odonata possess sensory neurons strongly inhibited by CO 2 , with the magnitude of the off-response depending upon the CO 2 concentration. The Odonata antennal sensory neurons responding to CO 2 are also sensitive to airborne odors; in particular, the impulse frequency is increased by isoamylamine and decreased by heptanoic and pentanoic acid. Further behavioral investigations are necessary to assign a biological role to carbon dioxide detection in Odonata. [ABSTRACT FROM AUTHOR]

Objective: In bariatric surgery, arterial carbon dioxide (PaCO2) and oxygen (PaO2) pressures are important but sometimes difficult to measure. The purpose of the present study was to investigate whether transcutaneous carbon dioxide (tcPCO2) and oxygen (tcPO2) pressures can be used to monitor PaCO2 and PaO2, respectively, in laparoscopic bariatric surgery. Methodology: This non-blind, comparadive study was conducted at operating room in the city hospital. Ten adult obese (Body Mass Index (BMI) > 35) patients for laparoscopic bariatric surgery (Bariatric group), and 10 normal weight (BMI < 30) adult patients for open gastric surgery (Control group) were studied. After an epidural catheter insertion at T6-7 or T 7-8, anesthesia was induced with midazolam, propofol, fentanyl, and vecuronium, and was maintained with continuous propofol and remifentanil, intermittent vecuronium and epidural lidocaine. After anesthesia induction, a radial artery catheter was inserted. The electrode of transcutaneous monitor was put on the chest ipsilateral to a radial artery catheter. Pressure controlled ventilation was used in both groups. During surgery at four random points in each patient samples were drawn for arterial blood gas analysis, and measurements of end-tidal carbon dioxide (EtCO2), tcPO2 and tcPCO2 were performed. Results: TcPCO2 and PaCO2 in the control group had good correlation, while no correlation was found in the bariatric group. TcPO2 and PaO2, tcPCO2 and EtCO2, and PaCO2 and EtCO2 had no correlation in both groups. The bias and limits of agreement of tcPCO2 - PaCO2, tcPO2 - PaO2, EtCO2 - tcPCO2, and PaCO2 - EtCO2 were larger in the bariatric group than the control group. Conclusion: Our study concludes that TcPO2 and tcPCO2 cannot be surrogate measurements of PaO2 and PaCO2, respectively in laparoscopic bariatric surgery. [ABSTRACT FROM AUTHOR]

This guideline updates and replaces the 4th edition of the AAGBI Standards of Monitoring published in 2007. The aim of this document is to provide guidance on the minimum standards for physiological monitoring of any patient undergoing anaesthesia or sedation under the care of an anaesthetist. The recommendations are primarily aimed at anaesthetists practising in the United Kingdom and Ireland. Minimum standards for monitoring patients during anaesthesia and in the recovery phase are included. There is also guidance on monitoring patients undergoing sedation and also during transfer of anaesthetised or sedated patients. There are new sections discussing the role of monitoring depth of anaesthesia, neuromuscular blockade and cardiac output. The indications for end-tidal carbon dioxide monitoring have been updated. [ABSTRACT FROM AUTHOR]

Respiratory disturbances frequently accompany stuttering. Their influence on lung ventilation can be assessed by measurement of the end-tidal CO2 concentration (EtCO2). The effectiveness of the CO2-based visual feedback method of breath regulation (VF) designed for stuttering therapy was tested in this study. The aim of the study was to answer the question if the VF helps to reduce respiratory disturbances in stuttering and increase speech fluency. 20 stuttering volunteers aged 13-45 years took part in the 3-parts test consisting of: 1. speaking without any techniques improving speech fluency, 2. learning the VF method, 3. VF-assisted speaking. The CO2/time signal and an acoustic signal of an utterance were recorded during the test. Significant increase of FE -- the factor of breath ergonomics during speaking (based on both signals), from 47% to 71% (P < 0.01), and significant decrease of %SS -- the percent of syllables stuttered, from 14% to 10% (P < 0.01) were received for VF-assisted utterances compared to the utterances without VF assistance. The results indicate that the VF can help to eliminate respiratory disturbances in stuttering and increase speech fluency. [ABSTRACT FROM AUTHOR]

The doubly labeled water (DLW) method is commonly used to measure energy expenditure in free-living wildlife and humans. However, DLW studies involving animals typically require three blood samples, which can affect behavior and wellbeing. Moreover, measurement of H (δ2H) and O (δl8O) isotope concentrations in H2O derived from blood using conventional isotope ratio mass spectrometry is technically demanding, timeconsuming, and often expensive. A novel technique that would avoid these constraints is the real-time measurement of δ2H and δ18O in the H20 vapor of exhaled breath using cavity ring-down (CRD) spectrometry, provided that S2H and δ180 from body H20 and breath were well correlated. Here, we conducted a validation study with CRD spectrometry involving five zebra finches (Taeniopygia guttata), five brown-headed cowbirds (Molothrus ater), and five European starlings (Sturnus vulgaris), where we compared δ2H, δ18O, and rCO 2 (rate of CO2 production) estimates from breath with those from blood. Isotope concentrations from blood were validated by comparing dilution-space estimates with measurements of total body water (TBW) obtained from quantitative magnetic resonance. Isotope dilutionspace estimates from δ2H and δ18O values in the blood were similar to and strongly correlated with TBW measurements (R2 = 0.99). The 2H and18O (ppm) in breath and blood were also highly correlated (R2 = 0.99 and 0.98, respectively); however, isotope concentrations in breath were always less enriched than those in blood and slightly higher than expected, given assumed fractionation values between blood and breath. Overall, rCO 2 measurements from breath were strongly correlated with those from the blood (R2 = 0.90). We suggest that this technique will find wide application in studies of animal and human energetics in the field and laboratory. We also provide suggestions for ways this technique could be further improved. [ABSTRACT FROM AUTHOR]

Background: There may be significant difference between measurement of end-tidal carbon dioxide partial pressure (PetCO2) and arterial carbon dioxide partial pressure (PaCO2) during one-lung ventilation with low tidal volume for thoracic surgeries. Transcutaneous carbon dioxide partial pressure (PtcCO2) monitoring can be used continuously to evaluate PaCO2 in a noninvasive fashion. In this study, we compared the accuracy between PetCO2 and PtcCO2 in predicting PaCO2 during prolonged one-lung ventilation with low tidal volume for thoracic surgeries. Methods: Eighteen adult patients who underwent thoracic surgeries with one-lung ventilation longer than two hours were included in this study. Their PetCO2, PtcCO2, and PaCO2 values were collected at five time points before and during one-lung ventilation. Agreement among measures was evaluated by Bland-Altman analysis. Results: Ninety sample sets were obtained. The bias and precision when PtcCO2 and PaCO2 were compared were 4.1 ± 6.5 mmHg during two-lung ventilation and 2.9 ± 6.1 mmHg during one-lung ventilation. Those when PetCO2 and PaCO2 were compared were -11.8 ± 6.4 mmHg during two-lung ventilation and -11.8 ± 4.9 mmHg during one-lung ventilation. The differences between PtcCO2 and PaCO2 were significantly lower than those between PetCO2 and PaCO2 at all five time-points (p < 0.05). Conclusions: PtcCO2 monitoring was more accurate for predicting PaCO2 levels during prolonged one-lung ventilation with low tidal volume for patients undergoing thoracic surgeries. [ABSTRACT FROM AUTHOR]

Background The Anesthesia Patient Safety Foundation has advocated the use of continuous electronic monitoring of oxygenation and ventilation to preemptively identify opioid-induced respiratory depression. In adults, capnography is the gold standard in respiratory monitoring. An alternative technique used in sleep laboratories is respiratory inductance plethysmography ( RIP). However, it is not known if either monitor is well tolerated by pediatric patients for prolonged periods of time. Aim The goal of this study was to determine whether capnography or RIP is better tolerated in nonintubated, spontaneously breathing pediatric patients being treated with intravenous patient-controlled analgesia ( IVPCA). Methods Nasal cannula capnography with oral sampling and thoracic and abdominal inductance plethysmography bands were placed along with the routine monitors on pediatric patients being treated for acute pain with IVPCA. Study monitors were left in place for as long as they were tolerated by the patient, up to a maximum of 24 consecutive hours. If the patient did not wear a particular study monitor for any reason, but tolerated the remaining monitor, participation in the study continued. If the patient would not wear either monitor, participation was terminated. Results Twenty-six patients (18 female, eight male, average age 10.1 ± 5.5 years) consented to participate, but only 14 patients attempted to wear one or both the devices. Among those who wore either device, median time to device removal was 8.33 h (range 0.3-23.6 h) for capnography and 23.5 h (range 0.7-24 h) for RIP bands. Conclusion Children did not tolerate wearing capnography cannulae for prolonged periods of time, limiting the usefulness of this device as a continuous monitor of ventilation in children. RIP bands were better tolerated; however, they require further assessment of their utility. Until more effective, child-friendly monitors are developed and their utility is validated, guidelines recommended for adult patients cannot be extended to children. [ABSTRACT FROM AUTHOR]

Background: Cachexia affects most patients with incurable cancer. We hypothesize that in metastatic cancer the mass of the tumor as well as its level of anaerobic energy metabolism play a critical role in describing its energetic cost, which results in elevated resting energy expenditure and glucose utilization, leading to cachexia. Prior models of cancer cachexia may have underestimated the specific energetic cost of cancer as they have not taken the range of tumor mass and anaerobic energy metabolism fully into account. Methods: We therefore modelled the energetic cost of cancer as a function of the percentage of energy the cancer produces anaerobically, based on resting energy expenditure, glucose turnover, glucose recycling, and oxygen consumption in cancer patients found in previous studies. Results: Data from two clinical studies where tumor burden was estimated and resting energy expenditure or oxygen consumption were measured lead to a broad range of estimates of tumor cost from 190 to 470 kcal/kg tumor/day. These values will vary based of the percentage of energy the cancer produces anaerobically (from 0 to 100 %), which in and of itself can alter the cost over a 2 to 3-fold range. In addition to the tumor cost/kg and the degree of anaerobic metabolism, the impact on a given individual patient will depend on tumor burden, which can exceed 1 kg in advanced metastatic disease. Considering these dimensions of tumor cost we are able to produce a 2-dimensional map of potential values, with an overall range of 100-1400 kcal/day. Conclusions: Quantifying the energetic cost of cancer may benefit an understanding of the tumor's causation of cachexia. Our estimates of the range of tumor cost include values that are higher than prior estimates and suggest that in metastatic disease the tumor cost could be expected to eclipse attempts to stabilize energy balance through nutrition support or by drug therapies. Tumor mass and the percentage of anaerobic metabolism in the tumor contribute to the cost of the tumor on the body and potentially lead directly to negative energy balance and increased muscle wasting. [ABSTRACT FROM AUTHOR]

Objective: There is limited number of studies conducted on the use of capnography for CO2 monitorization in sleep laboratories. In this study, it was aimed to investigate the correlation between the CO2 value measured by transcutaneous carbon dioxide (tcCO2) monitorization and partial pressure of carbon dioxide (PaCO2) levels measured with arterial blood gas analysis in patients diagnosed with obstructive sleep apnea syndrome (OSAS) and Sleep-related hypoventilation/hypoxemic syndromes (SRHHS). Materials and Methods: Patients with bilevel positive airway pressure (BiPAP) treatment indication who were diagnosed with OSAS and SRHHS via polysomnography (PSG), were prospectively included in the study. Four arterial blood gas analyses were conducted from all participants (preand post-PSG, before and after manual bi-level positive airway pressure titration) in order to find PaCO2 levels against tcCO2 monitorization. Results: Totally 30 patients with sleep-related respiratory disease (SRRD), consisting of 18 patients with OSAS and COPD, and 12 patients with OSAS and obesity hypoventilation syndrome (OHS), were included in the study. A correlation was detected between average tcCO2 level and average PaCO2 level in night PSG (r=0.600; p<0.0001). Similarly, we found a correlation between average tcCO2 level and average PaCO2 level in BiPAP titration night measurements as well (r=0.812; p=0.001). Finally, a correlation was detected between the average PaCO2 value obtained from four blood gas samples measured in both nights and the average tcCO2 value taken from two capnographies (r=0.783; p<0.001). Conclusion: Comparing tcCO2 and PaCO2 values, it was determined that the average CO2 values measured by capnography correlated with the average of simultaneous arterial CO2 values measured before and after BiPAP titration. [ABSTRACT FROM AUTHOR]

Migratory fishes encounter a variety of environmental conditions, including changes in salinity, temperature and dissolved gases, and it is important to understand how these fishes are able to acclimate to multiple environmental stressors. The gill is the primary site of both acid–base balance and ion regulation in fishes. Many ion transport mechanisms involved with acid–base compensation are also required for the regulation of plasma Na+ and Cl+, the predominant extracellular ions, potentially resulting in a strong interaction between ionoregulation and acid–base regulation. The present study examined the physiological interaction of elevated dissolved CO2 (an acid–base disturbance) on osmoregulation during seawater acclimation (an ionoregulatory disturbance) in juvenile white sturgeon (Acipenser transmontanus). Blood pH (pHe), plasma [HCO3−], [Na+], [Cl−] and osmolality, white muscle water content, and gill Na+/K+-ATPase (NKA) and Na+/K+/2Cl− co-transporter (NKCC) abundance were examined over a 10 day seawater (SW) acclimation period under normocarbia (NCSW) or during prior and continued exposure to hypercarbia (HCSW), and compared with a normocarbic freshwater (NCFW) control. Hypercarbia induced a severe extracellular acidosis (from pH 7.65 to pH 7.2) in HCSW sturgeon, and these fish had a 2-fold greater rise in plasma osmolarity over NCSW by day 2 of SW exposure. Interestingly, pHe recovery in HCSW was associated more prominently with an elevation in plasma Na+ prior to osmotic recovery and more prominently with a reduction in plasma Cl− following osmotic recovery, indicating a biphasic response as the requirements of osmoregulation transitioned from ion-uptake to ion-excretion throughout SW acclimation. These results imply a prioritization of osmoregulatory recovery over acid–base recovery in this period of combined exposure to acid–base and ionoregulatory disturbances. [ABSTRACT FROM AUTHOR]

The ability to accurately verify facial identity has important forensic implications, but this ability is fallible. Research suggests that anxiety at the time of encoding can impair subsequent recall, but no studies have investigated the effects of anxiety at the time of recall in an experimental paradigm. This study addresses this gap using the carbon dioxide (CO 2 ) model of anxiety induction. Thirty participants completed two inhalations: one of 7.5% CO 2 -enriched air and one of medical air (i.e., placebo). Prior to each inhalation, participants were presented with 16 facial images (50% own-ethnicity, 50% other-ethnicity). During the inhalation they were required to identify which faces had been seen before from a set of 32 images (16 seen-before and 16 novel images). Identification accuracy was lower during CO 2 inhalation compared to air ( F [1,29] = 5.5, p = .026, η p 2 = .16), and false alarm rate was higher for other-ethnicity faces compared to own-ethnicity faces ( F [1,29] = 11.3, p = .002, η p 2 = .28). There was no evidence of gas by ethnicity interactions for accuracy or false alarms ( p s > .34). Ratings of decision confidence did not differ by gas condition, suggesting that participants were unaware of differences in performance. These findings suggest that anxiety, at the point of recognition, impairs facial identification accuracy. This has substantial implications for eyewitness memory situations, and suggests that efforts should be made to attenuate the anxiety in these situations in order to improve the validity of identification. [ABSTRACT FROM AUTHOR]

This article describes the use of a time cycled flow generating pressure limited mechanical ventilator in combination with a Mapleson E circuit using an 'air piston'. The use of controlled rebreathing to maintain a normal end-tidal carbon dioxide concentration is explained, in combination with the practicalities of setting up the system. [ABSTRACT FROM AUTHOR]

Blood gas and tissue pH regulation depend on the ability of the brain to sense CO2 and/or H+ and alter breathing appropriately, a homeostatic process called central respiratory chemosensitivity. We show that selective expression of the proton-activated receptor GPR4 in chemosensory neurons of the mouse retrotrapezoid nucleus (RTN) is required for CO2-stimulated breathing. Genetic deletion of GPR4 disrupted acidosis-dependent activation of RTN neurons, increased apnea frequency, and blunted ventilatory responses to CO2. Reintroduction of GPR4 into RTN neurons restored CO2-dependent RTN neuronal activation and rescued the ventilatory phenotype. Additional elimination of TASK-2 (K2P5), a pH-sensitive K+ channel expressed in RTN neurons, essentially abolished the ventilatory response to CO2. The data identify GPR4 and TASK-2 as distinct, parallel, and essential central mediators of respiratory chemosensitivity. [ABSTRACT FROM AUTHOR]

The article discusses a study which tested the hypothesis that decreased end-tidal carbon dioxide (CO2) by cardiopulmonary exercise testing predicts central sleep apnea (CSA) in heart failure (HF) patients. Topics covered include the methods used to evaluate CO2 chemosensitivity, the measures used in the study, and the association of ventilatory drive in CO2 chemosensitivity and arterial CO2 set point.

A two-stage rotating packed bed with nickel foam packing (TSNF-RPB) was developed with the purpose of simplifying the combination of rotational packing and static rings in the rotor of a two-stage counter-current rotating packed bed (TSCC-RPB). A novel method called “five-point” was employed to determine the CO 2 absorption efficiency ( η ) and the effective interfacial area ( a e ) in this TSNF-RPB. Experimental results showed that the CO 2 absorption efficiency of the upper and the lower packing zones were obviously higher than that of the upper and the lower cavity zones at different rotational speed, gas and liquid flow rate. Values of a e of the upper packing zone were higher than that of the lower packing zone when the nickel foam packing with pore size of 0.64 mm was loaded. The TSNF-RPB has potential prospects for the applications of chemical processes which require long gas–liquid contact time. [ABSTRACT FROM AUTHOR]

Serotonin (5-hydroxytryptamine, 5-HT) neurons from the mouse and rat rostral medulla are stimulated by increased CO2 when studied in culture or brain slices. However, the response of 5-HT neurons has been variable when animals are exposed to hypercapnia in vivo. Here we examined whether halogenated inhalational anesthetics, which activate TWIK-related acid-sensitive K+ (TASK) channels, could mask an effect of CO2 on 5-HT neurons. During in vivo plethysmography in mice, isoflurane (1%) markedly reduced the hypercapnic ventilatory response (HCVR) by 78-96% depending upon mouse strain and ambient temperature. In a perfused rat brain stem preparation, isoflurane (1%) reduced or silenced spontaneous firing of medullary 5-HT neurons in situ and abolished their responses to elevated perfusate PCO2. In dissociated cell cultures, isoflurane (1%) hyperpolarized 5-HT neurons by 6.52 ± 3.94 mV and inhibited spontaneous firing. A subsequent decrease in pH from 7.4 to 7.2 depolarized neurons by 4.07 ± 2.10 mV, but that was insufficient to reach threshold for firing. Depolarizing current restored baseline firing and the firing frequency response to acidosis, indicating that isoflurane did not block the underlying mechanisms mediating chemosensitivity. These results demonstrate that isoflurane masks 5-HT neuron chemosensitivity in vitro and in situ and markedly decreases the HCVR in vivo. The use of this class of anesthetic has a particularly potent inhibitory effect on chemosensitivity of 5-HT neurons. [ABSTRACT FROM AUTHOR]

Background: The maximal oxygen uptake (VO2máx) assessment by indirect calorimetry is the most reliable method to determine VO2máx, but when repeated tests are conducted, the results have been controversial. Aim: To determine the reliability of the maximal oxygen uptake (VO2máx) in healthy adults following two consecutive trials with 10 min rest between trials using the Bruce protocol. Methods: Participants were 6 males apparently healthy physically active (Mean age=23,4±1,3 years), who performed twice the Bruce protocol and after reaching their VO2máx in the first trial they stepped down the treadmill and rested seated on a chair during 10 min. Results: The data analysis showed high reproducibility values between tests, indicated by the correlation coefficient Pearson product moment and R squared with confidence intervals at 95% (CI95%), the correlation of the maximum oxygen consumption was VO2máx=0.907 with a R²=0.823, the maximum heart rate was HR2máx=0.786, with R²=0.618 and the rate of ventilation and carbon dioxide elimination was VE/ACO2=0.868, with an R²=754. No adverse effects were reported during the 10 min rest between trials. Conclusion: Resting 10 min between consecutive maximal exercise tests using Bruce protocol treadmill tests does not affect VO2máx in healthy young adults. It is feasible and reliable to perform maximal treadmill tests in a single session without adverse effects for the participant. [ABSTRACT FROM AUTHOR]

In liver diagnostics, a simple, non-invasive test with high sensitivity and specificity is permanently being sought in order to assess the degree of liver damage. In addition to liver biopsy, algorithms using blood parameters or elastometry are used in clinical practice. However, these methods do not provide information about the true liver reserve, so the liver breath test seem to be a promising diagnostic tool. The basis of this test depends on the ability of particular hepatocyte enzyme systems to metabolise a tested substance labelled with a stable carbon isotope. The kinetics of 13CO2 elimination with expiratory air then permits quantitative assessment of the functional liver reserve and the degree of organ damage. In this paper the most commonly used tests, grouped according to the main metabolic pathways, are described. The usefulness of liver breath tests in specific clinical situations, both as a diagnostic and prognostic tool, is presented. [ABSTRACT FROM AUTHOR]