Transcutaneous Carbon Dioxide Measurement in Adult Patients with Neuromuscular Disorders: A quality Level Assessment

Background: Carbon dioxide tension (PCO2) monitoring during sleep, is crucial to identify respiratory failure in patients with neuromuscular disorders (NMD). Transcutaneous PCO2 monitoring is an available technique to measure PCO2. Objectives: To assess the quality level of transcutaneous blood gas measurements via SenTec monitor. Methods: A 12-month analysis of SenTec measurements was conducted in a Belgian Centre for Home Mechanical Ventilation (HMV). Over two consecutive nights; SpO2 and PCO2 measurements, the presence of PCO2 drift and drift correction with SenTec, were reviewed and scores (0, 1, 2 for poor, medium and high level) were assigned to estimate the quality of measurements. Results: Sixty-nine NMD patients met the inclusion criteria, of which 48/69 used HMV. PCO2 drift and drift correction were present in 15% and 68% of the 138 recordings, respectively. The quality level of measurements throughout night 1, scored 1.55 (0–2). The relevance of our clinical findings from SenTec scoring 1.94 (1–2); was considered highly satisfactory. HMV was ineffective in 24/48 patients. Among 12 patients with hypercapnia, 8 patients improved PCO2 between night 1 and 2. Among 12 patients with hypocapnia, PCO2 improved in 4/12 patients, who reached the range of normal PCO2 (35–47 mmHg). Conclusions: The quality of SenTec measurements was acceptable in the majority of recordings and clinical findings were deemed satisfactory in all cases. A single SenTec measurement was sufficient to determine the need for NIV. However, two SenTec registrations were insufficient to both improve NIV effectiveness in 50% of cases, and, to ensure follow-up of our interventions.

Novel Carbon Dioxide-Based Method for Accurate Determination of pH and pCO2 in Mammalian Cell Culture Processes

In mammalian cell culture, especially in pharmaceutical manufacturing, pH is a critical process parameter that has to be controlled as accurately as possible. Not only does pH directly affect cell culture performance, ensuring a comparable pH is also crucial for scaling and transfer of processes. A sample-based offline pH measurement is commonly used to ensure correct bioreactor pH probe signals after sterilization and as a detection measure for drifts of probe signals. However, the sample-based pH offline measurement does not necessarily deliver required accuracy. Offsets between bioreactor pH and sample pH heavily depend on equipment, local procedures and the offline measurement method that is used. This article adequately describes a novel, non-invasive method to determine pH and pCO2 in sterile bioreactors without the need to sample and measure offline. This method utilizes the chemical correlation between carbon dioxide in the gas phase, dissolved carbon dioxide, bicarbonate and dependent proton concentrations that directly affect the pH in carbonate buffered systems. The proposed carbon dioxide-based pH reference method thereby is able to accurately determine the true pH in the bioreactor without the need to sample. The proposed method is independent of scale and bioreactor configuration and does not depend on local procedures that may differ between sites, scales or operators. Applicability of the method for both stainless steel and single use bioreactors is shown. Furthermore, the very same principles are applicable for non-invasive, online pCO2 monitoring.

Experimental Study of Pyrite Oxidation at 100 °C: Implications for Deep Geological Radwaste Repository in Claystone

The oxidation of pyrite is one of the near field processes of the chemical evolution of clay rock planned to host a deep geological radioactive waste repository during operation. Indeed, this process can lead to transitory acidic conditions in the medium (i.e., production of sulphuric acid, carbonic acid) which may influence the corrosion kinetics of the carbon steel components of some disposal cells. In order to improve the geochemical modelling of the long-term disposal, the oxidation of pyrite in contact with clays and carbonates at 100 °C must be evaluated. In this study, special attention was paid to the pyrite oxidation rate thanks to an original experimental set-up, involving several pyrite/mineral mixtures and a reactor coupled to a micro gas chromatograph (PO2 and PCO2 monitoring). Although thermodynamic modelling expects that hematite is the most stable phase in a pure pyrite heated system (low pH), experiments show the formation of native sulfur as an intermediate product of the reaction. In the presence of calcite, the pH is neutralized and drives the lower reactivity of pyrite in the absence of native sulfur. The addition of clay phases or other detrital silicates from the claystone had no impact on pyrite oxidation rate. The discrepancies between experiments and thermodynamic modelling are explained by kinetic effects. Two laws were deduced at 100 °C. The first concerns a pure pyrite system, with the following law: r P y = 10 − 4.8 · P O 2 0.5 · t − 0.5 . The second concerns a pyrite/carbonates system: r P y + C a = 10 − 5.1 · P O 2 0.5 · t − 0.5 where PO2 corresponds to the partial pressure of O2 (in bar) and t is time in seconds. Different mechanisms are proposed to explain the evolution with time of the O2 consumption during pyrite oxidation: (i) decrease of the specific or reactive surface area after oxidation of fine grains of pyrite, (ii) decrease of O2 pressure, (iii) growing up of secondary minerals (Fe-oxides or anhydrite in the presence of calcium in the system) on the surface of pyrite limiting the access of O2 to the fresh surface of pyrite, and (iv) change in the pH of the solution.

Recent Advances Of Mucosal Capnometry And The Perspectives Of Gastrointestinal Monitoring In The Critically Ill. A Pilot Study

Mucosal capnometry involves the monitoring of partial pressure of carbon dioxide (PCO2) in mucous membranes. Different techniques have been developed and applied for this purpose, including sublingual or buccal sensors, or special gastrointestinal tonometric devices. The primary use of these procedures is to detect compensated shock in critically ill patients or patients undergoing major surgery. Compensatory mechanisms, in the early phases of shock, lead to the redistribution of blood flow towards the vital organs, within ostensibly typical macro-haemodynamic parameters. Unfortunately, this may result in microcirculatory disturbances, which can play a pivotal role in the development of organ failure. In such circumstances mucosal capnometry monitoring, at different gastrointestinal sites, can provide a sensitive method for the early diagnosis of shock. The special PCO2 monitoring methods assess the severity of ischaemia and help to define the necessary therapeutic interventions and testing of these monitors have justified their prognostic value. Gastrointestinal mucosal capnometry monitoring also helps in determining the severity of ischaemia and is a useful adjunctive in the diagnosis of occlusive splanchnic arterial diseases. The supplementary functional information increases the diagnostic accuracy of radiological techniques, assists in creating individualized treatment plans, and helps in follow-up the results of interventions. The results of a pilot study focusing on the interrelation of splanchnic perfusion and gastrointestinal function are given and discussed concerning recent advances in mucosal capnometry.