Validation of a New Transcutaneous tcPO2/tcPCO2 Sensor with an Optical Oxygen Measurement in Preterm Neonates

Metabolic Profiles of Critical Care Patients to Confirm Sepsis and Further Understand the Metabolic Phenotype of Sepsis

Sepsis remains a major concern in health care globally. Despite decades of research, incidence is on the rise, and mortality remains high. Costs are staggering. Additionally, the outdated sepsis bundle established based on SIRS, remains the standard by which providers are held accountable. It is now accepted that organ dysfunction in sepsis is secondary to cellular metabolic dysregulation. Technology for metabolic monitoring should be explored for improved, early recognition of sepsis. We sought to investigate the underlying metabolic profile of patients with sepsis, to determine the value of continuous metabolic monitoring technology. The investigators partnered with industry, to trial noninvasive monitoring of the cellular metabolite carbon dioxide, under a prospective, observational design. During the 6-month trial, the investigators collected data from the electronic medical record of patients using the technology, to determine the specific metabolic differences between patients with and without sepsis. The investigators found serum carbon dioxide (paCO2) was significantly lower in patients with sepsis, and, low paCO2 had a significant inverse relationship to serum lactate. This finding supports the notion that paCO2 is low in sepsis secondary to metabolic dysregulation and not hyperventilation, which had historically explained low paCO2 under the SIRS model. Metabolic monitoring is available, easy to apply and manage, and contributes valuable information in the detection of sepsis. Further research should be done to understand trends in serum CO2 and its relationship to the development of sepsis. This study also provides important further support for the emerging understanding of the dysregulated host response in sepsis.

A Moving Target: Studying the Effect of Continuous Transcutaneous CO2 Monitoring in ELBW Infants During an Equipoise Shift

Objectives: To assess whether continuous non-invasive pCO2 monitoring by transcutaneous pCO2 monitor (TCpCO2) among extremely low birth weight (ELBW) premature infants, during the first week of life, will decrease the rate of high-grade intraventricular hemorrhage (IVH) or periventricular leukomalacia (PVL) or the combined outcome of IVH/PVL and death. Methods: This was a prospective, observational, multicenter study. Due to ethical constraints, allocation was based on TCpCO2 monitor availability. ELBW infants were either monitored by TCpCO2 monitor (Sentec, Therwil, Switzerland) (study group), or recruited to the control group if a TCpCO2 monitor was not available. Results: A total of 132 ELBW infants participated in the study. The size of the study group (106 infants) and the control group (26 infants) differed because monitor availability increased during the study period reflecting change in standard of care. The groups had comparable gestational age and baseline characteristics. No difference was found in the rate of IVH/PVL in the study vs. control groups (10% vs. 4%; p = 0.7, respectively), or in the combined outcome of PVL/IVH and death (16% vs. 15%; p = 1.0, respectively). Conclusions: This study demonstrates the challenges in conducting a prospective controlled trial in a rapidly evolving medical field. While the study began with a clear equipoise, this balance shifted as the care team gained more experience with TCpCO2 monitoring among the study population, despite the absence of new clinical evidence to justify such a shift. Consequently, the small control group limited our ability to draw definitive conclusions regarding the study's objective. However, our findings may increase awareness of continuous non-invasive pCO2 monitoring in extremely premature infants.

Enhancing the estimation of PaCO2 from etCO2 during ventilation through non-invasive parameters in the ovine model

BACKGROUND

In mechanically ventilated neonates, the arterial partial pressure of CO 2 ( PaCO 2 ) is an important indicator for the adequacy of ventilation settings. Determining the PaCO 2 is commonly done using invasive blood gas analyses, which constitute risks for neonates and are typically only available infrequently. An accurate, reliable, and continuous estimation of PaCO 2 is of high interest for medical staff, giving the possibility of a closer monitoring and faster reactions to changes. We aim to present a non-invasive estimation method for PaCO 2 in neonates on the basis of end-tidal CO 2 ( etCO 2 ) with inclusion of different physiological and ventilation parameters. The estimation method should be more accurate than an estimation by unaltered etCO 2 measurements with regard to the mean absolute error and the standard deviation.

METHODS

Secondary data from 51 preterm lambs are used, due to its high comparability to preterm human data. We utilize robust linear regression on 863 PaCO 2 measurements below or equal to 75 mmHg from the first day of life. etCO 2 along with a set of ventilation settings and measurements as well as vital parameters are included in the regression. Included independent variables are chosen iteratively by highest Pearson correlation to the remaining estimation deviation.

RESULTS

The evaluation is carried out on 12 additional neonatal lambs with 246 PaCO 2 measurements below or equal to 75 mmHg from the first two days of life. The estimation method shows a mean absolute error of 3.80 mmHg with a 4.92 mmHg standard deviation of differences and a standard error of 0.31 mmHg in comparison to measured PaCO 2 by blood gas analysis.

CONCLUSIONS

The estimation of PaCO 2 by the proposed equation is less biased than unaltered etCO 2 . The usage of this method in clinical practice or in applications like the automation of ventilation needs further investigation.

Implementation Techniques for Transcutaneous Carbon Dioxide Monitoring: Approaches for Wearable Smart Health Applications

Wearable smart health applications aim to continuously monitor critical physiological parameters without disrupting patients' daily activities, such as giving a blood sample for lab analysis. For example, the partial pressure of arterial carbon dioxide, the critical indicator of ventilation efficacy reflecting the respiratory and acid-base status of the human body, is measured invasively from the arteries. Therefore, it can momentarily be monitored in a clinical setting when the arterial blood sample is taken. Although a noninvasive surrogate method for estimating the partial pressure of arterial carbon dioxide exists (i.e., transcutaneous carbon dioxide monitoring), it is primarily limited to intensive care units and comes in the form of a large bedside device. Nevertheless, recent advancements in the luminescence sensing field have enabled a promising technology that can be incorporated into a wearable device for the continuous and remote monitoring of ventilation efficacy. In this review, we examine existing and nascent techniques for sensing transcutaneous carbon dioxide and highlight novel wearable transcutaneous carbon dioxide monitors by comparing their performance with the traditional bedside counterparts. We also discuss future directions of transcutaneous carbon dioxide monitoring in next-generation smart health applications.

Transcutaneous CO2 Monitoring in Extremely Low Birth Weight Premature Infants

Extremely low birth weight (ELBW) premature infants are particularly susceptible to hypocarbia and hypercarbia, which are associated with brain and lung morbidities. Transcutaneous CO2 (TcCO2) monitoring allows for continuous non-invasive CO2 monitoring during invasive and non-invasive ventilation and is becoming more popular in the NICU. We aimed to evaluate the correlation and agreement between CO2 levels measured by a TcCO2 monitor and blood gas CO2 (bgCO2) among ELBW infants. This was a prospective observational multicenter study. All infants < 1000 g admitted to the participating NICUs during the study period were monitored by a TcCO2 monitor, if available. For each bgCO2 measured, a simultaneous TcCO2 measurement was documented. In total, 1828 pairs of TcCO2-bgCO2 values of 94 infants were collected, with a median (IQR) gestational age of 26.4 (26.0, 28.3) weeks and birth weight of 800 (702, 900) g. A moderate correlation (Pearson: r = 0.64) and good agreement (bias (95% limits of agreement)):(2.9 [-11.8, 17.6] mmHg) were found between the TcCO2 and bgCO2 values in the 25-70 mmHg TcCO2 range. The correlation between the TcCO2 and bgCO2 trends was moderate. CO2 measurements by TcCO2 are in good agreement (bias < 5 mmHg) with bgCO2 among premature infants < 1000 g during the first week of life, regardless of day of life, ventilation mode (invasive/non-invasive), and sampling method (arterial/capillary/venous). However, wide limits of agreement and moderate correlation dictate the use of TcCO2 as a complementary tool to blood gas sampling, to assess CO2 levels and trends in individual patients.

A Transcutaneous Carbon Dioxide Monitor Based on Time-Domain Dual Lifetime Referencing

The partial pressure of arterial carbon dioxide plays a critical role in assessing the acid-base and respiratory status of the human body. Typically, this measurement is invasive and can only be taken momentarily when an arterial blood sample is drawn. Transcutaneous monitoring is a noninvasive surrogate method that provides a continuous measure of arterial carbon dioxide. Unfortunately, current technology is limited to bedside instruments mainly used in intensive care units. We developed a first-of-its-kind miniaturized transcutaneous carbon dioxide monitor that utilizes a luminescence sensing film and a time-domain dual lifetime referencing method. Gas cell experiments confirmed the monitor's ability to accurately identify changes in the partial pressure of carbon dioxide within the clinically significant range. Compared to the luminescence intensity-based technique, the time-domain dual lifetime referencing method is less prone to measurement errors caused by changes in excitation strength, reducing the maximum error from  ∼ 40% to  ∼ 3% and resulting in more reliable readings. Additionally, we analyzed the sensing film by investigating its behavior under various confounding factors and its susceptibility to measurement drift. Finally, a human subject test demonstrated the effectiveness of the applied method in detecting even slight changes in transcutaneous carbon dioxide, as small as  ∼ 0.7%, during hyperventilation. The prototype, which consumes 30.1 mW of power, is a wearable wristband with compact dimensions of 37 mm× 32 mm.

European Consensus Guidelines on the Management of Respiratory Distress Syndrome: 2022 Update

Respiratory distress syndrome (RDS) care pathways evolve slowly as new evidence emerges. We report the sixth version of "European Guidelines for the Management of RDS" by a panel of experienced European neonatologists and an expert perinatal obstetrician based on available literature up to end of 2022. Optimising outcome for babies with RDS includes prediction of risk of preterm delivery, appropriate maternal transfer to a perinatal centre, and appropriate and timely use of antenatal steroids. Evidence-based lung-protective management includes initiation of non-invasive respiratory support from birth, judicious use of oxygen, early surfactant administration, caffeine therapy, and avoidance of intubation and mechanical ventilation where possible. Methods of ongoing non-invasive respiratory support have been further refined and may help reduce chronic lung disease. As technology for delivering mechanical ventilation improves, the risk of causing lung injury should decrease, although minimising time spent on mechanical ventilation by targeted use of postnatal corticosteroids remains essential. The general care of infants with RDS is also reviewed, including emphasis on appropriate cardiovascular support and judicious use of antibiotics as being important determinants of best outcome. We would like to dedicate this guideline to the memory of Professor Henry Halliday who died on November 12, 2022.These updated guidelines contain evidence from recent Cochrane reviews and medical literature since 2019. Strength of evidence supporting recommendations has been evaluated using the GRADE system. There are changes to some of the previous recommendations as well as some changes to the strength of evidence supporting recommendations that have not changed. This guideline has been endorsed by the European Society for Paediatric Research (ESPR) and the Union of European Neonatal and Perinatal Societies (UENPS).

Oxygenation in the NICU: there is more to it than meets the eye

Dormishian and colleagues in their study address an issue that care teams in the NICU encounter on a daily basis, regarding motion artifacts during oxygenation monitoring. In our commentary, we discuss the available tools that allow continuous noninvasive monitoring of oxygenation in the NICU, and modalities that increase the time premature infants spend in the desired SpO₂ range and impact their clinical outcomes.

Real-Time Monitoring of Blood Parameters in the Intensive Care Unit: State-of-the-Art and Perspectives

The number of patients in intensive care units has increased over the past years. Critically ill patients are treated with a real time support of the instruments that offer monitoring of relevant blood parameters. These parameters include blood gases, lactate, and glucose, as well as pH and temperature. Considering the COVID-19 pandemic, continuous management of dynamic deteriorating parameters in patients is more relevant than ever before. This narrative review aims to summarize the currently available literature regarding real-time monitoring of blood parameters in intensive care. Both, invasive and non-invasive methods are described in detail and discussed in terms of general advantages and disadvantages particularly in context of their use in different medical fields but especially in critical care. The objective is to explicate both, well-known and frequently used as well as relatively unknown devices. Furtehrmore, potential future direction in research and development of realtime sensor systems are discussed. Therefore, the discussion section provides a brief description of current developments in biosensing with special emphasis on their technical implementation. In connection with these developments, the authors focus on different electrochemical approaches to invasive and non-invasive measurements in vivo.

Accuracy of a Novel Transcutaneous PCO2 and PO2 Sensor with Optical PO2 Measurement in Neonatal Intensive Care: A Single-Centre Prospective Clinical Trial

BACKGROUND AND OBJECTIVES

Transcutaneous PCO2 and PO2 measurement systems offer non-invasive blood gas trend monitoring. The aim of this prospective study was to assess bias and precision of a transcutaneous PCO2 and PO2 measurement system incorporating a novel pO2 sensor (Sentec OxiVenT™) in neonates ≥34 weeks of gestational age (GA) admitted to intensive care.

METHODS

Transcutaneous PCO2 and PO2 were compared to arterial and capillary blood gas measurements. Bias and precision were calculated by fitting linear mixed models to account for repeated measurements, and influence of clinical covariates on bias and precision was assessed.

RESULTS

We obtained 611 paired transcutaneous and blood gas measurements in 110 patients (median GA 38.3 [interquartile range 36.1-39.7] weeks; age 9 [4-15] days; weight 3,000 [2,500-3,500] g). Transcutaneous PCO2 showed significant bias to arterial PCO2 (+0.61; 95% confidence interval 0.46, 0.76 kPa), but not to capillary PCO2 (-0.23; -0.46, 0.002 kPa). Bias of transcutaneous PO2 was significant to arterial PO2 (-2.50; -2.94, -2.06 kPa), while no significant bias compared to capillary PO2 was observed (+0.17; -0.30, 0.64 kPa). Precision intervals were ±1.8/2.0 kPa for arterial versus capillary PCO2 and ±4.9/3.3 kPa for arterial versus capillary PO2 comparisons, respectively. Further, sensor operating temperature (43°C vs. 42°C), soft tissue oedema, vasoactive drugs, weight, and GA significantly altered bias (p < 0.05).

CONCLUSIONS

The tested transcutaneous blood gas measurement system showed no significant bias compared to capillary PCO2 and PO2, acceptable bias to arterial PCO2, and limited agreement with arterial PO2. Precision intervals were wide for all comparisons.