A carbon dioxide monitor that does not show the waveform has value.

Newborns may require ventilatory support after birth; hence, confirmation of correct tracheal tube placement is vital. The most suitable method to determine intubation success and monitoring of carbon dioxide is a matter of contention, specifically regarding the use of capnography in the newborn population. In 2018, a UK survey on airway management in neonatal intensive care reported that only 18% of units always used capnography during neonatal tracheal intubations. The authors made recommendations for waveform capnography to be available and more widely implemented in order to improve safety [1]. Such recommendations, however, were extrapolated from studies in adult intensive care. The results of that survey [1] were thus met with scepticism from members of the British Association of Perinatal Medicine (BAPM), which highlighted differences in physiological characteristics of newborn infants compared with adults. Furthermore, BAPM emphasised alternative techniques in determining intubation success in neonates, such as qualitative colorimetric devices, flow sensors and clinical judgement [2]. The development of devices more suitable for use in newborns has subsequently provided clinicians with the means to continuously and non-invasively monitor carbon dioxide during resuscitation and mechanical ventilation. Novel capnographs are lightweight and have a small dead space, and are thus ideal for use in the newborn population. Indeed end-tidal carbon dioxide (ETCO2) values from small dead space sidestream capnographs have been shown to accurately reflect alveolar carbon dioxide levels in a cohort of healthy infants [3]. Capnography could also be utilised to alert clinicians to changing pulmonary pathology, with greater divergence of the end-tidal, compared with the arterial, carbon dioxide in those with more severe disease [4]. We therefore aimed to describe current clinical practice in UK neonatal units with respect to non-invasive carbon dioxide monitoring, specifically the use of capnography. All level two and level three neonatal ICUs (151 units) within the UK were identified from the BAPM Neonatal Network. The survey took place between January and May 2021 using a structured online questionnaire. Units that did not complete the survey online were followed-up with a maximum of three telephone calls by a member of the research team, with responses sought from senior clinical staff (as a minimum a registrar or band 7 nurse). A total of 126 (83.4%) units provided a complete response, 72/80 (90%) were level two and 54/71 (76.1%) were level three units. A total of 104 (82.5%) units reported monitoring carbon dioxide during all intubations. Seventy-nine (62.7%) units utilised colorimetric devices to confirm tracheal tube placement. Thirty-five (27.8%) reported use of continuous capnography monitoring, of which 10 (7.9%) also used qualitative colorimetry. Videolaryngoscopy was used to confirm successful intubation in 26 (20.6%) units. Furthermore, 23 (18.3%) confirmed tracheal tube position using clinical interpretation and chest radiography. Regarding the utility of capnography on the neonatal unit, 43 (34.1%) confirmed it formed part of routine clinical care. Specific criteria and other clinical settings for capnography use are shown in Table 1. Regarding capnography interpretation during day-to-day practice in neonatal intensive care, 14 (32.6%) units utilised only the ETCO2 value, six (13.9%) evaluated the carbon dioxide waveform trace and 21 (49%) reported evaluating both the ETCO2 value and the waveform in combination. Thirty-nine (30.9%) confirmed that capnography was part of their difficult airway trolley. We found that exhaled carbon dioxide monitoring during tracheal intubation was undertaken by over 80% of neonatal units in the UK, with the majority utilising qualitative methods. Previous concern was expressed over the lack of routine monitoring of exhaled carbon dioxide during neonatal intubation [1]; however, the 2018 survey considered only capnography to be an appropriate monitoring tool. Our results demonstrate that neonatal intensivists do now routinely monitor carbon dioxide during tracheal intubation, utilising either qualitative or quantitative methods. Indeed, one colorimetric ETCO2 device was shown to be 91% sensitive and 100% specific in confirming tracheal tube placement during neonatal resuscitation [5]. Quantitative waveform analysis during newborn resuscitation has, however, been shown to detect ETCO2 more rapidly than qualitative methods [6]. In conclusion, exhaled carbon dioxide during tracheal intubation is now monitored in the majority of neonatal units, but this is usually undertaken by qualitative methods despite increasing evidence that the new capnography devices are useable and accurate in the neonatal population. EW was supported by a grant from the Charles Wolfson Charitable Trust and a non-conditional educational grant from SLE. This research was supported by the National Institute for Health Research Biomedical Research Centre at Guy's and St Thomas' NHS Foundation Trust and King's College London. No competing interests declared.

The use of end-tidal carbon dioxide (FCO2) monitoring for confirmation of placement of tracheal tubes after intubation is mandatory in the operating theatre setting. Intubation in the intensive care unit (ICU) is a common procedure undertaken by trainees. Critically ill patients can pose specific technical difficulties during tracheal intubation. This survey was undertaken to investigate the use of FCO2 in ICUs across the United Kingdom for confirming tracheal tube placement. Anonymous questionnaires were sent to either the Lead Clinician or the Clinical Director of randomly selected general adult ICUs. One hundred and twenty-seven replies were received out of 215 questionnaires sent (response rate 59%). Twenty percent of ICUs did not have FCO2 monitoring, 20% had one carbon dioxide monitor per bed and 60% had one carbon dioxide monitor for multiple beds. A carbon dioxide monitor was used to confirm placement of tracheal tubes in only half of the ICUs which had one. Of these ICUs, the monitor was used for every intubation in only a third. Seventy-two percent of the respondents felt that FCO2 monitoring was better suited to confirm correct placement of the tracheal tube in critically ill patients than other methods, while 50% did not think that such monitoring should be mandatory for intubations outside the operating theatre. Half of the respondents from units without carbon dioxide monitors cited lack of resources as one of the reasons. Although four out of five intensive care units surveyed had a carbon dioxide monitor, only a small proportion of intensivists used it to confirm correct placement of the tracheal tube after intubation.

End-tidal carbon dioxide (EtCO2) measurement is an intriguing technology because it is non-invasive, portable, and reasonably inexpensive. The method has been widely used in the adult and paediatric intensive care settings, and it has been shown to be an accurate method of estimating PaCO2 in term infants; however, it has not been widely accepted in the NICU because it only provides a rough estimate of PaCO2 in infants with remarkable lung function. EtCO2 detectors determine the amount of carbon dioxide in exhaled breath. EtCO2 is carbon dioxide at its peak concentration at the end of expiration. A good end-tidal plateau in exhaled PaCO2 typically represents alveolar PaCO2, which is easily measurable in adults and older children with large tidal volumes. However, this can be strenuous in sick neonates who frequently have a fast respiratory rate. The carbon dioxide can be calculated by chemical response, referred to as calorimetry or actual measurement of carbon dioxide molecules. 1 The latter method is a better metric in intensive care since it delivers a numerical value. Carbon dioxide monitors are classified into two types: capnometers and capnographs, which employ infrared absorption or mass spectrometry to measure carbon dioxide and display the result in mmHg or percentage of carbon dioxide. The capnometer displays EtCO2 values, whereas the capnograph, which monitors carbon dioxide during each inspiratory/expiratory cycle, shows both a waveform and a numerical number 2. Capnometry, which measures the concentration of carbon dioxide (CO2) in the atmosphere, was originally employed during World War II to monitor the interior environment. It was originally used in medicine in 1950 to monitor the amount of CO2 exhaled during anaesthesia. However, it was not employed in practice until the early 1980s, when capnometry made its official debut in the anaesthesiology area with the introduction of smaller devices. There are two sorts of capnographs: "side stream" and "mainstream". The "mainstream" technique uses a sample window in the ventilator circuit to measure CO2, whereas the "side stream" technique uses a gas analyser outside of the ventilator circuit. Both types of gas analysers use infrared light, mass or Raman spectra, and photoacoustic spectra technology. The volumetric capnograph makes use of flow measurement equipment 3.

Transcutaneous carbon dioxide (PtcCO2) monitoring is known to be effective at estimating the arterial partial pressure of carbon dioxide (PaCO2) in patients with sedation-induced respiratory depression. We aimed to investigate the accuracy of PtcCO2 monitoring to measure PaCO2 and its sensitivity to detect hypercapnia (PaCO2 > 60 mmHg) compared to nasal end-tidal carbon dioxide (PetCO2) monitoring during non-intubated video-assisted thoracoscopic surgery (VATS). This retrospective study included patients undergoing non-intubated VATS from December 2019 to May 2021. Datasets of PetCO2, PtcCO2, and PaCO2 measured simultaneously were extracted from patient records. Overall, 111 datasets of CO2 monitoring during one-lung ventilation (OLV) were collected from 43 patients. PtcCO2 had higher sensitivity and predictive power for hypercapnia during OLV than PetCO2 (84.6% vs. 15.4%, p < 0.001; area under the receiver operating characteristic curve; 0.912 vs. 0.776, p = 0.002). Moreover, PtcCO2 was more in agreement with PaCO2 than PetCO2, indicated by a lower bias (bias ± standard deviation; −1.6 ± 6.5 mmHg vs. 14.3 ± 8.4 mmHg, p < 0.001) and narrower limit of agreement (−14.3–11.2 mmHg vs. −2.2–30.7 mmHg). These results suggest that concurrent PtcCO2 monitoring allows anesthesiologists to provide safer respiratory management for patients undergoing non-intubated VATS.

Mayo Clinic, Rochester, Minnesota. roy.tk@mayo.eduCapnography: Clinical Aspects. Edited by J. S. Gravenstein, M.D., Dr. med. h.c., Michael B. Jaffe, Ph.D., and David A. Paulus, M.D. Cambridge, United Kingdom, Cambridge University Press, 2004. Pages: 441. Price: $120.00.Practicing anesthesiologists and intensivists have come to take capnography for granted in the monitoring of surgical and critically ill patients. Although many standard anesthesiology texts contain a chapter about this important and useful technique, a comprehensive up-to-date treatment of the subject is not easy to find. Capnography: Clinical Aspects fills this void.The book is a multiauthored effort edited by two academicians and an engineer working in industry. The editors acknowledge significant overlap between chapters and characterize the book as more of a “symposium” than a textbook. There is adequate continuity of style between chapters, but as with any book written in this format, some chapters are more interesting to read than others.The book is organized into four parts. The first part is meant to be clinical and describes the interaction of respiratory, cardiovascular, and metabolic systems in determining the amount of exhaled carbon dioxide as measured by capnography. This is followed by parts on basic carbon dioxide physiology, the history of capnography, and the technology of capnography.The clinical part is divided into four sections: Ventilation, Circulation, Metabolism, and Organ Effects. The ventilation section is further divided into subsections on breathing assessment, airway management, monitoring of ventilation, weaning, and special situations. The first chapter (written by two of the editors) is a well-written introduction to time-based capnogram interpretation, the most commonly used form of capnography in the operating room setting. Of particular value is the introduction to the volume-based capnogram, a topic not commonly detailed in anesthesia texts. Subsequent chapters discuss capnography outside the operating room and in the prehospital setting for airway management, in particular to confirm tracheal intubation. The chapter on airway management in the intensive care unit includes a section on using capnography to confirm proper orogastric and nasogastric tube placement. The chapter on airway management in the operating room includes sections on confirming tracheal intubation and recognizing endobronchial tube placement.The chapter describing the use of capnography to monitor ventilation during anesthesia includes interesting comments on the Food and Drug Administration checkout relevant to capnography. This chapter also includes sections on equipment troubleshooting and how capnograms can be affected by positioning, pulmonary pathology, and several particular situations such as one-lung ventilation, laparoscopy, neurosurgery, cardiac surgery, tourniquet release, and high-frequency jet ventilation. Other chapters in this section focus on the use of capnography during transport and how it can be used in the field as a way to avoid deleterious effects of unintentional hyperventilation after intubation.A particularly comprehensive chapter describes the unique physiology and technological limitations of capnography in neonates and infants. Other chapters describe capnography in the sleep laboratory, capnography as a feedback tool for behavioral therapy in various disorders, and how the capnogram is affected by alterations in physiologic and technical limitations in high- and low-pressure environments.Chapters are also included on sedation and noninvasive ventilation. These chapters are valuable for their descriptions of how end-tidal carbon dioxide can be sampled during spontaneous ventilation in nonintubated patients and the clinical utility and limitations of end-tidal carbon dioxide as a method of estimating arterial carbon dioxide tension (PCO2) in noninvasive ventilation.Chapters relevant to critical care describe the use capnography to optimize tidal volume, alveolar minute ventilation, and positive end-expiratory pressure to wean patients from mechanical ventilation. These chapters also describe the use of volumetric capnography to assess carbon dioxide production and how the capnogram is affected by positive end-expiratory pressure, unilateral lung injury, tracheal gas insufflation, and various high-frequency ventilation modes.The circulation subsection includes chapters on how end-tidal carbon dioxide monitoring can be used to assess circulatory status during cardiopulmonary resuscitation and for prognostication during cardiac arrest in medical patients as well as the use of end-tidal and tissue carbon dioxide monitoring techniques to assess oxygen delivery in shock states. This section includes an elegant physiologic description of changes in alveolar dead space with pulmonary embolism and the use of capnography in diagnosis and treatment of pulmonary emboli and gas embolization in addition to a chapter on the utility of volumetric capnography for estimating arterial PCO2in patients with acute respiratory distress syndrome.The chapter on noninvasive pulmonary blood flow measurement describes complete and partial carbon dioxide rebreathing techniques as alternatives to invasive cardiac output monitoring. A variety of clinical scenarios illustrating the use of these techniques sets this chapter apart from other descriptions of this topic.The metabolism subsection includes a single chapter describing alterations in normal physiology induced by surgery and anesthesia that affect carbon dioxide elimination. The chapter discusses alterations in ventilation, circulation, and carbon dioxide metabolism that are influenced by temperature alterations, various anesthetic techniques, and pharmacologic agents as well as particular intraoperative situations such as laparoscopy, tourniquet release, vascular cross clamping, and cardiopulmonary bypass.The final chapter of the ventilation section describes the effects of hypercapnia and hypocapnia on tissue oxygenation and perfusion, focusing on the central nervous system, respiratory system, and cardiovascular system. This is an excellent introduction to the effect of carbon dioxide at the organ, tissue, and cellular/molecular level and could have been included in the section on physiology.The physiology section includes a chapter on carbon dioxide pathophysiology, which describes inherited and acquired mitochondrial and enzyme disorders as well as pharmacologic agents that alter carbon dioxide production. The chapter also discusses carbon dioxide embolism and the increase in PCO2during apnea testing for brain death. There is a complete if somewhat standard chapter on acid–base physiology, followed by an excellent description of how capnography can provide information on ventilation/perfusion mismatch from a physiologic standpoint, including examples of various disease states. Subsequent chapters describe clinical correlates of alterations in normal time and volume capnographic tracings and how capnograms can provide clues to the underlying pathophysiology.A particularly interesting chapter in this section summarizes a biomedical engineering approach to illustrate the underlying anatomical and physiologic processes that result in a normal volumetric capnogram. A mathematical model that accounts for bronchial airway structure, gas convection and diffusion, and the carbon dioxide release from alveolar capillary blood is shown to generate a computed washout curve that shows remarkable agreement with an experimentally measured capnogram from a healthy human subject. This illustrates the utility of physiologic modeling as a useful tool for investigating potentially complex pathophysiologies without placing patients at risk.A unique historical section describes the evolution of time and volumetric capnography with many interesting anecdotes, as well as a first-person account by Smalhout, an early proponent of capnography. A selection of capnographic tracings corresponding to clinical events that he made over a 20-yr period is one of the highlights of this book. Without reading this section of the book, few people would realize that the impetus for carbon dioxide analyzer development was to investigate the cause of death in patients who turned out to be rebreathing due to a channeling issue through carbon dioxide absorption devices, or that carbon dioxide analyzers enabled a reduction in mortality for polio patients by allowing clinicians to titrate ventilation to expired carbon dioxide instead of adjusting ventilation based on their weight.The technological section fulfills the editors’ wishes for providing clinicians with information necessary to appreciate the mechanism, design, and limitations of devices for measuring carbon dioxide. Various chapters address technical specifications and standards (e.g. , accuracy, range, drift, response time, interfering gases, alarm systems, calibration) for carbon dioxide analyzers and describe technological limitations for flow measurement, required to estimate carbon dioxide production. Another chapter describes various methods for carbon dioxide detection, including infrared, photoacoustic, colorimetric, and mass spectrometry methods. Unfortunately, Raman spectroscopy is not included simply because it is not currently commercially available. This chapter also includes a discussion of mainstream versus sidestream carbon dioxide analyzers.The book ends with a mini-atlas of capnographic waveforms typifying various physiologic states, which is useful although not exhaustive.As the editors acknowledge, there is a fair amount of redundancy; as an example, the fact that highly sensitive colorimetric carbon dioxide indicators can yield false positives with esophageal intubation is mentioned in multiple chapters along with the fact that false negatives in cardiac arrest have led to the removal of correctly placed endotracheal tubes. Other recurring themes include the predictive value of end-tidal carbon dioxide in assessing arterial PCO2and the utility of volumetric capnography. In general, I found the multiple perspectives to be helpful instead of confusing or irritating. As with any book, the onus is on the reader to formulate his or her judgment with the assistance of the most recent literature.The overall introduction to the book and the introduction chapters for each section are very short and could have been used to provide the reader with a more substantial description of the basic concepts or objectives of each section. The section and subsection titles are somewhat arbitrary, and some chapters are in fact assigned to their own sections. Although the terminology is relatively consistent, the book could also use a more comprehensive list of abbreviations and acronyms used in various chapters. I found most of the typographical and page-setting errors to be minor (with the exception of a reference to “title” volumes). In spite of these limitations, the book admirably maintains its focus on capnography; readers interested in the latest tissue oxygen tension (PO2) monitoring techniques, for example, will have to look elsewhere.In summary, Capnography: Clinical Aspects is a very readable introduction to a topic addressed by few textbooks. It is useful as a reference primarily because of its comprehensive index and contains much information useful to the practitioner of critical care as well as anesthesiology. It addresses the physiologic and technological considerations that need to be understood to make capnography a clinically useful tool and should be standard reading for those who depend on it as a basic anesthetic monitor.Mayo Clinic, Rochester, Minnesota. roy.tk@mayo.edu

The COVID-19 pandemic has highlighted the importance of environmental ventilation in reducing airborne pathogen transmission. Carbon dioxide monitoring is recommended in the community to ensure adequate ventilation. Dynamic measurements of ventilation quantifying human exhaled waste gas accumulation are not conducted routinely in hospitals. Instead, environmental ventilation is allocated using static hourly air change rates. These vary according to the degree of perceived hazard, with the highest change rates reserved for locations where aerosol-generating procedures are performed, where medical/anaesthetic gases are used and where a small number of high-risk infective or immunocompromised patients may be isolated to reduce cross-infection. We aimed to quantify the quality and distribution of ventilation in hospital by measuring carbon dioxide levels in a two-phased prospective observational study. First, under controlled conditions, we validated our method and the relationship between human occupancy, ventilation and carbon dioxide levels using non-dispersive infrared carbon dioxide monitors. We then assessed ventilation quality in patient-occupied (clinical) and staff break and office (non-clinical) areas across two hospitals in Scotland. We selected acute medical andrespiratory wards in which patients with COVID-19 are cared for routinely, as well as ICUs and operating theatres where aerosol-generating procedures are performed routinely. Between November and December 2022, 127,680 carbon dioxide measurements were obtained across 32 areas over 8 weeks. Carbon dioxide levels breached the 800 ppm threshold for 14% of the time in non-clinical areas vs. 7% in clinical areas (p < 0.001). In non-clinical areas, carbon dioxide levels were > 800 ppm for 20% of the time in both ICUs and wards, vs. 1% in operating theatres (p < 0.001). In clinical areas, carbon dioxide was > 800 ppm for 16% of the time in wards, vs. 0% in ICUs and operating theatres (p < 0.001). We conclude that staff break, office and clinical areas on acute medical and respiratory wards frequently had inadequate ventilation, potentially increasing the risks of airborne pathogen transmission to staff and patients. Conversely, ventilation was consistently high in the ICU and operating theatre clinical environments. Carbon dioxide monitoring could be used to measure and guide improvements in hospital ventilation.

Carbon dioxide is produced in the tissues as a byproduct of aerobic metabolism, then transported to the lungs by the venous circulation and is finally eliminated during the expiratory phase of ventilation. End-tidal CO2(ETCO2) is defined as the peak CO2 value during expiration and is dependent on adequate pulmonary blood flow to the ventilating areas of the lung. ETCO2 in healthy subjects differs normally by <5 mmHg from the arterial CO2(PaCO2). An increased ETCO2-PaCO2 gap can be found in association with a decreased pulmonary blood flow and/or increased dead-space. Capnometry is the measurement of CO2 concentration of tidal gas at the airway opening. Capnography is the graphic display of the measured CO2. Capnography is an important non-invasive technique that can monitor CO2 production, pulmonary perfusion and alveolar ventilation as well as respiratory patterns.[1] Capnography has been shown to be effective as a tool for early detection of complications during anesthesia including, hypoventilation, esophageal intubation and circuit disconnection. Tinker et al.[2] concluded after a closed claim analysis for the American Society of Anesthesiology that the application of capnography and pulse oximetry together could have helped prevent 93% of avoidable anesthesia mishaps identified in their study. Capnometry is now a standard of care during administration of general anesthesia, for confirmation of placement of endotracheal tube after intubation and during transportation of an intubated patient. It has been increasingly used in intubated ventilated patients in intensive care units to safely wean patients, decrease the number of arterial blood gases, detect endotracheal displacement and prevent hypercarbia. Nasal ETCO2 monitoring is useful during procedural sedation and post-operative monitoring in the recovery room. In addition, volumetric capnography can be used as a non-invasive method to measure cardiac output. In this journal, Mehta and colleagues presented their data showing good correlation between ETCO2 and PaCO2 in neonates and children.[3] As expected correlation between ETCO2 and PaCO2 was weaker when P/F ratio was 200. Although, the mean bias with the Bland-Altman plot was low in neonates as well as children the limits of agreement is large suggesting variability of PaCO2-ETCO2 gap in their sample. Their findings confirm previously published data in neonates. The gradient between PaCO2 and ETCO2 depends upon the amount of dead space during ventilation.[4] Many variables influence the percentage of dead space to total minute ventilation. Decreased pulmonary blood flow, pulmonary disease or hyperinflation of lungs can lead to increased dead space and consequently high PaCO2-ETCO2 gap. An important limitation of using ETCO2 as a surrogate for PaCO2 measurement is that the PaCO2-ETCO2 gap changes from patient to patient based on underlying pulmonary and cardiovascular conditions and ventilation strategies and within the same patient with significant changes in the cardiopulmonary condition. In a stable patient ETCO2 monitoring can be used as trending tool during weaning or after the change in ventilator setting. Periodic measurement of PaCO2 is necessary to make sure the PaCO2-ETCO2 gap is not significantly altered. Mehta et al.[3] confirmed previous reports of ETCO2 monitoring as a valid tool in sick, mechanically ventilated neonates and children. In addition to monitoring ventilation status, continuous ETCO2 is useful in early detection of dislodgement of endotracheal tube. Waveform of capnography may be useful in detecting certain type of pulmonary pathology, such as obstructive airway disease. ETCO2 monitoring is a valuable tool during cardiopulmonary resuscitation (CPR). ETCO2 levels fall to low levels at the onset of cardiac arrest, increases with effective CPR and returns to normal levels at return of spontaneous circulation. Although there are no absolute contraindications of use of ETCO2 monitoring there few limitations for its use.[5] Large main stream capnometers can add dead space and may cause kinking of endotracheal tubes. Fortunately, most modern capnometers add a small amount dead space and are of light weight. Gas sampling rate from a side stream capnometer can lead to auto triggering and sometimes inadequate tidal volume delivery in very small neonates. Secretions and condensation in the tubing and leaks in the ventilator circuit can affect the accuracy of ETCO2. End-tidal carbon dioxide monitoring is a useful tool in the management of acutely ill and is becoming a standard of care in many clinical situations. In ventilated patients, ETCO2 monitoring is best used as a trending device for ventilation in addition to detecting endotracheal position.

Carbon dioxide (CO2 ) monitoring is vital during mechanical ventilation of newborn infants, as morbidity increases when CO2 levels are inappropriate. Our aim was to review the uses and limitations of such noninvasive monitoring methods. Colorimetry is primarily utilized during resuscitation to determine whether successful intubation has occurred. False negative and positive results can however lead to delays in detecting tracheal versus esophageal intubation. Transcutaneous carbon dioxide sensors have limited use during resuscitation, but can be utilized to provide continuous trend data during on-going ventilation. End-tidal capnography can provide clinicians with quantitative end-tidal CO2 (EtCO2 ) values and a continuous real-time capnogram waveform trace. These devices are becoming more widely accepted for use in the neonatal population as the new devices are lightweight with minimal additional dead space. Nevertheless, they have been reported to have variable accuracy when compared to arterial CO2 measurements, however, divergence of results may be related to disease severity rather than technological limitations. During resuscitation EtCO2 can be detected by capnography more rapidly than by colorimetry. Furthermore, capnography can be currently utilized in neonatal research settings to determine the physiological dead space and ventilation inhomogeneity, and thus has potential to be beneficial to clinical care. In conclusion, novel modes of noninvasive carbon dioxide monitoring can be safely and reliably utilized in newborn infants during mechanical ventilation. Future randomized trials should aim to address which device provides the most optimal form of monitoring in different clinical contexts.

Various factors including severe obesity or increases in intra-abdominal pressure during laparoscopy can lead to inaccuracies in end-tidal carbon dioxide (PETCO2) monitoring. The current study prospectively compares ET and transcutaneous (TC) CO2 monitoring in severely obese adolescents and young adults during laparoscopic-assisted bariatric surgery. Carbon dioxide was measured with both ET and TC devices during insufflation and laparoscopic bariatric surgery. The differences between each measure (PETCO2 and TC-CO2) and the PaCO2 were compared using a non-paired t test, Fisher's exact test, and a Bland-Altman analysis. The study cohort included 25 adolescents with a mean body mass index of 50.2 kg/m2 undergoing laparoscopic bariatric surgery. There was no difference in the absolute difference between the TC-CO2 and PaCO2 (3.2±3.0 mmHg) and the absolute difference between the PETCO2 and PaCO2 (3.7±2.5 mmHg). The bias and precision were 0.3 and 4.3 mmHg for TC monitoring versus PaCO2 and 3.2 and 3.2 mmHg for ET monitoring versus PaCO2. In the young severely obese population both TC and PETCO2 monitoring can be used to effectively estimate PaCO2. The correlation of PaCO2 to TC-CO2 is good, and similar to the correlation of PaCO2 to PETCO2. In this population, both of these non-invasive measures of PaCO2 can be used to monitor ventilation and minimize arterial blood gas sampling.

Continuous end-tidal carbon dioxide (ETCO2) monitoring during normofrequent jet-ventilation (NFJV) has not previously been successful and no correspondence between ETCO2 and arterial carbon dioxide (PaCO2) demonstrated. During NFJV jet-ventilation in 19 healthy volunteers, continuous ETCO2 was measured and compared to PaCO2 values. The original ETCO2 sampling line from our Datex CO2 measuring equipment was placed longitudinally against a suction catheter and both were wrapped with aluminium foil. They were placed 4-5 cm above the carina and the position was verified with a fiberoptic bronchoscope. The correlation between methods gave a Pearson's product moment correlation (r value) of 0.836, significant at the P < 0.001 level, indicating a close correlation between methods. A difference against mean scatter diagram confirmed that ETCO2 and PaCO2 measurements are of equal value in monitoring healthy patients during NFJV. A valuable method of continuous ETCO2 monitoring during NFJV is presented.

Comparing arterial and end-tidal carbon dioxide values in hyperventilated neurosurgical patients

Continuous end-tidal carbon dioxide monitoring in pediatric intensive care units

The ocean is one of the most extensive ecosystems on Earth and can absorb large amounts of carbon dioxide. Changes in seawater carbon dioxide concentrations are one of the most important factors affecting marine ecosystems. Excess carbon dioxide can lead to ocean acidification, threatening the stability of marine ecosystems and species diversity. Dissolved carbon dioxide detection in seawater has great scientific significance. Conducting online monitoring of seawater carbon dioxide can help to understand the health status of marine ecosystems and to protect marine ecosystems. Current seawater detection equipment is large and costly. This study designed a low-cost infrared carbon dioxide detection system based on molecular theory. Using the HITRAN database, the absorption spectra and coefficients of carbon dioxide molecules under different conditions were calculated and derived, and a wavelength of 2361 cm-1 was selected as the measurement channel for carbon dioxide. In addition, considering the interference effect of direct light, an infrared post-splitting method was proposed to eliminate the interference of light and improve the detection accuracy of the system. The system was designed for the online monitoring of carbon dioxide in seawater, including a peristaltic pump to accelerate gas-liquid separation, an optical path structure, and carbon dioxide concentration inversion. The experimental results showed that the standard deviation of the gas test is 3.05, the standard deviation of the seawater test is 6.04, and the error range is within 20 ppm. The system can be flexibly deployed and has good stability and portability, which can meet the needs of the online monitoring of seawater carbon dioxide concentration.

CARBON DIOXIDE (CO2) monitoring is a mainstay of evaluation for any patient with a respiratory problem. Although CO2 monitoring is not a new modality, it is continuously changing as new methods are developed. The gold standard of carbon dioxide monitoring is measurement of PCO2 obtained as part of the arterial blood gas. Although this is the most accurate way to monitor the amount of CO2 in the blood, it is also the most costly to the neonate because it requires a blood sample. Neonatal care practitioners strive to minimize blood losses in order to reduce the need for blood transfusions. In addition, arterial blood gas monitoring is not always practical, because the time and equipment to obtain and run a sample are not always available, particularly in the delivery room or during transport. Another drawback to arterial blood gas monitoring is that it requires either the placement of a central line or an arterial puncture. As caregivers concerned with pain in the neonate, we strive to minimize the number of painful procedures our patients experience. Central lines may increase the risk of infections, a constant concern with the emergence of resistant organisms in our nurseries. For these reasons, noninvasive forms of carbon dioxide monitoring are on the forefront of neonatal care.

X-Linked myotubular myopathy (XLMTM) is a rare genetic neuromuscular disorder characterized by mild to severe muscle weakness. It is caused by a mutation in the myotubularin (MTM1) gene. The diagnosis is considered in young male neonates with muscle weakness and hypotonia. The disorder predominantly affects males, but female carriers develop a range of symptoms. Only 24 cases of symptomatic female carriers are reported in the literature. We present a case of a woman with XLMTM who was evaluated for nocturnal hypoventilation. A 24-year-old woman diagnosed in 2012 with XLMTM reported morning headaches and frequent gasping with waking. She denied daytime sleepiness, snoring, insomnia, or symptoms of restless legs or narcolepsy. Spirometry showed a restrictive pattern with a proportionate reduction of FVC and FEV1 that significantly decreased in the supine position. Daytime arterial blood gas demonstrated a normal pH of 7.44, pO2 of 92 mmHg, and pCO2 of 38 mmHg. A polysomnogram in November 2013 demonstrated mild obstructive sleep apnea with an AHI of 7.7 with an oxygen saturation nadir of 73.7% and oxygen desaturation less than 90% of 20.3 minutes. A BiPAP titration with transcutaneous carbon dioxide (TCO2) monitoring demonstrated a baseline awake TCO2 of 55–60 mmHg and sleep TCO2 of 60–70 mmHg. Respiratory muscle weakness due to neuromuscular disease can cause insufficient ventilation and result in excessive daytime sleepiness and morning headaches. Pulmonary function testing shows a restrictive pattern with a FVC reduction of >10% in the supine position, reduced maximal inspiratory and expiratory pressures, and reduced total lung capacity. A polysomnogram with carbon dioxide monitoring can assess for hypoventilation. Management of respiratory muscle weakness due to neuromuscular disease can provide symptomatic relief, improve quality of life, and prolong life. Options for respiratory support include noninvasive positive pressure ventilation (NPPV) or invasive positive pressure ventilation.