Carbon dioxide monitoring in children-A narrative review of physiology, value, and pitfalls in clinical practice.

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.

Table of content Abbreviations 3 Abstract 4 1.1 Rationale, frequency and indication 5 1.2 Special features of out-of-hospital Emergency Anaesthesia 7 1.3 Preparations, Performance and Monitoring of Emergency Anaesthesia 9 1.4 Anaesthesia Procedures for Common Emergency Situations 14 1.5 Drugs for Emergency Anaesthesia 18 References ?? Abbreviations ARDS Acute Respiratory Distress Syndrome AWMF Working Group of Scientific Medical Associations BMI Body Mass Index EAST Eastern Association for the Surgery of Trauma ECG Electrocardiogram EMS Emergency Medical Service DGAI German Society of Anaesthesiology and Intensive Care Medicine DIVI German Interdisciplinary Association for Intensive Care and Emergency Medicine etCO2 End-tidal carbon dioxide GCS Glasgow Coma Score ICP Intracranial pressure ICU Intensive Care Unit LIKS AirRescue Information and Communication Systems MIND German minimal emergency data record NIBP Noninvasive Blood Pressure NIV Noninvasive Ventilation BP Blood Pressure (according to Riva Rocci) SOP Standard operating procedure SpO2 Oxygen saturation TBI Traumatic Brain Injury Abstract Emergency anaesthesia is an important therapeutic measure in out-of-hospital emergency medicine. The associated risks are considerably higher than those of in-hospital anaesthesia. The primary objectives of emergency anaesthesia are hypnosis, analgesia, oxygenation and ventilation through airway management. The secondary objectives of emergency anaesthesia are amnesia, anxiolysis, the reduction of oxygen consumption and respiratory work, the protection of vital organs and the avoidance of secondary myocardial and cerebral damage. A critical evaluation of the indications for out-of-hospital emergency anaesthesia must take into consideration patient, case and provider-related factors. Rapid sequence induction of emergency anaesthesia includes standard monitoring, preoxygenation, standardised preparation of emergency anaesthesia, drug administration, manual in-line stabilisation during intubation (if necessary), airway management and checking of correct tube placement. Spontaneously breathing casualties should receive preoxygenation for at least 3 to 4 min with a tight-fitting facemask with reservoir using 12 to 15 l min_1 of oxygen or with a demand valve providing 100% oxygen. As an alternative, preoxygenation may be performed as noninvasive ventilation with 100% oxygen. Standardised anaesthesia preparation comprises filling drugs into syringes and labelling them, checking ventilation equipment, preparing endotracheal tube and syringe for inflating the cuff and the introducer, stethoscope and fixation material, preparing alternative instruments for airway management as well as checking suction, ventilation and standard monitoring devices, including capnography. Standard monitoring for out-of-hospital emergency anaesthesia comprises ECG, blood pressure measurement and pulse oximetry. Continuous capnography is always and exclusively performed to check the placement of airway devices, as well as to indirectly monitor haemodynamics. 1.1 Rationale, frequency and indication 1.1.1 Rationale Emergency anaesthesia, airway management and ventilation are important therapeutic measures in emergency medicine.1,2 In physician-based emergency medical service (EMS) systems, every EMS-physician – irrespective of his or her specialty – should be able to safely induce emergency anaesthesia in patients with various injury patterns, clinical pictures and risks despite adverse conditions outside the hospital.3 This leads to the question of what procedure should be recommended for out-of-hospital anaesthesia under complex conditions and what anaesthetic drugs should be used, especially with regard to different groups of patients. It must also be taken into consideration that the induction and performance of out-of-hospital anaesthesia is in many respects more difficult than routine anaesthesia in operating theatres or ICUs in hospitals.4,5 The following recommendations of the German Society of Anaesthesiology and Intensive Care Medicine (DGAI) have been prepared for EMS-physicians and paramedics in two-tier physician-staffed EMS systems. Table 1 shows a list of the central points of these recommendations.Table 1: Overview of the recommendations for out-of-hospital emergency anaesthesia1.1.2 Methods The recommendations contain measures based on the latest scientific findings, which ensure the appropriate provision of out-of-hospital emergency anaesthesia for critically ill or injured patients under various circumstances (e.g. infrastructure, specific situation, patient condition, individual capabilities, knowledge and experience of the physician). To achieve consensus on scientific findings and current practice of out-of-hospital emergency anaesthesia the Emergency Medicine Research Group of the DGAI invited 14 anaesthesiologists experienced in out-of-hospital emergency medicine from German and Austrian medical centres to participate in an Out-of-Hospital Emergency Anaesthesia Working Group. After constructing a frame of contents, single topics were distributed to teams of authors to review relevant literature and provide a first version of the text. In a second step, these results were assembled and a three-round digital Delphi study was conducted to reach consensus. The Delphi technique is a structured approach of debating by experts to converge a discussion towards group consensus, which was initially developed in the 1950s for complex problems exceeding the analytical capabilities of a single person.6 Working group opinion was fed back after each Delphi round to allow the participants to revise their previous opinions and so converge towards group consensus. Recommendations were approved with consensus when agreement of 12 out of 14 participants (> 85%) could be reached. 1.1.3 Frequency According to the German minimal emergency data record data base (82 000 ground deployments of emergency physicians) of Baden-Württemberg, Germany, and the AirRescue Information and Communication Systems data base (47 000 air rescue missions, Germany), every emergency physician induces out-of-hospital anaesthesia every 2 weeks in air rescue missions and every 1.4 months in ground deployments.7 Out-of-hospital anaesthesia is induced in approximate 3 to 5% of all EMS missions and in 4 to 7% of EMS missions to children (age <18 years).8–12 1.1.4 Indications for emergency anaesthesia Emergency anaesthesia must often be induced in unconscious (Glasgow coma scale, GSC <9), uncooperative, severely injured or critically ill patients with a full stomach and unstable cardiopulmonary conditions.13 Emergency anaesthesia is, in most cases, necessary for airway management. An exception to this rule are patients undergoing cardiopulmonary resuscitation who require airway management first and, if necessary, emergency anaesthesia later once spontaneous circulation has returned.14 Indications for emergency anaesthesia can be found in critically ill or injured patients with cardiopulmonary or neurological diseases, trauma patients, and patients who are intoxicated or have markedly impaired conscious level with a reduction in protective reflexes (GCS < 9) and a high risk of pulmonary aspiration.15,16 This does not include rapidly reversible causes of impaired consciousness (e.g. hypoglycaemia) or conditions in which the GCS does not correlate with the extent of the loss of protective reflexes (e.g. stroke with aphasia or dementia). Patients with markedly impaired consciousness (GCS < 9) require emergency anaesthesia to tolerate airway management.17Tables 2 and 3 provide an overview of the indications for and objectives of out-of-hospital emergency anaesthesia.Table 2: Indications for out-of-hospital emergency anaesthesiaTable 3: Objectives of out-of-hospital emergency anaesthesiaIf emergency anaesthesia is required, personnel must take into account the guideline on out-of-hospital airway management18 by the DGAI as well as the information on emergency anaesthesia, airway management and ventilation in the German S3 guideline on treatment of major trauma (S3-Guideline on Treatment of patients with severe and multiple injuries. German Trauma Society. 2011 www.awmf.org Nr. 012-019 Assessed 29 September 2015). Indications for, planning of and performance of emergency anaesthesia are influenced by the following factors: Training, experience and routines of the emergency physician and paramedics Out-of-hospital environment (e.g. illumination, space, weather) Time and type of transport (ground, air ambulance) Circumstances surrounding airway management and (foreseeable) intubation problems (e.g., expected difficult airways of emergency patients with sufficient spontaneous breathing). The EMS-physician must not only consider the situation of the patient but must also critically assess his own skills when deciding to perform out-of-hospital emergency anaesthesia. Emergency anaesthesia is an invasive measure, poses a lethal risk, places special requirements on performance, monitoring and complication management. Before inducing emergency anaesthesia, the EMS-physician must consider disadvantages and possible complications (e.g. vomiting, pulmonary aspiration, airway displacement, cardiovascular depression, allergic reaction) and analyse the risks and benefits. In addition, the skills of the EMS-physician and the paramedics as well as relevant team factors must also be considered. Unlike junior hospital doctors, EMS-physicians usually cannot request direct support from a medical specialist or a senior physician. Several incidents have been reported in which severe complications were caused by a lack of experience in out-of-hospital emergency anaesthesia.19 Mistakes are easily made by inexperienced personnel. Guidelines and standard operating procedures must define clear procedures to provide less experienced emergency teams with a standardised approach to out-of-hospital anaesthesia. Given the life-threatening risks for the patient, it is crucial that all EMS-physicians know the procedures for inducing and performing out-of-hospital anaesthesia. The Association of Anaesthetists of Great Britain and Ireland requests that physicians inducing out-of-hospital anaesthesia '... should have the same level of training and competence that would allow them to perform unsupervised ...' emergency intubation '... in the emergency department'.7,20,21 1.2 Special features of out-of-hospital emergency anaesthesia Emergency anaesthesia induced in the ICU, in the emergency department, and especially outside the hospital is associated with a high level of difficulty.1,4,22 According to Timmermann et al.18, these multifactorial risk-increasing conditions can be categorised as physician, patient and case-related factors. 1.2.1 Patient-related factors Patient-related factors complicating the induction and performance of emergency anaesthesia include a full stomach, injury of the airway, restricted mobility of the cervical spine (preexisting, on account of trauma or immobilisation), cardiopulmonary or other disorders because of preexisting diseases and/or injuries, a poor venous state and long-term medication. Full stomach: Out-of-hospital emergency patients must be assumed to have a full stomach. To reduce the risk of aspiration in adults, rapid sequence induction is the technique of choice. This involves rapid anaesthetic induction and airway management without intermittent ventilation. This has a considerable influence on the choice of anaesthetic. The DGAI Paediatric Anaesthesia Scientific Working Group recommends intermittent ventilation in paediatric patients to avoid hypoxia during rapid sequence induction.23 Difficult vascular access: If possible, early insertion of two peripheral venous catheters is recommended during out-of-hospital anaesthesia in critically ill or severely injured patients to always have a second access available during induction (e.g. in case of extravasation).24 If peripheral venous cannulation is difficult, anaesthetics may also be administered through intraosseous access.25,26 All drugs mentioned below may be administered through intraosseous access using the same dose. Haemorrhagic shock: Blood loss is underestimated in many patients (e.g. major trauma, internal haemorrhaging). Medical personnel must take into account that in such cases the number of red blood cells is critically reduced and patients must be carefully preoxygenated. Tests have shown that animals with severe haemorrhagic shock had oxygen saturation (SpO2) of less than 70% after only 1 to 2 min of apnoea despite preoxygenation.27 If emergency anaesthesia is induced in patients with severe haemorrhagic shock at the scene of the accident, sudden hypotension may occur, which is extremely difficult to correct. 1.2.2 Case-related factors Position of the patient: Trapped patients or patients in a confined area should be treated first by inducing appropriate analgesia and sedation and by maintaining spontaneous breathing. Rescued patients should then be appropriately positioned for anaesthesia induction and airway management. The best conditions outside hospital can be provided in an ambulance car.28,29 Equipment constraints: Clinical physicians have a wide range of equipment, devices and drugs at their disposal. In an out-of-hospital environment, however, the selection of equipment and drugs is considerably limited. Urgency: Depending on the condition of the patient, out-of-hospital anaesthesia must often be induced as quickly as possible. Medical personnel in an out-of-hospital environment must, therefore, have a high level of experience to ensure patient safety. 1.3 Preparation, performance and monitoring of emergency anaesthesia On account of the risks and hazards of out-of-hospital emergency anaesthesia, standardised procedures are necessary to avoid complications. Personnel performing out-of-hospital emergency anaesthesia must, therefore, take the following points into consideration: Thorough evaluation and examination of the patient Critical verification of the indications for out-of-hospital emergency anaesthesia Optimisation of patient condition through preoxygenation, haemorrhage control and infusion (if necessary) Standardised procedures for the preparation and performance of out-of-hospital emergency anaesthesia Management of complications 1.3.1 Critical verification of the indications for out-of-hospital emergency anaesthesia Information provided in sections 1.1.3 and 1.2 must be taken into account in this context. The decision to induce out-of-hospital anaesthesia must be communicated to the entire emergency team. The team must discuss the best location to induce anaesthesia, the tasks of each team member, the drugs selected and other important issues. A common approach must be agreed upon, which ideally is based on a standardised procedure. 1.3.2 Preparation of out-of-hospital anaesthesia Rapid sequence induction is performed to induce emergency anaesthesia. The goal is to rapidly and effectively bring about a state of unconsciousness in which airway management and ventilation are tolerated. This procedure involves the administration of a sedative followed by muscle relaxant.13 Analgesic drugs may be administered prior to or immediately after these two substances or after the airway is secured. Ventilation must be ensured after anaesthesia induction. Drugs must be filled into syringes and labelled beforehand.30 Airway management equipment must be prepared and checked for functionality (Table 4).Table 4: Standardised preparation of emergency anaesthesia equipment1.3.3 Performance and procedure of out-of-hospital emergency anaesthesia Table 5 and Figs. 1 and 2 provide an overview of the phases of out-of-hospital emergency anaesthesia.Table 5: Standardised performance of out-of-hospital anaesthesiaFig. 1: Schematic diagram of the performance and procedure of out-of-hospital emergency anaesthesia.Fig. 2: Phase model of the performance and procedure of out-of-hospital emergency anaesthesia.After paramedics prepare the drugs and the equipment for airway management and ventilation as instructed by the EMS-physician, preoxygenation is initiated as soon as the EMS-physician decides to induce emergency anaesthesia (Fig. 1). To prevent desaturation during anaesthesia induction and airway management or to prolong the time until the oxygen saturation level decreases (apnoeic tolerance), spontaneously breathing emergency patients are given oxygen for 3 to 4 min, whenever possible.31,32 Preoxygenation must be performed only with 100% oxygen through a face mask or the tightly fitting bag valve mask, each with an oxygen reservoir (at least 12 to 15 l/min of oxygen). A demand valve or noninvasive ventilation (NIV) may be used, which are even more effective and require less oxygen.32 A face mask without reservoir is not sufficient for preoxygenation even at the highest possible flow rates. During preoxygenation, optimal monitoring is ensured, and syringes are filled with anaesthetic and emergency agents according to the instructions of the emergency physician. Standard monitoring includes ECG (3-lead ECG: heart rate and rhythm), capnography, continuous automatic blood pressure (BP) monitoring (at least every 3 min), and pulse oximetry (heart rate and SpO2). The German Interdisciplinary Association for Intensive Care and Emergency Medicine (DIVI) recommends the use of standardised self-adhesive syringe labels to avoid confusion in critical situations. (DIVI-recommendation for labelling syringes in intensive care and emergency medicine 2012 http://www.divi.de/images/Dokumente/Empfehlungen/Spritzenetiketten/DIVI-Etiketten-Empfehlung_2012_07_02.pdf, Assessed 16 May 2016) To prevent regurgitation, the upper body should be elevated (but kept in line) if there is no contraindication (e.g. spinal immobilisation in trauma patients or a haemodynamically unstable patient). After the venous accesses are checked, anaesthesia is induced according to agreed team approaches and procedures. The paramedics confirm the names and doses of the drugs (in ml or mg) requested by the physician. The drugs are then administered. At this point, the cervical collar of patients with neck immobilisation is opened while ensuring manual in-line stabilisation provided by an assistant. After the patient has lost consciousness and the muscle relaxant has an effect, the airway is then secured. In adult patients, airway management is usually performed without intermittent ventilation. In some cases, intermittent ventilation may be necessary to maintain oxygenation despite the increased risk of aspiration (e.g. severe respiratory insufficiency).32,33 The application of cricoid pressure (Sellick's manoeuvre) is no longer recommended on account of a lack of evidence about its positive effects and because of potential problems at the tube site.33–35 The cuff of the endotracheal tube or the supraglottic airway (SGA) device (e.g. laryngeal mask, laryngeal tube) is inflated immediately after insertion, placement is confirmed and the device is fixed. In out-of-hospital environments, two procedures are used to verify endotracheal tube placement for intubation36: visually via direct laryngoscopy or video laryngoscopy, and via capnometry/capnography. German standard DIN EN 1789 stipulates that all ambulances must have equipment for monitoring end-tidal carbon dioxide. This equipment must be used. Capnography provides vital information about ventilation and thus about the placement of the tube or SGA device. In addition, end-tidal carbon dioxide monitoring indicates acute changes in cardiac output earlier than other out-of-hospital methods. Continuous capnography also can detect the displacement, disconnection or kinking of the endotracheal tube. As unrecognised oesophageal intubation can have devastating consequences, correct tube placement must be confirmed using capnography (100% sensitivity). This does not, however, rule out over-insertion of the tube (endobronchial intubation). Bilateral breath sounds and chest movement can confirm the correct depth (measured from the teeth: women: approximately 20 to 21 cm, men: approximately 22 to 23 cm).37 Continuous standard monitoring must be ensured during the entire duration of anaesthesia to adequately monitor vital signs and respond to any changes. 1.3.4 Management of complications and problems Out-of-hospital anaesthesia involves many risks. Complications must, therefore, be quickly identified and knowledgeably managed and eliminated. Insufficient depth of anaesthesia: If laryngospasms or bronchospasms occur during induction or if the patient resists airway management, attempts to intubate must be interrupted. Anaesthesia must be deepened or muscle relaxants must be administered. Resistance, laryngospasms and bronchospasms usually cease once anaesthesia is deepened. Intermittent ventilation during rapid sequence induction in adults is possible as hypoxia is more dangerous than aspiration. Hypotension: Temporary hypotension occurs in 7 to 18% of all cases of out-of-hospital anaesthesia.38,39Continuous automated oscillometric BP measurement is, therefore, vital. Patients with acute hypovolaemia have an increased risk of hypotension. Treat hypotension with fluids, cafedrine–theodrenaline, noradrenaline or, if necessary, adrenaline. The relevant drugs must be prepared before anaesthesia is induced. Fluid imbalances must be corrected through appropriate intravenous infusions. Heart failure should also be considered as a differential diagnosis, particularly in patients who have preexisting conditions. Allergic reactions: In rare cases, some drugs may release histamine and/or cause allergic In the of allergic the treatment is to avoid or using the and, on the and in and and Out-of-hospital anaesthesia involves a 14 to 12 higher risk of in and as well as aspiration than anaesthesia induced in performing rapid sequence personnel should have an device available at all In out-of-hospital anaesthesia, hypoxia occurs in 5 to 18% of all hypoxia by a of in patients with injury In many cases, hypoxia a longer and especially during rapid sequence To ensure the patient should be may occur especially on account of or airway Before anaesthesia is it should be that the can of two if If the does not the indications for anaesthesia induction must be critically If a is the cause of personnel may to a SGA device. If this cannot be the patient should be carefully through a mask as an As a emergency must be performed of the Difficult airway to the DGAI recommendations for out-of-hospital airway management and other In the operating the of a life-threatening cannot situation is approximately This is higher in out-of-hospital rare complications may to the of a patient in a In clinical anaesthesia and during a to spontaneous breathing is an in such This is however, even if has been used, which has a duration of If muscle has been induced by can be used for 3 to 4 min), which is than spontaneous from the effects of This however, and is not considered in the for out-of-hospital airway management and anaesthesia The management of difficult airways in the out-of-hospital also the for out-of-hospital airway management of the from a of tube the of airway management from mask ventilation to the use of and, if required, procedures to ensure sufficient The best to the risk of an difficult airway is the early of patients who have difficult this of a difficult airway a crucial prior to induction of anaesthesia (Table If of these are the induction of anaesthesia should be critically In some cases, a to the that anaesthesia must be possible, should be requested or, if spontaneous breathing can be the patient should be to a hospital in A of patient experienced anaesthesiologists to assess a difficult To optimal intubation conditions in such cases, the authors using a muscle relaxant when inducing anaesthesia, especially because a to spontaneous breathing is only a if the indication is correct of difficult airway management The of cases in which primary endotracheal intubation is not possible is higher in out-of-hospital emergency medicine than in a hospital As it can be assumed that out-of-hospital emergency patients have full alternative airway management must be performed if primary intubation is not possible. It is to optimal conditions and to use an The and the patient in the with the elevated on a an movement of the are two for the of the correct placement of the endotracheal tube can usually be by intubation the risk of complications with each intubation If the is poor (according to personnel must check muscle has been induced. If not, this should be If endotracheal intubation is not possible, a and approach is necessary to prevent hypoxia and thus long-term to the oxygenation SpO2 the first measure is mask with two if required, also for patients with full If the laryngeal is difficult to intubation if can be in SGA devices (e.g. laryngeal mask, laryngeal tube) should be used if the level is not their early use the complication rate in airway can be used to The rate of video intubation is as high for the induction of anaesthesia in the operating and in out-of-hospital but the time to ensure airway management is and in have been reported in some If the measures should emergency must be performed as a to ensure sufficient the rate and of this procedure All personnel performing these procedures must have sufficient training and experience in the use of devices and their 1.4 Anaesthesia procedures for common emergency trauma to the induction and management of emergency anaesthesia, important factors are in major trauma (e.g. patient in Difficult vascular access caused by and hypovolaemia caused by with of oxygen with risk of hypoxia complicating airway management trauma patients often have hypovolaemia caused by This hypovolaemia can initially be for or by in or long-term (e.g. in As many anaesthetics have the of cardiovascular depression, hypotension may occur after the induction of anaesthesia. If hypovolaemia is it is recommended that be given prior to the induction of anaesthesia. As it has only a on the is particularly for inducing emergency anaesthesia in patients. use of (e.g. of may be hypotension of BP only to patients without TBI who have

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.

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.

Monitoring carbon dioxide in patients on mechanical ventilation is crucial for critical care nurses. Monitoring the value of arterial carbon dioxide pressure involves invasive arterial blood gas analysis. Monitoring end-tidal carbon dioxide pressure using capnography is a non-invasive method. This study aims to compare end-tidal carbon dioxide values with arterial carbon dioxide pressure in mechanically ventilated patients. The research design is a literature review. Searches were conducted through Scopus, ScienceDirect, ProQuest, and PubMed from 2018 to 2023. The Preferred Reporting Items for Systematic Review and Meta-Analyses flowchart method was used to select articles. The Critical Appraisal Skills Programme was used to assess article quality. Out of 79 articles, nine articles met the criteria. The procedures for collecting end-tidal carbon dioxide pressure and arterial carbon dioxide pressure data varied in terms of instrument types used and the subjects studied. There was no significant difference in carbon dioxide values between the end-tidal carbon dioxide and arterial carbon dioxide pressure methods. The agreement in comparing carbon dioxide values was acceptable. Measuring end-tidal carbon dioxide pressure has the potential to monitor mechanically ventilated patients, reducing the need for invasive monitoring, high costs, and repetitive arterial blood gas analysis.

After completing this article, readers should be able to: 1. Define the indeterminate class of recommendations for neonatal resuscitation. 2. Describe the two areas of current investigation within the indeterminate class recommendations. 3. Describe the application of two techniques from other settings within the indeterminate class recommendations. 4. Describe the indeterminate class recommendation for which conflicting evidence is emerging. With the shift to evidence-based guidelines, the process of revising the scientific framework for neonatal resuscitation and the derivative educational efforts will become more predictable and accessible. Beginning with the International Guidelines 2000, an Indeterminate Class of recommendations appeared. These focused on areas of intense scientific research that may lead to clinically important therapies; technological developments widely adopted for use in other age groups that may find a role in neonatal resuscitation; or emerging evidence that conflicts substantially with previous data, resulting in a revision of recommendations to withdraw support of a particular therapeutic approach. The advent of changes in evidence-based guidelines carries the obligation to monitor the impact of such changes. Finally, entirely new questions and proposed guideline recommendations will be submitted to evidence evaluation in the future. Five Indeterminate Class recommendations appeared in the neonatal resuscitation portion of the International Guidelines 2000 (Table⇓ ). Cerebral hypothermia following hypoxic-ischemic insult and positive-pressure ventilation with room air represent proposals in the translational research phase, moving from animal and molecular models into clinical trials. The recommendations relating to adjunctive airway techniques, laryngeal mask airway and exhaled carbon dioxide detection, recognize the importance of these techniques in the older pediatric and adult populations, but acknowledge the significant limitations in their application to neonates. The statement regarding high-dose epinephrine reinforces the conflicting nature of evidence relating to this therapy, yet it acknowledges that available evidence is extrapolated largely from older age groups and falls short of supporting …

Arterial blood gas analysis is the 'gold standard' method to measure the arterial partial pressure of carbon dioxide (PaCO2). However, arterial sampling including arterial catheterization is invasive and expensive. Cutaneous carbon dioxide tension (PcCO2) measurement is used as a noninvasive surrogate measure of PaCO2, which is used to either estimate PaCO2 or determine trend changes in the measurement. There has been considerable progress in the technical aspects of PcCO2 monitoring in the last few years. In this article, we evaluate recent developments and the renewed interest in the subject of PcCO2 monitoring in adults and discuss the technical aspects, clinical applications and the future outlook for this technique in the clinical setting. With evolution in technology, PcCO2 monitoring is now less cumbersome than before. Combined PcCO2 measurement and pulse oximetry is now possible with a single earlobe sensor. The clinical settings in which PcCO2 monitoring can be applied include patient monitoring during and after anaesthesia, patients receiving noninvasive ventilation, post extubation, endoscopy under sedation, the sleep laboratory and the lung function laboratory. Although there is an overlap of the clinical indications when both PcCO2 and end-tidal carbon dioxide monitoring may be used, it is our opinion that both these methods have independent indications and are sometimes also complementary to each other in patient care.

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

Resuscitation highlights in 2013: Part 2

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.

Continuous Capnography in Pediatric Intensive Care

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.

Carbon dioxide monitoring in the newborn infant.

To investigate the effectiveness of capnometry (carbon dioxide monitoring) in verifying gastric placement of a stylet-guided nasogastric tube in intubated, mechanically ventilated patients. A prospective descriptive study. Fourteen-bed medical-surgical intensive care unit, 11-bed coronary care unit, and 18-bed chronic ventilator unit in a 700-bed teaching hospital. A total of 53 adult patients on mechanical ventilation and enteral feedings. After the feeding tube was inserted to 30-cm length and before the first chest roentgenogram was taken, the end-tidal carbon dioxide detector was attached to the proximal end of the feeding tube. It was left in place for 1 min and was observed for a change in color (originally purple, it will turn tan or even yellow on contact with carbon dioxide). If the end-tidal carbon dioxide detector remained purple, it was interpreted as gastrointestinal placement; if it turned tan or yellow, it was interpreted as airway placement. The first chest roentgenogram was taken to confirm observations made with the end-tidal carbon dioxide detector. The feeding tube was advanced and a final chest roentgenogram verified its position below the diaphragm. In 52 of the 53 placements, no carbon dioxide was detected. The position in the gastrointestinal tract was confirmed by the two-step procedure. There were no false positives; the technique was 100% specific. One placement out of the 53 was found to be in the trachea. The end-tidal carbon dioxide detector appropriately detected carbon dioxide. This indicated no false negatives. To verify the sensitivity, 20 placements were made directly into the trachea through an endotracheal tube. In all 20 cases, carbon dioxide was detected. No false negatives occurred, indicating 100% sensitivity. Testing in spontaneously breathing patients was not conducted. Capnometry is a safe method for verifying proper feeding tube placement. The first chest roentgeno-gram can be safely eliminated. With this method, less time and money will be expended in feeding tube placement, making capnometry an efficacious new method.