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Exacerbation of COVID-19 pandemic may lead to acute shortage of ventilators, which may require shared use of ventilator as a lifesaving concept. Two model lungs were ventilated with one ventilator to i) test the adequacy of individual tidal volumes via capnography, ii) assess cross-breathing between lungs, and iii) offer a simulation-based algorithm for ensuring equal tidal volumes. Ventilation asymmetry was induced by placing rubber band around one model lung, and the uneven distribution of tidal volumes (VT) was counterbalanced by elevating airflow resistance (HR) contralaterally. VT, end-tidal CO 2 concentration (ETCO 2 ), and peak inspiratory pressure (Ppi) were measured. Unilateral LC reduced VT and elevated ETCO 2 on the affected side. Under HR, VT and ETCO 2 were re-equilibrated. In conclusion, capnography serves as simple, bedside method for controlling the adequacy of split ventilation in each patient. No collateral gas flow was observed between the two lungs with different time constants. Ventilator sharing may play a role in emergency situations., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Purpose: To determine if end-tidal carbon dioxide (etCO 2 ) value increased nurses' perceptions of confidence in patients' readiness for postanesthesia care unit (PACU) discharge., Design: Prospective, cross-sectional, comparative, one-group (pre-post) design., Methods: Nurses completed 2 assessments of confidence in readiness for discharge, before and after etCO 2 monitoring. Patient (discharge pain level, body mass index, sleep apnea history, and opioid use) and nurse factors were assessed. Analyses included descriptive and comparative statistics., Findings: Of 133 patients, mean (standard deviation) etCO 2 was 36.1 (5.7) mm Hg. Nurses' confidence in readiness for discharge differed before and after etCO 2 assessment. Confidence score decreased when etCO 2 was low (P = .003) or high (P = .005), compared with normal values. In linear regression, etCO 2 remained a factor in nurses' confidence in readiness for discharge (P < .001)., Conclusions: In a PACU, etCO 2 monitoring changed nurses' perceptions of confidence in patients' readiness for discharge., (Copyright © 2019 American Society of PeriAnesthesia Nurses. Published by Elsevier Inc. All rights reserved.)

Purpose of Review: Capnography is an excellent tool for early detection of hypoxemia and apnea in patients undergoing sedation for gastrointestinal endoscopy. The current American Society of Anesthesiology (ASA) guidelines recommend the use of capnography in any patient undergoing moderate sedation. The purpose of this review was to compile the most recent data available on capnography use in gastrointestinal endoscopy with the focus primarily on the use of capnography in moderate sedation cases., Recent Findings: Recent high-quality studies have evaluated the utility of capnography in low risk patients undergoing moderate sedation and have found no benefit with addition of capnography., Summary: Capnography is beneficial when used for patients who are at a higher risk for sedation-related complications. There is no benefit when capnography is used in low risk patients undergoing routine upper endoscopy and colonoscopy under moderate sedation but there is benefit when used in advanced endoscopic procedures that require deeper sedation and have longer procedure times.

Background: One of the known weaknesses of spirometry is its dependence on patients' cooperation, which can only partially be alleviated by educational efforts. Therefore, procedures less dependent on cooperation might be of value in clinical practice. We investigated the diagnostic accuracy of ultrasound-based capnovolumetry for the identification of airway obstruction., Methods: Consecutive patients from a pulmonary outpatient clinic were included in the diagnostic study. As reference standard, the presence of airway obstruction was evaluated via spirometry and bodyplethysmography. Capnovolumetry was performed as index test with an ultrasound spirometer providing a surrogate measure of exhaled carbon dioxide. Receiver operating characteristic (ROC) analysis was performed using the ratio of slopes of expiratory phases 3 and 2 (s3/s2) ≥ 0.10 as primary capnovolumetric parameter for the recognition of airway obstruction. Logistic regression was performed as secondary analysis to identify further useful capnovolumetric parameters. The diagnostic potential of capnovolumetry to identify more severe degrees of airway obstruction was evaluated additionally., Results: Of 1400 patients recruited, 1287 patients were included into the analysis. Airway obstruction was present in 29% of patients. The area under the ROC-curve (AUC) of s3/s2 was 0.678 (95% CI 0.645, 0.710); sensitivity of s3/s2 ≥ 0.10 was 47.7 (95% CI 42.7, 52.8)%, specificity 79.0 (95% CI 76.3, 81.6)%. When combining this parameter with three other parameters derived from regression analysis (ratio area/volume phase 3, slope phase 3, volume phase 2), an AUC of 0.772 (95% CI 0.743, 0.801) was obtained. For severe airway obstruction (FEV 1  ≤ 50% predicted) sensitivity of s3/s2 ≥ 0.10 was 75.9 (95% CI 67.1, 83.0)%, specificity 75.8 (95% CI 73.3, 78.1)%; for very severe airway obstruction (FEV 1  ≤ 30% predicted) sensitivity was 86.7 (95% CI 70.3, 94.7)%, specificity 72.8 (95% CI 70.3, 75.2)%. Sensitivities increased and specificities decreased considerably when the combined capnovolumetric score was used as index test., Conclusions: Capnovolumetry by way of an ultrasound spirometer had a statistically significant albeit moderate potential for the recognition of airway obstruction in a heterogeneous population of patients typically found in clinical practice. Diagnostic accuracy of the capnovolumetric device increased with the severity of airway obstruction., Trial Registration: The study is registered under DRKS00013935 at German Clinical Trials Register (DRKS).

The Lancet Commission on Global Surgery emphasised the importance of access to safe anaesthesia care. Capnography is an essential monitor for safe anaesthesia, but is rarely available in low-income countries. The aim of this study was twofold: to measure the prevalence of capnography in the operating theatres and in intensive care units; and to determine whether its introduction was feasible and could improve the early recognition of critical airway incidents in a low-income country. This is the first project to do this. Forty capnographs were donated to eight hospitals in Malawi. Thirty-two anaesthesia providers received a 1-day capnography training course with pre- and post-course knowledge testing. Providers kept logbooks of capnography use and recorded their responses to abnormal readings. On follow-up at 6 months, providers completed questionnaires on any significant patient safety incidents identified using capnography. In January 2017, at the commencement of the project, only one operating theatre had a capnograph. Overall, 97% and 100% 'capnography gaps' were identified in the theatres and intensive care units, respectively. The mean (SD) scores of our capnography multiple choice questionnaires improved after training from 15.00 (3.16) to 18.70 (0.99), p = < 0.001. The capnography equipment was appropriately robust and performed well. Six months following implementation, 24 (77%) anaesthesia providers reported recognising 44 oesophageal intubations and 28 (90%) believed that capnography had saved lives. This study has shown it is feasible to introduce capnography in a low-income country, resulting in early recognition of critical airway incidents and ultimately helping to save lives. Building on the experience of the first trial of pulse oximetry implementation in low-income countries in 2007, we believe this is one of the most important projects in anaesthesia safety in the last decade., (© 2018 Association of Anaesthetists.)

Background: Capnography via a CO2/O2 nasal cannula is commonly used for respiratory monitoring during sedation. However, signal disturbances are frequently encountered, especially in young children., Objective: Sampling ports placed closer to the trachea have been shown to result in improved signal quality. In a manikin model of a 6-month-old infant we compared capnography from a modified Guedel airway with a CO2 port located at the tip with that from a CO2/O2 nasal cannula., Design: A comparison study using an artificial model of a breathing 6-month-old infant., Setting: Department of Paediatrics, Inselspital Bern, Switzerland, from March 2016 to June 2016., Material: Modified CO2/O2 Guedel airway., Interventions: Capnography using a modified CO2/O2 Guedel airway or a CO2/O2 nasal cannula was performed for tidal volumes of 20 to 80 ml (in steps of 20 ml), respiratory rates of 20 to 60 min (in steps of 10 min) and with different O2 flows (0 to 2 l min, in steps of 0.5 l)., Main Outcome Measures: Comparison of differences between tracheal and device CO2. Secondary outcomes included the effect of various respiratory settings and O2 flows on the CO2 difference., Results: The tracheal to device CO2 difference was significantly smaller when using a modified CO2/O2 Guedel airway vs. a CO2/O2 nasal cannula: Mean ± SD, 16.8 ± 4.9 vs. 24.1 ± 5.9 mmHg, P less than 0.0001. An O2 flow of 0.5 to 2 l min did not influence the tracheal to device CO2 difference with the modified CO2/O2 Guedel airway in contrast to the CO2/O2 nasal cannula where there were significant differences (P < 0.0001). The effect of various tidal volumes and respiratory rates proved to be similar in both devices., Conclusion: Capnography traces derived from a sample port at the tip of a modified CO2/O2 Guedel airway were more accurate than those obtained from a CO2/O2 nasal cannula., Trial Registration: Not applicable.

Background: Waveform capnography is considered the gold standard for verification of proper endotracheal tube placement, but current guidelines caution that it is unreliable in low-perfusion states such as cardiac arrest. Recent case reports found that long-deceased cadavers can produce capnographic waveforms. The purpose of this study was to determine the predictive value of waveform capnography for endotracheal tube placement verification and detection of misplacement using a cadaveric experimental model., Methods: We conducted a controlled experiment with two intubated cadavers. Tubes were placed within the trachea, esophagus, and hypopharynx utilizing video laryngoscopy. We recorded observations of capnographic waveforms and quantitative end-tidal carbon dioxide (ETCO 2 ) values during tracheal versus extratracheal (i.e., esophageal and hypopharyngeal) ventilations., Results: 106 and 89 tracheal ventilations delivered to cadavers one and two, respectively (n=195) all produced characteristic alveolar waveforms (positive) with ETCO 2 values ranging 2-113mmHg. 42 esophageal ventilations (36 to cadaver one and 6 to cadaver two), and 6 hypopharyngeal ventilations (4 to cadaver one and 2 to cadaver two) all resulted in non-alveolar waveforms (negative) with ETCO 2 values of 0mmHg. Esophageal and hypopharyngeal measurements were categorized as extratracheal (n=48). A binary classification test showed no false negatives or false positives, indicating 100% sensitivity (NPV 1.0, 95%CI 0.98-1.00) and 100% specificity (PPV 1.0, 95%CI 0.93-1.00)., Conclusion: Though current guidelines question the reliability of waveform capnography for verifying endotracheal tube location during low-perfusion states such as cardiac arrest, our findings suggest that it is highly sensitive and specific., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Background: Intermittent measurement of respiratory rate via observation is routine in many patient care settings. This approach has several inherent limitations that diminish the clinical utility of these measurements because it is intermittent, susceptible to human error, and requires clinical resources. As an alternative, a software application that derives continuous respiratory rate measurement from a standard pulse oximeter has been developed. We sought to determine the performance characteristics of this new technology by comparison with clinician-reviewed capnography waveforms in both healthy subjects and hospitalized patients in a low-acuity care setting., Methods: Two independent observational studies were conducted to validate the performance of the Medtronic Nellcor Respiration Rate Software application. One study enrolled 26 healthy volunteer subjects in a clinical laboratory, and a second multicenter study enrolled 53 hospitalized patients. During a 30-minute study period taking place while participants were breathing spontaneously, pulse oximeter and nasal/oral capnography waveforms were collected. Pulse oximeter waveforms were processed to determine respiratory rate via the Medtronic Nellcor Respiration Rate Software. Capnography waveforms reviewed by a clinician were used to determine the reference respiratory rate., Results: A total of 23,243 paired observations between the pulse oximeter-derived respiratory rate and the capnography reference method were collected and examined. The mean reference-based respiratory rate was 15.3 ± 4.3 breaths per minute with a range of 4 to 34 breaths per minute. The Pearson correlation coefficient between the Medtronic Nellcor Respiration Rate Software values and the capnography reference respiratory rate is reported as a linear correlation, R, as 0.92 ± 0.02 (P < .001), whereas Lin's concordance correlation coefficient indicates an overall agreement of 0.85 ± 0.04 (95% confidence interval [CI] +0.76; +0.93) (healthy volunteers: 0.94 ± 0.02 [95% CI +0.91; +0.97]; hospitalized patients: 0.80 ± 0.06 [95% CI +0.68; +0.92]). The mean bias of the Medtronic Nellcor Respiration Rate Software was 0.18 breaths per minute with a precision (SD) of 1.65 breaths per minute (healthy volunteers: 0.37 ± 0.78 [95% limits of agreement: -1.16; +1.90] breaths per minute; hospitalized patients: 0.07 ± 1.99 [95% limits of agreement: -3.84; +3.97] breaths per minute). The root mean square deviation was 1.35 breaths per minute (healthy volunteers: 0.81; hospitalized patients: 1.60)., Conclusions: These data demonstrate the performance of the Medtronic Nellcor Respiration Rate Software in healthy subjects and patients hospitalized in a low-acuity care setting when compared with clinician-reviewed capnography. The observed performance of this technology suggests that it may be a useful adjunct to continuous pulse oximetry monitoring by providing continuous respiratory rate measurements. The potential patient safety benefit of using combined continuous pulse oximetry and respiratory rate monitoring warrants assessment.

Purpose of Review: Standards for capnography inside operating theatres in high and middle-income countries are well recognized and implemented. This review examines recent standards and recommendations for the use of capnography outside the operating room and their rationale and development., Recent Findings: The landmark publication of the Royal College of Anaesthetists and Difficult Airway Society's National Audit Project 4 report provided compelling evidence of airway deaths and a significant patient harm occurring outside the operating room, particularly in ICUs and to a lesser extent in emergency departments. Up to 74% of these ICU deaths could have been prevented by capnography. This provided a serious wake up call for relevant clinicians. As a result, there have recently been new standards published for the use of capnography in these and other areas of the hospital. Waveform capnography can also reflect cardiac output, as the 2015 resuscitation guidelines emphasized. Work still needs to be done on implementing all of these new standards., Summary: Established standards for using capnography within the operating theatre have significantly improved patient safety and it is hoped that the recent publication of new but similar capnography standards for application outside the operating theatre will do the same there. The reasons for the current low levels of implementation of some of these standards outside the operating room are worthy of further research.

Dead space is an important component of ventilation-perfusion abnormalities. Measurement of dead space has diagnostic, prognostic and therapeutic applications. In the intensive care unit (ICU) dead space measurement can be used to guide therapy for patients with acute respiratory distress syndrome (ARDS); in the emergency department it can guide thrombolytic therapy for pulmonary embolism; in peri-operative patients it can indicate the success of recruitment maneuvers. A newly available technique called volumetric capnography (Vcap) allows measurement of physiological and alveolar dead space on a regular basis at the bedside. We discuss the components of dead space, explain important differences between the Bohr and Enghoff approaches, discuss the clinical significance of arterial to end-tidal CO2 gradient and finally summarize potential clinical indications for Vcap measurements in the emergency room, operating room and ICU.

Introduction: Capnography is used to monitor the endtidal carbon dioxide tension (EtCO2) in exhaled gas. Sidestream capnography has great potential to monitor mechanically ventilated pediatric patients, given the continuous sampling from the endotracheal tube into a gas sensor. However, hemodynamic and respiratory impairments may reduce reliability and validity of sidestream capnography to monitor arterial carbon dioxide tension (PaCO2) in critically ill, mechanically ventilated children., Methods: In 47 mechanically ventilated pediatric patients (aged 0-14 years, median age 17.2 months), a total of 341 consecutive measurements of PaCO2, EtCO2, respiratory and hemodynamic parameters were performed, and capnogram shape was determined. Validity was assessed with the Bland-Altman limit of agreement (loa), mixed models were used to adjust for variation between patients, and potential confounders were considered with multivariable analyses., Results: EtCO2 (mean 4.50 ± 0.96 kPa) underestimated PaCO2 (mean 5.37 ± 0.87) considerably, resulting in a loa of 0.87 kPa [95% confidence interval (95% CI) -1.03;2.77] and 42.2% percentage error. The association improved significantly b = 0.54 [95 %CI = 0.45;0.64, P < 0.001] when corrected for individual differences. The association between EtCO2 and PaCO2 was not influenced by any of the potential confounders., Conclusions: Sidestream capnography in mechanically ventilated infants and children seems moderately reliable and valid when corrected for individual differences. Therefore, it could only be used with caution for trend estimation in the individual patient., (© 2015 John Wiley & Sons Ltd.)

Introduction: Fresh frozen cadavers are effective training models for airway management. We hypothesised that residual carbon dioxide (CO2) in cadaveric lung would be detectable using standard clinical monitoring systems, facilitating detection of tracheal tube placement and further enhancing the fidelity of clinical simulation using a cadaveric model., Methods: The tracheas of two fresh frozen unembalmed cadavers were intubated via direct laryngoscopy. Each tracheal tube was connected to a self-inflating bag and a sidestream CO2 detector. The capnograph display was observed and recorded in high-definition video. The cadavers were hand-ventilated with room air until the capnometer reached zero or the waveform approached baseline., Results: A clear capnographic waveform was produced in both cadavers on the first postintubation expiration, simulating the appearances found in the clinical setting. In cadaver one, a consistent capnographic waveform was produced lasting over 100 s. Maximal end-tidal CO2 was 8.5 kPa (65 mm Hg). In cadaver two, a consistent capnographic waveform was produced lasting over 50 s. Maximal end-tidal CO2 was 5.9 kPa (45 mm Hg)., Conclusions: We believe this to be the first work to describe and quantify detectable end-tidal capnography in human cadavers. We have demonstrated that tracheal intubation of fresh frozen cadavers can be confirmed by life-like waveform capnography. This requires further validation in a larger sample size., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

The importance of appropriate equipment to manage the difficult airway has been highlighted by the publication of the Australian and New Zealand College of Anaesthetists (ANZCA) guidelines in 2012. We set out to audit compliance with these guidelines in all public and private sites providing general anaesthesia in metropolitan Perth. Public and private health care websites identified 39 sites of which 37 were studied. Institutional and ethics approval was obtained. A tick-box design audit tool, based on the ANZCA guidelines, was used to collect information regarding the dedicated difficult airway container (DDAC) at each site. As recommended in the guidelines, only equipment within the DDAC was considered. Further data about each site, including the number of theatre suites, satellite anaesthetic areas, use of capnography and categories of patients treated (adult, obstetric and paediatric) were collected. An adult DDAC was found at 92% of all sites, but none of the sites had all the essential equipment listed in the ANZCA guidelines. There was limited provision of adult difficult airway equipment within private sites compared to public, and less provision of paediatric difficult airway equipment across all sites treating paediatric patients in metropolitan Perth. Capnography was available in 76% of post anaesthesia care units and used regularly in 27%. Adherence to the ANZCA guidelines regarding the DDAC could be improved. Standardised equipment across a metropolitan region would be of value in the management of the difficult airway.

This clinical policy from the American College of Emergency Physicians is the revision of a 2005 clinical policy evaluating critical questions related to procedural sedation in the emergency department.1 A writing subcommittee reviewed the literature to derive evidence-based recommendations to help clinicians answer the following critical questions: (1) In patients undergoing procedural sedation and analgesia in the emergency department,does preprocedural fasting demonstrate a reduction in the risk of emesis or aspiration? (2) In patients undergoing procedural sedation and analgesia in the emergency department, does the routine use of capnography reduce the incidence of adverse respiratory events? (3) In patients undergoing procedural sedation and analgesia in the emergency department, what is the minimum number of personnel necessary to manage complications? (4) Inpatients undergoing procedural sedation and analgesia in the emergency department, can ketamine, propofol, etomidate, dexmedetomidine, alfentanil and remifentanil be safely administered? A literature search was performed, the evidence was graded, and recommendations were given based on the strength of the available data in the medical literature.

Background: Measuring and monitoring end-tidal carbon dioxide (PETCO2) is an important aspect of caring for critically ill patients. The 2 methods used for PETCO2 measurement are the mainstream and sidestream methods., Objective: To assess the agreement between PETCO2 measurements performed by mainstream and sidestream methods with the PaCO2 values., Methods: This was a prospective observational study. A total of 114 subjects were enrolled in the study. PETCO2 measurements using mainstream and sidestream methods were performed simultaneously with the arterial blood sampling in subjects who were observed in the emergency department and required arterial blood gas analysis. Agreement between the PETCO2 measurements and the PaCO2 values obtained from arterial blood gas analysis were evaluated using the Bland-Altman method., Results: Sixty subjects (52.6%) were female, and the mean age was 60.9 years (95% CI 58.3-63.6). The mean PaCO2 was 35.16 mm Hg (95% CI 33.81-36.51), the mainstream PETCO2 was 22.11 (95% CI 21.05-23.18), and the sidestream PETCO2 was 25.48 (95% CI 24.22-26.75). Bland-Altman analysis showed an average difference between mainstream PETCO2 and PaCO2 values of 13 mm Hg (95% limits of agreement -0.6 to 25.5) and moderate correlation (r = 0.55, P < .001). The average difference between the sidestream PETCO2 and PaCO2 values was 9.7 mm Hg (95% limits of agreement -5.4 to 24.7) and poor correlation (r = 0.41, P < .001)., Conclusions: PETCO2 values obtained by mainstream and sidestream methods were found to be significantly lower than the PaCO2 values. There was essentially no agreement between the measurements obtained by 2 different methods and the PaCO2 values.

Background: Current methods for monitoring ventilatory rate have limitations including poor accuracy and precision and low patient tolerance. In this study, we evaluated a new acoustic ventilatory rate monitoring technology for accuracy, precision, reliability, and the ability to detect pauses in ventilation, relative to capnometry and a reference method in postsurgical patients., Methods: Adult patients presenting to the postanesthesia care unit were connected to a Pulse CO-Oximeter with acoustic monitoring technology (Rad-87, version 7804, Masimo, Irvine, CA) through an adhesive bioacoustic sensor (RAS-125, rev C) applied to the neck. Each subject also wore a nasal cannula connected to a bedside capnometer (Capnostream20, version 4.5, Oridion, Needham, MA). The acoustic monitor and capnometer were connected to a computer for continuous acoustic and expiratory carbon dioxide waveform recordings. Recordings were retrospectively analyzed by a trained technician in a setting that allowed for the simultaneous viewing of both waveforms while listening to the breathing sounds from the acoustic signal to determine inspiration and expiration reference markers within the ventilatory cycle without using the acoustic monitor- or capnometer-calculated ventilatory rate. This allowed the automatic calculation of a reference ventilatory rate for each device through a software program (TagEditor, Masimo). Accuracy (relative to the respective reference) and precision of each device were estimated and compared with each other. Sensitivity for detection of pauses in ventilation, defined as no inspiration or expiration activity in the reference ventilatory cycle for ≥30 seconds, was also determined. The devices were also evaluated for their reliability, i.e., the percentage of the time when each displayed a value and did not drop a measurement., Results: Thirty-three adults (73% female) with age of 45 ± 14 years and weight 117 ± 42 kg were enrolled. A total of 3712 minutes of monitoring time (average 112 minutes per subject) were analyzed across the 2 devices, reference ventilatory rates ranged from 1.9 to 49.1 bpm. Acoustic monitoring showed significantly greater accuracy (P = 0.0056) and precision (P- = 0.0024) for respiratory rate as compared with capnometry. On average, both devices displayed data over 97% of the monitored time. The (0.95, 0.95) lower tolerance limits for the acoustic monitor and capnometer were 94% and 84%, respectively. Acoustic monitoring was marginally more sensitive (P = 0.0461) to pauses in ventilation (81% vs 62%) in 21 apneic events., Conclusions: In this study of a population of postsurgical patients, the acoustic monitor and capnometer both reliably monitored ventilatory rate. The acoustic monitor was statistically more accurate and more precise than the capnometer, but differences in performance were modest. It is not known whether the observed differences are clinically significant. The acoustic monitor was more sensitive to detecting pauses in ventilation. Acoustic monitoring may provide an effective and convenient means of monitoring ventilatory rate in postsurgical patients.

Background: Transportable capnometers(EMMA) can be useful in the emergency department or Rapid Response System. Before EMMA can be implemented, it must be compared with currently employed capnography methods. Methods : The concentration of CO2 in a reference gas was measured by two EMMA machines and a side-stream capnometer (CAPNOX ), respectively. Next, Etco2 in twelve patients under general anesthesia was measured by both EMMA machines and the side-stream capnometer, respectively. Results were analyzed using Pearson's correlation coefficient and the Bland-Altman plot. Results : With regard to the reference gas ([CO2] of 38 mmHg), the EMMA machines reported CO, concentrations of 37.2 mmHg and 35 mmHg, and the capnometer reported 38 mmHg. For the 12 anesthetized patients, 47 Etco2 readings were taken. Pearson's correlation coefficient between the first EMMA machine and the capnometer was 0.98 (P<0.0001, bias 3.6 mmHg, 95% limits of agreement 1.3-5.9mmHg) and between the second EMMA machine and the capnometer was 0.99 (P<0.0001, bias 0.85 mmHg, 95% limits of agreement-0.7-2.4 mmHg)., Conclusions: In patients under general anesthesia, EMMA measured Etco2 within 4 mmHg of side-stream capnography, indicating sufficient accuracy for clinical use. At the same time, discrepancies in readings between individual machines must be taken into consideration.

Introduction: Due to complexities in its measurement, adequacy of ventilation is seldom used to categorize disease severity and guide ventilatory strategies. Ventilatory ratio (VR) is a novel index to monitor ventilatory adequacy at the bedside. VR=(VEmeasured × PaCO₂measured)/(VEpredicted × PaCO₂ideal). VEpredicted is 100 mL.Kg-1.min-1 and PaCO₂ideal is 5 kPa. Physiological analysis shows that VR is influenced by dead space (VD/VT) and CO₂ production (VCO₂). Two studies were conducted to explore the physiological properties of VR and assess its use in clinical practice., Methods: Both studies were conducted in adult mechanically ventilated ICU patients. In Study 1, volumetric capnography was used to estimate daily VD/VT and measure VCO₂ in 48 patients. Simultaneously, ventilatory ratio was calculated using arterial blood gas measurements alongside respiratory and ventilatory variables. This data was used to explore the physiological properties of VR. In Study 2, 224 ventilated patients had daily VR and other respiratory variables, baseline characteristics, and outcome recorded. The database was used to examine the prognostic value of VR., Results: Study 1 showed that there was significant positive correlation between VR and VD/VT (modified r = 0.71) and VCO₂ (r = 0.14). The correlation between VR and VD/VT was stronger in mandatory ventilation compared to spontaneous ventilation. Linear regression analysis showed that VD/VT had a greater influence on VR than VCO₂ (standardized regression coefficient 1/1-VD/VT: 0.78, VCO₂: 0.44). Study 2 showed that VR was significantly higher in non-survivors compared to survivors (1.55 vs. 1.32; P < 0.01). Univariate logistic regression showed that higher VR was associated with mortality (OR 2.3, P < 0.01), this remained the case after adjusting for confounding variables (OR 2.34, P = 0.04)., Conclusions: VR is an easy to calculate bedside index of ventilatory adequacy and appears to yield clinically useful information.

A short cut review was carried out to establish whether capnography should be routinely used during procedural sedation in Emergency Departments. 206 papers were found using the reported searches, of which nine presented the best evidence to answer the clinical question. The author, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses of these best papers are tabulated. It is that capnography may provide early warning of ventilatory changes that could result in hypoxia.

The Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society (NAP4) has published an extensive report examining both current practices in the United Kingdom regarding airway management during anaesthesia and the complications of airway management during anaesthesia and in intensive care units and emergency departments. The report makes more than 160 recommendations designed to improve care of patients. These recommendations have implications for individuals, departments, organisations and potentially for national policy in terms of training, standards of practice and the need for guidelines. The report also indicates several specific areas where future research might be directed. This article focuses on the implementation phase of NAP4, emphasising the importance of taking the lessons derived from NAP4 and turning them into actions to improve the safety of airway care delivered to patients, wherever in hospital this takes place., (© 2011 The Authors. Anaesthesia © 2011 The Association of Anaesthetists of Great Britain and Ireland.)

Introduction: We attempted to adapt a METI Emergency Care Simulator to support anesthesia scenarios but faced two challenges: the CO2 gas exhaled by the mannequin does not represent the simulated patient's physical status, and the METI Waveform Display software does not support capnography monitoring., Methods: We developed a software application that simulates a CO2 trace that corresponds to the mannequin's ventilation. The software generated a range of CO2 waveform shapes whereas the mannequin was either spontaneously breathing or being mechanically ventilated. We tested the software in three environments: (1) a full-scale simulator research study of advanced anesthesia monitoring displays, (2) simulator-based training courses at the Royal Adelaide Hospital, and (3) at the Sydney Medical Simulation Centre., Results: The research study participants successfully used the simulated monitor to confirm correct intubation and detect airway events. Instructors at the Royal Adelaide Hospital reported improvement in the fidelity of simulations for anesthesia trainees. Simulation coordinators at the Sydney Medical Simulation Centre were able to use their Emergency Care Simulator for anesthesia training scenarios, which they were previously unable to run., Conclusion: We were able to substantially increase the realism of our anesthetic scenarios for research studies and training participants with only a small increase in the fidelity of our capnography monitoring.

Background: Monitoring CO2 levels in preterm infants receiving mechanical ventilation is designed to avoid the harmful consequences of hypocapnia or hypercapnia. Capnography is of questionable accuracy for monitoring PCO2 in preterm infants., Objectives: To determine the accuracy of sidestream capnography in ventilated preterm infants by comparing end-tidal carbon dioxide (EtCO2) values to mixed venous carbon dioxide pressure (PvCO2) and to transcutaneous carbon dioxide pressure (TcPCO2)., Methods: Simultaneous recordings of EtCO2, TcPCO2 and PvCO2 in 37 ventilated preterm infants. The PvCO2-EtCO2 gradient was calculated. The Bland-Altman technique and the intra-class correlation coefficient (ICC) were used to assess agreement between methods. The area under the curve (AUC) was calculated., Results: Ninety-nine EtCO2/PvCO2 pairs were studied from 37 preterm infants with a mean gestational age of 27.7 +/- 1.9 weeks and a mean birth weight of 1,003 +/- 331 g. The mean PvCO2-EtCO2 gradient was 11.2 +/- 8.0 mmHg, and the ICC was 0.28. The mean PvCO2-TcPCO2 gradient was 0 +/- 7.8 mmHg, and the ICC was 0.78. AUCs for EtCO2 and TcPCO2 were similar in detecting high or low PvCO2., Conclusion: Despite an insufficient correlation between EtCO2 and PvCO2, capnography was able to detect low and high CO2 warning levels with a similar efficacy to that of TcPCO2, and may therefore be of clinical interest.

Invasive or endotracheal mechanical ventilation can lead to numerous complications likely to burden morbidity and mortality of patients in the intensive care unit. Various safety practices for mechanical ventilation may involve intubation, the mechanical ventilation period, weaning and extubation, the use of tracheostomy as well as non-invasive ventilation. The main objective of safety practices described in this chapter is to prevent or avoid the main risks due to invasive mechanical ventilation.

Purpose of Review: Procedural sedation and monitored anesthesia care have become increasingly common in locations outside of the operating room. The different types of procedures are presented along with pertinent safety issues with the use of different drug combinations., Recent Findings: Based on the annual data from one hospital, of approximately 63,000 patients undergoing diagnostic or therapeutic procedures under sedation or anesthesia, 41% were sedated by non-anesthesiologists. Monitored anesthesia care was given to 0.4% of patients outside of the operating room. Events associated with monitored anesthesia care have been related to age, American Society of Anesthesiologists physical status, and obesity. Without the use of capnography, significant delays in the detection of apnea were demonstrable. Respiratory compromise with propofol for sedation appears less than that described for sedation using opiates and benzodiazepines., Summary: The number and types of procedures done outside of the operating room are steadily increasing. Sedation for these is often provided by nonanesthesiologists. A quality assurance system dedicated to track events associated with procedural sedation and anesthesia done outside of the operating room is instrumental for the maintenance of exemplary quality of sedation and safety of our patients.

During neonatal resuscitation, the routine use of capnography to verify correct placement of the endotracheal tube is not an established international practice. We present four cases that illustrate the successful use of immediate capnography to verify correct tracheal tube placement even in extremely low birthweight (ELBW) prematures (< 1000 g) during resuscitation. Based on this limited experience, we reached institutional consensus among paediatricians and anaesthesiologists that capnography should become standard monitoring during all endotracheal intubations in premature babies.

Background: Most patients with suspected pulmonary embolism (PE) have a positive D-dimer test and undergo diagnostic imaging. Additional non-invasive bedside tests are required to reduce the need for further diagnostic tests., Objectives: We aimed to determine whether a combination of clinical probability assessment and alveolar dead space fraction measurement can confirm or exclude PE in patients with an abnormal D-dimer test., Methods: We assessed clinical probability of PE and alveolar dead space fraction in 270 consecutive in- and outpatients with suspected PE and positive D-dimer. An alveolar dead space fraction < 0.15 was considered normal. PE was subsequently excluded or confirmed by venous compression ultrasonography, spiral computed tomography and a 3-month follow-up. Radiologists were unaware of the results of clinical probability and capnography., Results: PE was confirmed in 108 patients (40%). Capnography had a sensitivity of 68.5% (95% confidence interval [CI]: 58.9-77.1%) and a specificity of 81.5% (95% CI: 74.6-87.1%) for PE. Forty-five patients (16.6%) had both a low clinical probability and normal capnography (sensitivity: 99.1%, 95% CI: 94.9-100%) and 34 patients (12.6%) had both a high clinical probability and abnormal capnography (specificity: 100%, 95% CI: 97.7-100%)., Conclusion: Capnography alone does not exclude PE accurately. The combination of clinical probability and capnography accurately excludes or confirms PE and avoids further testing in up to 30% of patients.

Factors affecting the results of carbon dioxide (CO2) concentration measurements and methods of their automatic compensation are considered for capnometers of two types: lateral flow (LF) and main flow (MF) capnometers. Advantages of the use of one-channel photometer in LF capnometer with automatic calibration were demonstrated. Compensation for temperature, pressure, and presence of concomitant gases and vapors in inhalation mixture is implemented automatically by introducing correction factors in CO2 concentration value. Calibration curves could be obtained empirically for specific capnometer model integrated into the gas analyzer. Carbon dioxide concentration values measured with LF and MF capnometers should be reduced to standard physical conditions STPD and BTPS conditions, respectively (body temperature and pressure, saturation with water vapors).

This article provides the reader with information and education regarding the use of capnography for both adult and pediatric patients undergoing procedural sedation during endoscopy by: reviewing the basics of capnography, in addition to the physiology of ventilation and oxygenation; illustrating how capnography may provide an earlier warning of hypoxemia than does pulse oximetry; briefly discussing current guidelines for procedural sedation and the potential role of capnography; and reviewing clinical situations causing changes in the capnogram waveforms and the nursing interventions that should be made in response to such changes.

Objective: The purpose of this study was to determine the prognostic value of sublingual PCO2 (P(SL)CO2), lactate concentration, and mixed venous oxygen saturation (S(MV)O2) in hemodynamically unstable intensive care patients and, additionally, to compare the temporal changes of these variables in response to treatment., Setting: Medical/surgical intensive care unit., Subjects: Fifty-four patients, mean age 58 +/- 8 yrs., Interventions: Oxyhemodynamic variables, arterial lactate concentration, and P(SL)CO2 were recorded in unselected sequential intensive care patients undergoing pulmonary artery catheterization. A data set was obtained immediately after insertion of the pulmonary artery catheter and repeated 4 and 8 hrs later., Measurements and Main Results: Twenty-one patients had severe sepsis or septic shock. Twenty-seven (50%) patients died. The initial P(SL)CO2&#95;PaCO2 gradient (P(SL)CO2-diff) and the initial P(SL)CO2 were highly predictive of outcome (p =.0004 and p =.004, respectively); however, there was no difference in the arterial lactate concentration and S(MV)O2 between the survivors and nonsurvivors. The P(SL)CO2-diff had the best receiver operator characteristic characteristics (area under the curve, 0.75), with a P(SL)CO2-diff >25 mm Hg being the best discriminator of outcome. With treatment, the P(SL)CO2-diff decreased in both survivors and nonsurvivors; however, the lactate and S(MV)O2 remained relatively unchanged during the study period., Conclusions: The baseline P(SL)CO2-diff and P(SL)CO2 were better predictors of outcome than traditional markers of tissue hypoxia and were more responsive to therapeutic interventions. The P(SL)CO2-diff and/or P(SL)CO2 may prove to be a useful marker for goal-directed therapy and for assessing the response to clinical interventions aimed at improving tissue oxygenation.

Objectives: Critically ill children often require endotracheal intubation prior to transport to a tertiary care center. Correct endotracheal tube (ETT) placement (trachea vs esophagus) and maintenance of ETT position during transport are of utmost importance. We evaluated the use of a Capno-Flo resuscitator (ventilation bag with a pH-sensitive colorimetric strip in the patient connector; Kirk Specialty Systems, Carrollton, TX) during transport of critically ill children., Methods: Thirty-nine intubations were evaluated in 38 patients (one patient was intubated twice) aged 1 day to 19 years (median age, 13 mo) and weighing 0.9 to 80 kg (median weight, 11 kg) who were intubated and transported by air ( = 26, 68%) and ground ambulance ( = 12, 32%). ETT position was confirmed by physical examination, pulse oximetry, and in some patients, arterial blood gases and chest roentgenograms. ETT position was also assessed using the Capno-Flo after six breaths after intubation and was read as positive if the color changed from purple to yellow (tracheal tube position) and negative if the strip remained purple (esophageal tube position). The Capno-Flo ambu-bag was used continuously during transport and evaluated by the nurses or respiratory therapists, who also completed a brief questionnaire., Results: Two esophageal and 37 tracheal tube positions were correctly identified by the device. There were no false-positive or false-negative results; the device was 100% sensitive and specific for the initial reading. It sometimes took longer to obtain this initial reading (> six breaths) in three patients. During transport, most personnel (36/38) noted minimal or no color change during inspiration and expiration, and therefore, it was not helpful in the continued verification of ETT position., Conclusions: The Capno-Flo resuscitator is useful in the initial confirmation of ETT position but not for continuous evaluation of ETT position during transport.

Objectives: To evaluate the relationship between the arterial end-tidal partial pressure of carbon dioxide (PCO2) difference (deltapCO2) and the degree of desaturation in children with cyanotic heart disease (CHD) and to come to a more reliable estimation of the arterial carbon dioxide partial pressure (PaCO2) from the end-tidal carbon dioxide partial pressure (PET-CO2)., Design and Setting: In part retrospective, in part prospective observational study at a university children's hospital., Subjects and Interventions: We retrospectively assessed the relationship between the arterial oxygen saturation as measured by means of pulse oximetry (SpO2) and the arterial to end-tidal PCO2 differences (deltaPCO2) from the records of medical or surgical interventions in 43 patients with CHD. We derived a PaCO2-PET-CO2 correction formula that was prospectively validated in 34 patients with CHD., Measurements and Results: In the retrospective part we found a significant correlation between SpO2 and deltaPCO2 ( r (2)=0.84, p<0.001). The regression equation (corrected PET-CO2=raw PET-CO2-0.36xSpO2+39) was used in the prospective part to calculate the corrected PET-CO2. The r (2)s for the correlations between PaCO(2) and uncorrected and corrected PET-CO2 were 0.17 ( p<0.05) and 0.94 ( p<0.001), respectively. The uncorrected PET-CO2 bias was 13.0 mmHg, the bias +/- 2SDs was -0.1 and 26.2 mmHg. The corrected PET-CO2 bias was -0.6 mmHg, the bias +/- 2SD's was -4.0 and 2.9 mmHg., Conclusions: Correcting the PET-CO2 for the degree of hypoxia using the SpO2 in artificially ventilated infants and children with CHD results in a clinically applicable estimation of the PaCO2. As both SpO2 and PET-CO2 can be monitored continuously and non-invasively, this could facilitate artificial ventilation management in children with CHD.

This study was undertaken to determine the time interval for changes in end-tidal CO2, oxygen saturation (SaO2), heart rate (HR), and blood pressure (BP) in response to an acute airway obstruction or hypopharyngeal extubation in a hyperoxemic model. Complete and partial airway obstructions were simulated with complete and partial cross-clamping of an endotracheal (ET) tube in five anesthetized, nonparalyzed, mechanically ventilated Yorkshire minipigs with initial PAo2 of > 400 mm Hg. Placement of the ET tube into the hypopharynx was performed to simulate accidental extubation. Both sidestream (SS) and mainstream (MS) capnography were used. Continuous pulse oximetry monitored SaO2, femoral arterial catheter monitored systolic BP, and electrocardiograph monitored HR. The time intervals for the capnograph wave to flatten and for the monitor to display zero were recorded after each airway alteration. The time interval to a change in the initial HR of 10 beats/min, a change of initial systolic BP of 10 mm Hg, and a change of initial SaO2 of 5% were recorded. Experiments were carried out for 180 seconds, and 25 trials were performed. HR, systolic BP, and SaO2 did not change for the 180-second duration of the trials. Complete obstruction produced a flattening of the SS and MS waveform in 8 +/- 2 seconds and 6 +/- 2 seconds, respectively. The SS and MS monitors displayed zero in 19 +/- 1 seconds and 68 +/- 7 seconds, respectively. Partial obstruction did not produce flattening of the wave or a monitor displaying zero. Hypopharyngeal extubation produced a flattening of the SS and MS waveform in 7 +/- 1 seconds and 7 +/- 2 seconds, respectively. The SS and MS monitors displayed zero in 18 +/- 3 seconds and 76 +/- 16 seconds, respectively. Continuous end-tidal CO2 capnography detects acute airway obstruction and hypopharyngeal extubation more rapidly than does pulse oximetry or vital sign monitoring in a hyperoxemic porcine model.

Objective: To evaluate instrument placement and accuracy of indirect physiologic monitoring techniques in anesthetized domestic ferrets., Animals: 10 healthy adult female ferrets (Mustela putorius furo)., Procedure: Direct arterial blood pressure measurement and arterial blood sample collection were performed in ferrets. A pulse oximeter probe was clipped to a forefoot or hind foot; an airway adaptor for capnography was attached to the endotracheal tube; and a sphygmomanometer cuff and Doppler flow probe were positioned on the tail. Isoflurane and nitrous oxide concentrations were varied to induce episodes of hypotension or hypoxia, respectively. Aforementioned noninvasive techniques were compared with direct methods of arterial blood gas analysis, hemoximetry, and arterial blood pressure measurement. Simultaneously obtained direct and indirect measurements were statistically evaluated for mean and SD of the differences, and SEM, and subjectively, for ease of use and relevance to the clinical situation., Results: Values obtained from pulse oximetry were closely related to oxygen saturation measured by blood gas analysis (O2sat). The mean (+/- SD) difference for all results was -0.49 (+/- -4.09)%. The most precise measurements were obtained when O2sat was between 90 and 100%. Capnography measurements varied between ranges. The most accurate measurements were obtained when PaCO2 was < 25 mm of Hg, when the mean difference was 1.6 (+/- -3.01) mm of Hg. Indirect blood pressure measurement consistently underestimated the direct blood pressure value., Conclusions and Clinical Relevance: Pulse oximetry is a convenient and accurate method for monitoring oxygen saturation in domestic ferrets. Capnography is useful for monitoring respiratory rate and pattern, but may present difficulties in interpretation of actual PaCO2. Indirect blood pressure monitoring is not accurate by use of current methods in ferrets.