Skip to main content

End-tidal carbon dioxide monitoring during bag valve ventilation: the use of a new portable device



For healthcare providers in the prehospital setting, bag-valve mask (BVM) ventilation could be as efficacious and safe as endotracheal intubation. To facilitate the evaluation of efficacious ventilation, capnographs have been further developed into small and convenient devices able to provide end- tidal carbon dioxide (ETCO2). The aim of this study was to investigate whether a new portable device (EMMA™) attached to a ventilation mask would provide ETCO2 values accurate enough to confirm proper BVM ventilation.


A prospective observational trial was conducted in a single level-2 centre. Twenty-two patients under general anaesthesia were manually ventilated. ETCO2 was measured every five minutes with the study device and venous PCO2 (PvCO2) was simultaneously measured for comparison. Bland- Altman plots were used to compare ETCO2, and PvCO2.


The patients were all hemodynamically and respiratory stable during anaesthesia. End-tidal carbon dioxide values were corresponding to venous gases during BVM ventilation under optimal conditions. The bias, the mean of the differences between the two methods (device versus venous blood gases), for time points 1-4 ranges from -1.37 to -1.62.


The portable device, EMMA™ is suitable for determining carbon dioxide in expired air (kPa) as compared to simultaneous samples of PvCO2. It could therefore, be a supportive tool to asses the BVM ventilation in the demanding prehospital and emergency setting.


In a prehospital setting, it is necessary that airway management is easily attempted and maintained [1]. Endotracheal intubation (ETI) is regarded as the gold standard for airway management in advanced life support but the procedure requires training and experience [24]. Prehospital ETI does neither increase survival rate nor neurologic outcome in trauma patients [5]. Therefore, bag-valve mask (BVM) ventilation should be the preferred technique as it is as efficacious and safe, particularly if healthcare providers are unexperienced [1, 3, 4, 6]. On the other hand, it is most important to provide successful airway management using BVM [7]. Guidelines from the European Resuscitation Council (ERC) describes that all health care providers should be traind to use BVM for ventilation during cardiopulmonary resuscitation [8]. BVM, however, is dependent on provider technique and to facilitate the evaluation of this it could be beneficial to use a small capnography device (EMMA™).

The aim of this study was to investigate whether a new portable device attached to a ventilation mask can give end- tidal carbon dioxide (ETCO2) values corresponding to carbon dioxide measurements from venous blood gases (PvCO2).


This was a prospective observational study. The study was approved by the Ethical Board of the Stockholm County, Stockholm, Sweden (2009/652-31/3). Twenty-two women undergoing breast surgery were included after they had given their written informed consent to participate. The surgeries consisted of mastectomies with or without evacuation of the axilla as well as other breast reconstruction work. The patient median age was 56 years (range 40-77) and they were all classified as ASA I or II according to the American Society of Anesthesiologists. The procedure was as follows: The patients were brought to the operating room where venous cannulas for sampling of blood were inserted antecubitally. They were monitored by ECG, pulsoxymetry, non invasive blood pressure (AISYS, Datex Ohmeda, WI, USA) and capnography built with mainstream technology (EMMA™ Emergency Capnometer, PHASEIN AB, Danderyd, Sweden) attached to a bag-valve apparatus. Before the patients were anaesthetized, vital signs were recorded and the patients were all hemodynamic and respiratory stabile prior to anaesthesia. The values are shown in Table 1.

Table 1 Vital signs prior anaesthesia

The patients were anaesthetized with a dose of fentanyl (1.4 micrograms/kg) followed by propofol for induction (2 mg/kg). After induction, the patients were put on an infusion of propofol (0.1-0.2 milligrams/kg/min) according to hospital practice. To establish the level of adequate anaesthesia, a clinical assessment (unconsciousness, cessation of spontaneous ventilation, absence of eye lash and bulb reflexes) was made by the attending anaesthesiologist to evaluate that the patient was properly anesthetized. The patient was ventilated by bag-valve mask during the whole study period. The total time of bag-valve ventilation for evaluation of the new device lasted at least 20 minutes. After the study period ended, a laryngeal mask was inserted and the breast surgery was performed. The same anaesthesiologist was the sole provider of bag-valve ventilation for all twenty-two patients. Every 5 minutes during the study period, sampling occurred for PvCO2 readings together with simultaneous readings from the EMMA™ device (time points 1-4, with 5 minutes in between). The blood samples for venous blood gases and vital signs were collected by the same nurse. All blood gases (PvCO2) were analysed at a nearby analyzer (Radiometer ABL 520, Copenhagen). See flowchart for the study procedure (Fig 1).

Figure 1
figure 1

Flowchart for the study procedure.


Bland-Altman plots were used to investigate the differences between the EMMA™ device and venous blood gases at time points 1, 2, 3 and 4, where most of the differences between the two methods (95%) were expected to lie within the limits of agreement. The assumption of normality was investigated with QQ-plots and the Shapiro-Wilk W test. The Bland-Altman plots were performed using R version 2.9.2. All descriptive statistics used to illustrate the hemodynamic profile of the women undergoing breast surgery during bag-valve ventilation analysis was carried out using Microsoft Excel.


There were no missing data concerning measurement of vital signs and ETCO2 during the study. Regarding to PvCO2 there were three (3) missing observations in blood sample two, three and four for the same patient. The patients were all hemodynamic and respiratory stable during anaesthesia. The hemodynamic and respiratory values are shown in Table 2. Bland-Altman plots are displayed for time points 1 and 3 (Fig 2). The bias, limits of agreement (LoA), and the associated confidence intervals are displayed in Table 3. A violation to the distributional assumption of normality was detected for time point 2. Due to interpretability and comparability over the time points no transformation was however performed and therefore the results should be considered with some caution for this time point. The bias, the mean of the differences between the two methods (device versus venous blood gases), for time points 1-4 ranges from -1.37 to -1.62. The associated limits of agreement were similar for all time points and ranged from -3.17 (lower) to 0.25 (higher).

Table 2 Hemodynamic and respiratory values during study
Figure 2
figure 2

Bland-Altman plots.

Table 3 Bias, limits of agreement and the associated confidence intervals


The aim of this study was to compare the efficacy of a new portable device, EMMA™, for measuring carbon dioxide in expired air compared to carbon dioxide levels in venous blood. The point was to see whether this device could be used as an auxiliary tool for evaluating the accuracy of bag-valve mask ventilation. The main conclusion is that when patients are well under anaesthesia, are hemodynamically stable and adequately ventilated by a trained provider, the device gives acceptable values for exhaled carbon dioxide as compared to venous blood gases. However, our results may not necessarily be transferable to less experienced BVM provider and patients in the prehospital settings. Further studies should include patients and health care providers from the prehospital setting. In an emergency setting, patients are not normally well monitored. Furthermore, many untrained personnel are involved and adequate airway management is sometimes difficult to evaluate. Conventionally, for unconscious patients, ETI is regarded as the gold standard for airway management in ALS, even if the airway management can be easily maintained [1]. However, several studies point to difficulties in using ETI in prehospital settings [3, 4, 6]. Furthermore, prehospital ETI does not appear to have benefits over BVM ventilation and it does not seem to improve neither survival nor neurologic outcome [5]. Particularly, there are disadvantages using ETI in prehospital settings when the procedure is performed by less experienced paramedics or when the tube cannot be inserted due to the lack of experience from necessary anaesthetic drugs. BVM ventilation is the basic technique for all health care providers [1] and guidelines from ERC states that all health care providers should be familiar with the BVM for ventilation during cardiopulmonary resuscitation [8].

There is an increasing interest for the use of end-tidal carbon dioxide measurement in the emergency care and previous studies have for i.e. described how nasal entidal carbon dioxide measurement could assess patients' acute respiratory problems in prehospital settings [9, 10]. In this study we evaluated the EMMA™ device during BVM ventilation under ideal conditions with a trained provider and healthy patients were included.

Capnography is a non-invasive infrared spectroscopy technology for continuous measurement of carbon dioxide (CO2) content throughout the respiratory cycle. When capnograms are used to evaluate the end-tidal concentration of carbon dioxide it must be interpreted in conjunction with other clinical findings such as the work of breathing, CO2 transport and elimination as well as changes in cardiac output during volume resuscitation [11]. Normally, when the partial pressure of carbon dioxide is measured invasively there is a slight discrepancy between blood values and expired carbon dioxide due to dead space of the lung and bronchial tree. This gradient is low, usually around 0.66 kPa at a lower ETCO2 level. This gradient, however, could increase due to patient aging [12]. This was not adjusted for in this study. The results in this study underlines that when the patients are comfortably anaesthetized there is an acceptable agreement between ETCO2 values by the device and simultaneously collected PvCO2 blood samples. The Bland-Altman plots (Fig 2) show agreement between ETCO2 and PvCO2 within 2 SD. The limits of agreement are wide, reflecting the large variation, but considered clinically acceptable in view of the normal difficulties of providing an adequate airway by using BVM and also the spread of different ages of the patients. The strength in the study is that the same experienced anaesthesiologist was the sole provider of ventilation for all the patients. This can also be a limitation as he is able to influence the measurement from the device during BVM. The study did not start until the patients were fully anaesthetized and hemodynamically stable. The patients chosen were all ASA I and II and therefore easily maintained. A weakness could be the difficulty of keeping an adequate airway by BVM. This is highly dependable on the provider skill and technique. Furthermore, we used venous blood gases for simplicity and the lack of an arterial line. Mixed venous blood gases reflect desaturated blood which should more easily attract CO2 due to the Haldane effect [11, 13]. However, a recent study illuminates that peripheral venous blood correlates reasonably well with arterial values, at least for ph, bicarbonate and PCO2[14].


We conclude that, the portable device, EMMA™ is suitable for determining carbon dioxide in expired air (kPa) as compared to simultaneous samples of PvCO2. It could therefore, when the patient has an inadequate respiration, be a supportive tool to assess the BVM ventilation provided there is adequate circulation.


  1. Kurola JO, Turunen MJ, Laakso J-P, Gorski JT, Paakkonen HJ, Silfvast TO: Acomparison of the laryngeal tube and bag-valve mask ventilation by emergency medical technicians: a feasibility study in anesthetized patients. Anesthesia & Analgesia. 2005, 1015: 1477-81.

    Article  Google Scholar 

  2. Dorges V, Wenzel V, Knacke P, Gerlach K: Comparison of different airway management strategies to ventilate apneic, nonpreoxygenated patients. Critical Care Medicine. 2003, 313: 800-4. 10.1097/01.CCM.0000054869.21603.9A.

    Article  Google Scholar 

  3. Wang HE, Lave JR, Sirio CA, Yealy DM: Paramedic intubation errors: isolated events or symptoms of larger problems?. Health Affairs. 2006, 252: 501-9. 10.1377/hlthaff.25.2.501.

    Article  Google Scholar 

  4. Cobas MA, De la Pena MA, Manning R, Candiotti K, Varon AJ: Prehospital intubations and mortality: a level 1 trauma center perspective. Anesthesia & Analgesia. 2009, 1092: 489-93.

    Article  Google Scholar 

  5. Stockinger ZTMD, McSwain NEJMD: Prehospital Endotracheal Intubation for Trauma Does Not Improve Survival over Bag-Valve-Mask Ventilation. Journal of Trauma-Injury Infection & Critical Care. 2004, 563: 531-6.

    Article  Google Scholar 

  6. Sollid SJM, Heltne JK, Soreide E, Lossius HM: Pre-hospital advanced airway management by anaesthesiologists: is there still room for improvement?. Scandinavian Journal of Trauma, Resuscitation & Emergency Medicine. 2008, 161: 2-

    Article  Google Scholar 

  7. Belpomme VMDa, Ricard-Hibon AMD, Devoir CMD, Dileseigres SMD, Devaud M-LMD, Chollet CMD, et al: Correlation of arterial PCO2 and PETCO2 in prehospital controlled ventilation. American Journal of Emergency Medicine. 2005, 237: 852-9.

    Article  Google Scholar 

  8. Latorre F, Nolan J, Robertsson C, Chamberlain D, Baskett P: European Resuscitation Council Guidlines 2000 for Adult Advanced Life Support A statement from the Advanced Life Support Working Group and approved by the Executive Committee of the European Resucitation Council. Resuscitation. 2001, 48: 211-221. 10.1016/S0300-9572(00)00379-8.

    Article  PubMed  Google Scholar 

  9. Klemen P, Golub M, Grmec S: Combination of quantitative capnometry, N-terminal pro-brain natriuretic peptide, and clinical assessment in differentiating acute heart failur from pulmonary disease as cause of acute dyspnea in pre-hospital emergency setting: study of diagnostic accuracy. Croat med J. 2009, 50 (2): 133-142. 10.3325/cmj.2009.50.133.

    Article  PubMed Central  CAS  PubMed  Google Scholar 

  10. Rumpf TH, Krismaric M, Grmec S: Capnometry in suspected pulmonary embolism with positive D-dimer in the field. Critical Care. 2010, 13 (6): 10.1186/cc8197.

  11. Ledingham I, Hanning C, eds: Textbook of Critical Care. 1983, Philadelphia: WB Saunders

  12. Yosefy C, Hay E, Nasri Y, Magen E, Reisin L: End tidal carbon dioxide as a predictor of the arterial PCO2 in the emergency department setting. Emerg Med J. 2004, 215: 557-9. 10.1136/emj.2003.005819.

    Article  Google Scholar 

  13. Weil MH, Rackow EC, Trevino R, Grundler W, Falk JL, Griffel MI: Difference in acid-base state between venous and arterial blood during cardiopulmonary resuscitation. New England Journal of Medicine. 1986, 3153: 153-6. 10.1056/NEJM198607173150303.

    Article  Google Scholar 

  14. Toftegaard M, Rees SE, Andreassen S: Correlation between acid-base parameters measured in artrial blood and venous blood sampled peripherally, from vena cavae superior, and from the pulmonary artery. Eur J Emerg Med. 2008, 15: 86-91. 10.1097/MEJ.0b013e3282e6f5c5.

    Article  PubMed  Google Scholar 

Download references


Lina Benson, Karolinska Institutet/Södersjukhuset, Department of Clinical Science and Education made contributions during the statistical analysis. The study was supported by PHASEIN AB, Danderyd, Sweden.

Author information

Authors and Affiliations


Corresponding author

Correspondence to Veronica Lindström.

Additional information

Competing interests

The authors declare that they have no competing interests.

Authors' contributions

VL, CS and MC conceived and designed the study. VL and PM collected data. Analyses were made by VL, CS, MC and all authors contributed substantially to the manuscript. All authors have read and approved the final manuscript.

Authors’ original submitted files for images

Below are the links to the authors’ original submitted files for images.

Authors’ original file for figure 1

Authors’ original file for figure 2

Rights and permissions

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Reprints and permissions

About this article

Cite this article

Lindström, V., Svensen, C.H., Meissl, P. et al. End-tidal carbon dioxide monitoring during bag valve ventilation: the use of a new portable device. Scand J Trauma Resusc Emerg Med 18, 49 (2010).

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: