Comparison between mainstream (Capnostat 5) and a low-flow sidestream capnometer (Capnostream) in mechanically ventilated, sevoflurane-anesthetized rabbits using a Bain coaxial delivery system

Published:November 17, 2022DOI:



      To evaluate agreement between end-tidal carbon dioxide (Pe′CO2) and PaCO2 with sidestream and mainstream capnometers in mechanically ventilated anesthetized rabbits, with two ventilatory strategies.

      Study design

      Prospective experimental study.


      A total of 10 New Zealand White rabbits weighing 3.6 ± 0.3 kg (mean ± standard deviation).


      Rabbits anesthetized with sevoflurane were intubated with an uncuffed endotracheal tube (3.0 mm internal diameter) and adequate seal. For Pe′CO2, the sidestream capnometer sampling adapter or the mainstream capnometer was placed between the endotracheal tube and Bain breathing system (1.5 L minute–1 oxygen). PaCO2 was obtained from arterial blood collected every 5 minutes. A time-cycled ventilator delivered an inspiratory time of 1 second and 12 or 20 breaths minute–1. Peak inspiratory pressure was initially set to achieve Pe′CO2 normocapnia of 35–45 mmHg (4.6–6.0 kPa). A total of five paired Pe′CO2 and PaCO2 measurements were obtained with each ventilation mode for each capnometer. Anesthetic episodes were separated by 7 days. Agreement was assessed using Bland-Altman analysis and linear mixed models; p < 0.05.


      There were 90 and 83 pairs for the mainstream and sidestream capnometers, respectively. The mainstream capnometer underestimated PaCO2 by 12.6 ± 2.9 mmHg (proportional bias 0.44 ± 0.06 mmHg per 1 mmHg PaCO2 increase). With the sidestream capnometer, ventilation mode had a significant effect on Pe′CO2. At 12 breaths minute–1, Pe′CO2 underestimated PaCO2 by 23.9 ± 8.2 mmHg (proportional bias: 0.81 ± 0.18 mmHg per 1 mmHg PaCO2 increase). At 20 breaths minute–1, Pe′CO2 underestimated PaCO2 by 38.8 ± 5.0 mmHg (proportional bias 1.13 ± 0.10 mmHg per 1 mmHg PaCO2 increase).

      Conclusions and clinical relevance

      Both capnometers underestimated PaCO2. The sidestream capnometer underestimated PaCO2 more than the mainstream capnometer, and was affected by ventilation mode.


      To read this article in full you will need to make a payment

      Purchase one-time access:

      Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'


      Subscribe to Veterinary Anaesthesia and Analgesia
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect


        • Bland J.M.
        • Altman D.G.
        Statistical methods for assessing agreement between two methods of clinical measurement.
        Lancet. 1986; 327: 307-310
        • Colman Y.
        • Krauss B.
        Microstream capnography technology: a new approach to an old problem.
        J Clin Monit Comput. 1999; 15: 403-409
        • Desprez I.
        • Pelchat J.
        • Beaufrère H.
        • et al.
        Agreement of caudal aortic arterial blood pressure with oscillometry using two cuff widths placed on the thoracic or pelvic limbs of sevoflurane-anesthetized rabbits.
        Vet Anaesth Analg. 2022; 49: 390-397
        • Dorsch J.A.
        • Dorsch S.E.
        Gas monitoring.
        in: Dorsch J.A. Dorsch S.E. Understanding Anesthetic Equipment. 5th edn. Lippincott Williams & Wilkins, USA2008: 685-726
        • Duke-Novakovski T.
        Basics of monitoring equipment.
        Can Vet J. 2017; 58: 1200-1208
        • Duke-Novakovski T.
        • Fujiyama M.
        • Beazley S.G.
        Comparison of mainstream (Capnostat 5) and two low-flow sidestream capnometers (VM-2500-S and Capnostream) in spontaneously breathing rabbits anesthetized with a Bain coaxial breathing system.
        Vet Anaesth Analg. 2020; 47: 537-546
        • Ehrenwerth J.
        • Eisenkraft J.B.
        • Berry J.M.
        Breathing circuits.
        in: Ehrenwerth J. Eisenkraft J.B. Berry J.M. Anesthesia Equipment: Principles and Applications. 3rd edn. Elsevier Saunders, USA2013: 95-124
        • Fantoni D.T.
        • Ida K.K.
        • Lopes T.F.T.
        • et al.
        A comparison of the cardiopulmonary effects of pressure controlled ventilation and volume controlled ventilation in healthy anesthetized dogs.
        J Vet Emerg Crit Care. 2016; 26: 524-530
        • Fiorello C.V.
        • Divers S.J.
        in: Carpenter J.W. Exotic Animal Formulary. 4th edn. Elsevier Saunders, USA2012: 517-559
        • Fordyce W.E.
        • Kanter R.K.
        Arterial-end tidal PCO2 equilibration in the cat during acute hypercapnia.
        Respir Physiol. 1988; 73: 257-272
        • Glen J.B.
        A comparison of arterial and tracheal end tidal carbon dioxide tensions during clinical anaesthesia in dogs.
        J Vet Anaesth Analg. 1972; 3: 29-33
        • Gravenstein N.
        • Lampotang S.
        • Beneken J.E.W.
        Factors influencing capnography in the Bain circuit.
        J Clin Monit. 1985; 1: 6-10
        • Hendricks J.C.
        • King L.G.
        Practicality, usefulness, and limits of end-tidal carbon dioxide monitoring in critical small animal patients.
        J Vet Emerg Crit Care (San Antonio). 1994; 4: 29-39
        • Jaffe M.B.
        Respiratory gas analysis – technical aspects.
        Anesth Analg. 2018; 126: 839-845
        • Jin Z.
        • Yang M.
        • Lin R.
        • et al.
        Application of end-tidal carbon dioxide monitoring via distal gas samples in ventilated neonates.
        Pediatr Neonatol. 2017; 58: 370-375
        • Kelmer E.
        • Scanson L.C.
        • Reed A.
        • Love L.C.
        Agreement between values for arterial and end-tidal partial pressures of carbon dioxide in spontaneously breathing, critically ill dogs.
        J Am Vet Med Assoc. 2009; 235: 1314-1318
        • Kruljc P.
        • Nemec A.
        • Vintar N.
        • Butinar J.
        Relation between end-tidal and arterial carbon dioxide partial pressure during general anesthesia with spontaneous breathing and controlled ventilation in dogs – an experimental study.
        Acta Veterinaria (Beograd). 2003; 53: 283-296
        • Lai D.
        • Shiao S.Y.P.K.
        Comparing two clinical measurements: a linear mixed model approach.
        J Applied Stat. 2006; 32: 855-860
        • Lin H.J.
        • Huang C.T.
        • Hsiao H.F.
        • et al.
        End-tidal carbon dioxide measurement in preterm infants with low birth weight.
        PLoS One. 2017; 12e0186408
        • McEvedy B.A.B.
        • McLeod M.E.
        • Kirpalani H.
        • et al.
        End-tidal carbon dioxide measurements in critically ill neonates: a comparison of side-stream and mainstream capnometers.
        Can J Anaesth. 1990; 37: 322-326
        • Nobel J.J.
        Carbon dioxide monitors: exhaled gas (capnographs, capnometers, end-tidal CO2 monitors).
        Pediatr Emerg Care. 1993; 9: 244-246
        • Onodi C.
        • Bühler P.K.
        • Thomas J.
        • et al.
        Arterial to end-tidal carbon dioxide difference in children undergoing mechanical ventilation of the lungs during general anaesthesia.
        Anaesthesia. 2017; 72: 1357-1364
      1. Penlon InterMed, Nuffield 200 Ventilator: User Instruction Manual, 2000, Penlon Ltd; UK. (Accessed 5 October 2022).

      2. Penlon InterMed, Nuffield 200 Ventilator. Anaesthesia Solutions: The Versatile Ventilator, 2005, Penlon Ltd; UK. (Accessed 5 October 2022)

        • Rich G.F.
        • Sullivan M.P.
        • Adams J.M.
        Is distal sampling of end-tidal CO2 necessary in small subjects?.
        Anesthesiology. 1990; 73: 265-268
        • Schieber R.A.
        • Namnoum R.
        • Sugden A.
        • et al.
        Accuracy of expiratory carbon dioxide using the coaxial and circle breathing circuits in small subjects.
        J Clin Monit. 1985; 1: 149-155
        • Singh B.S.
        • Gilbert U.
        • Singh S.
        • Govindaswami B.
        Sidestream microstream end tidal carbon dioxide measurements and blood gas correlations in neonatal intensive care unit.
        Pediatr Pulmonol. 2013; 48: 250-256
        • Takahashi D.
        • Goto K.
        • Goto K.
        Effect of tidal volume and end tracheal tube leakage on end-tidal CO2 in very low birth weight infants.
        J Perinatol. 2021; 41: 47-52
        • Teixeira Neto F.J.
        • Carregaro A.B.
        • Mannarino R.
        • et al.
        Comparison of a sidestream capnograph and a mainstream capnograph in mechanically ventilated dogs.
        J Am Vet Med Assoc. 2002; 221: 1582-1585
        • Tingay D.G.
        • Mun K.S.
        • Perkins E.J.
        End tidal carbon dioxide is as reliable as transcutaneous monitoring in ventilated postsurgical neonates.
        Arch Dis Child Fetal Neonatal Ed. 2013; 98: F161-F164
        • West J.B.
        in: West J.B. Respiratory Physiology: The Essentials. 9th ed. Lippincott Williams & Wilkins, USA2012: 12-23
        • Wickham H.
        Wickham H. Ggplot2: Elegant Graphics for Data Analysis. 2nd edn. Springer, USA2016
        • Williams E.
        • Dassios T.
        • Greenough A.
        Assessment of sidestream end-tidal capnography in ventilated infants on the neonatal unit.
        Pediatr Pulmonol. 2020; 55: 1468-1473
        • Wu C.H.
        • Chou H.C.
        • Hsieh W.S.
        • et al.
        Good estimation of arterial carbon dioxide by end-tidal dioxide monitoring in the neonatal intensive care unit.
        Pediatr Pulmonol. 2003; 35: 292-295