Intensive Care Medicine

, Volume 34, Issue 8, pp 1454–1460 | Cite as

Carbon dioxide rebreathing during non-invasive ventilation delivered by helmet: a bench study

  • Francesco MojoliEmail author
  • Giorgio A. Iotti
  • Maddalena Gerletti
  • Carlo Lucarini
  • Antonio Braschi



To define how to monitor and limit CO2 rebreathing during helmet ventilation.


Physical model study.


Laboratory in a university teaching hospital.


We applied pressure-control ventilation to a helmet mounted on a physical model. In series 1 we increased CO2 production (V'CO2) from 100 to 550 ml/min and compared mean inhaled CO2 (iCO2,mean) with end-inspiratory CO2 at airway opening (eiCO2), end-tidal CO2 at Y-piece (yCO2) and mean CO2 inside the helmet (hCO2). In series 2 we observed, at constant V'CO2, effects on CO2 rebreathing of inspiratory pressure, respiratory mechanics, the inflation of cushions inside the helmet and the addition of a flow-by.

Measurements and results

In series 1, iCO2,mean linearly related to V'CO2. The best estimate of CO2 rebreathing was provided by hCO2: differences between iCO2,mean and hCO2, yCO2 and eiCO2 were 0.0 ± 0.1, 0.4 ± 0.2 and −1.3 ± 0.5%. In series 2, hCO2 inversely related to the total ventilation (MVtotal) delivered to the helmet–patient unit. The increase in inspiratory pressure significantly increased MVtotal and lowered hCO2. The low lung compliance halved the patient:helmet ventilation ratio but led to minor changes in MVtotal and hCO2. Cushion inflation, although it decreased the helmet's internal volume by 33%, did not affect rebreathing. A 8-l/min flow-by effectively decreased hCO2.


During helmet ventilation, rebreathing can be assessed by measuring hCO2 or yCO2, but not eiCO2. It is directly related to V'CO2, inversely related to MVtotal and can be lowered by increasing inspiratory pressure or adding a flow-by.


Non-invasive ventilation Helmet Carbon dioxide Rebreathing Monitoring Physical model 


  1. 1.
    Patroniti N, Foti G, Manfio A, Coppo A, Bellani G, Pesenti A (2003) Head helmet versus face mask for non-invasive continuous positive airway pressure: a physiological study. Intensive Care Med 29:1680–1687PubMedCrossRefGoogle Scholar
  2. 2.
    Tonnelier JM, Prat G, Nowak E, Goetghebeur D, Renault A, Boles JM, L'her E (2003) Non-invasive continuous positive airway pressure ventilation using a new helmet interface: a case-control prospective pilot study. Intensive Care Med 29:2077–2080PubMedCrossRefGoogle Scholar
  3. 3.
    Principi T, Pantanetti S, Catani F, Elisei D, Gabbanelli V, Pelaia P, Leoni P (2004) Noninvasive continuous positive airway pressure delivered by helmet in haematological malignancy patients with hypoxemic acute respiratory failure. Intensive Care Med 30:147–150PubMedCrossRefGoogle Scholar
  4. 4.
    Squadrone V, Coha M, Cerutti E, Schellino MM, Biolino P, Occella P, Belloni G, Vilianis G, Fiore G, Cavallo F, Ranieri VM (2005) Continuous positive airway pressure for treatment of postoperative hypoxemia: a randomized controlled trial. JAMA 293:589–595PubMedCrossRefGoogle Scholar
  5. 5.
    Scandroglio M, Piccolo U, Mazzone E, Agrati P, Aspesi M, Gamberoni C, Severgnini P, Di Stella R, Chiumello D, Minoja G, Pelosi P (2002) Use and nursing of the helmet in delivering non invasive ventilation. Minerva Anestesiol 68:475–480PubMedGoogle Scholar
  6. 6.
    Chiumello D, Pelosi P, Carlesso E, Severgnini P, Aspesi M, Gamberoni C, Antonelli M, Conti G, Chiaranda M, Gattinoni L (2003) Noninvasive positive pressure ventilation delivered by helmet vs. standard face mask. Intensive Care Med 29:1671–1679PubMedCrossRefGoogle Scholar
  7. 7.
    Antonelli M, Conti G, Pelosi P, Gregoretti C, Pennisi MA, Costa R, Severgnini P, Chiaranda M, Proietti R (2002) New treatment of acute hypoxemic respiratory failure: noninvasive pressure support ventilation by helmet-A pilot controlled trial. Crit Care Med 30:602–608PubMedCrossRefGoogle Scholar
  8. 8.
    Rocco M, Dell'Utri D, Morelli A, Spadetta G, Conti G, Antonelli M, Pietropaoli P (2004) Noninvasive Ventilation by helmet or face mask in immunocompromised patients: a case-control study. Chest 126:1508–1515PubMedCrossRefGoogle Scholar
  9. 9.
    Antonelli M, Pennisi MA, Pelosi P, Pelosi P, Gregoretti C, Squadrone V, Rocco M, Cecchini L, Chiumello D, Severgnini P, Proietti R, Navalesi P, Conti G (2004) Noninvasive positive pressure ventilation using a helmet in patients with acute exacerbation of chronic obstructive pulmonary disease. a feasibility study. Anesthesiology 100:16–24PubMedCrossRefGoogle Scholar
  10. 10.
    Piastra M, Antonelli M, Chiaretti A, Polidori G, Polidori L, Conti G (2004) Treatment of acute respiratory failure by helmet-delivered non-invasive pressure support ventilation in children with acute leukaemia: a pilot study. Intensive Care Med 30:472–476PubMedCrossRefGoogle Scholar
  11. 11.
    Navalesi P, Costa R, Ceriana P, Carlucci A, Prinianakis G, Antonelli M, Conti G, Nava S (2007) Non-invasive ventilation in chronic obstructive pulmonary disease patients: helmet versus facial mask. Intensive Care Med 33:74–81PubMedCrossRefGoogle Scholar
  12. 12.
    Conti G, Cavaliere F, Costa R, Craba A, Catarci S, Festa V, Proietti R, Antonelli M (2007) Noninvasive positive-pressure ventilation with different interfaces in patients with respiratory failure after abdominal surgery: a matched-control study. Respire Care 52:1463–1471Google Scholar
  13. 13.
    Taccone P, Hess D, Caironi P, Bigatello L (2004) Continuous positive airway pressure delivered with a “helmet”: effects on carbon dioxide rebreathing. Crit Care Med 32:2090–2096PubMedCrossRefGoogle Scholar
  14. 14.
    Hill NS (2004) Noninvasive interfaces: Should we go to helmets? Crit Care Med 32:2162–2163PubMedCrossRefGoogle Scholar
  15. 15.
    Costa R, Navalesi P, Antonelli M, Cavaliere F, Craba A, Proietti R, Conti G (2005) Physiologic evaluation of different levels of assistance during noninvasive ventilation delivered through a helmet. Chest 128:2984–2990PubMedCrossRefGoogle Scholar
  16. 16.
    Racca F, Appendini L, Gregoretti C, Stra E, Patessio A, Donner CF, Ranieri M (2005) Effectiveness of mask and helmet interfaces to deliver non-invasive ventilation in a human model of resistive breathing. J Appl Physiol 99:1262–1271PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • Francesco Mojoli
    • 1
    • 2
    Email author
  • Giorgio A. Iotti
    • 3
  • Maddalena Gerletti
    • 1
  • Carlo Lucarini
    • 1
  • Antonio Braschi
    • 1
    • 2
  1. 1.Servizio di Anestesia e Rianimazione IFondazione IRCCS Policlinico S. MatteoPaviaItaly
  2. 2.Cattedra di Anestesiologia e RianimazioneUniversità degli Studi di PaviaPaviaItaly
  3. 3.Servizio di Anestesia e Rianimazione IIFondazione IRCCS Policlinico S. MatteoPaviaItaly

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