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Nitrogen washout/washin, helium dilution, and computed tomography in the assessment of end-expiratory lung volume

Critical Care201317:453

https://doi.org/10.1186/cc13100

  • Published:

Keywords

  • Public Health
  • Nitrogen
  • Standard Deviation
  • Compute Tomography
  • Helium

We read thoroughly the article published by Chiumello and colleagues [1] in a past issue of Critical Care, along with its corresponding erratum [2], and we believe that the authors have erroneously computed the limits of agreement on several occasions in their article. Indeed, according to the original article by Bland and Altman [3], which was cited by the authors in their Materials and methods section, the limits of agreement should be computed as bias ± 2 standard deviations.

Chiumello and colleagues [1] claimed that the average difference ± 1 standard deviation in the values of end-expiratory lung volume (EELV) measured with the Engström Carestation ventilator (GE Healthcare, Little Chalfont, Buckinghamshire, UK) and with the computed tomography scan amounted to 93 ± 143 mL and the limits of agreement to −50 to 236 mL. With 143 mL as the standard deviation of the bias, limits of agreement should hence become this: [93 − 2 × 143] − [93 + 2 × 143] mL = −193 to 379 mL. The graphical representation of these limits of agreement in the authors’ Figure one [2] is, however, correctly drawn in the interval (green lines) of −193 to 379 mL. So, there is a discrepancy between incorrect computation but a correct graphical representation of the limits of agreement for EELV with both techniques.

Abbreviations

EELV: 

End-expiratory lung volume.

Declarations

Authors’ Affiliations

(1)
Université de Lyon, Université LYON I, 43 boulevard du 11 Novembre 1918, 69622 Villeurbanne cedex, France
(2)
Service de Réanimation Médicale, Hôpital De La Croix Rousse, Hospices Civils de Lyon, 103 Grande Rue de la Croix Rousse, 69004 Lyon, France

References

  1. Chiumello D, Cressoni M, Chierichetti M, Tallarini F, Botticelli M, Berto V, Mietto C, Gattinoni L: Nitrogen washout/washin, helium dilution and computed tomography in the assessment of end expiratory lung volume. Crit Care 2008, 12: R150. 10.1186/cc7139PubMed CentralView ArticlePubMedGoogle Scholar
  2. Chiumello D, Cressoni M, Chierichetti M, Tallarini F, Botticelli M, Berto V, Mietto C, Gattinoni L: Correction: Nitrogen washout/washin, helium dilution and computed tomography in the assessment of end expiratory lung volume. Crit Care 2009, 13: 405. 10.1186/cc7743PubMed CentralView ArticleGoogle Scholar
  3. Bland JM, Altman DG: Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986, 327: 307-310. 10.1016/S0140-6736(86)90837-8View ArticleGoogle Scholar

Copyright

© BioMed Central Ltd. 2013

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