- Letter
- Published:
Nitrogen washout/washin, helium dilution, and computed tomography in the assessment of end-expiratory lung volume
Critical Care volume 17, Article number: 453 (2013)
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.
References
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/cc7139
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/cc7743
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)90837-8
Author information
Authors and Affiliations
Corresponding author
Additional information
Competing interests
The authors declare that they have no competing interests.
Rights and permissions
About this article
Cite this article
Richard, J.C., Guerin, C. Nitrogen washout/washin, helium dilution, and computed tomography in the assessment of end-expiratory lung volume. Crit Care 17, 453 (2013). https://doi.org/10.1186/cc13100
Published:
DOI: https://doi.org/10.1186/cc13100
Keywords
- Public Health
- Nitrogen
- Standard Deviation
- Compute Tomography
- Helium