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Table 4 Intra-individual changes between 58 pairs of consecutive CT scans in sheep

From: Extrapolation in the analysis of lung aeration by computed tomography: a validation study

 

Changes between CTs

(whole-lung analysis)

Bias

(limits of agreement)

Vtotal (ml)

551 (121 to 1863)

6.5 (-72.5 to 85.5)

Vnon (%)

2.6 (0.0 to 11.6)

-0.1 (-0.5 to 0.4)

Vpoor (%)

4.8 (0.3 to 20.7)

-0.2 (-1.1 to 0.8)

Vnorm (%)

8.5 (0.0 to 22.2)

-0.2 (-1.4 to 0.9)

Vhyper (%)

0.5 (0.0 to 4.5)

0.0 (-0.8 to 0.8)

Vgas (%)

6.4 (1.6 to 16.0)

-0.1 (-0.9 to 0.7)

Mtotal (g)*

43 (0 to 189)

-1.5 (-33.0 to 30.0)

Mnon (%)

6.7 (0.0 to 34.4)

-0.1 (-1.6 to 1.4)

Mpoor (%)

8.7 (0.2 to 28.4)

-0.3 (-2.0 to 1.3)

Mnormal (%)

21.0 (0.7 to 38.7)

-0.4 (-2.3 to 1.5)

Mhyper (%)

0.2 (0.0 to 1.9)

0.0 (-0.3 to 0.3)

  1. Data are median (range) for changes of lung volume and masses between two consecutive CTs given in the left column. Bias (95% limits of agreement) from the Bland-Altman analysis of the agreement of changes calculated by extrapolation from 10 CT slices or whole-lung analysis are given in the right column. CT, computed tomography; g, grams; Mhyper, hyperaerated volume or mass; ml, milliliters; Mnon, nonaerated volume or mass; Mnormal, normally aerated volume or mass; Mpoor, poorly aerated volume or mass; Vgas, pulmonary gas volume; Vtotal/Mtotal, total lung volume or mass. Volumes and masses of differently aerated lung compartments were calculated as percentage of Vtotal or Mtotal, respectively. *The sheep studied had gross atelectasis of otherwise normal lungs; the change in airway pressure therefore resulted in large changes in lung volume but only small changes in total lung mass.
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Critical Care

ISSN: 1364-8535