Measurement variability of the mediastinum (vascular pedicle and cardiothoracic index) on the chest radiograph with position and respiration

Variabilidad de la medida del mediastino (Pedículo vascular e Índice cardiotorácico) en la radiografía de tórax con la posición y respiración

Objective: to quantify the measurements of the mediastinum, cardiothoracic index and vascular pedicle in the radiographs taken with the patient in the supine position and in expiration, compared with those taken in vertical and in inspiration, and thus propose a standardization of the mediastinal evaluation process.
Materials and methods: a prospective inter-observer correlation study, carried out in the diagnostic imaging service of the Hospital de San José, in the period between January and December of 2003. The patients selected within the inclusion criteria underwent four radiographs in vertical and decubitus, in inspiration and expiration, and the IC and PV were determined, measurements made independently by two expert radiologists. The degree of correlation between the two observers was evaluated using the Pearson coefficient (p <0.01). In addition, the difference of the indices obtained according to the projections was calculated, creating a variable for each difference and determining the average difference of the indices according to age and sex.
Results: 158 patients were analyzed, 85 women (54%) and 73 men (46%). The average age was 35 ± 7 years, with a range between 18 and 65, being 36 ± 12.6 years for women and 35.5 ± 11.2 for men. Values ​​were found for the PV in the vertical inspiration projection of 4.81 cm ± 0.572 (SD) for women and of 5.11 cml- 0.654 (SD) for men (value of p <0.05); the IC in the same projection for women is 0.43 ± 0.045 and in men, 0.45 ± 0.050 (SD) (p value <0.05). In the decubitus projection in expiration, the PV for women was 5.99 cm ± 0.882 (SD) and for men 6.46 cm ± 0.855 (SD) (p value <0.05); the IC of the women is 0.52 ± 0.047 (DS) and of the men of 0.51 ± 0.050 (DS) (value of p> 0.05).
Conclusion: the variability in men with the change of position to decubitus in expiration is 0.06 for the IC and 1.35 cm for the PV. In women, the variability is 0.09 for the IC and 1.18 cm for the PV independent of age. It was found that the findings correlate with the scarce publications, but the data obtained in our population sample are lower than those reported in the international literature.
Abbreviations: MM, mediastinal measurements; IC, cardiothoracic index; PV, vascular pedicle; DS, standard deviation; VI, vertical inspiration; VE, vertical expiration; DI, decubitus inspiration; DE, decubitus expiration.

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