Correspondence  |   March 2018
Accurate Quantification of Pleural Effusion and Cofactors Affecting Weaning Failure
Author Notes
  • Hiroshima University, Hiroshima, Japan (S.O.). ohshimos@hiroshima-u.ac.jp
  • (Accepted for publication November 21, 2017.)
    (Accepted for publication November 21, 2017.)×
Article Information
Correspondence
Correspondence   |   March 2018
Accurate Quantification of Pleural Effusion and Cofactors Affecting Weaning Failure
Anesthesiology 3 2018, Vol.128, 678-679. doi:10.1097/ALN.0000000000002041
Anesthesiology 3 2018, Vol.128, 678-679. doi:10.1097/ALN.0000000000002041
In a recent issue of Anesthesiology, we read with great interest the article by Dres et al.,1  who prospectively studied the prevalence and risk factors of pleural effusion in patients in the intensive care unit. They showed that the prevalence of pleural effusion had no significant impact on weaning failure, the duration of mechanical ventilation, or the intensive care unit length of stay. We appreciate this research for providing insight into the presence of pleural effusion at the time of liberation from mechanical ventilation among patients in the intensive care unit.
However, several factors that could potentially affect the study results should be discussed. First, the procedure for quantification of pleural effusion is still controversial. The authors adopted the procedure recommended by Balik et al.,2  who quantified the pleural effusion volume using the following formula: pleural effusion volume (ml) = 20 × Sep (mm), where Sep was defined by Balik et al. as the maximal end-expiratory distance between the parietal and visceral pleura on ultrasound. However, Balik et al.2  suggested several potential limitations associated with this procedure. They excluded patients with a small volume of pleural effusion (Sep less than 10 mm), Sep and pleural effusion were not linearly correlated in patients with a Sep of less than 17 mm (i.e., pleural effusion of less than 340 ml), and the Sep value was affected by patient height (size of the thoracic cavity). However, Dres et al.1  included patients with a small volume of pleural effusion, and information regarding the patients’ height is lacking. An additional analysis with consideration of these factors would be helpful. Furthermore, whether the pleural effusions were detected unilaterally or bilaterally and whether the total volumes were calculated as a sum remains unclear. Because the effect of pleural effusion on the respiratory condition and gas exchange might differ, unilateral and bilateral effusions should be analyzed separately.
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