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Correspondence  |   March 2018
In Reply
Author Notes
  • Service de Pneumologie et Réanimation, Groupe Hospitalier Pitié-Salpêtrière, Paris, France. martin.dres@aphp.fr
  • (Accepted for publication November 21, 2017.)
    (Accepted for publication November 21, 2017.)×
Article Information
Correspondence
Correspondence   |   March 2018
In Reply
Anesthesiology 3 2018, Vol.128, 679-680. doi:10.1097/ALN.0000000000002042
Anesthesiology 3 2018, Vol.128, 679-680. doi:10.1097/ALN.0000000000002042
We thank Dr. Vetrugno et al., Drs. Jacobsohn and Grocott, and Dr. Iwasaki et al. for their interest and positive appreciations of our study, “Prevalence and Impact on Weaning of Pleural Effusion at the Time of Liberation from Mechanical Ventilation: A Multicenter Prospective Observational Study,” recently published in Anesthesiology.1 
As pointed out by Dr. Vetrugno et al., we used a slightly different method of estimating pleural effusion volume than the method used by Balik et al.2  In the study by Balik et al.,2  patients were investigated supine with a mild torso elevation of 15°, whereas in our study pleura ultrasound was performed while patients were semirecumbent. We choose this approach because pleura ultrasound was performed at the end of the spontaneous breathing trial, which requires the patients to be semiseated. Accordingly, Dr. Vetrugno et al., as well as Dr. Iwasaki et al., suggested that our method could misclassify some patients and potentially bias our findings. We wish to point out, however, that in our study, patients were classified as “no or small pleural effusion” or “moderate to large pleural effusion” based on the British Thoracic Society (BTS) classification3  rather than on the Balik formula.2  Dr. Vetrugno et al. also challenged the sample size of our study given that the majority of patients with pleural effusion had “no or small” pleural effusion. This comment is legitimate, and we agree that further studies are required to investigate specifically the impact of large pleural effusion on weaning outcome.
Drs. Jacobsohn and Grocott suggested that pleural effusion may influence weaning outcome through a mechanism that we did not consider, the increase in pulmonary vascular resistance. Although we are ready to believe that this mechanism may be of relevance, we were not able to find any study dealing with this interesting topic.
Dr. Iwasaki et al. commented on the lack of information regarding laterality, calculation of total pleural effusion volume, and height of the patient. We would like to point out that most of these data are shown in the Results section of our article as well as in figures. In fact, it is noted in the Methods section that “On average, the mean fluid volume was (mean ± SD) 509 ± 408 ml on the left side and 411 ± 329 ml on the right side.” Table 1 displays the sum of volume of pleural effusion (left + right), which is (median [interquartile range]) 80 (0 to 150) ml for “no or small pleural effusion” and 900 (600 to 1,200) ml for “moderate to large.” In addition, Table 2 displays information on laterality: Pleural effusion was bilateral in 17/79 (21%) patients with weaning success and in 12/57 (22%) patients with weaning failure. As per request by Dr. Iwasaki et al., we provide here the height of our patients, which was 168 ± 14 cm in patients with “moderate to large pleural effusion” and 168 ± 24 cm in patients with “no or small pleural effusion.” Later, Dr. Iwasaki et al. suggested that the impact of pleural effusion might differ according to the postextubation ventilation strategy: noninvasive ventilation, high-flow oxygen, or standard oxygen. Although we definitely share the concerns raised, we are unable to address this issue. A comprehensive understanding of the interaction between postextubation ventilation strategy and the impact of pleural effusion would require specific measurements of breathing pattern and lung mechanics. Given that our study was mostly observational, we did not aim at investigating this question. Dr. Iwasaki et al. suggested that our findings would have been different if, rather than comparing weaning success versus weaning failure, we had compared success versus failure of spontaneous breathing trial. In response to this comment, we reassessed our data and found a “moderate to large” pleural effusion in 7/45 (16%) of patients who failed the spontaneous breathing trial and in 11/91 (12%) of patients in whom the spontaneous breathing trial was successful (P = 0.60).
Research Support
Dr. Dres was supported by the French Intensive Care Society (Paris, France; bourse de mobilité 2015); The 2015 Short Term Fellowship program of the European Respiratory Society (Lausanne, Switzerland); The 2015 Bernhard Dräger Award for advanced treatment of acute respiratory failure of the European Society of Intensive Care Medicine (Brussels, Belgium); the Assistance Publique Hôpitaux de Paris (Paris, France), and the Foundation for Medical Research (Paris, France [FDM 20150734498]).
Competing Interests
Research contracts with Medtronic (Dublin, Ireland; to Dr. Dres), Maquet (Rastatt, Germany; to Dr. Dres), and Philips (Amsterdam, The Netherlands; to Dr. Dres). Dr. Dres also has received personal fees from Medtronic (Dublin, Ireland), Maquet (Rastatt, Germany), and MSD (Courbevoie, France). Dr. Demoule received personal fees from Pulsion Medical System (Feldkirchen, Germany) and Astra Zeneca (Cambridge, United Kingdom).
Martin Dres, M.D., Alexandre Demoule, M.D., Ph.D. Service de Pneumologie et Réanimation, Groupe Hospitalier Pitié-Salpêtrière, Paris, France. martin.dres@aphp.fr
References
Dres, M, Roux, D, Pham, T, Beurton, A, Ricard, JD, Fartoukh, M, Demoule, A . Prevalence and impact on weaning of pleural effusion at the time of liberation from mechanical ventilation: A multicenter prospective observational study. Anesthesiology 2017; 126:1107–15 [Article] [PubMed]
Balik, M, Plasil, P, Waldauf, P, Pazout, J, Fric, M, Otahal, M, Pachl, J . Ultrasound estimation of volume of pleural fluid in mechanically ventilated patients. Intensive Care Med 2006; 32:318 [Article] [PubMed]
Havelock, T, Teoh, R, Laws, D, Gleeson, F . BTS Pleural Disease Guideline Group: Pleural procedures and thoracic ultrasound: British Thoracic Society Pleural Disease Guideline 2010. Thorax 2010; 65 Suppl 2:ii61–76 [Article] [PubMed]