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Arnaud Galbois, MD; Eric Maury, MD, PhD
Author and Funding Information

From the Université Pierre et Marie Curie, Paris Universitas; and AP-HP, Hôpital Saint-Antoine, Service de Réanimation Médicale.

Correspondence to: Arnaud Galbois, MD, Service de Réanimation Médicale, Hôpital Saint-Antoine, 184 rue du faubourg Saint-Antoine, 75571 Paris Cedex 12, France; e-mail: galbois@gmail.com


Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestpubs.org/site/misc/reprints.xhtml).


© 2011 American College of Chest Physicians


Chest. 2011;139(3):728-729. doi:10.1378/chest.10-2891
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To the Editor:

This pilot monocentric study1 provides data that must be confirmed on a more significant number of patients before being generalized. We acknowledge that the study used a single investigator and that pleural ultrasonography (PU) is an operator-dependant technique, but the semiology used in the study is easy to learn, and physicians with no knowledge in ultrasound become confident after very minimal training. This point is confirmed by the fact that residents’ performance was reliable after 2 h of training and has already been observed for other focused ultrasound examinations.2-4

Dr Alrajab noted that chest radiographs (CXRs) were read by the caring physician rather than by independent experienced radiologists. In France, CXRs performed on patients in the ICU are never read by radiologists.5 Because physicians in our ICU read > 4,600 CXRs in 2009, we would consider that they have a certain degree of experience. Moreover, Ball et al6 showed that < 24% of missed pneumothoraces on CXR might have been inferred from subtle radiologic findings and concluded that most of occult pneumothoraces on CXR are really occult and not simply missed.

The Fisher exact test was used to test whether lung point, a specific feature of pneumothorax at PU, was more prevalent in pneumothoraces detected only by PU than in pneumothoraces detected by both CXR and PU. To maximize power, the analysis was made PU-wise but yielded a nonsignificant difference. Therefore, analyzing on the basis of the patient would not have altered the conclusion. Our results show that in this population, more pneumothoraces were detected by PU than by CXR (McNemar test, P < .006), and this was especially true for evaluation at 6 h after clamping. Based on this significant difference, we believe that the study had sufficient power on which to base our conclusion.

Dr Alrajab is right to be cautious with PU use in patients with nonprimary spontaneous pneumothoraces. Abolition of lung sliding has been reported with conditions other than pneumothorax, explaining the nonperfect specificity of this sign.7 As highlighted in the “Discussion” section of our study, physicians must be aware that in the absence of lung point (the only sign with a specificity of 100%), a pneumothorax diagnosis should not be made if other causes of lung sliding abolition have not been ruled out.1 In the present study, pneumothorax was deemed to be related to emphysema in 9%. Nevertheless, PU results were inaccurate in only one of these patients with giant dystrophic emphysema (Fig 5B of our study). Whereas the incidence of emphysema is important in general population, the incidence of giant dystrophic emphysema is fairly low, minimizing the concerns about the ability to generalize our findings.

Finally, Dr Alrajab seems to imply that pneumothoraces missed by CXR are always small. In fact, some pneumothoraces are not seen on CXR because of their anterior location, not because they are too small to be detected. The example reported in Figure 5A of our study illustrates why a bedside CXR cannot detect this anterior pneumothorax, whereas it is a large-tension pneumothorax that pushes the heart to the right side of the thorax.1 Because we did not performed CT scans in each patient, we are not able to assess the incidence of tension pneumothoraces among those missed by CXR, but this was 16/34 (47%) in the study of Tocino et al.8

Compared to CXR, PU performs better in following pneumothoraces after drainage, is reliable when performed by physicians after a brief training session, gives faster results, is radiation free, and is economical because numerous ICUs already have an ultrasound system.

Galbois A, Ait-Oufella H, Baudel JL, et al. Pleural ultrasound compared with chest radiographic detection of pneumothorax resolution after drainage. Chest. 2010;1383:648-655. [CrossRef] [PubMed]
 
Noble VE, Lamhaut L, Capp R, et al. Evaluation of a thoracic ultrasound training module for the detection of pneumothorax and pulmonary edema by prehospital physician care providers. BMC Med Educ. 2009;9:3. [CrossRef] [PubMed]
 
Chalumeau-Lemoine L, Baudel JL, Das V, Arrivé L, et al. Results of short-term training of naïve physicians in focused general ultrasonography in an intensive-care unit. Intensive Care Med. 2009;3510:1767-1771. [CrossRef] [PubMed]
 
Vignon P, Dugard A, Abraham J, et al. Focused training for goal-oriented hand-held echocardiography performed by noncardiologist residents in the intensive care unit. Intensive Care Med. 2007;3310:1795-1799. [CrossRef] [PubMed]
 
Hejblum G, Chalumeau-Lemoine L, Ioos V, et al. Comparison of routine and on-demand prescription of chest radiographs in mechanically ventilated adults: a multicentre, cluster-randomised, two-period crossover study. Lancet. 2009;3749702:1687-1693. [CrossRef] [PubMed]
 
Ball CG, Kirkpatrick AW, Fox DL, et al. Are occult pneumothoraces truly occult or simply missed? J Trauma. 2006;602:294-298. [CrossRef] [PubMed]
 
Lichtenstein DA, Menu Y. A bedside ultrasound sign ruling out pneumothorax in the critically ill. Lung sliding. Chest. 1995;1085:1345-1348. [CrossRef] [PubMed]
 
Tocino IM, Miller MH, Fairfax WR. Distribution of pneumothorax in the supine and semirecumbent critically ill adult. AJR Am J Roentgenol. 1985;1445:901-905. [PubMed]
 

Figures

Tables

References

Galbois A, Ait-Oufella H, Baudel JL, et al. Pleural ultrasound compared with chest radiographic detection of pneumothorax resolution after drainage. Chest. 2010;1383:648-655. [CrossRef] [PubMed]
 
Noble VE, Lamhaut L, Capp R, et al. Evaluation of a thoracic ultrasound training module for the detection of pneumothorax and pulmonary edema by prehospital physician care providers. BMC Med Educ. 2009;9:3. [CrossRef] [PubMed]
 
Chalumeau-Lemoine L, Baudel JL, Das V, Arrivé L, et al. Results of short-term training of naïve physicians in focused general ultrasonography in an intensive-care unit. Intensive Care Med. 2009;3510:1767-1771. [CrossRef] [PubMed]
 
Vignon P, Dugard A, Abraham J, et al. Focused training for goal-oriented hand-held echocardiography performed by noncardiologist residents in the intensive care unit. Intensive Care Med. 2007;3310:1795-1799. [CrossRef] [PubMed]
 
Hejblum G, Chalumeau-Lemoine L, Ioos V, et al. Comparison of routine and on-demand prescription of chest radiographs in mechanically ventilated adults: a multicentre, cluster-randomised, two-period crossover study. Lancet. 2009;3749702:1687-1693. [CrossRef] [PubMed]
 
Ball CG, Kirkpatrick AW, Fox DL, et al. Are occult pneumothoraces truly occult or simply missed? J Trauma. 2006;602:294-298. [CrossRef] [PubMed]
 
Lichtenstein DA, Menu Y. A bedside ultrasound sign ruling out pneumothorax in the critically ill. Lung sliding. Chest. 1995;1085:1345-1348. [CrossRef] [PubMed]
 
Tocino IM, Miller MH, Fairfax WR. Distribution of pneumothorax in the supine and semirecumbent critically ill adult. AJR Am J Roentgenol. 1985;1445:901-905. [PubMed]
 
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