Lung ultrasound versus chest radiography for the diagnosis of pneumothorax in critically ill patients: A prospective, single-blind study.

Sir,

I read the interesting study by Abdalla et al. on the lung ultrasound (US) versus chest radiography (CR) for diagnosing pneumothorax (PTX) in critically ill patients.[1] I am a pediatrician, and I believe it is worthy to comment on that study as the fundamental role of lung US in diagnosing PTX has similarly gained attraction in the pediatric practice.[2] The authors mentioned that the overall lung US showed a considerable higher sensitivity than bedside CR (86.1% vs. 52.7%) while CR had a slightly higher specificity than lung US (99.4% vs. 97.4%).[1] The authors did well in addressing four limitations that might question the study results. I presume that the following methodological limitation is additionally contributory. The conventional lung US consists of a step-by-step procedure targeted toward the detection of four classic US signs, the lung sliding, the B lines, the lung point, and the lung pulse. In most cases, a combination of these signs allows a safe diagnosis of PTX. I presume that ultrasonographers in Abdalla et al.'s study[1] entirely relied on the classical US signs in detecting PTX. It is noteworthy that the widespread application of sonographic methodology in the clinical practice has brought out unusual PTX cases with new three sonographic signs. These include the following: (1) the double lung point consists of the alternating patterns of sliding and nonsliding lung intermittently appearing at the two opposite sides of the scan. (2) The septate PTX allows B lines and lung pulse to be still visible in a condition of PTX with absent sliding. (3) Hydropneumothorax, the air/fluid border, is imaged by lung US as the interposition between an anechoic space and a nonsliding A-pattern, a sign that might be named hydro-point.[3] I presume that there were variations in the awareness of the ultrasonographers on the conventional and new sonographic signs of PTX. This will raise some concerns on the operators' proficiency and hence, the precision of the study results. Despite the aforementioned limitations, the sensitivity and specificity of lung US and CR in Abdalla et al.'s study[1] looked nearly similar to the recently published systematic review and meta-analysis on that issue. The analysis showed that the pooled sensitivity and specificity of lung US were 0.87 (95% confidence interval [CI]: 0.81–0.92; I2 = 88.89, P < 0.001) and 0.99 (95% CI: 0.98–0.99; I2 = 86.46, P < 0.001), respectively. The pooled sensitivity and specificity of CR were 0.46 (95% CI: 0.36–0.56; I2 = 85.34, P < 0.001) and 1.0 (95% CI: 0.99–1.0; I2 = 79.67, P < 0.001).[4] Due to the high diagnostic accuracy of lung US in detecting PTX, as well as its numerous advantages in term of being easily available, noninvasive, bedside, easily examined with no radiation risk, evidence-based guidelines for using bedside US by specialists in the Intensive Care Units for diagnostic, and therapeutic purposes for various organs have been recently launched. Key strong recommendations for the chest included using US for ruling in pleural effusion and assisting its drainage, ascites drainage, ruling in PTX, and central venous cannulation, particularly for internal jugular site.[5]

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