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22-12-2011 | Cardiology | Article

Ultrasound ‘lung sliding sign’ aids emergency intubation

Abstract

Free abstract

MedWire News: The "lung sliding sign" on ultrasound is a reliable method for confirming proper endotracheal intubation in the emergency setting, Taiwanese researchers say.

Ultrasound guidance is particularly accurate in patients with cardiac arrest and is much quicker to perform than chest radiography, Shyh-Shyong Sim (National Taiwan University Hospital, Taipei) and colleagues report in the journal Resuscitation.

Sim's team conducted a prospective observational study to assess the usefulness of the lung sliding sign during emergency endotracheal intubation. This ultrasonographic sign indicates the gliding of parietal pleura and visceral pleura as the lung inflates and deflates with respiration.

A total of 115 patients were enrolled, all of whom needed emergency intubation because of respiratory failure or cardiac arrest. Their mean age was 67.5 years and mean body mass index (BMI) was 23.5 kg/m2.

Following intubation, all patients were evaluated for lung position using ultrasound and chest radiography. The latter method, considered the gold standard, identified nine patients (7.8%) with one-lung intubation - a serious complication that can lead to hypoventilation, atelectasis, barotrauma, and death.

The ultrasonographic lung sliding sign had a sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 91.5%, 55.6%, 96.0%, and 35.7%, respectively, giving an overall accuracy of 88.7%.

The accuracy of the lung sliding sign was higher in the subgroup of patients with cardiac arrest, however, with a sensitivity, specificity, PPV, and NPV, and overall accuracy of 93.1%, 100%, 100%, 50.0%, and 93.6%, respectively.

Ultrasound was considerably quicker than radiography, note the researchers, with a median operating time of 88 versus 1349 seconds. This difference was seen in both cardiac arrest and other patients.

Finally, logistic regression showed that the diagnostic accuracy of ultrasound was not influenced by patient age, gender, BMI, the length of intubation time, the length of ultrasound operating time, time of day, or individual sonographers.

Sim et al say their results suggest that ultrasound was not equivalent to chest radiography in identifying tube position. "However, among patients with cardiac arrest, the positive the positive predictive value of bilateral lung sliding for confirming proper endotracheal intubation was very high," they write.

Noting that there is no single method or rule that can prevent or detect one-lung intubation with 100% accuracy, they conclude: "We believe that one-lung intubation can be prevented maximally by practicing the combination of clinical assessment, respecting optimal endotracheal tube insertion depths, and ultrasound examination.

"Further studies, which take these variables into account, will need to be undertaken."

By Joanna Lyford

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