Ultrasound diagnosis of pneumothorax

Introduction

Diagnosis of pneumothorax needs radiographic confirmation, which has numerous drawbacks in emergency (time-consuming, poor sensitivity, irradiation) or even CT. Can lung ultrasound play a role?

Methods

Eighty-five pneumothoraces were studied in 78 consecutive ICU patients (mean age 43 years, range 17–99, 60 men, 18 women). The diagnosis was radiologic in 71 cases and only scanographic (radioccult cases) in 14. The control group included 254 lungs in 127 consecutive patients (mean age 57 years, range 20–85, 87 men, 40 women) who required CT and were free of pneumothorax. Three signs were assessed: (1)absence of 'lung sliding', (2)absence of pathologic 'comet-tail artifacts', (3)fleeting inspiratory visualization of 'lung sliding' or pathologic 'comet-tails' at the limit of the pathologic area, a sign called 'lung point'. Intensivists trained in emergency ultrasound used a Hitachi-405 with a 5 MHz probe in strictly supine patients.

Results

Ultrasound analysis was prevented in eight cases (parietal emphysema in six cases). In 79 analyzable cases, 'lung sliding' was always absent, at least at the lower anterior half, with complete absence of pathologic 'comet-tails' at the same location. A 'lung point' was present in 53 cases. In 249 controls with anterior aerated pattern, 'lung sliding' was present in 190 cases, pathologic 'comet-tails' in 158 cases, and the 'lung point' was visible in no case.

By considering only absent 'lung sliding', ultrasound had a sensitivity of 100% and a specificity of 78%. By considering absent 'lung sliding' plus absence of pathologic 'comet-tails', sensitivity was 100%, specificity 95%. By considering 'lung sliding' plus absence of pathologic 'comet-tails' plus 'lung point', sensitivity was 67% but specificity 100%. For radioccult cases only, 'lung point' sensitivity was 80% and specificity 100%.

Conclusions

Anterior 'lung sliding' or pathologic 'comet-tails' allow pneumothorax to be discounted. The presence of a 'lung point' indicates pneumothorax. Ultrasound proved more sensitive than bedside radiography. Ultrasound use may therefore obviate the need for CT in a majority of cases.

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