Department of Research and Development, Norwegian Air Ambulance Foundation, Mailbox 94, Droebak, 1441, Norway.
Scand J Trauma Resusc Emerg Med. 2013 Mar 1;21:11. doi: 10.1186/1757-7241-21-11.
Small pneumothoraxes (PTXs) may not impart an immediate threat to trauma patients after chest injuries. However, the amount of pleural air may increase and become a concern for patients who require positive pressure ventilation or air ambulance transport. Lung ultrasonography (US) is a reliable tool in finding intrapleural air, but the performance characteristics regarding the detection of small PTXs need to be defined. The study aimed to define the volume threshold of intrapleural air when PTXs are accurately diagnosed with US and compare this volume with that for chest x-ray (CXR).
Air was insufflated into a unilateral pleural catheter in seven incremental steps (10, 25, 50, 100, 200, 350 and 500 mL) in 20 intubated porcine models, followed by a diagnostic evaluation with US and a supine anteroposterior CXR. The sonographers continued the US scanning until the PTXs could be ruled in, based on the pathognomonic US "lung point" sign. The corresponding threshold volume was noted. A senior radiologist interpreted the CXR images.
The mean threshold volume to confirm the diagnosis of PTX using US was 18 mL (standard deviation of 13 mL). Sixty-five percent of the PTXs were already diagnosed at 10 mL of intrapleural air; 25%, at 25 mL; and the last 10%, at 50 mL. At an air volume of 50 mL, the radiologist only identified four out of 20 PTXs in the CXR pictures; i.e., a sensitivity of 20% (95% CI: 7%, 44%). The sensitivity of CXR increased as a function of volume but leveled off at 67%, leaving one-third (1/3) of the PTXs unidentified after 500 mL of insufflated air.
Lung US is very accurate in diagnosing even small amounts of intrapleural air and should be performed by clinicians treating chest trauma patients when PTX is among the differential diagnoses.
胸部受伤后，小量气胸（PTX）可能不会立即对创伤患者构成威胁。然而，当需要正压通气或空运时，胸腔内的空气量可能会增加，从而引起患者的关注。肺部超声（US）是发现胸腔内空气的可靠工具，但需要确定检测小量 PTX 的性能特征。本研究旨在确定 US 准确诊断 PTX 时胸腔内空气的体积阈值，并将其与胸部 X 线（CXR）进行比较。
在 20 例气管插管的猪模型中，通过单侧胸腔导管逐步注入空气（10、25、50、100、200、350 和 500ml 各 7 个增量），然后分别用 US 和仰卧前后位 CXR 进行诊断评估。超声医师继续进行 US 扫描，直到根据特征性 US“肺点”征象可以明确诊断 PTX 为止。记录相应的阈值体积。一名资深放射科医师对 CXR 图像进行解读。
使用 US 确认 PTX 诊断的平均阈值体积为 18ml（标准差为 13ml）。65%的 PTX 在胸腔内有 10ml 空气时即可确诊；25%在 25ml 时；最后 10%在 50ml 时。在空气量为 50ml 时，放射科医师仅在 20 张 CXR 图片中识别出 4 个 PTX；即灵敏度为 20%（95%CI：7%，44%）。CXR 的灵敏度随容量增加而增加，但在 67%时趋于平稳，在注入 500ml 空气后仍有三分之一（1/3）的 PTX 无法识别。
肺部 US 对诊断少量胸腔内空气非常准确，在 PTX 为鉴别诊断之一时，应在治疗胸部创伤患者的临床医生中进行。
