• 
• 

Three Part Question

In [patients with suspected pneumothorax] is [transthoracic ultrasound or chest x-ray] better at [detecting the pneumothorax].

Clinical Scenario

A 26-year-old man presents to the ED with a history of blunt trauma to the left trunk. Clinical signs are inconclusive and a supine chest x ray (CXR) demonstrates no pneumothorax. A subsequent CT scan demonstrates a left anterior pneumothorax. You have heard that focused thoracic ultrasound can detect pneumothorax and wonder whether this imaging modality is superior to plain x ray and whether there is any evidence to support this.

Search Strategy

Medline search via NELH from 1950 until November 2008.
[(exp PNEUMOTHORAX/) OR (exp PNEUMOTHORAX, ARTIFICIAL/) ] AND [exp RADIOGRAPHY, THORACIC/] AND [(exp ULTRASONOGRAPHY/) OR (ultrasound.ti,ab) OR (sonography.ti,ab)]

Search Outcome

29 papers were found of which 6 papers were relevant

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Sartori et al 2007 Italy	285 patients post lung biopsy of whom 8 developed pneumothorax	Prospective diagnostic study -single blind	USS vs CXR, if disagree CT requested.	Sensitivity 100% vs 87.5% CXR. Specifity 100% vs 100% CXR.	-Low prevalence of pneumothorax in study population (2.8%) -No gold standard in study group (only one CT)
Chung et al 2005 South Korea	97 post needle aspiration and lung biopsy: of whom 35 developed Pneumothorax	Prospective diagnostic study -single blind	USS vs CXR, CT as gold standard	Sensitivity 80% vs 47% CXR. Specificity 94% vs 94% CXR.	-Small study -Single sonographer
Blaivas et al 2005 USA	176 non-consecutive blunt trauma patients	Prospective diagnostic study -single blind	Pneumothorax on CT or rush of air on insertion of chest drain USS vs CXR	Sensitivity 98.1% (89.9-99.9) USS vs 75.5% (61.7-86.2) CXR. Specificity 99.2%(95.6-99.9) USS vs 100% (97.1-100) CXR.	-Convenience sampling
Kirkpatrick et al 2004 Canada	225 post-trauma patients	Prospective diagnostic study	Pneumothorax on USS v CXR, CT part of composite standard	Sensitivity 48.8% (33.3-64.5) USS vs 20.9% CXR. Specificity 98.7% (96.1-99.7) USS vs 99.6% (97.5-100) CXR.	-Unclear whether the investigators were blinded
Knudtson et al 2004 USA	328 consecutive trauma patients	Prospective diagnostic study	USS v CXR	Sensitivity 92.3% (74.4-97.9) USS. Specificity 99.7% (98.9-99.9) USS.	-Not clearly blinded -CXR used as gold standard.
Dulchavsky SA et al, 2001 USA	382 stable surgical patients (95% post-traumatic)	prospective diagnostic study	USS v CXR	Sensitivity 95%(89-95) Specificity 100% (99-100)	-Only stable patients were recruited -CXR used as gold standard

Comment(s)

These studies were relatively small and only two were obviously blinded. The sensitivity of transthoracic ultrasound for the diagnosis of pneumothorax varied between 58.9% and 100% and specificity varied between 94% and 100%. The CT gold standard was used in four studies. In such cases CT may be able to find small pneumothoraces not visible on CXR. The clinical relevance of such small pneumothoraces in the resuscitation room is debatable (unless intermittent positive pressure ventilator is being considered). There is agreement on diagnostic ultrasonographic signs used to confirm pneumothorax. These papers suggest that transthoracic ultrasound is a superior modality for the diagnosis of pneumothorax, especially when the patient must remain supine. All ultrasound examinations are known to be operator dependent. These studies do address the training requirements for clinicians wanting to perform this investigation.

Clinical Bottom Line

ED transthoracic ultrasound is better than plain x ray in the diagnosis of pneumothorax in the supine patient. CT thorax is the gold standard for diagnosis.

Level of Evidence

Level 2 - Studies considered were neither 1 or 3.

References

1. Sartori S, Tombesi P, Trevisani L et al. Accuracy of Thoracic Sonography in Detection of Pneumothorax After Sonographically Guided Comparison with Chest Radioigraphy. American Journal of Roentgenol 2007;188:37-41
2. Chung MJ, Goo MJ, Im JG, Cho MJ, Kim JS. Value of high resolution ultrasound in detecting a Pneumothorax. Eur Radiol 2005;15:930-935
3. Blaivas M, Lyon M, Duggal S. A Prospective Comparison of Supine Chest Radiography and Bedside Ultrasound for the Diagnosis of Traumatic Pneumothorax. Academic Emergency Medicine 2005; 12(9): 844-850
4. Kirkpatrick AW, Sirois M, Laupland KB et al. Hand-held Sonography for detecting post-traumatic pneumothoraces: The extended focussed assessment with sonography for trauma (FAST). J Trauma 2004;57:2
5. Knudtson JL, Dort JM, Helmer SD, & Smith RS. Surgeon-performed ultrasound for pneumothorax in the trauma suite. J Trauma 2004 2004;56:527-530
6. Dulchavsky SA, Schwarz KL, Kirkpatrick AW et al. Prospective evaluation of thoracic ultrasound in the detection of pneumothorax 6. Dulchavsky SA, Schwarz KL, Kirkpatrick AW et al. Prospective evaluation of thoracic ultrasound in the detection of pneumothorax. J Trauma 2001. 50; 201-205. 2001. 50:201-205