Diagnosis and Management of Pneumothorax

Introduction to Pneumothorax Diagnosis

Pneumothorax can be classified as small (<2 cm) or large (>2 cm) based on the visible distance between the lung margin and the chest wall on a chest radiograph, as per the British Thoracic Society guidelines 1
The British Thoracic Society and the American College of Radiology recommend a standardized approach to diagnosing pneumothorax, with a focus on accurate measurement and classification of pneumothorax size 1, 2

Posteroanterior (PA) radiographs are the standard initial method for diagnosing pneumothorax, with small pneumothoraces defined as <2 cm and large pneumothoraces defined as >2 cm 1
Expiratory radiographs are not recommended as routine but may provide additional information in up to 14% of cases with high clinical suspicion and a normal PA radiograph 1
Lateral decubitus radiographs are superior to upright or supine radiographs and are as sensitive as CT for detecting pneumothorax 1
A two-view chest radiograph (PA and lateral) provides greater diagnostic accuracy than a single-view chest radiograph for detecting pulmonary anomalies, as recommended by the American College of Radiology 3, 4

CT is the most accurate method for quantifying the exact size of pneumothorax, with a sensitivity of 85-95% and specificity of 94-99% 1
CT is recommended for difficult cases, such as patients with bullous lung disease, suspected aberrant tube placement, or radiographs obscured by surgical emphysema, with a moderate level of evidence supporting this statement 1

Lung ultrasound is recommended as the first-line imaging technique for diagnosing pneumothorax when available, due to its ability to show absence of lung sliding, absence of B-lines, and presence of lung point for non-loculated pneumothorax, as per the American College of Radiology 2
Lung ultrasound has several advantages, including bedside availability, no radiation exposure, real-time assessment, and superior accuracy in critically ill patients, but may have technical limitations such as subcutaneous emphysema and severe obesity 5, 6

Pneumothorax Size	Visible Rim
Small	<2 cm
Large	>2 cm

The size of a pneumothorax can be classified based on the visible rim, with small pneumothoraces having a visible rim of <2 cm and large pneumothoraces having a visible rim of >2 cm, as classified by the British Thoracic Society 1

Clinical history is not a reliable indicator of pneumothorax size, and patients with secondary pneumothorax (with underlying lung disease) often present with more severe symptoms even with smaller air collections 1
Pulmonary function tests are weakly sensitive measures of pneumothorax size or presence and are not recommended, with a low level of evidence supporting this statement 1
Patients with respiratory distress should not be left without intervention, regardless of pneumothorax size on chest radiograph, as emphasized by the American Thoracic Society and the British Thoracic Society 1

Relying solely on single-view images to evaluate subtle findings such as small pneumothoraces can lead to misdiagnosis, as warned by the American College of Radiology 3, 4
Failing to consider the possibility of skin folds that can simulate a pneumothorax can also lead to errors, highlighting the need for careful image interpretation, as emphasized by the British Thoracic Society 1
False positives can occur with lung bullae, contusions, and adhesions on lung ultrasound, and absence of lung sliding alone is insufficient for diagnosis of pneumothorax on lung ultrasound, with a moderate level of evidence supporting this statement 6
Underestimating the importance of the lateral view in doubtful cases can result in missed diagnoses, according to the American Thoracic Society and the American College of Radiology 3, 4, 1

The diagnostic sequence for suspected pneumothorax should start with lung ultrasound, followed by chest X-ray for documentation purposes or when ultrasound expertise is unavailable, and CT scan when ultrasound and X-ray findings are equivocal, according to the American College of Radiology 2
A lower threshold for advanced imaging is recommended in patients with underlying lung disease, with a moderate level of evidence supporting this statement 1