Lung Ultrasound for Pneumothorax

Transducer
1. Linear probe (preferred) or
2. Cardiac phased array probe (more convenient during eFAST Exam)
Transducer positioning
1. Placement: Lung Apex (3rd intercostal space in a supine patient), mid-clavicular line
2. Axis: Long axis with indicator at 12:00
3. Direction: Perpendicular to chest
Landmarks
1. Third rib (with shadowing)
2. Third Interspace
  1. Chest wall
  2. Pleural line
  3. Sliding Lung Sign present (normal findings)
    1. Marching-ants appearance
      1. More prominent with color power doppler mode
    2. Changes on M-mode
      1. Top: Bar code pattern (skin to pleura)
      2. Bottom
        Normal: Seashore granular appearance (lung)
        Pneumothorax: Bar code throughout (known as stratosphere sign)
  4. Artfacts
    1. A-Lines: Pleural line reverberation artfacts (horizontal lines at regular intervals)
    2. B-Lines: Comet tail artifacts (vertical wedges)
3. Fourth rib (with shadowing)
Images

B-Lines (ray artifacts) absent
A-Lines present
1. Typically present in Pneumothorax (and increases Test Specificity)
Sliding-lung sign absent
1. No marching ants appearance
2. Sliding Lung Sign is lost with even a 1 mm gap between parietal and visceral pleura
3. Image
Lung pulse absent
1. Cardiac pulsation may normally be present when parietal and visceral pleura are directly opposed
M-Mode with bar code appearance continuously from top to bottom
1. Confirm by having patient hold their breath
Distinguish from heart motion artifact which can appear similar to sliding-lung sign
1. Staying high in the chest (2nd intercostal space) avoids this potential False Negative finding
Differential diagnosis of absent sliding lung sound includes apnea and shallow respirations
1. Treat absence of Sliding Lung Sign with Chest Tube in a crashing patient with suspicion for Tension Pneumothorax
2. May confirm absent Sliding Lung Sign by identifying the Lung Point
3. Reasonable to obtain additional imaging to confirm Pneumothorax if patient stable without Tension Pneumothorax
  1. However, chest XRay Test Sensitivity for Pneumothorax is lower, especially in a supine patient
Lung Point
1. Can be used to estimate size of Pneumothorax
2. Transition between normal lung and Pneumothorax
3. Transition between Ultrasound seashore appearance and continuous bar code throughout

Single view (third interspace) for Sliding Lung Sign is equivalent to four view on each side (each 93% Test Sensitivity)
1. Helland (2016) Acad Emerg Med 23(10): 1170-5 +PMID: 27428394 [PubMed]