Anesthesiology APPLIED Exam › OSCE: echocardiography and POCUS

Lung ultrasound: pleura, A/B-lines, effusion, pneumothorax

OSCE: echocardiography and POCUS·~5 min read· Physician-reviewed✓ Sourced · 3

Stem

Monitors and echo station. A 74-year-old woman, 68 kg, is short of breath in the PACU two hours after a hip fracture repair, with an SpO2 of 89% on 4 L of nasal oxygen and fine crackles at both bases. The loop is from a linear probe on the right anterior chest: the pleural line shimmers, and four bright vertical lines run from the pleura to the bottom of the screen between two ribs, moving with breathing and erasing the horizontal lines. The left side looks the same.

Question

How do you scan the chest with ultrasound, and what does this loop show?

Ideal answer

HeadlineSliding, so no pneumothorax, and three or more B-lines between two ribs on both anterior chests: lung rockets, an interstitial syndrome,¹ most likely cardiogenic pulmonary edema in her.

Linear probe, sagittal, marker to the head: two ribs and their shadows frame the pleural line, the "bat sign."¹
Is the pleura sliding? Sliding excludes pneumothorax at that point.
Which lines lie beneath? Horizontal A-lines are reverberations of a normal or air-filled pleura; vertical B-lines to the screen bottom, erasing A-lines, mean interstitial fluid.
Posterolateral bases, curvilinear or phased-array probe, right for anything deeper than pleura:² anechoic effusion or tissue-like consolidation above the diaphragm. Air rises, fluid falls: anterior for pneumothorax, bases for fluid.
Pair it with a cardiac view: poor LV and plethoric IVC, diuresis and inotropic support; normal LV, toward ARDS, TRALI or aspiration.

Breaking down the answer

Pleural effusion, pneumothorax and pulmonary edema are named echo diagnoses, and lung, pleura, diaphragm and A/B-lines are named acquisition targets; lung M-mode is in scope.³

Finding	How it looks	What it means
Lung sliding	Shimmer along the pleural line; M-mode "seashore"	Pleural layers apposed; no pneumothorax at this point
Absent sliding	Static pleura; M-mode "barcode" or stratosphere sign	Pneumothorax, mainstem intubation, apnea, ARDS adhesions, pleurodesis or bullae¹
Lung point	Sliding and non-sliding meet and move with breathing	Pneumothorax confirmed; pathognomonic¹
Lung pulse	Pleura pulses with the heartbeat but does not slide	Lung is apposed but not ventilated: mainstem intubation or atelectasis¹
A-lines	Horizontal echoes at multiples of pleural depth	Normal aerated lung, or pneumothorax if no sliding
B-lines	Comet tails from the pleural line, laser-like, move with sliding, erase A-lines	≥3 between two ribs ("lung rockets"): interstitial syndrome, pulmonary edema, ARDS, contusion¹
Effusion	Space above the diaphragm, quad and sinusoid signs, "spine sign"	Pleural fluid; the vertebrae are visible through it;² hemothorax and empyema may be echoic
Consolidation	Liver-like tissue with air bronchograms	Pneumonia or atelectasis; dynamic bronchograms favor pneumonia, a lung pulse favors atelectasis¹

Absent sliding is consistent with pneumothorax, not proof — a lung pulse, or any B-line, rules it out at that spot, and a lung point rules it in.¹
Bilateral anterior B-lines — diffuse anterior lung rockets with preserved sliding (the BLUE-protocol B-profile) point to cardiogenic edema; patchy B-lines with spared areas and pleural-line changes favor ARDS.¹
Effusion size — maximal lung-to-chest-wall distance at the base, in millimeters, times 20 approximates milliliters supine. A large effusion with hypoxemia supports ultrasound-guided drainage.
Diaphragm — excursion with a curvilinear probe below the costal margin; paradoxical cranial motion on a sniff means hemidiaphragmatic paralysis, the expected consequence of an interscalene block.

Follow-up question

Second scenario: a ventilated patient becomes hypoxemic and hypotensive with rising airway pressure after a subclavian line. The loop shows no sliding in the left anterior chest and A-lines only. What do you say, and what do you do?

Follow-up answer

Headline"Absent sliding with A-lines on the left; a lung point would confirm, but in this patient I treat tension pneumothorax now."

I tell the surgeon and the room, 100% oxygen, and decompress with a needle in the fourth or fifth intercostal space just anterior to the midaxillary line, or the second space midclavicular, then a chest tube; no delay for a lung point in a crashing patient. I reassess pressure, airway pressure and sliding on that side. The quieter variant: absent left sliding with a lung pulse and a tube recently advanced is right mainstem intubation; withdraw the tube and confirm bilateral sliding.

Pitfalls that cost points

Calling absent sliding a pneumothorax without considering mainstem intubation.
Counting one or two B-lines as pathology; isolated B-lines are normal at the bases.
Leaving the depth too deep to see the pleura clearly with a linear probe.
Waiting for imaging confirmation before decompressing a tension pneumothorax.

Rapid-fire

Q: Why do A-lines appear? A: Ultrasound reverberates between the probe and the highly reflective pleura-air interface, producing copies at multiples of the pleural depth.

Q: Why are B-lines a sign of fluid? A: Thickened, fluid-filled interlobular septa next to air create a reverberating comet-tail that the beam cannot pass.

Q: Why is the lung point so specific? A: It is the exact edge where the collapsed lung touches the chest wall, which only exists in a pneumothorax.

Q: Why look anterior for pneumothorax in a supine patient? A: Free air rises to the least dependent part of the chest, which is anterior and medial.

Numbers to know

Item	Value
Linear probe	Pleura only;² 6–15 MHz, depth 4–6 cm
Curvilinear or phased probe for bases	1–5 MHz
Pathologic B-lines	≥3 between two ribs¹
Effusion volume estimate	Distance (mm) × 20 = mL
Lung point	Pathognomonic of pneumothorax¹
Normal quiet diaphragm excursion	~1–2 cm

Sources

1.Lung ultrasound in the critically ill · Annals of Intensive Care (Lichtenstein), 2014 · ebi.ac.ukOpen-access full text (PMC3895677) via Europe PMC; B-line definition, lung point, lung pulse, BLUE-protocol.
2.Defining minimum image quality criteria for common diagnostic point-of-care ultrasound images: A position statement of the Society of Hospital Medicine · SHM (J Hosp Med), 2025 · ebi.ac.ukOpen-access full text (PMC12865264) via Europe PMC; Table 3, lung and pleural images.
3.APPLIED Exam Objective Structured Clinical Examination (OSCE) Content Outline · ABA · theaba.org

Facts on this page were checked against these sources on Oct 14, 2026. Guidelines change; confirm doses against current institutional protocols.