Bedside interpretation: ECG, CXR, CT and labs

Chest X-ray in the ICU: lines, tubes and lung patterns

Reviewed Nov 2026·4 references
New· views rounded down, updated weekly

Checking devices on supine films, recognising ARDS, oedema, pneumothorax and effusion, and when ultrasound beats the X-ray.

Definition
The ICU portable (AP supine) film is mainly for device position and gross pathology; it underestimates effusions and pneumothoraces. Bilateral opacities not fully explained by effusion, collapse or nodules are part of the ARDS definition (CXR, CT or lung ultrasound under the 2023 global definition).

At the bedside

  1. 1

    Check the film

    Patient, date, AP/PA, supine/erect, rotation (clavicle heads vs spinous processes), inspiration.

  2. 2

    Endotracheal tube

    Tip 3-7 cm above the carina (about T2-T4, between clavicle heads); head flexion moves the tip down, extension up.

  3. 3

    Central venous catheter

    Tip at the lower SVC / cavo-atrial junction (about at or just below the carina); check for loops, crossing into the contralateral subclavian or the azygos vein; exclude pneumothorax.

  4. 4

    Nasogastric tube

    Follows midline down the oesophagus, bisects the carina, crosses the diaphragm and the tip lies below the left hemidiaphragm in the stomach; never feed if uncertain.

  5. 5

    Other devices

    Chest drain side hole inside the pleura; IABP tip 2-3 cm below the top of the aortic arch (aortic knob); pacing wire in the RV apex.

  6. 6

    Lungs

    ARDS: bilateral opacities, often peripheral, normal heart size; cardiogenic oedema: upper-lobe diversion, septal lines, perihilar 'bat-wing', effusions, cardiomegaly; pneumonia: lobar consolidation with air bronchograms.

  7. 7

    Pleura on a supine film

    Pneumothorax: deep sulcus sign, hyperlucent hemithorax; effusion: hazy veil over the hemithorax with preserved vascular markings.

  8. 8

    Use ultrasound

    Lung ultrasound detects pneumothorax (absent sliding, lung point), effusion and B-lines more accurately than a supine CXR.

Device position targets

DeviceCorrect positionCommon error
ETT3-7 cm above carinaRight main bronchus intubation
CVC (IJ/SC)Lower SVC / cavo-atrial junctionContralateral subclavian, IJ loop, too deep in RA
NG tubeBelow left hemidiaphragm, ≥ 10 cm into stomachBronchial placement
IABP2-3 cm below aortic knobToo high (left subclavian) or low (renal/mesenteric)
Chest drainAll side holes inside pleuraSubcutaneous or fissural placement
Red flag · call your senior now
NG tube in a bronchus on X-ray: remove before any feed is given.
Red flag
Deep sulcus sign in a ventilated patient with hypotension: tension pneumothorax until proven otherwise.
Pitfall
Accepting radiology of a different tube position after repositioning without a repeat check.
Pitfall
Diagnosing ARDS without excluding cardiogenic oedema (echo).
Pearl
The 2023 global ARDS definition allows SpO₂/FiO₂ ≤ 315 (with SpO₂ ≤ 97%) and lung ultrasound for bilateral opacities - useful where ABG or CT is limited.

Calculators for this topic

PaO₂/FiO₂ ratio

Oxygenation ratio with ARDS severity bands (Berlin; PEEP ≥ 5 cmH₂O).

References

  1. 1

    Matthay MA, Arabi Y, Arroliga AC, et al. A new global definition of acute respiratory distress syndrome. Am J Respir Crit Care Med 2024;209:37-47.

  2. 2

    American Society of Anesthesiologists Task Force on Central Venous Access. Practice Guidelines for Central Venous Access 2020. Anesthesiology 2020;132:8-43.

  3. 3

    Roberts ME, Rahman NM, Maskell NA, et al. British Thoracic Society Guideline for pleural disease. Thorax 2023;78(Suppl 3):s1-42.

  4. 4

    Farkas J. The Internet Book of Critical Care (IBCC). EMCrit Project; continuously updated.

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