Chest Radiograph Interpretation for Respiratory Therapists

Why Respiratory Therapists Read Chest Radiographs

Chest radiograph (CXR) interpretation is a core clinical skill for respiratory therapists (RTs). You will use CXRs every shift to confirm airway device placement, monitor disease progression, guide ventilator management, and recognize life-threatening emergencies such as tension pneumothorax. You are not diagnosing—that is the physician's role—but you must be able to recognize and report critical findings immediately. Patient safety depends on your ability to act quickly when a CXR shows a misplaced endotracheal tube or a new pneumothorax.

Image Quality: The Starting Point

Before interpreting any CXR, assess image quality using three checks:

• Rotation: The medial ends of the clavicles should be equidistant from the spinous processes. Rotation shifts the mediastinum and can mimic pathology.
• Inspiration: A good inspiratory effort shows at least eight to ten posterior rib pairs above the diaphragm. A poor inspiratory effort makes the lung bases appear dense and the heart appear enlarged.
• Exposure (penetration): On a properly exposed film you can faintly see the thoracic vertebral bodies through the cardiac shadow. Overexposure makes densities disappear; underexposure makes everything appear white.

Always note quality issues before drawing conclusions.

The Structured ABCDE Review Approach

Using a consistent sequence prevents missed findings. One widely used framework is:

A – Airway: Trace the trachea from the neck to the carina. The trachea should be midline; deviation suggests tension pneumothorax, large effusion, or atelectasis pulling it toward the affected side. Identify the carina and any visible endotracheal tube (ETT).

B – Bones and soft tissues: Check the ribs, clavicles, scapulae, and visible spine for fractures or abnormalities. Look at the soft tissues for subcutaneous emphysema (air tracking under the skin, seen as streaky lucencies).

C – Cardiac silhouette: The heart should occupy no more than half the transverse diameter of the thorax (cardiothoracic ratio ≤ 0.5 on a PA film). Enlargement may indicate cardiomegaly or pericardial effusion. Haziness at the lung bases extending from a large heart suggests pulmonary edema.

D – Diaphragm and below: The right hemidiaphragm is normally slightly higher than the left (the liver sits below it). Free air under the diaphragm indicates bowel perforation. Blunting of the costophrenic angles suggests pleural effusion.

E – Everything else (lung fields and mediastinum): Systematically compare the right and left lung fields, upper to lower. Look for areas of increased opacity (white = consolidation, atelectasis, edema, effusion) or increased lucency (black = pneumothorax, hyperinflation, pneumatocele).

Key Pathological Findings for RTs

Endotracheal tube position: On an AP chest film, the tip of an oral ETT should sit approximately 3–5 cm above the carina with the patient's head in a neutral position. The carina is usually at the level of the aortic knob or around T4–T5. If the tip is at or beyond the carina, right mainstem intubation is likely—you will see the left lung collapse or hyperinflate. If the tip is too high (above the vocal cords), accidental extubation is imminent. Esophageal intubation may show the tube running lateral to or overlapping the spine, with gastric distension visible, though a CXR alone is not the primary method to confirm esophageal placement (waveform capnography and clinical assessment are used first).

Pneumothorax: Loss of lung markings at the periphery with a visible pleural line. Tension pneumothorax is a clinical emergency: the mediastinum shifts away from the affected side, the diaphragm flattens, and venous return is compromised. Do not wait for a CXR to treat a tension pneumothorax if clinical signs are present.

Pulmonary edema: Bilateral fluffy or hazy opacities, often in a perihilar (bat-wing) distribution, with Kerley B lines (horizontal lines at the lung bases) and possible pleural effusions. In the ICU, cardiogenic pulmonary edema is a common cause of worsening oxygenation.

Consolidation: A homogeneous opacity that obscures vascular markings but may show air bronchograms (air-filled bronchi visible against the opaque lung tissue). Lobar or segmental consolidation is typical of pneumonia or aspiration. Consolidation without air bronchograms is more likely an atelectasis.

Hyperinflation: Flattened diaphragms, increased AP diameter, and increased lucency throughout both lung fields. Classic finding in severe obstructive disease (COPD, acute asthma exacerbation). On a lateral view, the retrosternal air space is increased.

Lines, Tubes, and Devices

Beyond ETTs, RTs must recognize:

• Central venous catheters: Tip should lie in the superior vena cava or cavoatrial junction, not in the right ventricle (arrhythmia risk).
• Chest tubes: Should be directed toward the area of concern (apex for pneumothorax, base for effusion); all side holes must be inside the thoracic cavity.
• Nasogastric tubes: Should cross midline at the carina and project below the left hemidiaphragm; a misplaced NG tube in the right bronchus can cause aspiration.

Safety Principles

1. Act on critical findings immediately. A CXR showing right mainstem intubation or tension pneumothorax requires immediate notification of the provider and, within your scope of practice, corrective action such as withdrawing the ETT to the proper position per protocol.

2. Never remove an ETT based on CXR alone without confirming ventilation status and having re-intubation equipment ready.

3. Document what you see and what you reported. Communication of CXR findings is a patient safety event and must be recorded.

4. CXR is a supplement, not a substitute, for clinical assessment. Always correlate with the patient's breath sounds, SpO₂, ABGs, and ventilator waveforms.