Chest X-ray interpretation

Chest X-ray interpretation

X-rays are a form of radiant energy, whose wavelength can penetrate substances that are opaque to light rays. When passing through an object they are variably absorbed, depending on the radio density of the object.

Daily portable chest x-rays are used to monitor the status of postoperative cardio- thoracic surgical patients. Additional X-rays are also required following invasive line insertion and post intubation. Second or third daily X-rays may be indicated for longer-term patients.

· identification and prompt rectification of pulmonary and cardiac conditions

· ensures correct placement of invasive lines and devices.

· adjunct to ongoing respiratory therapy

Positioning of patient

Positioning can affect the quality of the X-ray. Any change in how the patient, X-ray, tube or film is positioned alters the angle and distorts the appearance of the chest organs on the film.

A portable Anterior - Posterior chest X-ray shows the patient’s heart larger .It is not as sharply defined as it appears on a Posterior- Anterior film taken in the X-ray department, because the heart is further away from the film plate and appears magnified in the portable A/P film.

Cardiac patients

X-rays are taken in the supine position while intubated then in the upright position once extubated and stable.

Thoracic patients

X-rays are taken in the upright position once the patient is fully conscious post-operatively.

Technical interpretation

Once the portable X-ray is returned to the unit

· check the name and date is correct

· place the left side of the X-ray to your right on the viewing box

· assess the degree of penetration. The vague outline of the thoracic vertebra should be just visible behind the heart shadow

· make sure the patient is not rotated on the film. Rotation distorts the mediastinal border and makes the right and left lung fields appear different

· check whether there has been adequate inspiration. Good inspiration exposes the 6^th rib anteriorly at the middle of the R) hemi-diaphragm

· compare with the patient’s old films

Guidelines for Chest X-ray interpretation

Devices

· Endotrachael tube - should have their tip 2cm above the carina. Too far down will cause a (R) main bronchus intubation and possible (L) lung collapse

· Tracheostomy tube - should end well above the carina, and above the mid clavicular junction

· CVP Catheter – the tip should be positioned in the Superior Vena Cava, approximately to the right of the middle of the aortic arch

· Swan Ganz Catheter - will be visible through the right atrium and the right ventricle with the tip of the catheter placed about 5-6 cm beyond the bifurcation of the main pulmonary artery. It should not be seen beyond the mediastinal shadow

· IABP catheter - the tip should be below the level of the aortic notch and at approximately the 4^th intercostal rib

· Naso-gastric Tube - visible in the stomach

· Pleural tubes - visible in the pleural cavity

· Temporary pacemaker wires - A thin lead visible at its attachment to the outside of the atrium or ventricle.

· Permanent pacemaker - if placed transvenously (often via subclavian vein) then it is positioned in the right ventricle with the tip seen at the apex of the heart in the AP view. Wires are thicker for permanent pacemakers and easily visible in proximity to the heart.