RCP 100 - Cardiopulmonary Imaging: Chest X-Ray Terminology

• Cardiopulmonary imaging is an important part of diagnosing patients with cardiopulmonary disease
• Respiratory Care Practitioners should be able to evaluate and understand cardiopulmonary images to better treat and understand patient diagnoses
• Chest radiographs are popular, inexpensive and generally reliable
• CXR, CT scans, MRIs, diagnostic ultrasounds studies, PET studies, and V/Q Scans will be studies, along with common imaging findings related to cardiopulmonary diseases

Chest X-Ray Terminology

• Radiolucent is a dark pattern indicating normal air
• Radiodense or opacity is a white pattern indicating solid or fluid, normal for bones and organs
• Infiltrate is an ill-defined radiodensity indicating atelectasis
• Consolidation is a solid white area indicating pneumonia or pleural effusion
• Hyperlucency is an extra pulmonary air indicating COPD, asthma, or pneumothorax
• Vascular markings refer to lymphatics, vessels, and lung tissue; these increase with CHF and are absent with pneumothorax

Chest X-Ray Terminology (Adjectives)

• Diffuse means spread throughout, as seen in atelectasis or pneumonia
• Opaque means fluid or solid, as seen in consolidation
• Bilateral means both sides
• Unilateral means one side
• Fluffy infiltrates are diffuse whiteness with a butterfly/batwing pattern, indicating pulmonary edema
• Patchy infiltrates are scattered densities indicating atelectasis
• Platelike infiltrates are thin-layered densities indicating atelectasis
• Ground glass or honeycomb refers to reticulogranular distribution through both lung fields seen in ARDS or fibrosis

Chest X-Ray Densities

• Air absorbs the least X-rays, resulting in a dark radiolucent shadow seen in lungs, stomach, or intestines
• Bone absorbs the most X-ray energy resulting in a white radiopaque shadow seen in ribs and clavicles
• Fat, soft tissue, and fluid result in varying degrees of gray

Chest X-Ray Positions

• Posteroanterior
• Lateral
• Right anterior oblique
• Anteroposterior
• Anteroposterior supine
• Right lateral decubitus

PA Chest Film

• Created in the radiology department while the patient is usually standing
• The X-ray beam passes from posterior to anterior (PA) with film placed against the patient's chest
• Results in high-quality film with minimal magnification of the heart shadow

AP Chest Film

• Taken with a portable X-ray machine, the X-ray source is in front of the patient, with film behind them
• AP films are difficult to read because of quality
• The heart shadow is more magnified because the heart is closer to the X-ray source and further from the film
• A patient rotation is more likely

Technical Factors in Reading a Chest X-Ray

• The diaphragm is elevated in a supine position
• The heart appears larger on an AP film because it is more anterior
• Penetration refers to the amount of X-ray exposure
• Overpenetrated film will appear too black
• Underpenetrated film will appear too white

Indications for a CXR

• Unexplained dyspnea
• Severe persistent cough
• Hemoptysis
• Fever and sputum production
• Acute severe chest pain
• Positive TB skin test
• ETT placement
• Placement of Pulmonary artery catheter or central venous pressure catheter
• Elevated or changing plateau pressure during mechanical ventilation
• Sudden decline in oxygenation

Approach to Reading a Chest Film

• Use a disciplined approach
• Less obvious items in the image are just as important
• First, ensure name on the film matches the patient being evaluated
• Second, evaluate the technical quality of the film for proper patient position and X-ray penetration
• Third, systematically evaluate all anatomical structures seen on the film

Other Important Factors to Note About Chest X-Rays

• A CXR may appear normal at first in a PE
• Chronic COPD patients' CXRs may also appear normal
• There may be a lag time behind the clinical condition of the patient
  • For example: Aspiration pneumonia or fever with cough, can take 12 – 24 hours to show

Chest X-Ray Assessment

• Check airways (trachea midline or shift)
• Bones & soft tissue (vertebral bodies, spinal process)
• Check Cardiac Silhoutte & mediastinum (enlarged, deviated)
• Note Diaphragm (gastric bubble, flattening, Right slightly higher than left because of liver)
• Check for Effusions (Pleura), use lateral decub to R/O effusion
• Fields - Inspect lung fields
• Note any lines, tubes, or previous surgeries
• Ensure images are taken on full inspiration; otherwise, it may make the heart appear larger, and airways experience volume loss

Assessment of Structures in Chest X-Ray

• Chest Wall & Mediastinum: Check symmetry of chest, rib fractures, bone changes, heart size, and presence of free air or fluid.
• Lung Evaluation: Verify size, density, symmetry, lung edges in frontal & lateral films, vascular markings, presence of free air or fluid, consolidations & infiltrates.

Hydrothorax/Pleural Effusions

• Pleural effusion is the more common term
• A blunted costophrenic angle on chest X-ray indicates pleural effusion is present
• Approximately 200 ml of pleural fluid will blunt the costophrenic angle
• Lateral decubitus is the best chest X-ray view for detecting small pleural effusion
• Pus in pleural space equals empyema

Pneumothorax

• Air collects in the pleural space
• It may occur spontaneously, with trauma, or with an invasive procedure such as mechanical ventilation, called barotrauma
• Pneumothorax causes lung margin to pull away from the chest wall in the affected region
• The presence of air can be better visualized by comparing inspiratory vs. expiratory CXR

Tension Pneumothorax

• Tension pneumothorax is a serious medical emergency occurring when air within the pleural space is under pressure
• Air accumulates in the pleural space on inspiration but cannot exit on exhalation
• The chest film will show a shift of the mediastinum away from the pneumothorax
• Requires immediate decompression with a chest tube or needle aspiration of trapped air
• Can lead to cardiac tamponade and hemodynamic collapse

Pulmonary Infiltrates

• They are seen on chest radiograph when alveoli fill with watery fluid (edema), pus (pneumonia), blood (alveolar hemorrhage), or fat-rich material (alveolar proteinosis)
• Opacities are seen as white shadows in the lung
• Air bronchogram refers to the phenomenon of air-filled bronchi (dark) being made visible by the opacification of surrounding alveoli (grey/white).

Pulmonary Edema

• Pulmonary edema due to left heart failure is a common finding on chest radiograph
• Left heart failure causes enlargement of pulmonary blood vessels in the apex of the lung, know as cephalization
  • Cephalization is when blood vessels to the apices of the lungs are the same size or larger than the blood vessels to the bases
• Kerley B-lines are often seen with pulmonary edema due to left heart failure
• The chest radiograph often shows an enlarged heart and pleural effusion with CHF

Interstitial Disease

• The chest radiograph usually shows diffuse, bilateral infiltrates
• Infiltrates may look like scattered ill-defined nodules
• There are many different types of ILDs, including idiopathic pulmonary fibrosis and sarcoidosis
• A "honeycomb" appearance can occur with idiopathic pulmonary fibrosis, collagen vascular disease, asbestosis, chronic hypersensitive pneumonitis, and medication induced (amiodarone)

ARDS

• Ground glass appearance
• Honeycomb pattern
• Diffuse bilateral radiopacity

Atelectasis

• It is defined as collapsed or airless condition of the lung
• It is a common finding on chest radiograph, especially in postoperative patients
• "Plate atelectasis" is is localized to a subsegmental portion of the lung
• Lobar atelectasis occurs when the major bronchus is obstructed by a mucus plug, tumor, or foreign body
• Signs of volume loss include elevation of hemidiaphragm & shift of hilum towards the affected side
• Transcription may read “infiltrate” which describes an ill-defined radiodensity

Hyperinflation

• Commonly seen with emphysema
• Other signs of hyperinflation: flattening of hemidiaphragms, large retrosternal airspace, narrowed mediastinum, increased AP diameter
• Emphysema causes loss of visible blood vessels in the lung

Catheters, Lines, & Tubes

• A chest radiograph is obtained after placement of endotracheal tube, CVP line, or pulmonary artery catheter to confirm the correct position
• The tip of endotracheal tube should be 2-6 cm above carina with patient's head in neutral position; it is below the vocal cords and at the level of the aortic knob or notch
• A pacemaker should be positioned in the right ventricle
• Pulmonary artery catheter is placed in the right lower lung field
• Chest tubes are in the pleural space surrounding the lungs
• Nasogastric and feeding tubes should be positioned in the stomach 2-6cm below the diaphragm

CT Scan

• Computed tomography (CT) is very helpful in certain situations
• CT visualizes structures cross-sectionally with great detail up to ~2 mm structures inside lung
• CT scanning creates images looking like "slices" of patient's chest (5 to 7 mm thick)
• Conventional CT scanning is used to evaluate lung nodules & masses, great vessels, mediastinum, & pleural disease
• Iodinated contrast is sometimes used to make the blood appear more dense and allows blood vessels to be distinguished from soft tissue structures; dyes can cause fatal responses

High-Resolution CT Scan

• HRCT scanning examines 1-mm slices of lung, producing greater lung detail
• High-resolution CT scanning is ideal for evaluating diffuse parenchymal lung diseases, including interstitial lung disease, emphysema, and bronchiectasis

Magnetic Resonance Imaging

• Uses radio waves from realigning Hydrogen nuclei to generate MRI image without using x-rays
• Most often used to image mediastinum, hilar regions, & large vessels in the lung
• It cannot be used in patients with a pacemaker or if there are metal objects (i.e., gas cylinders or regular ICU ventilators) near the MRI machine

Ultrasound

• Images are created by passing high-frequency sound waves into the body and detecting sound waves that bounce back (echo) from tissues
• Ultrasonic evaluation of the lung is limited
• Uses very portable equipment
• It is commonly used to guide the placement of central & arterial catheters and to detect & quantify pleural effusions
• Common in an emergency setting or the ICU

Ventilation Perfusion Scan (V/Q)

• For the perfusion component, radioactive particles are injected into a vein like albumin, tagged with iodine
• These particles are too large to pass through, trapping them in the lung capillaries
• High flow areas appear “hot”/black; low flow, “cold”/clear
• The ventilation part utilizes a radioactive gas(xenon)is inhaled during the lung scan. Well-ventilated areas absorb a lot of radioactivity, thus appearing “hot”/black.
• Poorly ventilated areas have fewer particles, thus appearing “cold” or clear
• The two scans are compared to identify correlations between ventilation and perfusion
• Often used to diagnose pulmonary embolism where ventilation is normal, but perfusion shows a defect
• Not a 100% confirmation of PULMONARY EMBOLISMS; just indicates a high probability or indicates PE is ruled out if the scan is normal