Respiratory Diagnostic Tests: Chest X-Ray & CT Scan

• Diagnostic imaging, lab work, and invasive measures assess respiratory status and identify conditions. Nurses should be familiar with these tests to prepare patients.

Chest X-Ray

• Chest x-rays can visualize the thoracic cavity, lungs, heart, and major thoracic vessels.
• They show changes in the pulmonary structures' size and location, as well as blood flow.
• Enable identification of lesions, infiltrates, foreign bodies, or fluid.
• Can show whether a disorder involves the lung parenchyma or interstitial spaces.
• Chest x-rays can confirm pneumothorax, pneumonia, pleural effusion, and pulmonary edema.

Computed Tomography (CT) Chest Scan

• CT scans take pictures of small layers of pulmonary tissue to identify pulmonary lesions.
• Views can be diagonal or cross-sectional using a rotating scanner.
• The test is painless and noninvasive, but patient teaching is necessary to decrease anxiety.
• Helical (spiral) CT obtains images continuously, producing faster and more accurate images than traditional CT scans.
• Helical CT can scan the abdomen and chest in under 30 seconds, allowing the entire study to be performed with one breath-hold.
• Contrast dye, injected or swallowed, helps organs or tissues show up more clearly.

Pulmonary Angiography (Pulmonary Arteriography)

• Pulmonary angiography uses radiographic contrast material injected into the pulmonary arteries to visualize the pulmonary vasculature.
• Angiography detects pulmonary embolism (PE) and congenital/acquired lesions of the pulmonary vessels.
• Typically a CT scan is performed first when PE is suspected; if normal, PE is ruled out.
• If the CT scan is uncertain, diagnosis of PE is questionable because conditions like emphysema or pneumonia can cause abnormalities on the lung scan.
• Definitive diagnosis for PE may require pulmonary angiography.

Ventilation-Perfusion Scan (V/Q Scan)

• V/Q scanning checks for PE.
• Ventilation (V) refers to the air reaching the alveoli; perfusion (Q) refers to the blood reaching the alveoli.
• A radioisotope is given intravenously for perfusion, and an image of the pulmonary vasculature is obtained.
• For ventilation, the patient inhales a radioactive gas, and an image of the outlines of the alveoli is obtained.
• Normal scans show homogeneous radioactivity; a high V/Q indicates impaired blood circulation to the alveoli, suggesting PE.

Pulmonary Function Testing

• Pulmonary function tests (PFTs) assess the presence and severity of disease in the large and small airways, including lung volume, ventilation, pulmonary spirometry, and gas exchange.
• Lung volume tests measure the volume of air that can be exhaled completely and slowly after a maximum inhalation (vital capacity).
• Inspiratory capacity is the largest amount of air that can be inhaled in one breath from the resting expiratory level.
• Total lung capacity determines the volume of air in the lung after a maximal inhalation.
• Ventilation tests evaluate the volume of air inhaled or exhaled in each respiratory cycle.
• Pulmonary spirometry tests evaluate the amount of air that can be exhaled forcefully after maximum inhalation, using a spirometer.
• Determining gas exchange is one of the most important PFTs to diagnose respiratory diseases.
• The DLCO (diffusing capacity of the lungs for carbon monoxide) test determines how well oxygen diffusing from the alveoli is taken up by blood in the pulmonary capillary bed.
• Carbon monoxide is used instead of oxygen because such a small amount is utilized, the test is not dangerous.
• Post DLCO test the rate of oxygen transfer can then be accurately determined.

Mediastinoscopy

• Mediastinoscopy is a surgical endoscopic procedure involving an incision in the suprasternal notch.
• An endoscope is passed into the upper mediastinum and a biopsy is performed to gather lymph nodes.
• Lymph nodes are examined for tumors as they receive lymphatic drainage from the lungs.
• Tumors in the mediastinum can also be biopsied through the mediastinoscope.
• The procedure is performed in the operating room under general anesthesia.

Laryngoscopy

• Laryngoscopy can be performed for either direct or indirect visualization of the larynx.
• Indirect laryngoscopy uses a laryngeal mirror positioned in the mouth and is the most common procedure for assessing respiratory difficulties.
• Direct laryngoscopy with a laryngoscope can be used for biopsy or polyp excision.
• It requires local or general anesthesia and exposes the vocal cords as the laryngoscope is passed down over the tongue.

Bronchoscopy

• Bronchoscopy is performed by passing a bronchoscope into the trachea and bronchi.
• A flexible fiberoptic bronchoscope is the instrument of choice, this allows visualization of the larynx, trachea, and bronchi.
• Diagnostic bronchoscopic examination includes observation of the tracheobronchial tree for abnormalities, tissue biopsy, and collection of secretions for cytologic/bacteriologic examination.
• A local anesthetic agent may be used, but an IV general anesthetic agent is usually given, and the patient is treated as a surgical patient.
• Nursing interventions post bronchoscopy:
  • Keep the patient NPO until the gag reflex returns (usually about 2 hours).
  • Keep the patient in semi-Fowler’s position and turn on either side to facilitate removal of secretions (unless specified otherwise).
  • Monitor for signs of laryngeal edema or laryngospasms (stridor or increasing dyspnea).
  • If lung tissue biopsy is taken, monitor sputum for hemorrhage (blood-streaked sputum is expected for a few days).

Sputum Specimen

• Sputum samples are obtained for microscopic evaluation, such as Gram stain and culture and sensitivity.

Cytologic Studies

• Cytologic tests can be performed on any body secretion, such as sputum or pleural fluid, to detect abnormal or malignant cells.

Lung Biopsy

• Lung biopsy may be done transbronchially or as an open-lung biopsy to obtain tissue, cells, or secretions for evaluation.
• Transbronchial lung biopsy involves passing a forceps or needle through the bronchoscope to obtain a specimen, with specimens cultured or examined for malignant cells.
• Nursing interventions are the same as for fiberoptic bronchoscopy.
• Open-lung biopsy is used when pulmonary disease cannot be diagnosed by other procedures.
• The patient is anesthetized, the chest is opened with a thoracotomy incision, and a biopsy specimen is obtained.