ventilation scan

ventilation scan

A radionuclide study of pulmonary ventilation; in a commonly used protocol, the scan is performed after inhalation of 133Xe. See Ventilation-perfusion scan.

Lung Ventilation Scan

Synonym/acronym: Aerosol lung scan, radioactive ventilation scan, ventilation scan, VQ lung scan, xenon lung scan.

Common use

To assess pulmonary ventilation to assist in diagnosis of pulmonary embolism.

Area of application

Chest/thorax.

Contrast

Done with inhaled radioactive material (xenon gas or technetium-DTPA).

Description

The lung ventilation scan is a nuclear medicine study performed to evaluate a patient for pulmonary embolus (PE) or other pulmonary disorders. It can evaluate respiratory function (i.e., demonstrating areas of the lung that are patent and capable of ventilation) and dysfunction (e.g., parenchymal abnormalities affecting ventilation, such as pneumonia). The procedure is performed after the patient inhales air mixed with a radioactive gas through a face mask and mouthpiece. The radioactive gas delineates areas of the lung during ventilation. The distribution of the gas throughout the lung is measured in three phases:
  • Wash-in phase: Phase during buildup of the radioactive gas
  • Equilibrium phase: Phase after the patient rebreathes from a closed delivery system
  • Wash-out phase: Phase after the radioactive gas has been removed

This procedure is usually performed along with a lung perfusion scan. When PE is present, ventilation scans display a normal wash-in and wash-out of radioactivity from the lung areas. Parenchymal disease responsible for perfusion abnormalities will produce abnormal wash-in and wash-out phases. This test can be used to quantify regional ventilation in patients with pulmonary disease.

This procedure is contraindicated for

  • high alert Patients who are pregnant or suspected of being pregnant, unless the potential benefits of a procedure using radiation far outweigh the risk of radiation exposure to the fetus and mother.

Indications

  • Aid in the diagnosis of PE
  • Differentiate between PE and other pulmonary diseases, such as pneumonia, pulmonary effusion, atelectasis, asthma, bronchitis, emphysema, and tumors
  • Evaluate regional respiratory function
  • Identify areas of the lung that are capable of ventilation
  • Locate hypoventilation (regional), which can result from chronic obstructive pulmonary disease (COPD) or excessive smoking

Potential diagnosis

Normal findings

  • Equal distribution of radioactive gas throughout both lungs and a normal wash-out phase

Abnormal findings related to

  • Atelectasis
  • Bronchitis
  • Bronchogenic carcinoma
  • COPD
  • Emphysema
  • PE
  • Pneumonia
  • Regional hypoventilation
  • Sarcoidosis
  • Tuberculosis
  • Tumor

Critical findings

  • PE

  • It is essential that a critical finding be communicated immediately to the requesting health-care provider (HCP). A listing of these findings varies among facilities.

  • Timely notification of a critical finding for lab or diagnostic studies is a role expectation of the professional nurse. Notification processes will vary among facilities. Upon receipt of the critical value the information should be read back to the caller to verify accuracy. Most policies require immediate notification of the primary HCP, Hospitalist, or on-call HCP. Reported information includes the patient’s name, unique identifiers, critical value, name of the person giving the report, and name of the person receiving the report. Documentation of notification should be made in the medical record with the name of the HCP notified, time and date of notification, and any orders received. Any delay in a timely report of a critical finding may require completion of a notification form with review by Risk Management.

Interfering factors

  • Factors that may impair clear imaging

    • Inability of the patient to cooperate or remain still during the procedure because of age, significant pain, or mental status.
    • Metallic objects (e.g., jewelry, body rings) within the examination field, which may inhibit organ visualization and cause unclear images.
    • Other nuclear scans done within the preceding 24 to 48 hr.

  • Other considerations

    • The presence of conditions that affect perfusion or ventilation (e.g., tumors that obstruct the pulmonary artery, vasculitis, pulmonary edema, sickle cell disease, parasitic disease, emphysema, effusion, infection) can simulate a perfusion defect similar to PE.
    • Consultation with a health-care provider (HCP) should occur before the procedure for radiation safety concerns regarding younger patients or patients who are lactating. Pediatric & Geriatric Imaging Children and geriatric patients are at risk for receiving a higher radiation dose than necessary if settings are not adjusted for their small size. Pediatric Imaging Information on the Image Gently Campaign can be found at the Alliance for Radiation Safety in Pediatric Imaging (www.pedrad.org/associations/5364/ig/).
    • Risks associated with radiation overexposure can result from frequent x-ray or radionuclide procedures. Personnel working in the examination area should wear badges to record their level of radiation exposure.

Nursing Implications and Procedure

Pretest

  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this procedure can assist in assessing air flow to the lungs.
  • Obtain a history of the patient’s complaints or clinical symptoms, including a list of known allergens, especially allergies or sensitivities to latex, anesthetics, sedatives, or radionuclides.
  • Obtain a history of the patient’s respiratory system, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Note any recent procedures that can interfere with test results, including examinations using iodine-based contrast medium.
  • Record the date of the last menstrual period and determine the possibility of pregnancy in perimenopausal women.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
  • Review the procedure with the patient. Address concerns about pain related to the procedure and explain that some pain may be experienced during the test, and there may be moments of discomfort. Reassure the patient that the radionuclide poses no radioactive hazard and rarely produces side effects. Inform the patient that the procedure is performed in a nuclear medicine department, usually by an HCP who specializes in this procedure, with support staff, and takes approximately 30 to 60 min.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Instruct the patient to remove jewelry and other metallic objects from the area to be examined.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.
  • Make sure a written and informed consent has been signed prior to the procedure and before administering any medications.

Intratest

  • Potential complications:

  • Although it is rare, there is the possibility of allergic reaction to the radionuclide.

  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient.
  • Ensure that the patient has removed all external metallic objects from the area to be examined prior to the procedure.
  • Administer ordered prophylactic steroids or antihistamines before the procedure if the patient has a history of allergic reactions to any substance or drug.
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Have emergency equipment readily available.
  • Instruct the patient to void prior to the procedure and to change into the gown, robe, and foot coverings provided.
  • Record baseline vital signs and assess neurological status. Protocols may vary among facilities.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to remain still throughout the procedure because movement produces unreliable results.
  • Administer sedative to a child or to an uncooperative adult, as ordered.
  • Place the patient in a supine position on a flat table with foam wedges, which help maintain position and immobilization.
  • The radionuclide is administered through a mask, which is placed over the patient’s nose and mouth. The patient is asked to hold his or her breath for a short period of time while the scan is taken.
  • Monitor the patient for complications related to the procedure (e.g., allergic reaction, anaphylaxis, bronchospasm).

Post-Test

  • Inform the patient that a report of the results will be made available to the requesting HCP, who will discuss the results with the patient.
  • Advise patient, unless contraindicated, to drink increased amounts of fluids for 24 to 48 hr to eliminate the radionuclide from the body. Inform the patient that radionuclide is eliminated from the body within 6 to 24 hr.
  • No other radionuclide tests should be scheduled for 24 to 48 hr after this procedure.
  • Evaluate the patient’s vital signs. Monitor vital signs and neurological status every 15 min for 1 hr, then every 2 hr for 4 hr, and then as ordered by the HCP. Compare with baseline values. Protocols may vary among facilities.
  • Instruct the patient to resume medication or activity, as directed by the HCP.
  • If a woman who is breastfeeding must have a nuclear scan, she should not breastfeed the infant until the radionuclide has been eliminated. This could take as long as 3 days. She should be instructed to express the milk and discard it during the 3-day period to prevent cessation of milk production.
  • Instruct the patient to immediately flush the toilet and to meticulously wash hands with soap and water after each voiding for 24 hr after the procedure.
  • Instruct all caregivers to wear gloves when discarding urine for 24 hr after the procedure. Wash gloved hands with soap and water before removing gloves. Then wash hands after the gloves are removed.
  • Nutritional Considerations: A low-fat, low-cholesterol, and low-sodium diet should be consumed to reduce current disease processes and/or decrease risk of hypertension and coronary artery disease.
  • Recognize anxiety related to test results, and be supportive of perceived loss of independent function. Discuss the implications of abnormal test results on the patient’s lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate.
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be needed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include α-1 antitrypsin, alveolar/arterial ratio, ACE, angiography pulmonary, biopsy lung, blood gases, blood pool imaging, bronchoscopy, carbon dioxide, chest x-ray, CBC, CBC WBC count and differential, CT thorax, culture and smear mycobacteria, culture blood, culture sputum, culture throat, culture viral, cytology sputum, d-dimer, gallium scan, lung perfusion scan, MRI chest, MRI venography, mediastinoscopy, plethysmography, pleural fluid analysis, PET heart, PFT, TB skin tests, US venous Doppler extremity studies, and venography.
  • Refer to the Respiratory System table at the end of the book for related tests by body system.