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Information ⬇

Lung Scans(Perfusion and Ventilation Studies)

Synonym/Acronym

Lung Perfusion Scan: Lung perfusion scintigraphy, lung scintiscan, pulmonary scan, radioactive perfusion scan, radionuclide lung scan, ventilation-perfusion scan, V/Q scan. Lung Ventilation Scan: Aerosol lung scan, radioactive ventilation scan, ventilation scan, VQ lung scan, xenon lung scan.

Rationale

To assess pulmonary blood flow and ventilation to assist in diagnosis of pulmonary embolism.

Patient Preparation

There are no food, fluid, activity, or medication restrictions unless by medical direction. The health-care provider (HCP) may request a chest x-ray 24 to 48 hr before or immediately after this procedure is performed. Protocols may vary among facilities.

Normal Findings

Lung Perfusion Scan

  • Diffuse and homogeneous uptake of the radioactive material by the lungs.

Lung Ventilation Scan

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

Critical Findings and Potential Interventions ⬆ ⬇

Overview ⬆ ⬇

Study type: Nuclear scan; related body system: Respiratory system.

The lung perfusion scan is a nuclear medicine study performed to evaluate a patient for pulmonary embolus (PE) or other pulmonary disorders. Technetium (Tc-99m) is injected by IV access and distributed throughout the pulmonary vasculature. The scan, which produces a visual image of pulmonary blood flow, is useful in diagnosing or confirming pulmonary vascular obstruction. The diameter of the IV-injected macroaggregated albumin (MAA) is larger than that of the pulmonary capillaries; therefore, the MAA becomes temporarily lodged in the pulmonary vasculature. A gamma camera detects the radiation emitted from the injected radioactive material, and a representative image of the lung is obtained. This procedure is often done in conjunction with the lung ventilation scan to obtain clinical information that assists in differentiating among the many possible pathological conditions revealed by the procedure; the combined study is a V/Q scan. The results are correlated with other diagnostic studies, such as chest CT, pulmonary function, chest x-ray, pulmonary angiography, ECG, and ABGs. A recent chest x-ray is essential for accurate interpretation of the lung perfusion scan. An area of nonperfusion seen in the same area as a pulmonary parenchymal abnormality on the chest x-ray indicates that a PE is not present; the defect may represent some other pathological condition, such as pneumonia.

The lung ventilation scan is used to 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 (xenon gas or technetium-DTPA) 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:

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.

Indications ⬆ ⬇

General

Lung Perfusion Scan

Lung Ventilation Scan

Interfering Factors ⬆ ⬇

Contraindications

General

Pregnancy is a general contraindication to procedures involving radiation.

Lung Perfusion Scan

Patients with atrial and ventricular septal defects, because the MAA particles will not reach the lungs.

Patients with pulmonary hypertension.

Factors That May Alter the Results of the Study

  • 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, COPD, effusion, infection) can simulate a perfusion defect similar to PE.
  • Metallic objects (e.g., jewelry, body rings) within the examination field or other nuclear scans done within the previous 24 to 48 hr which may inhibit organ visualization and cause unclear images.
  • Improper injection of the radionuclide that allows the tracer to seep deep into the muscle tissue can produce erroneous hot spots.
  • Inability of the patient to cooperate or remain still during the procedure because movement can produce blurred or otherwise unclear images.

Potential Medical Diagnosis: Clinical Significance of Results ⬆ ⬇

Abnormal Findings Related to

The radioactive tracer accumulates in abnormal tissue, and “hot spots” in areas that would otherwise be expected to demonstrate a diffusely uniform distribution of radionuclide identify specific areas of concern.

General

Lung Perfusion Scan

Lung Ventilation Scan

Nursing Implications, Nursing Process, Clinical Judgement ⬆

Before the Study: Planning and Implementation

Teaching the Patient What to Expect

  • Discuss how this procedure can assist in assessing blood flow to the lungs.
  • Explain that the procedure takes about 30 to 60 min and is performed in a nuclear medicine department.
  • Review the procedure with the patient.
  • Explain that pregnancy testing may be required.
  • Discuss how there may be moments of discomfort or pain when the IV line is inserted, allowing for infusion of fluids such as saline, anesthetics, sedatives, medications used in the procedure, or emergency medications.
  • Reassure the patient that the radionuclide poses no radioactive hazard and rarely produces adverse effects.

Procedural Information

  • Policies regarding breastfeeding before and after an imaging procedure may vary among facilities. For additional information see Appendix A: Patient Preparation and Specimen Collection, subsection: Potential Contraindications and Complications Associated with Diagnostic Procedures.
  • Baseline vital signs are recorded and monitored throughout the procedure.
  • Positioning for the study is in the supine position on a flat table with foam wedges to help maintain position and immobilization.

Lung Perfusion Scan

  • Once the IV radionuclide is administered, a camera rotates around the patient, taking pictures in various positions and in multiple views (anterior, posterior, lateral, and oblique).
  • Once the study is completed, the needle or catheter is removed and a pressure dressing applied over the puncture site.

Lung Ventilation Scan

  • The radionuclide is administered through a mask placed over the nose and mouth.
  • One’s breath is held for a short period of time while the scan is taken.

Potential Nursing Actions

Make sure a written and informed consent has been signed prior to the procedure and before administering any medications.

After the Study: Implementation & Evaluation Potential Nursing Actions

Avoiding Complications

  • Monitor the patient for complications related to the procedure.
  • Establishing an IV site and injection of radionuclides are invasive procedures that can cause rare complications. For additional information see Appendix A: Patient Preparation and Specimen Collection, subsection: Potential Contraindications and Complications Associated with Diagnostic Procedures.
  • Discuss the importance of immediately reporting symptoms such as fast heart rate, difficulty breathing, skin rash, itching, or chest pain.
  • Observe/assess the needle insertion site for bleeding, inflammation, or hematoma formation.

Treatment Considerations

  • Follow postprocedure vital sign and assessment protocol.
  • Explain that the radionuclide is eliminated from the body within 6 to 24 hr.
  • Advise drinking increased amounts of fluids for 24 to 48 hr to eliminate the radionuclide from the body, unless contraindicated.
  • Resume the usual medication and activity, as directed by the HCP.
  • Assess respiratory status baseline regarding rate, rhythm, and depth, cyanosis, work of breathing.
  • Consider use of oxygen and pulse oximetry to manage oxygenation.
  • Consider elevating the head of the bed to facilitate breathing.
  • Administer ordered analgesics, instruct patient to cough and deep breathe as appropriate, and prepare for intubation.
  • Instruct the patient in the care and assessment of the injection site.
  • Explain that application of cold compresses to the puncture site may reduce discomfort or edema.

Safety Considerations

  • Refer to organizational policy for additional precautions that may include instructions on temporary suspension of breastfeeding, hand washing, toilet flushing, limited contact with others, and other aspects of nuclear medicine safety.

Clinical Judgement

  • Consider ways to decrease the fear and anxiety associated with compromised respiratory function.

Follow-Up and Desired Outcomes

  • Is aware of reportable signs of bleeding: bleeding gums, black tarry stools, blood in urine, and hematoma when taking thrombolytics.
  • Acknowledges the importance of remaining on bedrest to prevent movement of the embolus if present.