Norm of Gas Ventilation Lung Scan
Radioactive gas is distributed equally in both lungs with normal “wash-in” and “wash-out” phases.
Usage of Gas Ventilation Lung Scan
Used with a lung perfusion scan to diagnose, identify, and evaluate regions of lung tissue that are not ventilated during respirations. Some conditions in which this may occur include pulmonary embolism, chronic obstructive pulmonary disease, and parenchymal disease (bronchogenic carcinoma).
Description of Gas Ventilation Lung Scan
A nuclear medicine scan in which the client inhales air mixed with radiolabeled gas (xenon-133) through a mask. A gamma (Anger) camera images the gas distribution of the posterior lung fields through three phases: phase 1 is the “wash-in” phase in which the buildup of radioactive gas occurs. In phase 2, equilibrium occurs. Phase 3 is the “wash-out” phase, in which the gas is removed from the lungs. Decreased areas of ventilation will appear lighter with longer than normal wash-out phases.
Professional Considerations of Gas Ventilation Lung Scan
Consent form NOT required.
Dizziness, fetal damage.
In clients who are unable to follow directions.
During pregnancy, risks of cumulative radiation exposure to the fetus from this and other previous or future imaging studies must be weighed against the benefits of the procedure. Although formal limits for client exposure are relative to this risk:benefit comparison, the United States Nuclear Regulatory Commission requires that the cumulative dose equivalent to an embryo/fetus from occupational exposure not exceed 0.5 rem (5 mSv). Radiation dosage to the fetus is proportional to the distance of the anatomy studied from the abdomen and decreases as pregnancy progresses. For pregnant clients, consult the radiologist/radiology department to obtain estimated fetal radiation exposure from this procedure.
- Obtain baseline vital signs and continue to monitor vital signs every 10–15 minutes.
- Remove jewelry and metal objects.
- The client is positioned erect or supine throughout the scan.
- The client inhales a mixture of air and radioactive xenon-133 gas through a mask and holds his or her breath for 20 seconds. For mechanically ventilated clients, krypton-85 gas should be substituted for xenon-133.
- The client's chest is scanned with a gamma camera as he or she exhales.
Client and Family Teaching
- The test is painless and takes about 15–30 minutes.
- Results are normally available after interpretation by a radiologist.
Factors That Affect Results
- An improperly fitting or loose seal on the ventilation mask interferes with the proper mixing of air and gas and allows radioactive gas to contaminate the surrounding air.