With COVID-19 Status Evolving - SNMMI Shifts VQ Ventilation Recommendation

On March 19th, as the acute COVID-19 infection risk to healthcare workers, their facilities and other patients was being initially evaluated, the Society of Nuclear Medicine and Molecular Imaging (SNMMI) released a safety recommendation statement. This statement included a recommendation that Nuclear Medicine Departments to stop performing the ventilation portion of a standard ventilation perfusion (VQ) scan.

With so many new daily reports from around the country of rapid, uncontrolled population infection rates, this move by the SNMMI, was felt to be in the short term, a simplistic solution. COVID-19 Polymerase Chain Reactive (PCR) testing was not as available. Reducing the overall exam time and elimination of potential aerosol release of extra airborne particles appeared to be an appropriate solution. However, going to a Perfusion-Only VQ protocol, severely affected the diagnostic capability of the exam, in this highly respiratory complicated population. Specificity suddenly became, at best, a coin toss, in the 50% range.

Previously, adopting the lower dose, Perfusion-Only protocol in the low respiratory complicated female pregnant population was felt to be a reasonable tradeoff. There would be far less underlying pulmonary abnormalities present to continually impact the specificity of the exam and reduce the confidence of the interpretation. If the low dose perfusion images were normal, there was a high degree of confidence that there were no pulmonary emboli present. On the other hand, if that initial perfusion scan showed abnormalities, it wasn't as problematic to bring those patients back to perform the compulsory ventilation portion. Some nuclear medicine departments, very concerned about accuracy, continued to perform the full VQ protocol, but lowered the standard VQ doses for these pregnant patients.

Throughout the spring and summer of the global COVID-19 pandemic many nuclear medicine departments continued administering the full dose VQ protocol. They combined a personal protection and cleaning program along, with strategizing to properly identify and safely treat these potential riskier VQ patients. The strategy also included the use of best efforts to allow for adequate room air volume turnover. It was believed that by following effective, tried-and-true infection control guidelines, their staff and patient safety was not being jeopardized.

On September 3, 2020 the SNMMI released a new updated VQ Ventilation status statement. By safely reintroducing the ventilation portion, "ventilation images provide important information about airway patency and obstructive lung disease that may help to explain symptoms."

Their new updated six step proposal can be summarized as follows:

1. Patients should have a document demonstrating their negative COVID-19 polymerase chain reaction test. Local policies may differ on a case-to-case basis.

2. Technologists should wear personal protective equipment for aerosol-generating and non-aerosolizing procedures.

3. Airflow within the exam room should be analyzed to determine the turnover time required between studies.

4. Providers should consider the availability and feasibility of using ventilation agents such as ^99mTc -DTPA and ¹³³Xe gas, among others, prior to performing the exam.

5. Local infection control groups should be consulted to evaluate facilities, equipment and PPE for performing ventilation.

6. Completing perfusion imaging before ventilation, or vice versa should be determined based on the clinical situation and with the referring physician.

Now, with clear and simple steps to follow, nuclear medicine departments should quickly reintroduce this safe and accurate exam, especially to all those patients at risk for high breast radiation and contrast induced nephropathy.