Updated Statement: COVID-19 and Ventilation/Perfusion (V/Q) Lung Studies

September 3, 2020

On March 19, 2020, SNMMI released a statement responding to concerns regarding ventilation/perfusion (V/Q) lung scans and, specifically, the inherent risk of spread of COVID-19 to patients and staff related to the ventilation portion of this study. At that time, many institutions opted not to perform ventilation studies. When lung perfusion images are normal, the perfusion scan alone essentially rules out acute pulmonary embolism, and no further studies are needed. When lung perfusion images show a high-probability appearance in the setting of a normal chest radiograph, this also provides helpful information. However, there are cases in which perfusion-only images are indeterminate and a ventilation study may be felt to be clinically necessary to make a definitive interpretation, with recognition of the need for diagnostic accuracy given the potential risks of anticoagulation in this population. In addition, ventilation images provide important information about airway patency and obstructive lung disease that may help to explain symptoms.

Since the time of the original statement, the COVID-19 pandemic has evolved differently in various regions of the world, and questions have arisen as to the safety of resuming performance of the ventilation study.  

There remain unknowns about the transmissibility of COVID-19 using ventilation systems. In some situations, it may remain appropriate not to perform ventilation studies. These situations may include when institutions or practices are in regions where there is a high or increasing number of COVID-19 cases or where there is inadequate access to COVID-19 testing.

The goal of this updated statement is to recognize that in some regions and clinical situations, a ventilation study may be felt to be clinically necessary to help diagnose lung disease, including vascular and airway disease. In these settings, performance of ventilation studies may be considered, with local and institutional COVID-19 policies and procedures for aerosol-generating and non-aerosolizing procedures serving as the primary source of guidance. The following considerations, which typically are included in facility policies and procedures, should be reviewed prior to performing ventilation studies:

1. In general, patients should have documentation of a negative COVID-19 polymerase chain reaction (PCR) test; however, in some cases, local policies or regulations may be different.
2. Technologists should wear appropriate personal protective equipment (PPE) when performing ventilation studies, according to local policies for the performance of aerosol-generating and non-aerosolizing procedures.
3. Airflow in the room in which the ventilation studies are performed should be evaluated, which may help determine the required time for room turnover after the performance of a ventilation study.
4. The availability and feasibility of administering ventilation agents—including FDA-approved agents such as ^99mTc-DTPA and ¹³³Xe gas and other non-FDA-approved agents, including but not limited to ^99mTc-labeled ultra-fine carbon particles (e.g., Technegas™)—should be considered for performance of the ventilation study.
5. It is recommended to engage local infection control groups for guidance and to help evaluate facilities, equipment and staff PPE use for performing ventilation studies.
6. The approach to performing a ventilation scan in relation to the perfusion scan (i.e., ventilation then perfusion vs. perfusion then ventilation) should be considered on a case-by-case basis, according to the clinical indication and in consultation with the referring physician. 
   
   

SNMMI will continue to monitor the COVID-19 pandemic and provide updated information whenever possible.