INTRODUCTION AND BACKGROUND
The use of chest computed tomography (CT) during the COVID-19 pandemic may introduce contamination risk to staff and nearby patients during imaging procedures. Chest CT in patients with COVID-19 may be of tremendous clinical and epidemiological value, however, this may put pressure on CT scanners to examine large numbers of patients without spreading the infection. Chest CT can provide valuable information but it often requires 3090 minutes of CT room decontamination and passive air exchange, which takes a heavy toll on workflow and productivity. The exact decontamination time after CT of a patient with a diagnosis or suspicion for Covid-19 depends upon air exchange rate per hour and passive airflow (1,2), ideally in a negative pressure setting. While advanced staff training, dedicated equipment and hallways, and pre-emptive standardized operating procedures may reduce risk to staff, a single infected patient or breach in technique can have profound implications. Risk can be mitigated by reducing the chance of viral spread by human to human transmission as well as direct transmission via imaging equipment (1) via detailed decontamination procedures, cleaning all surfaces in between patients, and having all patients wear masks, or in specific settings, other personal protective equipment (PPE)-like isolation devices. Some thoracic radiologists in less CT dense countries feared the risk of contamination of CT scanners (2). Designating CT scanners as either “Dirty” or “Clean” CT suites, does not resolve the fact that the “dirty” CT scanner needs a deep cleaning and a delay in between patients. One well-established strategy is to control the respiratory source of airborn or droplet transmission of infection with a face mask. An isolation bag provides a layer of security, in addition to a face mask. The COVID-19 pandemic has the potential to completely stall radiology department throughput due to excessive delays in between patients for decontamination and airflow exchanges. In the setting of a pandemic from a droplet-transmitted novel virus and an immune-naïve population, there is a critical clinical need for cost-effective disposable PPE for the infected patient’s isolation while undergoing CT procedures. This may be even more impactful for the clandestine infection which causes presymptomatic transmission of SARS-CoV-2 which may account for nearly half of all transmissions (3). Custom prototype isolation PPE devices for the patient were designed, test fit, and custom fabricated. Center for Disease Control (CDC) guidelines are reviewed as relevant to CT decontamination and isolation. A portable isolation bag device for patients with symptomatic or asymptomatic upper respiratory infectious diseases was designed to reduce contamination in imaging suites, which could facilitate containment during the COVID pandemic.
The potential cost impact of a theoretical isolation device was assessed in terms of enhanced efficiency and patient throughput. The functional requirements and clinical and engineering features for a portable isolation bag device were reviewed and specifications were defined. Methods of practice and risk mitigation plans were outlined including donning and doffing procedures and failure modes. Alternatives methods such as portable CT anterooms or zippered plastic pseudo-walls are briefly reviewed for enhancing CT room safety and workflow efficiency. Air exchange rates and requirements dictate the length of time in between patients known or suspected to have COVID-19 to allow for passive air flow. CDC guidelines for air exchange and optimal airflow relevant to radiology and CT rooms are reviewed (Table 1), along with specific methods for enhancing those exchange rates or mitigating poor exchange rates.