Radiographic Sign May Identify Patients at Risk for Pulmonary Barotrauma

A new study suggests that a radiographic sign called the Macklin effect correlates closely with pulmonary barotrauma in patients who are acutely ill and intubated with COVID-19 infection. 

The study, published in Clinical Imaging last month, was an international collaboration led by researchers in Columbia's Department of Radiology and designed to validate prior research from the IRCCS San Raffaele Scientific Institute in Milan, Italy.

Barotrauma refers to tissue injuries that are caused by a pressure difference between a space inside the body and its surrounding area. Pulmonary barotrauma is most often due to the rupture of air sacks (alveoli) in the lungs, which can result in the release of air into other locations. Barotrauma occurs in 15 to 20 percent of patients who are COVID-19 positive and receiving mechanical ventilation.

The study found a close correlation between the Macklin radiographic sign and the development of pulmonary barotrauma in critically ill patients with COVID-19, a finding that could potentially guide management of patients with acute respiratory distress syndrome (ARDS).

Senior author and cardiothoracic imaging fellow Kathleen M. Capaccione, MD, PhD, and her colleagues in the Division of Cardiothoracic Imaging, evaluated CT scans of patients who were critically ill, intubated, and COVID-19 positive. 10 patients exhibited the Macklin effect, and nine of those patients developed barotrauma.  

In particular, they found that the Macklin effect correlated closely with the incidence of pneumomediastinum, a form of barotrauma in which air leaks into the area between the lungs.

Their results correlated closely with the findings of the group from the IRCCS San Raffaele Scientific Institute and suggest that the Macklin effect could be used to guide care of complex patients in the critical care setting.

"The Macklin effect could indicate that the patient has a higher risk of a bad outcome," says Capaccione. "Additionally, there are certain maneuvers that can be done in the ICU, such as positive pressure ventilation and higher ventilation settings, which our findings suggest may be contraindicated in patients that have this particular sign because they are more likely to have a traumatic outcome due to extra pressure in their alveoli."

The study was limited to patients with COVID-19, but Capaccione emphasizes that further studies will determine whether the results also apply to patients with ARDS due to causes other than COVID-19. "Then we will have learned something from the pandemic that we can use more broadly to help guide management," she says.