You may have heard the Type L and Type H phenotypes mentioned during recent discussions about the current COVID-19 pandemic. These terms were coined by Luciano Gattinoni et al in an attempt to describe the two main manifestations that they were seeing while treating COVID-19 infected patients in their Intensive Care Units. In the Emergency Department, we see a variety of phenotypes, with many atypical and low acuity presentations, but those admitted for respiratory support, often eventually progress to these two phenotypes.
The Type L phenotype is characterized by normally compliant lungs but with profound hypoxemia. This is often the initial phenotype, but Type L occasionally progresses to the more severe Type H. The Type H phenotype is similar to ARDS in that the lungs demonstrate low compliance, significant edema, and high recruitability.
Identifying these phenotypes is important for determining the best way to manage these patients. Type H is managed like ARDS, while the Type L is managed very differently. Not understanding these differences could easily lead to harm and iatrogenic injury in patients who fit into the Type L phenotype. Below is a lengthy, but enlightening discussion on the management considerations from multiple critical care gurus around the world. Enjoy.