Are ARDS lungs considered small or large due to the patchy functional areas?

In patients with Acute Respiratory Distress Syndrome (ARDS), the lung function is significantly compromised due to widespread inflammation and injury, resulting in a heterogeneous pattern of lung compromise. This patchy nature of affected lung areas leads to impaired gas exchange, contributing to regional variations in ventilation and perfusion.

The term "small" in the context of ARDS lungs reflects the compromised areas that are functioning poorly and the overall reduced capacity for effective gas exchange. The effective lung units are diminished due to the presence of edema, atelectasis, and consolidated lung tissue, which creates regions of non-compliance and poor oxygenation.

While it might seem intuitive to think of the lungs as "large" due to the overall size of the organ, the crucial factor here is the functional capacity that is severely reduced in ARDS. The small functional areas result in an overall decrease in effective lung volume, leading to a situation where, despite their physical size, the ability to adequately ventilate and oxygenate the blood is significantly compromised. Thus, the descriptor "small" appropriately characterizes the impaired efficacy of the lung function in ARDS.