The Variable Ventilation Trial (Part A)

The goal of this clinical trial is to learn if a breathing machine (ventilator) method called "variable ventilation" can help protect the lungs of adult patients with acute respiratory distress syndrome (ARDS) who need help breathing through a ventilator. In variable ventilation, the size of each breath given by the machine changes slightly from breath to breath, instead of staying the same size in every breath. The study has two parts, A (safety and feasibility) and B (efficacy). This entry will cover the part A (safety study). The main questions part A aims to answer are: 1. Is variable ventilation safe to use in adults with ARDS? 2. Is it feasible to deliver this method of ventilation to patients? Researchers will compare variable ventilation to the standard breathing machine method used today to see if variable ventilation is safe and feasible. Participants will be placed on an FDA approved ventilator that can deliver conventional mechanical ventilation and variable ventilation. Participants will: * Have a period of stabilization on conventional ventilation, followed by 24 hours of variable ventilation, followed by 24 hours of conventional ventilation. * Be checked regularly for breathing, oxygen levels, lung function, and plasma biomarkers.