D. Estimating Lung Volumes Currently, the ability to determine whether a patient is at, below or above their ideal functional residual capacity is deduced from surrogate measurements, including lung appearance of the chest radiograph, vital sign trends (particularly oxygenation), and pressure-volume (P-V) curves generated by modern ventilators. In this study, we will utilize an established method of determining lung volume (MBNW) to study lung volumes.