Functional Residual Capacity (FRC) is defined as the volume of air remaining in the lungs after a normal, passive exhalation. Determining this lung volume is crucial in assessing respiratory function and diagnosing certain pulmonary conditions. Several methods exist to measure it, each with its own underlying principles and practical considerations. These methods can be broadly categorized into gas dilution techniques and body plethysmography.
Accurate determination of the air volume remaining in the lungs after exhalation is important in evaluating the severity of obstructive or restrictive lung diseases. For instance, in emphysema, FRC is typically increased due to air trapping, while in pulmonary fibrosis, it might be decreased due to reduced lung compliance. Monitoring FRC helps clinicians track disease progression and assess the effectiveness of therapeutic interventions. Historically, measurement of these volumes provided foundational data for understanding pulmonary physiology and gas exchange.
