Office evaluation of pulmonary function: Beyond the numbers

Pulmonary function testing is useful in evaluating dyspnea, wheezing and cough, determining the severity of pulmonary disease, monitoring the response to therapy and assessing preoperative pulmonary risk. Accurate office spirometry requires routine preventive maintenance, cleaning and calibration of equipment and quality control measures. To obtain a flow-volume loop, the seated or standing patient is instructed to inspire maximally to total lung capacity, exhale as hard, fast and completely as possible (forced vital capacity [FVC]), and inhale quickly and deeply to total lung capacity (TLC). Spirometry reveals both obstructive and restrictive airway disease. Obstruction is characterized by reduced forced expiratory volume in one second (FEV₁) and FEV₁/forced vital capacity (FEV₁/FVC%), and normal to increased TLC and residual volume. Restriction is characterized by reduced TLC and residual volume and normal FEV₁/FVC%. Spirometry may also reveal abnormalities of the upper airway, including the nasopharynx, vocal cords, trachea and proximal large airways.