Patient Assessment and Preparation
Assess before you instrument
Patient assessment has two jobs: confirming the test is appropriate and safe, and capturing the demographic data that reference equations depend on. Review the order and history for indications (dyspnea, cough, known or suspected obstructive or restrictive disease, preoperative evaluation, disability rating, bronchodilator responsiveness).
Screen for contraindications before every forced maneuver: recent myocardial infarction or unstable angina, recent thoracic, abdominal, or ocular surgery, pneumothorax, hemoptysis of unknown origin, thoracic/abdominal/cerebral aneurysm, and acute illness such as vomiting or severe pain. When in doubt, defer and document.
Preparation standards: no smoking for at least 1 hour, no vigorous exercise for 30 minutes, no heavy meal for about 2 hours, and bronchodilator withholding when a baseline or reversibility study is planned - short-acting agents 4 to 6 hours, long-acting agents 12 to 24 hours. Record age to the nearest year, sex, and ethnicity; these drive predicted values.
Measure height without shoes, heels together, back against the stadiometer, head in the horizontal plane, to the nearest 0.5 cm. Never accept a reported height without questioning it. Loose clothing, an upright seated position, a nose clip, and demonstration-quality coaching matter more than most candidates expect. Use hand hygiene, a new mouthpiece, and a bacterial/viral filter; treat valves as contaminated.
Trap: questionnaires treat standing height as trivial, but a 3-cm error shifts predicted FEV1 by roughly 100 mL.
Rule of thumb: when standing height cannot be measured (kyphosis, amputation, wheelchair), fingertip-to-fingertip arm span approximates height within a few centimeters.