Pulmonary function testing

Pulmonary function testing is a group of measurements of lung volumes, airflow, and gas exchange. It helps characterize respiratory impairment and monitor lung disease.

Spirometry: A breathing test that measures how much and how quickly air a person can exhale. Its airflow measurements provide the core indices used to detect obstructive patterns.
Obstructive lung disease: A group of conditions that narrow or obstruct airways and limit expiratory airflow. Spirometry identifies the airflow limitation characteristic of this disease pattern.
Tidal volume: The volume of air inhaled or exhaled during an ordinary breath. It is one component of the larger volumes measured during lung-function testing.
Obstructive ventilatory defect: A spirometric pattern in which airflow is disproportionately reduced relative to exhaled lung volume. It contrasts with restriction, where lung capacity rather than the airflow ratio is reduced.
Lung volumes: Measurements of the air contained in the lungs during different phases of breathing. They show whether reduced lung expansion reflects restriction or air trapped after exhalation.
Restrictive lung disease: A group of conditions that limit lung expansion and reduce total lung capacity. Lung-volume measurements help confirm the reduced capacity that defines restriction.
Forced vital capacity: The maximum volume of air forcibly exhaled after a full inhalation. It is a principal spirometric measure of the volume exhaled during a forced maneuver.
Restrictive ventilatory defect: A pattern of reduced lung volume, confirmed by a low total lung capacity. It differs from obstruction and cannot be confirmed from a low forced vital capacity alone.
Diffusing capacity of the lung for carbon monoxide: A test estimating how efficiently gas passes from lung air sacs into the blood. It adds a measure of gas transfer that spirometry cannot provide.
Chronic obstructive pulmonary disease: A chronic lung disease characterized by persistent airflow limitation, usually from emphysema or chronic bronchitis. Spirometry is used to establish airflow obstruction and assess its severity.

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