RPFT key terms

The total volume of air a person can blow out as forcefully and completely as possible after a full inhalation. It is a core spirometry measurement used to detect restrictive patterns and to calculate the FEV1/FVC ratio.

The volume of air exhaled during the first second of a forced expiratory maneuver begun from full inspiration. It reflects how quickly the lungs empty and is central to diagnosing obstructive disease.

The FEV1 divided by the FVC, often expressed as a percentage or decimal. A reduced value supports airflow obstruction; comparing it with the lower limit of normal helps avoid age-related misclassification.

The average flow rate during the middle half of a forced expiration. It is thought to reflect small-airway function but is highly variable and should not be used alone to diagnose obstruction.

The highest flow rate reached during a forced expiration, usually reported in liters per minute. It depends on effort and airway caliber and is used in asthma monitoring and to assess maneuver quality.

The largest volume exhaled slowly and completely after a full inspiration. Comparing SVC with FVC can reveal air trapping or collapse of small airways during forced exhalation.

The volume of air remaining in the lungs after a maximal exhalation. It cannot be measured by spirometry alone and requires gas dilution, plethysmography, or imaging techniques.

The total volume of air in the lungs at maximal inflation, equal to vital capacity plus residual volume. Elevated TLC supports hyperinflation; reduced TLC supports restriction.

The volume of air left in the lungs at the end of a normal quiet expiration. It represents the balance point between lung elastic recoil and chest wall outward pull and is measured by dilution or plethysmography.

A measure of how readily carbon monoxide moves from alveolar gas into pulmonary capillary blood. It estimates alveolar-capillary membrane function and is reduced in emphysema, interstitial disease, and anemia.

The lung volume participating in gas exchange during a diffusing capacity test, usually derived from a single-breath tracer gas dilution. It is used to correct DLCO and to calculate DLCO/VA.

A technique in which a person sits in a sealed cabinet and performs panting maneuvers against a shutter. It measures thoracic gas volume and airway resistance, allowing calculation of residual volume and total lung capacity.

A closed-circuit method for measuring lung volumes in which a known amount of helium is breathed and diluted by gas already in the lungs. It underestimates volumes in poorly ventilated areas.

An open-circuit method that measures functional residual capacity by having the subject breathe oxygen and tracking the exhaled nitrogen concentration until it falls to a low level.

A change in spirometry values after inhaling a short-acting bronchodilator, compared with baseline. Significant improvement suggests reversible airflow obstruction and is reported with the drug, dose, and timing used.

A bronchoprovocation test in which increasing inhaled doses of methacholine are given to assess airway hyperresponsiveness. A fall in FEV1 of a specified percentage defines a positive response.

The highest negative pressure a person can generate against an occluded airway after exhaling to residual volume. It helps evaluate respiratory muscle strength and is effort dependent.

The highest positive pressure a person can generate against an occluded airway after inhaling to total lung capacity. It is used with MIP to assess respiratory muscle weakness.

A submaximal exercise test that measures the distance walked on a flat course in six minutes. It assesses functional exercise capacity and is used in chronic lung disease and pulmonary rehabilitation.

A noninvasive method that estimates arterial oxygen saturation by measuring light absorption through a finger or earlobe. It is affected by poor perfusion, motion, nail polish, and abnormal hemoglobin.

A blood sample from an artery analyzed for pH, oxygen, carbon dioxide, and bicarbonate. It provides direct information about ventilation, oxygenation, and acid-base status and is more accurate than pulse oximetry.

A precise syringe, commonly three liters, used to deliver a known volume into a spirometer. It verifies volume accuracy and is part of routine spirometer quality control.

A healthy staff member who performs spirometry regularly so that their results can be tracked over time. A shift outside a set range suggests equipment or procedural problems.

A check that the spirometer and breathing circuit hold pressure without escaping air. It is usually performed before volume calibration and helps prevent falsely low or inaccurate measurements.

Adjustment of measured gas volumes to body temperature, ambient pressure, and saturated with water vapor. This standardizes lung volumes because gas expands when warmed and humidified in the body.

Conversion of gas volumes to standard temperature, pressure, and dry conditions. It is used for gas exchange measurements such as oxygen consumption and carbon monoxide uptake.

Expected test results derived from equations based on healthy people of similar age, sex, height, and race or ethnicity. They are used to calculate percent predicted and lower limits of normal.

The value below which a test result is considered abnormal, usually the fifth percentile of a healthy reference population. It is preferred over a fixed percent predicted for classifying spirometry.

Standards used to judge whether a spirometry maneuver is technically satisfactory, such as good start, no cough, no leak, and a satisfactory end-of-test plateau.

Standards for how closely the best two acceptable spirometry efforts should agree. FEV1 and FVC usually must match within a specified small volume or percentage for the session to be complete.

A period at the end of a forced expiration when flow is very low and the volume change is minimal. It indicates the subject has exhaled as fully as possible.

The volume estimated by extending the steepest part of the volume-time curve back to time zero. It estimates the starting volume and flags a hesitant or slow start.

A graph plotting airflow against lung volume during a forced breath. Its shape helps identify obstruction, restriction, and upper airway problems and can show variable effort.

Retention of excess air in the lungs after exhalation, reflected by an increased residual volume or residual volume to total lung capacity ratio. It is common in obstructive disease and can increase with forced breathing.

Infection control practices applied to all patients, including hand hygiene, gloves, and safe handling of body fluids. They are the foundation for preventing transmission during pulmonary function testing.

Infection control measures used for pathogens spread by large respiratory droplets, such as influenza. They include a mask and sometimes eye protection, and spatial separation during testing.

Measures for pathogens that remain infectious in small particles over long distances, such as tuberculosis. They require an airborne infection isolation room and a fit-tested N95 or higher respirator.

A procedure that checks whether a respirator seals properly against a person's face. It is required before staff use N95 respirators in airborne precautions and should be repeated periodically.

A procedure in which hypertonic saline mist is inhaled to stimulate coughing and collect airway secretions. It is used to examine airway inflammation and requires infection control precautions.

Written procedures for responding to medical emergencies during testing, including oxygen, rescue equipment, calling for help, and staff training. It should be reviewed and practiced regularly.