Pulmonary Function Measurements

Vocabulary flashcards covering key terms from the lecture notes on pulmonary function measurements, lung volumes/capacities, expiratory flow measures, diffusion capacity, and related concepts.

Tidal Volume (VT)

The amount of air moved in or out of the lungs during normal, quiet breathing.

Inspiratory Reserve Volume (IRV)

The extra amount of air that can be inhaled after a normal inhalation.

Expiratory Reserve Volume (ERV)

The extra amount of air that can be exhaled after a normal exhalation.

Residual Volume (RV)

The volume of air remaining in the lungs after a maximal exhalation.

Vital Capacity (VC)

The total amount of air that can be exhaled after a maximal inhalation (VT + IRV + ERV).

Inspiratory Capacity (IC)

The maximum amount of air that can be inhaled after a normal exhalation (VT + IRV).

Functional Residual Capacity (FRC)

The volume remaining in the lungs after a normal exhalation (RV + ERV).

Total Lung Capacity (TLC)

The maximum volume of air in the lungs after a maximal inspiration (RV + VC).

Forced Vital Capacity (FVC)

The maximum volume of gas exhaled forcefully and rapidly after a maximal inhalation.

Forced Expiratory Volume Timed (FEVT)

The volume of air exhaled in a specified time during the FVC maneuver (most commonly in 1 second).

FEV1

Volume exhaled in the first second of the FVC maneuver; a key indicator of airway obstruction.

FEV1/FVC Ratio

The proportion of the FVC exhaled in the first second; used to distinguish obstructive from restrictive disease.

FEF25%-75%

Average flow rate during the middle 50% of the FVC; reflects mid-sized airway function.

FEF200-1200

Average flow rate between 200 and 1200 mL of FVC; another index of mid-flow rates.

Peak Expiratory Flow Rate (PEFR)

Maximum flow rate achieved during a forced expiration; normal values ~10 L/s for men and ~7.5 L/s for women; decreases with age and obstructive disease.

Maximum Voluntary Ventilation (MVV)

Largest volume of gas that can be breathed in and out in 1 minute; measure of overall ventilatory capacity.

Flow-Volume Loop

Graphic representation of the FVC maneuver followed by a forced inspiratory maneuver (FIV) showing relationships between flow and volume.

Diffusion Capacity for Carbon Monoxide (DLCO)

Measures the amount of carbon monoxide that diffuses across the alveolar–capillary membrane; resting average ~25 mL/min/mmHg in healthy males.

CBABE

Mnemonic for common obstructive diseases: Cystic fibrosis, Bronchitis, Asthma, Bronchiectasis, Emphysema.

GOLD Stages of COPD

Stage I–IV (mild to very severe) used to categorize COPD severity based on FEV1.

Dynamic Compression

Effort-dependent portion of the forced expiratory maneuver; first ~30% of FVC; involves large airways; higher effort increases FEF200-1200 and PEFR.

Effort-Independent Phase of FVC

Portion of the forced expiratory maneuver after peak flow is reached; flow cannot be increased by more effort.

Rapid Shallow Breathing Index (RSBI)

Ratio of respiratory frequency (f) to tidal volume (VT); normal 60–105; values <105 predict weaning success.

Open-Circuit Nitrogen Washout

Indirect method to estimate residual volume by washing out nitrogen from the lungs.

Closed-Circuit Helium Dilution

Indirect method to estimate residual volume using helium as a tracer gas.

Body Plethysmography (Body Box)

Indirect method to measure thoracic gas volumes, including RV, using pressure changes in a closed box.

Flow-Volume Loop Patterns

Normal loop shows typical shape; obstructive pattern shows scooped expiratory limb with reduced peak flow; restrictive pattern shows reduced volumes with relatively preserved shape.

Factors Affecting Predicted Normal Values

Height, weight, age, gender, and race influence predicted pulmonary function values.

Distinguishing Obstructive vs Restrictive with FEV1 and FVC

Obstructive disorders show decreased FEV1 and FEV1%; restrictive disorders show normal or increased FEV1 but decreased FVC.