What does a decreased forced expiratory volume in one second (FEV1) to forced vital capacity (FVC) ratio indicate in the supplied material?

### Why this is right The material states that a decreased forced expiratory volume in one second (FEV1) to forced vital capacity (FVC) ratio indicates airflow obstruction. A lower ratio means that the amount of air expelled rapidly in the first second is reduced relative to the total forced amount. ### The concept Spirometry is a breathing test that measures how much air a person can move and how quickly it can be expelled. The material lists reduced FEV1 and FVC, a decreased FEV1/FVC ratio, and lower peak expiratory flow as changes in active smokers. It directly links the decreased ratio with airflow obstruction, which can arise when airways are narrowed or affected by inflammation and mucus. ### The other options - **B. Improved oxygen transport**: This is not what the ratio indicates; the material describes smoking as reducing lung function. - **C. Increased alveolar elasticity**: The material describes loss of lung elasticity, not an increase. - **D. Reduced mucus production**: Smoke exposure can increase mucus production, and the ratio does not measure mucus production directly. ### Terms - **Spirometry**: A test that measures how much and how quickly a person can breathe air out. - **FEV1**: Forced expiratory volume in one second, the air expelled during the first second of a forced breath out. - **FVC**: Forced vital capacity, the total air forcibly breathed out after a full breath in. - **Airflow obstruction**: Difficulty moving air through narrowed or affected airways. ### Remember The supplied material links a decreased FEV1/FVC ratio with airflow obstruction.