The FEV1/FVC ratio represents the measurement of what? And a value below which threshold indicates obstruction?

The FEV1/FVC ratio represents the measurement of what? And a value below which threshold indicates obstruction?

• A. Absolute volume exhaled in the first second.
• B. The ratio of FEV1 to FVC expressed as a percentage of predicted values.
• C. The amount exhaled during the first second of effort.
• D. Percentage of lung volume exhaled in the first second; <0.7 indicates obstruction.

Answer: (D)

The FEV1/FVC ratio tells you what portion of the total forced vital capacity is expelled in the first second of a forced exhalation. In other words, it’s the percentage of the lung volume that comes out in the opening portion of the breath. Clinically, this ratio is used to detect obstructive airflow limitation, with a value below 0.7 indicating obstruction. This happens because FEV1 (the amount exhaled in the first second) drops more than the total capacity (FVC) in obstructive diseases, lowering the ratio. The other descriptions either refer to FEV1 alone, or describe the ratio as a percentage of predicted values rather than the actual measured fraction, which is not the best fit for defining obstruction.

The FEV1/FVC ratio tells you what portion of the total forced vital capacity is expelled in the first second of a forced exhalation. In other words, it’s the percentage of the lung volume that comes out in the opening portion of the breath. Clinically, this ratio is used to detect obstructive airflow limitation, with a value below 0.7 indicating obstruction. This happens because FEV1 (the amount exhaled in the first second) drops more than the total capacity (FVC) in obstructive diseases, lowering the ratio. The other descriptions either refer to FEV1 alone, or describe the ratio as a percentage of predicted values rather than the actual measured fraction, which is not the best fit for defining obstruction.