Final answer:
The FEV1/FVC ratio is used to assess lung function in PFTs, with high ratios indicating stiff lungs and low ratios indicating increased resistance such as in asthma. Resistance, lung compliance, and surfactant levels are among the key factors that affect this measurement.
Step-by-step explanation:
Several variables impact lung function and are taken into account when performing pulmonary function tests (PFTs). One key measurement is the forced expiratory volume in one second (FEV1) in relation to the total forced vital capacity (FVC). The FEV1/FVC ratio is crucial for assessing lung diseases such as asthma, emphysema, and fibrosis. Factors that may affect this ratio include airway diameter (resistance), lung compliance, surface tension within the alveoli, and the presence of pulmonary surfactant. High rat ios imply noncompliant or stiff lungs, while low ratios suggest increased resistance characteristic of conditions like asthma.
Other factors that influence lung function include muscle strength, the presence or absence of lung disease, and environmental factors affecting lung health. Doctors can detect increased resistance in patients' lungs through physical examinations, symptoms, and the use of diagnostic tests like spirometry. A low FEV1/FVC ratio indicates difficulty in expelling air from the lungs, reflecting increased resistance. Additionally, the residual volume of the lungs prevents alveolar collapse and allows for continuous gas exchange, which can be affected by changes in lung compliance or obstruction.