Final Answer:
In obstructive diseases such as chronic bronchitis and asthma, airway radius is decreased. Thus, FEV1 will decrease.
Therefore, correct option is b. Decrease.
Step-by-step explanation:
In obstructive diseases like chronic bronchitis and asthma, the airway radius is diminished due to factors such as inflammation, bronchoconstriction, and mucus production. This constriction hinders the smooth flow of air during breathing. Forced Expiratory Volume in one second (FEV1), which measures the amount of air a person can forcefully exhale in the first second of a forced breath, is adversely affected. With the reduced airway radius, it becomes challenging for individuals with obstructive diseases to expel air effectively, causing a decrease in FEV1 (b). This reduction in expiratory volume is a key characteristic of obstructive lung conditions.
In conditions like chronic bronchitis and asthma, the decreased FEV1 reflects the difficulty in moving air out of the lungs promptly, leading to symptoms such as wheezing, shortness of breath, and coughing. Monitoring FEV1 is crucial in assessing the severity of obstructive lung diseases and guiding appropriate treatment interventions.
Therefore, correct option is b. Decrease.