What would pulmonary function tests (PFTs) typically show in a cystic fibrosis patient?

In patients with cystic fibrosis, pulmonary function tests (PFTs) typically reveal decreased flow rates, particularly reflecting an obstructive pattern. This occurs primarily due to the accumulation of thick, viscous mucus in the airways, which causes blockages and limits airflow. As a result, airway resistance increases, leading to decreased expiratory flow rates measured during PFTs, especially in tests such as forced vital capacity (FVC) and forced expiratory volume in one second (FEV1).

The obstructive pattern seen in cystic fibrosis is characterized by a reduced FEV1/FVC ratio, indicating that while total lung capacity may remain normal, the rate at which air can be exhaled is compromised. This pattern of decreased flow rates is crucial for diagnosing and monitoring the progression of the disease, as well as for evaluating the effectiveness of therapeutic interventions.

Normal flow rates would not be expected in this population due to the chronic nature of the disease and its effects on lung function. Irregular flow patterns can occur in many different lung pathologies, but they are not the hallmark finding in cystic fibrosis. Increased flow rates would suggest improved clearance and airflow, which is not typical given the obstructive nature of the condition.