Which of the following best describes the expiratory flow pattern typically seen in cystic fibrosis on spirometry?

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Multiple Choice

Which of the following best describes the expiratory flow pattern typically seen in cystic fibrosis on spirometry?

Cystic fibrosis produces obstructive changes in the airways because thick mucus and inflammation narrow the passages, especially during expiration. On spirometry this shows up as reduced expiratory flow. FEV1 falls because the large airways are obstructed, and flows reflecting small-airways function, such as FEF25-27, also decrease due to mucus plugging and airway narrowing. This combination—lower FEV1 and decreased small-airway flow—is the hallmark of the expiratory pattern in CF. Normal flow rates wouldn’t fit the disease, and DLCO measures diffusion capacity rather than expiratory flow, so an increased DLCO isn’t the pattern you’d expect here.

Cystic fibrosis produces obstructive changes in the airways because thick mucus and inflammation narrow the passages, especially during expiration. On spirometry this shows up as reduced expiratory flow. FEV1 falls because the large airways are obstructed, and flows reflecting small-airways function, such as FEF25-27, also decrease due to mucus plugging and airway narrowing. This combination—lower FEV1 and decreased small-airway flow—is the hallmark of the expiratory pattern in CF. Normal flow rates wouldn’t fit the disease, and DLCO measures diffusion capacity rather than expiratory flow, so an increased DLCO isn’t the pattern you’d expect here.

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