Site and Nature of Airway Obstruction in Chronic Obstructive Lung Disease

TLDR

Small airway disease is a common feature of various chronic obstructive lung diseases. The study measured central and peripheral airway resistance using a small catheter in excised lungs and found that peripheral resistance was elevated due to mucus plugging, narrowing, and obliteration of small airways. Peripheral airway resistance was markedly increased—up to 40‑fold in emphysema and also in bronchiectasis and bronchiolitis—while central resistance remained near normal, indicating that small‑airway obstruction can be severe yet under‑detected by standard tests.

Abstract

We have wedged a small catheter in airways 2 to 3 mm in diameter in excised human lungs to have measure airway resistance central (Rc) and peripheral (Rp) to this site. In five normal lungs, R accounted for only 25 per cent total airway resistance (RL) and averaged 0.18 cm of water per liter per second. In seven patients with emphysema Rp was increased from four to 40 times. Rp was also increased in one case of bronchiectasis and another of bronchiolitis. In all, Rc scattered around the normal value. Bronchographic and histologic studies showed that Rp was increased because of mucus plugging, narrowing and obliteration of the small airways. Disease of small airways may be common to various chronic obstructive lung diseases. Because Rp is normally so small, there may be considerable obstruction in peripheral airways that would affect ventilation distribution and gas exchange but would have little effect on function tests designed to reveal obstruction. When total airway resistance is elevated to a clinically detectable level by disease in the small airways, obstruction is much more severe than is generally recognized.