Figure 4.

A, Normal lung lobule containing six terminal bronchioles. B, Leopold and Gough’s³⁰ original diagram of a primary centrilobular emphysematous lesion described almost simultaneously by themselves in the UK and by McLean³¹ in Australia. C, Bronchogram of a centrilobular emphysematous space formed by the coalescence of several primary lesions.³² D, The electrical analog of the peripheral lung used by Otis et al,³³ where S is the power source, R is resistance, and C is capacitance. E, Modification of the normal electrical analogue to include collateral channels R4, that have very high resistance in the normal lung and fall to very low levels in emphysematous regions of lungs affected by COPD.^34,35 We postulate that the primary centrilobular lesions develop beyond surviving terminal bronchioles and that the fall in collateral resistance associated with emphysematous destruction provides ventilation to the normal alveoli located beyond destroyed terminal bronchioles. CLE=centrilobular emphysematous space.