Collateral Ventilation in Man

To determine whether collateral ventilation (defined as the ventilation of alveolar structures through passages or channels that bypass the normal airways) changes with age or emphysema, we compared the mechanics of collateral ventilation in seven young normal subjects, three old normal subjects and five patients with emphysema. In supine normal subjects at the end of a quiet expiration, resistance to airflow was greater through collateral channels than through bronchi and bronchioles. In emphysema, airways resistance could exceed collateral resistance, causing air to flow preferentially through collateral pathways. We conclude that high collateral resistance minimizes collateral airflow in supine normal subjects. When peripheral airways become obstructed or obliterated in emphysema, collateral channels may provide for more even distribution of ventilation. (N Engl J Med 298:10–15, 1978) CLINICIANS have long observed that atelectasis of lung parenchyma does not invariably occur with segmental or lobar obstruction. In 1930 Van Allen and Lindskog obstructed sublobar bronchi in dog lungs and noted no collapse distal to the obstructed bronchus. They used the term “collateral respiration” to explain how “gases may enter one lobule from another in the lung without resorting to known anatomical pathways.”¹ Subsequently, pores of Kohn,² interbronchiolar channels of Martin³ and alveolar bronchiolar channels of Lambert⁴ have been suggested as pathways for collateral ventilation. The extent to which collateral channels contribute to the distribution of ventilation in human.