Disparity between the development of the airways (especially their diameter) and the size of the lungs explaining the presence of an obstacle to air flow in the airways (VEMS/CVF or Tiffeneau ratio too low) despite a maximal expiratory volume/second (VEMS) and a normal maximum vital capacity on spirometry. The cause is anatomical: the presence of either too narrow airways compared to a normal alveolar surface, or normal airways in the presence of too large lungs.

Long considered as a variant of normal, this anomaly is now recognized as the cause of airway obstruction that does not respond to bronchodilators: for example, this explains the ineffectiveness of bronchodilator treatment in patients with COPD patients with no history of smoking, or in obese children and adolescents, asthmatic or not, or exertional dyspnea in otherwise healthy adolescents.

Anesthetic implications:

avoid all causes of bronchospasm, use an I/E ratio of 1:2, apply light PEEP

References :

-        Thompson BR.
Dysanapsis - once believed to be a physiological curiosity - is now considered as clinically important.
Am J Resp Crit Care Med 2017; 195: 277-8

-        Forno E, Weiner DJ, Mullen J, Sawicki G, Kurland G et al.
Obesity and airway dysanapsis in children with and without asthma.
Am J Resp Crit Care Med 2017; 195: 314-23.

-        Pianosi PT.
Flow limitation and dysanapsis in children and adolescents with exertional dyspnea.
Respir Physiol Neurobiol 2018; 252-253: 58-63

Updated: June 2020