Bronchoconstriction in response to deep inhalation during spirometry testing.

In healthy individuals, airway resistance has an inverse relationship with lung volume.1 Moreover, deep inhalation is thought to maintain airway smooth muscle homeostasis and to possess bronchodilating and bronchoprotective properties against challenge agents.2-6 The bronchodilatory effect of deep inhalation is clearly impaired in asthma patients2,7,8; however, the bronchoprotective properties of deep inhalation against challenge test agonists (eg, methacholine) remain robust in many asthma patients with mild airway hyper-responsiveness.5,6 In some asthma patients, however, deep inhalation can produce paradoxical bronchoconstriction.5,9,10 This case describes a patient who developed significant bronchoconstriction in response to deep inhalation during spirometry testing.