Paradoxical bronchoconstriction is a rare phenomenon in which airway obstruction worsens after inhalation therapy. Although uncommon, it is clinically important because it may lead to severe deterioration and is often underrecognized in emergency and critical care settings.

A woman in her 50s with a history of asthma presented with acute respiratory distress. Initial treatment with dry powder inhalers was tolerated; however, immediately after nebulized inhalation therapy, her respiratory status rapidly deteriorated, necessitating endotracheal intubation and mechanical ventilation. During intensive care, nebulized therapy was re-administered using a different nebulizer device, which reproducibly induced bronchoconstriction, characterized by severe coughing, elevated airway pressure, and impaired ventilation. Nebulized therapy was discontinued, and alternative non-nebulized inhalation strategies were adopted, resulting in gradual clinical improvement. The patient was successfully extubated and discharged without recurrence after modification of the inhalation therapy.

Previous studies have reported that paradoxical bronchoconstriction is uncommon in asthma but is associated with an increased risk of exacerbations, and rare cases requiring mechanical ventilation have been described. The reproducible induction of paradoxical bronchoconstriction during mechanical ventilation, as observed in this case, has been extremely limited in previous reports. The underlying mechanisms are thought to be multifactorial, involving not only pharmacological agents but also other factors related to inhalation therapy.

Paradoxical bronchoconstriction should be considered when acute respiratory worsening occurs immediately after inhalation therapy, even in patients receiving mechanical ventilation. Early recognition and reassessment of inhalation strategies may help prevent inappropriate escalation of treatment and improve patient outcomes.