Introduction: Deep inspiration temporarily reduces induced airways obstruction in healthy subjects. This bronchodilatory effect of deep inspiration is impaired in asthma. Passive machine-assisted lung inflation may augment bronchodilation as compared to an active deep inspiration in patients with asthma by either opening closed airways or by reducing fluid flux across the airway wall during deep inspiration, and thereby increasing the tethering forces on the airway wall. Methods: We recruited 24 patients with asthma (18-46 yrs, FEV₁ > 70% pred, PC₂₀methacholine < 8 mg/ml), with either an impaired (n=12) or an intact (n=12) bronchodilatory response to deep inspiration (DI). Two methacholine challenges were performed on separate days. At a 50% increase in respiratory resistance (forced oscillation technique at 8 Hz) the change in resistance by a positive pressure inflation (computer driven syringe) or an active deep inspiration was measured in randomized order. Results: The reduction in resistance by positive pressure inflation was significantly greater than by active DI in the impaired DI response group (mean change ± SEM: -0.6 ± 0.1 vs. -0.03 ± 0.2 cmH₂O/L/s, p = 0.002). No significant difference was found between positive pressure inflation and active DI in the intact DI response group (-0.6 ± 0.2 vs. -1.0 ± 0.3 cmH₂O/L/s, p = 0.18). Conclusion: Positive pressure inflation of the lungs can significantly enhance deep inspiration-induced bronchodilation in patients with asthma.