Rationale: During pressure support ventilation, the ventilator cycles into expiration when inspiratory flow decreases to a given percentage of peak inspiratory flow ("expiratory trigger"). In obstructive disease, the slower rise and decrease of inspiratory flow entails delayed cycling, an increase in intrinsic positive end-expiratory pressure and non-triggering breaths. Objectives: We hypothesized that setting expiratory trigger at a higher than usual percentage of peak inspiratory flow would attenuate the adverse effects of delayed cycling. Methods: Ten intubated obstructive patients undergoing pressure support were studied at expiratory trigger settings of 10, 25, 50 and 70 % of peak inspiratory flow. Measurements: Continuous recording of diaphragmatic electromyographic activity with surface electrodes, and esophageal and gastric pressures with a dual-balloon naso-gastric tube. Main results: Compared to expiratory trigger 10, expiratory trigger 70 reduced the magnitude of delayed cycling (0.25 ± 0.18 vs. 1.26 ± 0.72 seconds, p < 0.05), intrinsic positive end-expiratory pressure (4.8 ± 1.9 vs. 6.5 ± 2.2 cmH₂O, p < 0.05), non-triggering breaths (2 ± 3 vs. 9 ± 5 breaths per minute, p < 0.05), and triggering pressure-time product (0.9 ± 0.8 vs. 2.1 ± 0.7 cmH₂O.s, p < 0.05). Conclusions: Setting expiratory trigger at a higher percentage of peak inspiratory flow in obstructive patients during pressure support improves patient-ventilator synchrony and reduces inspiratory muscle effort. Further studies should explore whether these effects can influence patient outcome.