Effects of change in the expiratory trigger during pressure support ventilation in COPD

Introduction

During pressure support ventilation (PSV) the ventilator cycles from inspiration to expiration when the inspiratory flow reaches a given percentage of the peak inspiratory flow 'expiratory trigger' (ET). On the most recent available ventilators it is possible to modify the percentage of the ET.

Objective

We evaluated in a group of COPD patients during PSV the change of ET (high 40% and low 5% of the peak inspiratory flow, respectively) in terms of the pattern of breathing and inspiratory effort (pressure time product [PTP]).

Materials and methods

Nine COPD patients were studied during respiratory failure (PaO₂/FiO₂ 295 ± 108, PEEP 6.2 ± 1.7 cmH₂O, mean age 70 ± 2 years, and BMI 25.4 ± 4.3). PSV was set at 5 cmH₂O without PEEP while the oxygen fraction remained constant during the study. Airway, esophageal, gastric pressures and airflow were measured.

Results

See Table 1.

Table 1 (abstract P39

Conclusion

The change of percentage of ET at a low level of PSV did not modify the inspiratory effort and pattern of breathing.