Physiological effects of meals in difficult-to-wean tracheostomised patients with chronic obstructive pulmonary disease

Objectives To evaluate effects of meals in difficult-to-wean tracheostomised patients with chronic obstructive pulmonary diseases during spontaneous breathing or Inspiratory Pressure Support.Design Prospective, crossover, randomised, and physiological study.Setting Weaning centre.Patients Sixteen COPD undergoing either decreasing levels of pressure support or increasing periods of spontaneous breathing.Measurements Each patient underwent monitoring during a 30-min procedure, during and after meals either under pressure support or spontaneous breathing on two consecutive days. Inductance plethysmography was used to monitor respiratory rate and tidal volume. Tidal volume by a flow transducer, arterial oxygen saturation, pulse rate, end-tidal CO2_, and dyspnoea by a visual analogue scale were also assessed.Results ANOVA analysis showed a significant increase under spontaneous breathing for respiratory rate (P<0.001) and for end tidal CO₂ (P<0.03) induced by the meals. Inspiratory pressure support was associated to significantly greater tidal volume (P<0.001), lower respiratory rate (P<0.032), lower respiratory rate/tidal volume (P<0.001), and lower pulse rate (P<0.047) than spontaneous breathing. Under spontaneous breathing but not under pressure support a statistically worsening in meal-induced dispnoea (P<0.001) was found.Conclusions In tracheostomised difficult-to-wean COPD patients: 1) under unassisted breathing, meals may induce an increase in respiratory rate, end-tidal CO₂, and dyspnoea; 2) inspiratory pressure support ventilation prevents dyspnoea from worsening during meals.