Activation of respiratory muscles during weaning from mechanical ventilation.

PURPOSE: Respiratory muscle dysfunction is a key component of weaning failure. Balancing respiratory muscle loading and unloading by applying different ventilation modes along with spontaneous breathing episodes are established weaning strategies. However, the effects of body positioning on the respiratory muscles during weaning remains unclear.

MATERIALS AND METHODS: This study aimed at assessing respiratory drive by surface electromyography (EMG) of the diaphragm (EMGdia ) and parasternal muscles (EMGpara ) in tracheotomized patients during prolonged weaning in 3 randomized body positions-supine, 30° semirecumbent, and 80° sitting-during mechanical ventilation and spontaneous breathing.

RESULTS: Nine patients were included for analysis. Cardiorespiratory parameters (heart rate, blood pressure, arterial oxygen saturation, dyspnea) did not change under each condition (all P>.05). EMGpara and EMGdia did not change under mechanical ventilation (both P>.05). EMGdia changed under spontaneous breathing from supine to sitting (0.45±0.26 vs 0.32±0.19; P=.012) and between semirecumbent to sitting (0.41±0.23 vs 0.32±0.19; P=.039), whereas EMGpara did not change.

CONCLUSIONS: This is the first study to show that body positioning influences respiratory drive to the diaphragm in tracheotomized patients with prolonged weaning from mechanical ventilation during unassisted breathing. Sitting position reduces respiratory drive compared with semirecumbent and supine positioning and might therefore be favored during spontaneous breathing trials.