A comparative study on the effects of noninvasive pressure control ventilation and pressure support ventilation in patients with respiratory failure due to chronic obstructive pulmonary disease

Objective To compare the effects of two noninvasive positive pressure ventilation(NPPV) modes,pressure control ventilation(PCV) and pressure support ventilation(PSV),on respiratory mechanics in patients with respiratory failure due to chronic obstructive pulmonary disease(COPD).Methods 35 conscious patients with respiratory failure due to acute exacerbations of chronic obstructive pulmonary disease(AECOPD)were ventilated by NPPV via face mask for at least 1 hour.Continuous positive airway pressure(CPAP) mode was applied at first in all patients with a bias flow of 20 L/min and positive end expiratory pressure(PEEP)of(4 cm) H_2O.Then the patients were ventilated with PCV or PSV mode at random.Inspiratory time(T_I) during PCV was preset and regulated by observing the waveform.Respiratory mechanics and arterial blood gas(ABG)were measured at 60 min after ventilation of different modes.Results Compared with CPAP and PSV,minute ventilation(MV) and respiratory rate(RR) were much lower in PCV mode(all P0.05),but T_I during PCV was much longer than those during PSV and CPAP[(1.23±0.09)sec versus(1.06±0.11)sec and(0.89±(0.10)sec),P0.05].Inspiratory duty cycle(T_I/Ttot) and rapid shallow breath index(RSBI) during PCV and PSV were obviously decreased while tidal volume(V_T) was markedly increased(all P0.05).No difference of PaO_2/FiO_2 in PSV and PCV was found.Conclusions By adjusting the T_I and back-up rate,PCV is capable of reducing patient workload and provides similar level of respiratory support with PSV under the same airway pressure.Compared with PSV,PCV reduces the patients work of breathing (WOB)more effectively,however,the difference of oxygenation improvement is not significant.