Objective To evaluate the effects of inhaled bronchodilators on respiratory mechanics in moderate and severe chronic obstructive pulmonary disease（COPD） patients during eupnea.Methods Twenty moderate to severe COPD subjects were divided into three groups.Lung function，Borg score，breathing pattern and respiratory mechanics indexes were measured at baseline and 30 min after inhaled placebo，salbutamol 400 μg (or ipratropium 80 μg)，and ipratropium 80 μg (or salbutamol 400 μg) in sequence at interval as specified in different groups.Results In all groups，inhaled bronchodilators improved lung function (FEV1，FVC，IC) (Plt;0.05)，decreased Pdi，Peso，PTPdi，PTPeso and Raw (Plt;0.05，respectively)，in comparison with placebo.The reduction of PTPeso was positively correlated with the reduction of Peso (r=0.713，Plt;0.01）and Raw (r=0.602，Plt;0.01).Borg score decreased after inhaled bronchodilators (Plt;0.05).The reduction of dyspnea was positively correlated with the reduction of inspiratory work of breathing (ΔPTPeso%) (r=0.339，Plt;0.05) and Raw (ΔRaw) (r=0.358，Plt;0.05)，while was not associated with the changes of FEV1，FVC and IC.Conclusions In COPD patients，inhaled bronchodilators can reduce inspiratory work of breathing and airway resistance，the reduction of inspiratory work of breathing contributed to the reduction of airway resistance.Alleviation of dyspnea by inhaled bronchodilators is suggested to be ascribed to reduction of airway resistance and inspiratory work of breathing.
Objective To investigate the correlation between dynamic intrinsic positive endexpiratory pressure ( PEEPidyn) and volume dependence of elastance and resistance of respiratory system ( Evd/Rvd) derived from nonlinear analysis of respiratory mechanics in COPD patients during pressure support ventilation ( PSV) . Methods Twenty-five COPD patients mechanically ventilated using mode of PSV were ventilated at a PSV level of no less than 20 cm H2O in a period of 15 minutes to attain so-callednear-relaxation state. The pressure( P) , flow( V′) and volume( V) data were analyzed by nonlinear mode of respiratory motion. PEEPidyn was determined by esophageal balloon-tipped catheter technique. The correlations between PEEPidyn and Evd, Rvd as well as Evd ×Rvd were analyzed. Results The correlation coefficients between PEEPidyn and Evd, Rvd as well as Evd ×Rvd were 0. 85,0. 80, and 0. 90, respectively. Conclusions Nonlinear mode of respiratory motion is suitable to analyze respiratory mechanics of COPD patients mechanically ventilated using mode of PSV. There are good correlations between PEEPidyn and Evd,Rvd as well as Evd ×Rvd which may be used to noninvasively monitor PEEPidyn in mechanically ventilated COPD patients using mode of PSV.