Effect of inhaled salbutamol on dynamic intrinsic positive end-expiratory pressure in spontaneously breathing patients with stable severe chronic obstructive pulmonary disease.

Background: The objective was to determine the effect of inhaled salbutamol on PEEPi dyn in spontaneously breathing patients with stable severe chronic obstructive pulmonary disease (COPD).

Material/methods: Eleven patients with COPD were studied (mean age: 63 years, average FEV1 0.71 +/- 0.31 L). The patients were evaluated before and after inhaling 400 pg of salbutamol. Spirometry, slow vital capacity, breathing pattern, and PEEPi dyn pre- and post-bronchodilator administration were performed. PEEPi dyn was measured as the difference in esophageal pressure between the onset of inspiratory effort and the point of zero flow.

Results: Pre-BD PEEPi dyn fell on average by 56% after inhalation of salbutamol (1.89 +/- 1.24 cm H2O to 0.83 +/- 0.81 cm H2O, p<0.001). This was accompanied by bronchodilation and a reduction of air trapping (FEV1: 0.71 +/- 0.31 L to 0.91 +/- 0.35 L, p<0.001; IC: 1.5 +/- 0.53 L to 1.94 +/- 0.56 L, p<0.001). A significant positive correlation between deltaPEEPi dyn, deltaFEV1 (r=0.64, p<0.05), and deltaIC (r=0.69, p<0.05) was observed. The breathing pattern did not change significantly after bronchodilation. Stepwise multiple regression analysis of pre-BD spirometric and breathing pattern parameters selected IC and Ti/Ttot as the strongest predictors of pre-BD PEEPi dyn (p=0.039 and 0.006, respectively).

Conclusions: The inhalation of 400 microg of salbutamol produced bronchodilation, reduction of air trapping, and a decrease in PEEPi dyn in spontaneously breathing patients with stable severe COPD.