PT  - JOURNAL ARTICLE
AU  - Kondili, Eumorfia
AU  - Alexopoulou, Christina
AU  - Prinianakis, George
AU  - Xirouchaki, Nektaria
AU  - Vaporidi, Katerina
AU  - Georgopoulos, Dimitris
TI  - Effect of Albuterol on Expiratory Resistance in Mechanically Ventilated Patients
AID  - 10.4187/respcare.00984
DP  - 2011 May 01
TA  - Respiratory Care
PG  - 626--632
VI  - 56
IP  - 5
4099  - http://rc.rcjournal.com/content/56/5/626.short
4100  - http://rc.rcjournal.com/content/56/5/626.full
AB  - BACKGROUND: In mechanically ventilated patients with COPD, the response of the expiratory resistance of the respiratory system (expiratory RRS) to bronchodilators is virtually unknown. OBJECTIVE: To examine the effect of inhaled albuterol on expiratory RRS, and the correlation of albuterol-induced changes in expiratory RRS with end-inspiratory resistance and the expiratory flow-volume relationship. METHODS: We studied 10 mechanically ventilated patients with COPD exacerbation, before and 30 min after administration of albuterol. We obtained flow-volume curves during passive expiration, divided the expired volume into 5 equal volume slices, and then calculated the time constant and dynamic effective deflation compliance of the respiratory system (effective deflation CRS) of each slice via regression analysis of the volume-flow and post-occlusion volume-tracheal pressure relationships, respectively. For each slice we calculated expiratory RRS as the time constant divided by the effective deflation CRS. RESULTS: Albuterol significantly decreased the expiratory RRS (mean expiratory RRS 42.68 ± 17.8 cm H2O/L/s vs 38.08 ± 16.1 cm H2O/L/s) and increased the rate of lung emptying toward the end of expiration (mean time constant 2.51 ± 1.2 s vs 2.21 ± 1.2 s). No correlation was found between the albuterol-induced changes in expiratory RRS and that of end-inspiratory resistance. Only at the end of expiration did albuterol-induced changes in the expiratory flow-volume relationship correlate with changes in expiratory RRS in all patients. CONCLUSIONS: In patients with COPD, albuterol significantly decreases expiratory resistance at the end of expiration. In mechanically ventilated patients, neither inspiratory resistance nor the whole expiratory flow-volume curve may be used to evaluate the bronchodilator response of expiratory resistance.