The Change of Respiratory Mechanics by a Bronchodilator Inhalation Under the Variable Level of PEEP in Patients with Acute Respiratory Distress Syndrome

Hong, Sang Bum; Koh, Youn Suck

Abstract

BACKGROUND: Reduced lung compliance and increased lung resistance are the primary lung mechanical abnomalities in acute respiratory distress syndrome (ARDS). Although there is little information regarding the mecha nisms responsible for the increases in the respiratory resistance of ARDS, bronchodilators have been frequently administered in mechanically ventilated ARDS patient. To determine the effect of a bronchodilator on the respiratory mechanics depending on the level of applied positive end-expiratory pressure (PEEP), the change in the respiratory mechanics by salbutamol ingalation was measured under the variable PEEP level in patients with ARDS.
METHODS
Fifteen mechanically ventilated paralyzed ARDS patientss (14 of male, mean age 57 years) were enrolled in this study. The respiratory system compiance, and the maximum and minimun inspiratory occlusion method during constant flow inflaction using the CP-100 pulmonary monitor (Bicore, Irvine, CA, USA). The measurements were performed at randomly applied 8, 10 and 12 cm H2O PEEP before and 30 mins after administrating salbutamol using a meter-dose-inhaler (100 micro gram X 6).
RESULTS
1) The maximum inspiratory resistance of the lung was higher than the reported normol values due to an increase in the minimal inspiratory resistance and additional resistance. 2) The maximum inspiratory resistance and peak airway pressure were significantly higher at 12 cm H2O of PEEP compared with those at 10cm H2O of PEEP. 3) Salbutamol induced a significant decrease in the maximum and the minimum inspiratory resistance but no significant change in the additional resistance only was observed at 12 cm H2O of PEEP (from 15.66+/-1.99 to 13.54+/-2.41, from 10.24+/-2.98 to 8.04+/-2.34, and from 5.42+/-3.41 to 5.50+/-3.58 cm H2O/l/sec, respectively). 4) The lung compliance did not change at the applied PEEP and salbutamol inhalation levels.
CONCLUSIONS
The bronchodiator response would be different depending on the level of applied PEEP despite the increased respiratory resistance in patients with ARDS.