Prediction and Assessment of Bronchodilator Response in Mechanically Ventilated Patients

Abstract

Background

Bronchodilators are commonly prescribed for mechanically ventilated patients, yet uniform indications for and objective assessment of the efficacy of aerosolized bronchodilator use in this population are generally lacking. In this prospective study of consecutive mechanically ventilated patients, we asked, Can we identify a priori those patients who are most likely to respond to inhaled bronchodilators?

Materials & Methods

54 consecutive mechanically ventilated patients in acute respiratory failure participated in the study. We recorded auto-PEEP, PIP, and whether wheezing was present on auscultation before and 15 minutes after the first dose of bronchodilator. Evidence for the presence of reversible airway obstruction (RAO)—diagnosis of COPD or asthma and/ or use of inhaled corticosteroids or bronchodilators—was obtained from the patient's chart. The bronchodilator was delivered via metered-dose inhaler with an Aerovent chamber as prescribed by the primary physician. The therapy was deemed indicated if the patient had a history of RAO or if auto-PEEP or wheezing was present. A positive response to bronchodilator was defined as a decrease in wheezing, > 2 cm H₂O decrease in auto-PEEP, or > 4 cm H₂O decrease in PIP.

Results

42/54 (78%) patients had at least one indication for bronchodilator. Of these 42, 27 were positive on at least 1 of the 3 response criteria. Of the 12 patients without an indication, only 1 had a positive response (xβ, p < 0.001). Of the 22 patients who were not wheezing prior to treatment, only 5 showed decreased PIP or auto-PEEP, whereas 23 of 32 who were wheezing responded (xβ, p < 0.001). A presumptive history of RAO was not associated with a bronchodilator response: 9/17 patients with a history of RAO and 18/37 patients with no history of RAO responded (xβ, p > 0.05).

Conclusions

Using the information often available to the clinician (eg, limited patient history, physical exam, PIP, and auto-PEEP), it is not possible to predict reliably which patients will benefit from bronchodilator treatment. Based on the results of this study, we recommend an empirical trial of bronchodilator in mechanically ventilated patients for whom a potential indication exists. In the absence of such an indication or if objective measurements fail to document a response, continued bronchodilator administration may not be clinically useful or cost-effective.