Objective: We investigated the clinical response to equivalent doses of salbutamol delivered, via metered dose inhaler (MDI) during non-invasive mechanical ventilation (NIMV-MDI), during spontaneous breathing using a spacer (MDI-Spacer), and also during intermittent positive pressure breathing (IPPB).
Setting: A respiratory intensive care unit.
Design: Prospective, randomized, and placebo-controlled study.
Patients: Eighteen stable patients with chronic obstructive pulmonary disease (mean FEV1=38.5+/-8.8% predicted).
Results: Overall salbutamol administration induced, compared to placebo, a significant improvement in FEV1, irrespective of the mode of administration (+7.9+/-7.1% or +108+/-91 ml for IPPB, +9.6+/-8.8% or 112+/-67 ml for MDI-NIMV (inspiratory pressure=14.3+/-1.8 cmH2O; expiratory pressure=none), and +10.8+/-11.4% or 119+/-114 ml for MDI-Spacer, respectively). DeltaFVC significantly increased from placebo only in MDI-NIMV (+214+/-182 ml P=0.02). A second set of experiments performed in eight patients to ascertain the possible effect of NIMV on pulmonary function tests, showed a significant improvement from baseline values in FVC both after the delivering of placebo or salbutamol via NIMV-MDI (+206+/-147 ml and 208+/-145, respectively). FEV1 significantly increased only after salbutamol. No changes in gas exchange were observed after bronchodilator delivery.
Conclusions: We show that delivery of bronchodilators via MDI with a spacer chamber during NIMV is feasible and induces a significant bronchodilator effect compared to placebo, even though it may be slightly less effective than the classical delivery system (MDI-Spacer).