Study objective: To determine whether bolus instillation of a mucolytic agent (mesna) could diminish airway resistance, endotracheal tube resistance, or both in patients mechanically ventilated for acute respiratory failure.
Design: Randomized, double-blind, placebo-controlled, crossover trial.
Setting: Medical-surgical ICU of a county hospital covering 350,000 inhabitants.
Patients: Twenty sedated and paralyzed patients with an endotracheal tube (ET) in place more than 72 h.
Interventions: Data were recorded in three steps: (1) basal; (2) 10 min after endotracheal instillation of 3 mL of either saline solution or mesna; and (3) 10 min after instillation of the opposite drug. A 2-h washout period was allowed between data collection.
Measurements and results: We measured tidal volume (VT), inspiratory flow (VI), auto-PEEP, peak pressure (both at airway opening [Pmax.aw] and trachea [Pmax-.tr]) and plateau pressure (Pplat), and we calculated respiratory system compliance (Crs) and the inspiratory resistances of airways+tube (Rmax.aw), airways (Rmax.tr), and ET (Rtube). We found significant differences after the instillation of mesna compared with baseline in the following: airway plus tube resistance (Rmax.aw) (16.9 +/- 7.1 vs 18.9 +/- 7.7 cm H2O); airways resistance (Rmax.tr) (9.8 +/- 6.2 vs 12.0 +/- 6.4 cm H2O), PaO2 (96 +/- 28.5 vs 80 +/- 24.8 mm Hg), PaO2/PAO2 (0.360 +/- 0.152 vs 0.296 +/- 0.127), and PaCO2 (42 +/- 12.9 vs 43 +/- 14.1 mm Hg). We found no changes in compliance, auto-PEEP, and hemodynamics during the study. Instillation of saline solution had no effect on the physiologic variables studied.
Conclusions: In our patients, bolus tracheal instillation of mesna does not improve airway resistance; in fact, mesna instillation induces episodes of bronchospasm that disappear 2 h later.