Differences between Midazolam and Propofol Sedation on Upper Airway Collapsibility Using Dynamic Negative Airway Pressure

Background: Upper airway obstruction (UAO) during sedation can often cause clinically significant adverse events. Direct comparison of different drugs' propensities for UAO may improve selection of appropriate sedating agents. The authors used the application of negative airway pressure to determine the pressure that causes UAO in healthy subjects sedated with midazolam or propofol infusions.

Methods: Twenty subjects (12 male and 8 female) completed the study. After achieving equivalent levels of sedation, the subjects' ventilation, end-tidal gases, respiratory inductance plethysmographic signals, and Bispectral Index values were monitored for 5 min. Negative airway pressure was then applied via a facemask in steps of 3 cm H2O from -3 to -18 cm H2O. UAO was assessed by cessation of inspiratory airflow and asynchrony between abdomen and chest respiratory inductance plethysmographic signals.

Results: Equivalent levels of sedation were achieved with both drugs with average (+/- SD) Bispectral Index levels of 75 +/- 5. Resting ventilation was mildly reduced without any changes in end-tidal pressure of carbon dioxide. There was no difference between the drugs in the negative pressure resulting in UAO. Five female subjects and one male subject with midazolam and four female subjects and one male subject with propofol did not show any UAO even at -18 cm H2O. Compared with males, female subjects required more negative pressures to cause UAO with midazolam (P = 0.02) but not with propofol (P = 0.1).