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 H(2)O from -3 to -18 cm H(2)O. 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 H(2)O. Compared with males, female subjects required more negative pressures to cause UAO with midazolam (P = 0.02) but not with propofol (P = 0.1).


CONCLUSIONS
At the mild to moderate level of sedation studied, midazolam and propofol sedation resulted in the same propensity for UAO. In this homogeneous group of healthy subjects, there was a considerable range of negative pressures required to cause UAO. The specific factors responsible for the maintenance of the upper airway during sedation remain to be elucidated.
Norton
J Russell
JR
Department of Anesthesiology, University of Rochester, New York, New York 14642, USA.
Ward
Denham S
DS
Karan
Suzanne
S
Voter
William A
WA
Palmer
Linda
L
Varlese
Anna
A
Rackovsky
Ori
O
Bailey
Peter
P
D000328:Adult; D000399:Air Pressure; D000402:Airway Obstruction / Q000139:chemically induced*; D004569:Electroencephalography / Q000187:drug effects; D005260:Female; D006801:Humans; D006993:Hypnotics and Sedatives / Q000009:adverse effects*; D008297:Male; D008874:Midazolam / Q000009:adverse effects*; D015742:Propofol / Q000009:adverse effects*; D012727:Sex Characteristics
D006993:Hypnotics and Sedatives; D008874:Midazolam; D015742:Propofol