Effets du midazolam sur la commande ventilatoire chez le volontaire sain

Abstract

• Objective : To compare the effects of a sedative dose of midazolam on mean inspiratory flow (VT/TI = index of central respiratory activity), known as being decreased by midazolam and the intercostal muscle activity, known as being increased by this agent. • Study design : Laboratory study. • Patients : Seven healthy volunteers. • Methods : After assessment of baseline values of ventilatory variables and intercostal electromyographic activity (in arbitrary units), midazolam 0.1 mg·kg −1 was administered by iv route. The measurements were repeated after 5 and 10 min, and finally 2 min after the i.v. injection of flumazenil 1 mg. • Results : Midazolam decreased V̇E and VT. Similarly VT/TI ratio decreased from 0.44 ± 0.04 (baseline value) to 0.26 ± 0.03 (5 min) and 0.3 ± 0.03 L·s −1 (10 min later) respectively (P < 0.05). Conversely, midazolam increased the intercostal electromyographic activity from 4.0 ± 0.7 (baseline value) to 26.5 ± 16.6 (5 min) and 28.4 ± 16.6 U (10 min later) respectively (P < 0.05). Within 2 min after flumazenil administration all variables returned to baseline values. • Conclusions : The decrease of VT/TI ratio is probably linked to increased resistances in the upper airways. This ratio cannot act as an indicator of respiratory drive during sedation or anaesthesia. The assessment of the ventilatory effects of benzodiazepines must be based simultaneously of the various other indicators of the ventilatory drive, as these agents act on the different stages of the ventilatory cycle and therefore cannot be characterized by a unique variable.