Noninvasive evaluation of breathing pattern and thoraco-abdominal motion following the infusion of ketamine or droperidol in humans.
The authors compared the respiratory effects of an intravenous infusion of ketamine (1 mg X kg-1) with droperidol (0.1 mg X kg-1), or placebo on three different occasions in a double-blind, randomized fashion in eight healthy volunteers. Breathing pattern, thoraco-abdominal motion, end-expiratory positions of the rib cage and abdomen, arterial hemoglobin oxygen saturation (SaO2), and end-tidal carbon dioxide concentration (FECO2) were continuously measured with noninvasive techniques. During the 1-h monitoring period following drug injection, droperidol produced occasionally significant but clinically unimportant differences in respiratory variables when compared with placebo. In contrast, ketamine induced a significant (P less than 0.001) and persistent increase in minute ventilation (+75%) from 5 to 20 min after start of infusion by increasing both the driving (i.e., tidal volume/inspiratory time [VT/Ti]) and the timing (i.e., inspiratory time/total respiratory cycle time [Ti/Ttot]) components of ventilation (Milic-Emili J, Grunstein MM: Chest 70 (Suppl): 131-133, 1976). This was obtained without any significant change in end-expiratory positions or change in relative rib cage contribution to tidal volume. Despite multiple apneic episodes observed with ketamine, the subjects maintained a stable SaO2 and FECO2, indicating no resting respiratory depression. This study, performed with a noninvasive respiratory monitoring technique, confirms that droperidol infused over 5 min at a clinically used dosage does not cause respiratory depression in healthy subjects, whereas ketamine produces an important ventilatory stimulation.
D000005:Abdomen; D000328:Adult; D000704:Analysis of Variance; D004311:Double-Blind Method; D004329:Droperidol / Q000494:pharmacology*; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D007649:Ketamine / Q000494:pharmacology*; D008297:Male; D008838:Microcomputers; D011897:Random Allocation; D012119:Respiration / Q000187:drug effects*; D013909:Thorax; D013990:Tidal Volume; D013997:Time Factors
D006454:Hemoglobins; D007649:Ketamine; D004329:Droperidol