Coupling of spontaneous ventilation to heart beat during benzodiazepine sedation.

We have examined in eight male volunteers the effect of midazolam sedation on the relationship between timing of spontaneous ventilations and heart beat. On 2 study days, subjects received either midazolam 0.1 mg kg-1 or saline placebo while recordings were made of ECG and ventilatory impedance pneumography. We observed in all midazolam-treated subjects clear evidence of synchronous or non-synchronous coupling between ventilation and heart beat. Non-synchronous coupling was seen in two placebo-treated subjects, one of whom had slept during the recording period. We conclude that cardioventilatory coupling is a major determinant of ventilatory timing in sedated subjects.