CIRCADIAN VARIATIONS IN MINUTE VENTILATION CAN BE REPRODUCED BY A PACEMAKER SENSOR

Special software allowing the memorization of 24-hour min ute ventilat ion can be loaded into the memory of the Chorus RM, a DDDR pacemaker d riven by minute ventilation. This feature was tested in the postimplan t period in 13 patients. Measurements of minute ventilation, respirato ry rate, and respiratory amplitude were analyzed according to prospect ively defined diurnal and nocturnal time periods. Minute ventilation d ecreased by 39% (P < 0.001) from the diurnal to the nocturnal phase, w hile respiratory rate and amplitude decreased by 18% and 28%, respecti vely (P < 0.001 each). Thus, minute ventilation allowed discrimination between sleep and waking hours. This information could be utilized to modulate the backup rate of the pacemaker.