A method and system for operating a non-invasive blood pressure monitor that utilizes an SpO.sub.2 plethysmographic signal to reduce the time required to obtain an estimation of a patient's blood pressure. During operation of the NIBP monitor, the NIBP monitor utilizes the SpO.sub.2 plethysmographic signal to determine a timing period and a deflation period for each pulse associated with the patient's heartbeat. Upon receiving an oscillation pulse, the NIBP monitor determines the oscillation amplitude during the timing period and deflates the blood pressure cuff during the deflation period immediately following the timing period. Preferably, the deflation period occurs during the same oscillation pulse used to calculate the oscillation pulse amplitude to decrease the amount of time required to obtain a blood pressure estimate from the patient.