The invention relates to pulsed oximeters used to measure blood oxygenation. The current trend towards mobile oximeters has brought the problem of how to minimize power consumption without compromising on the performance of the device. To tackle this problem, the present invention provides a method for controlling optical power in a pulse oximeter. The signal-to-noise ratio of the received baseband signal is monitored, and the duty cycle of the driving pulses is controlled in dependence on the monitored signal-to-noise ratio, preferably so that the optical power is minimized within the confines of a predetermined lower threshold set for the signal-to-noise ratio. In this way the optical power is made dependent on the perfusion level of the subject, whereby the power can be controlled to a level which does not exceed that needed for the subject.
RELATED APPLICATION
This application claims priority under 35 U.S.C. .sctn. 119 to prior U.S. Provisional Patent Application No. 60/410,526, filed Sep. 13, 2002, entitled "PULSE OXIMETER", the entire contents of which are incorporated herein as if set forth herein in full.
This invention consists of a sock, a sending unit, a receiving unit, a sensor light, and a line that can be connected to a pulse-oximeter cord. A medical professional places the sock over a patient's foot and adjusts its position until the equipment is properly aligned. The cord from the pulse-oximeter can then be attached to the line from the sending unit. The sending unit activates the sensor light that emits radiation at a minimum of two wavelengths. The receiving unit detects the radiation after it passes through the skin and produces an electrical signal in response to the radiation that can be decoded by the pulse-oximeter.
A method of producing narrow optical pulses includes receiving first and second optical pulses having first and second widths, respectively, the second optical pulse having a delay relative to the first optical pulse, and selectively interfering the first and second optical pulses to produce a third optical pulse having a third width narrower than both said first and second widths.
Low power techniques for sensing cardiac pulses in a signal from a sensor are provided. A pulse detection block senses the sensor signal and determines its signal-to-noise ratio. After comparing the signal-to-noise ratio to a threshold, the drive current of light emitting elements in the sensor is dynamically adjusted to reduce power consumption while maintaining the signal-to-noise ratio at an adequate level. The signal component of the sensor signal can be measured by identifying systolic transitions. The systolic transitions are detected using a maximum and minimum derivative averaging scheme. The moving minimum and the moving maximum are compared to the scaled sum of the moving minimum and moving maximum to identify the systolic transitions. Once the signal component has been identified, the signal component is compared to a noise component to calculate the signal-to-noise ratio.
A physiological sensor is provided that includes an emitter and detector disposed on a frame such that the emitter and detector define an optical axis. The frame includes one or more pair of flexible elements disposed generally symmetric relative to the optical axis. In one embodiment, the emitter and detector remain aligned when moved relative to one another along the optical axis.
A clip-style sensor may be constructed from materials having shape memory. A clip-style sensor is provided that is able to be flattened in order to simplify transport and storing. The sensors may be held flat by shipping restraints. Such a sensor is able to recover from being flattened and resume a curved shape.
