US 12,064,242 B2
Systems and methods for measuring oxygen in a patient's bloodstream
John Jude O'Donnell, Quin (IE); Colin G. Lyden, Baltimore (IE); and Michael C. W. Coln, Lexington, MA (US)
Assigned to Analog Devices International Unlimited Company, Limerick (IE)
Filed by Analog Devices International Unlimited Company, Limerick (IE)
Filed on Apr. 21, 2020, as Appl. No. 16/854,657.
Application 16/854,657 is a continuation of application No. 15/622,846, filed on Jun. 14, 2017, abandoned.
Prior Publication US 2020/0245915 A1, Aug. 6, 2020
Int. Cl. A61B 5/1455 (2006.01); A61B 5/00 (2006.01); G01J 1/08 (2006.01); G01J 1/46 (2006.01)
CPC A61B 5/14552 (2013.01) [A61B 5/00 (2013.01); A61B 5/1455 (2013.01); G01J 1/08 (2013.01); G01J 1/46 (2013.01); A61B 5/6826 (2013.01); A61B 2560/0209 (2013.01)] 13 Claims
OG exemplary drawing
 
1. A photometry circuit for measuring a characteristic of a target, comprising:
a pulse sub-circuit configured to generate a first variable amplitude current pulse;
a first light source electrically coupled to the pulse sub-circuit, the first light source configured to receive the first variable amplitude current pulse from the pulse sub-circuit and emit first emitted light towards the target, the first emitted light being based on an amount of charge provided to the first light source by the first variable amplitude current pulse;
a first charge storage element electrically coupled to the first light source, the first charge storage element configured to store a stored amount of charge received from the first light source, the stored amount of charge being based on the amount of charge provided to the first light source by the first variable amplitude current pulse;
a photosensor positioned to detect first received light received from at least a portion of the target in response to the first emitted light;
an integrator configured to integrate a current associated with the first received light to generate a first integrated current indicating an amount of charge corresponding to the first received light;
a second light source;
a switch positioned to, when actuated, release the stored amount of charge stored at the first charge storage element to provide a second variable amplitude current pulse to the second light source, wherein the second light source is configured to emit second emitted light towards the target using the second variable amplitude current pulse, wherein the photosensor is also positioned to detect second received light received from at least a portion of the target in response to the second emitted light, and wherein the integrator is also configured to integrate a current associated with the second received light to generate a second integrated current; and
a control circuit configured to determine a characteristic of the target based at least in part on the first integrated current, the stored amount of charge, the second received light and the second integrated current.