Monitoring arterial and venous blood flow during treatments

1 . A method, comprising:

detecting an amplitude of blood flow through an artery of a subject during a time interval;

detecting an amplitude of blood flow through a vein of the subject during the time interval;

determining a ratio of the amplitude of the blood flow through the artery during the time interval and the amplitude of the blood flow through the vein during the time interval; and

determining whether blood is spontaneously flowing through a body of the subject by comparing the ratio to a threshold.

2 . The method of claim 1 , wherein detecting the amplitude of the blood flow through the artery of the subject during the time interval comprises determining a Doppler shift of a first ultrasound beam reflected from blood in the artery, and

wherein detecting the amplitude of the blood flow through the vein of the subject during the time interval comprises determining a Doppler shift of the first ultrasound beam or a second ultrasound beam reflected from blood in the vein.

3 . The method of claim 1 , wherein the artery and the vein are parallel to each other.

4 . The method off claim 1 , wherein the artery comprises a carotid artery and the vein comprises a jugular vein.

5 . The method of claim 1 , wherein determining whether blood is spontaneously flowing through the body of the subject further comprises:

determining that both a direction of the blood flow through the artery of the subject during the time interval and a direction of the blood flow through the vein of the subject are away from a heart of the subject or toward the heart of the subject; and

in response to determining that both the direction of the blood flow through the artery of the subject during the time interval and the direction of the blood flow through the vein of the subject are away from a heart of the subject or toward the heart of the subject, determining that the subject has received a chest compression during the time interval.

6 . The method of claim 1 , wherein determining whether blood is spontaneously flowing through the body of the subject further comprises:

determining that the blood flow through the vein during the time interval is indicative of pulsatile flow; and

in response to determining that the blood through the vein during the time interval is indicative of pulsatile flow, determining that the subject has received a chest compression during the time interval.

7 . The method of claim 1 , wherein determining whether blood is spontaneously flowing through the body of the subject by comparing the ratio to the threshold comprises:

determining that the ratio is below the threshold; and

in response to determining that the ratio is below the threshold, determining that the subject has a received a chest compression during the time interval.

8 . The method of claim 1 , wherein determining whether blood is spontaneously flowing through the body of the subject further comprises:

determining that a direction of the blood flow through the artery of the subject during the time interval is different than a direction of the blood flow through the vein of the subject; and

in response to determining that the direction of the blood flow through the artery of the subject during the time interval is different than the direction of the blood flow through the vein of the subject, determining that blood is spontaneously flowing through the body of the subject.

9 . The method of claim 1 , wherein determining whether blood is spontaneously flowing through the body of the subject further comprises:

determining that the blood flow through the vein during the time interval is non-pulsatile; and

in response to determining that the blood through the vein during the time interval is non-pulsatile, determining that blood is spontaneously flowing through the body of the subject.

10 . The method of claim 1 , wherein determining whether blood is spontaneously flowing through the body of the subject by comparing the ratio to the threshold comprises:

determining that the ratio is above the threshold; and

in response to determining that the ratio is above the threshold, determining that blood is spontaneously flowing through the body of the subject.

11 . The method of claim 1 , further comprising:

determining a velocity or volume of the blood flow through the artery during the time interval;

determining a velocity or volume of the blood flow through the vein during the time interval;

determining an efficacy of chest compression administered during the time interval by analyzing the velocity or volume of the blood flow through the artery during the time interval and the velocity or volume of the blood flow through the vein during the time interval; and

outputting an indication of the efficacy of the chest compression.

12 . The method of claim 1 , wherein determining whether blood is spontaneously flowing through the body of the subject further comprises:

determining that a direction of the blood flow through the artery of the subject during the time interval is away from a heart of the subject;

determining that a direction of the blood flow through the vein of the subject during the time interval is toward the heart of the subject; and

in response to determining that the direction of the blood flow through the artery of the subject during the time interval is away from the heart of the subject and determining that the direction of the blood flow through the vein of the subject during the time interval is toward the heart of the subject, determining that blood is spontaneously flowing through the body of the subject.

13 . The method of claim 12 , further comprising:

in response to determining that blood is spontaneously flowing through the body of the subject, outputting an instruction to cease chest compressions on the subject.

14 . A device comprising:

a first sensor configured to detect an amplitude of blood flow through an artery of a subject during a time interval;

a second sensor configured to detect an amplitude of blood flow through a vein of the subject during the time interval; and

a processor configured to:

determine a ratio of the amplitude of the blood flow through the artery during the time interval and the amplitude of the blood flow through the vein during the time interval; and

determine whether blood is spontaneously flowing through a body of the subject by comparing the ratio to a threshold.

15 . The device of claim 14 , wherein the processor is configured to determine whether the blood is spontaneously flowing through the body of the subject by determining that a direction of the blood flow through the artery of the subject during the time interval is parallel to a direction of blood flow through the vein of the subject during the time interval.

16 . The device of claim 14 , wherein the processor is configured to determine whether the blood is spontaneously flowing through the body of the subject by:

determining that the blood flow through the vein during the time interval is indicative of pulsatile flow; and

in response to determining that the blood through the vein during the time interval is indicative of pulsatile flow, determining that the subject has received a chest compression during the time interval.

17 . The device of claim 14 , wherein the processor is configured to determine whether the blood is spontaneously flowing through the body of the subject by:

determining that the ratio is below the threshold; and

in response to determining that the ratio is below the threshold, determining that the subject has a received a chest compression during the time interval.

18 . The device of claim 17 , further comprising:

a display,

wherein the first sensor comprises:

a first transmitter configured to emit a first incident beam;

a first receiver configured to detect a reflection of the first incident beam from the artery of the subject during the time interval, the amplitude of the blood flow through the artery being dependent on the reflection of the first incident beam, wherein the second sensor comprises:

a second transmitter configured to emit a second incident beam;

a second receiver configured to detect a reflection of the second incident beam from the vein of the subject during the time interval, the amplitude of the blood flow through the vein being dependent on the reflection of the second incident beam, and wherein the processor is further configured to cause the display to visually output an indication of the chest compression.

19 . The device of claim 18 , further comprising:

a housing; and

an adhesive configured to attach the housing to a neck of the subject,

wherein the artery comprises a carotid artery and the vein comprises a jugular vein.

20 . The device of claim 18 , the time interval being a first time interval, wherein the first receiver is configured to detect a reflection of the first incident beam from the artery of the subject during a second time interval,

wherein the second receiver is configured to detect a reflection of the second incident beam from the vein of the subject during the second time interval, and

wherein the processor is further configured to:

determine, by analyzing the reflection of the first incident beam from the artery of the subject during the second time interval, a direction of blood flowing through the artery during the second time interval;

determine, by analyzing the reflection of the second incident beam from the vein of the subject during the second time interval, a direction of blood flowing through the vein during the second time interval;

determine that blood is spontaneously circulating in the subject by comparing the direction of blood flowing through the artery during the second time interval and the direction of blood flowing through the vein during the second time interval; and

cause the display to visually output an indication that blood is spontaneously circulating in the subject.