NONINVASIVELY DETECTING BLOOD FLOW TO THE BRAIN

1 . A resuscitation system, comprising:

a mechanical chest compression device configured to administer chest compressions to a subject; and

an external flow monitor comprising:

a housing;

a strap coupled to the housing and configured to hold the external flow monitor on an external surface of a head of the subject;

an emitter disposed in the housing and configured to output an ultrasound beam toward the subject;

a receiver disposed in the housing and configured to detect a reflection of the ultrasound beam from blood vessels in a brain of the subject;

a transceiver;

a processor configured to:

determine a magnitude of blood flowing in the blood vessels in the brain of the subject by analyzing the reflection of the ultrasound beam from the blood vessel in the brain of the subject;

determine that the magnitude of blood flowing in the blood vessels in the brain is below a threshold; and

in response to determining that the magnitude of blood flowing in the blood vessels in the brain is below the threshold, cause the transceiver to transmit, to the mechanical chest compression device, a signal instructing the mechanical chest compression device to change a position, frequency, timing, or depth of the chest compressions.

2 . The resuscitation system of claim 1 , wherein the emitter is configured to output the ultrasound beam through an orbital cavity, a temple, or an ear canal of the subject, and

wherein the blood vessels are located in a circle of Willis of the subject.

3 . The resuscitation system of claim 1 , wherein the ultrasound beam has a frequency in a range of 100 kHz to 2 MHz.

4 . An external flow monitor, comprising:

an emitter configured to output an incident beam toward a brain of an adult subject;

a receiver configured to detect a reflection of the incident beam from blood vessels in the brain;

a processor configured to:

determine, by analyzing data indicative of the reflection of the incident beam, a magnitude of blood flowing through the brain during an event, the event comprising a cardiac cycle or chest compression; and

output a signal indicative of the magnitude of blood flowing in the brain.

5 . The external flow monitor of claim 4 , wherein the incident beam comprises ultrasound having a frequency in a range of 100 kHz to 2 MHz.

6 . The external flow monitor of claim 4 , wherein the incident beam comprises infrared light.

7 . The external flow monitor of claim 4 , wherein the emitter is configured to output the incident beam through an orbital cavity, a temple, or an ear canal of the subject.

8 . The external flow monitor of claim 4 , wherein the processor is configured to determine the magnitude of the blood flowing in the brain by comparing a frequency of the reflection of the incident beam to a frequency of the incident beam.

9 . The external flow monitor of claim 4 , wherein the receiver is configured to detect a reflection of the incident beam from a contrast agent disposed in the blood in the blood vessel.

10 . The external flow monitor of claim 4 , further comprising:

a transceiver,

wherein the processor is configured to output the signal by causing the transceiver to transmit the signal to a medical device or a mobile device.

11 . The external flow monitor of claim 4 , further comprising:

an output device,

wherein the processor is configured to output the signal by causing the output device to output the signal to a user.

12 . The external flow monitor of claim 4 , wherein the processor is further configured to:

determine a volume of the blood flowing through the brain by integrating a velocity of the blood flowing in the blood vessel with respect to time; and

determine that the volume of the blood flowing through the brain is below a threshold,

wherein the signal indicative of the magnitude of blood flowing in the blood vessel comprises an instruction to initiate or change additional chest compressions administered to the subject.

13 . A method, comprising:

transmitting an incident beam toward a brain of a subject;

detecting a reflection of the incident beam from blood in blood vessels in the brain of the subject;

estimating a magnitude of blood flowing through the brain by analyzing data indicative of the reflection of the incident beam; and

outputting a signal indicative of the magnitude of blood flowing through the brain.

14 . The method of claim 13 , wherein the incident beam comprises ultrasound having a frequency in a range of 100 kHz to 2 MHz.

15 . The method of claim 13 , wherein the incident beam comprises infrared light.

16 . The method of claim 13 , wherein transmitting the incident beam toward the blood vessel in the brain of the subject comprises transmitting the incident beam through an orbital cavity, a temple, or an ear canal of the subject.

17 . The method of claim 13 , wherein determining the magnitude of the blood flowing through the brain comprises comparing a frequency of the reflection of the incident beam to a frequency of the incident beam.

18 . The method of claim 13 , wherein outputting the signal indicative of the magnitude of blood flowing through the brain comprises transmitting the signal to a medical device or to a mobile device.

19 . The method of claim 13 , wherein outputting the signal indicative of the magnitude of blood flowing through the brain comprises causing an output device to output the signal to a user.

20 . The method of claim 13 , further comprising:

determining that the magnitude of the blood flowing through the brain is below a threshold,

wherein the signal indicative of the magnitude of blood flowing through the brain comprises an instruction to initiate or change chest compressions administered to the subject.