Devices and methods for controlling inflation rate in blood pressure measurements
An aspect of the disclosure pertains to a blood pressure measurement device and methods of controlling an inflation rate in a blood pressure measurement. An inflatable bladder of the blood pressure measurement device defines, at least in part, a pressurizable volume. The inflatable bladder may be inflated to pressurize a user's appendage and temporarily occlude blood flow in the user's appendage. A pressure sensor of the blood pressure measurement device is configured to obtain blood pressure measurements, and a pump of the blood pressure measurement device is configured to inflate the inflatable bladder and control an inflation rate by controlling at least one of a duty cycle, a voltage, or a drive frequency.
1. A device for estimating a user's blood pressure, the device comprising:
an inflatable bladder defining, at least in part, a pressurizable volume;
a pump in fluidic communication with the inflatable bladder and configured to pressurize the pressurizable volume and cause the inflatable bladder to inflate and contact a user's appendage when the pump is activated, wherein an inflation rate of the pump is controllable by controlling a duty cycle;
a pressure sensor in fluidic communication with the inflatable bladder and configured to produce pressure data indicative of pressure within the pressurizable volume as a function of time; and
a controller coupled with the pump, wherein the controller is configured with instructions to gradually increase the duty cycle of the pump from a first duty cycle to a second duty cycle at a first selected rate of change and to gradually increase the duty cycle from the second duty cycle to a third duty cycle at a second selected rate of change different than the first selected rate of change such that an inflation profile of the inflatable bladder is linear.
2. The device of claim 1 , wherein the inflatable bladder is an inflatable elastic bladder disposed about an inward-facing surface of a hole in the device, wherein the pump is configured to pressurize the pressurizable volume when a user's finger is positioned in the hole of the device.
3. The device of claim 1 , wherein the inflation rate of the pump is controlled to be between about 1 mmHg per second and about 10 mmHg per second.
4. The device of claim 1 , wherein the first selected rate of change and the second selected rate of change are each between about 0.1% and about 20% increase in duty cycle per second.
5. The device of claim 4 , wherein the first selected rate of change is about 1% increase in duty cycle per second and the second selected rate of change is about 5% increase in duty cycle per second.
6. The device of claim 1 , wherein the controller is further configured with instructions to change the increase of the duty cycle from the first selected rate of change to the second selected rate of change when the pressure within the pressurizable volume reaches a threshold pressure.
7. The device of claim 1 , wherein the controller is further configured with instructions to control a peak-to-peak voltage (V pp ) of the pump.
8. The device of claim 7 , wherein the controller is further configured with instructions to increase the peak-to-peak voltage (V pp ) of the pump from a first peak-to-peak voltage to a second peak-to-peak voltage at a selected rate of change.
9. The device of claim 8 , wherein the first peak-to-peak voltage is between about 2 V pp and about 10 V pp and the second peak-to-peak voltage is between about 20 V pp and about 40 V pp , the selected rate of change from the first peak-to-peak voltage to the second peak-to-peak voltage being between about 2 V pp per second and about 10 V pp per second.
10. The device of claim 1 wherein the controller is further configured with instructions to modify a drive frequency of the pump to change the inflation rate of the pump.
11. The device of claim 1 , wherein a drive frequency of the pump is equal to or greater than about 23 kHz.
12. A method of controlling an inflation rate of an inflatable bladder, the method comprising:
inflating, using a pump, an inflatable bladder to cause the inflatable bladder to contact a user's appendage;
producing pressure data indicative of pressure within the inflatable bladder as a function of time using a pressure sensor in fluidic communication with the inflatable bladder; and
controlling, via a controller, a duty cycle and a selected rate of change of the duty cycle to achieve a substantially linear inflation profile of the inflatable bladder, wherein controlling the duty cycle and the selected rate of change of the duty cycle to achieve the substantially linear inflation profile further comprises:
gradually increasing the duty cycle of the pump from a first duty cycle to a second duty cycle at a first selected rate of change; and
gradually increasing the duty cycle of the pump from the second duty cycle to a third duty cycle at a second selected rate of change different than the first selected rate of change.
13. The method of claim 12 , wherein the first selected rate of change and the second selected rate of change are each between about 0.1% and about 20% increase in duty cycle per second.
14. The method of claim 12 , further comprising:
obtaining pressure data indicative of a pressure within a pressurizable volume of the inflatable bladder as a function of time, wherein gradually increasing the duty cycle from the second duty cycle to the third duty cycle occurs when the pressure within the pressurizable volume reaches a threshold pressure.
15. The method of claim 12 , further comprising:
obtaining pressure data indicative of pressure within a pressurizable volume of the inflatable bladder as a function of time; and
dynamically changing the duty cycle of the pump based at least in part on the pressure data of the pressurizable volume.