Inflatable mattress and control methods

• US 9,468,307 B2
• Filed: 03/15/2013
• Issued: 10/18/2016
• Est. Priority Date: 09/05/2012
• Status: Active Grant

• Current Assignee: Stryker Corporation
• Original Assignee: Stryker Corporation
• Inventors: Lafleche, Patrick, Bhimavarapu, Krishna Sandeep, Seshadrinathan, Manikantan, Robertson, Donna-Marie
• Primary Examiner(s): Santos, Robert G
• Application Number:
  US13/836,813
• Publication Number:
  US 20140059781A1
• Time in Patent Office: 1,313 Days
• Field of Search: 571/3, 571/0, 570/6, 565/53, 565/4, 564/4
• US Class Current: 1/1
• CPC Class Codes: A47C 27/083 with pressure control, e.g. with pressure sensors
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/6892 Mats
• CPC Class Codes: A61G 2203/16 Touchpads
• CPC Class Codes: A61G 2203/20 Displays or monitors
• CPC Class Codes: A61G 2203/34 for pressure
• CPC Class Codes: A61G 2203/40 for distance
• CPC Class Codes: A61G 2203/42 for inclination
• CPC Class Codes: A61G 2203/44 for weight
• CPC Class Codes: A61G 7/05769 with inflatable chambers

Abstract

A patient support, such as a mattress, includes a plurality of inflatable bladders. Depth sensors are included in the support that measure the degree of penetration of a patient into the mattress. An air pressure sensor is also included that measures the pressure inside at least one bladder. A suitable inflation level of the mattress is determined by monitoring the rate of change of the depth with respect to air pressure as the bladder is either inflated or deflated. By detecting an inflection point in the graphical relationship of the depth and pressure outputs, a suitable inflation point for the bladders is determined that reduces interface pressures experienced by the patient, yet does not overly sink the patient into the mattress to a degree of discomfort. Analyzing the outputs of the depth and pressure sensors can also be used to detect a patient'"'"'s heart rate and respiration rate.

Claims

1. A patient support comprising:

an inflatable bladder;

a depth sensor adapted to generate a depth signal indicative of how deeply a patient positioned on said patient support sinks into said inflatable bladder;

an air pressure sensor adapted to generate an air pressure signal indicative of a level of air pressure inside of said inflatable bladder; and

a controller adapted to determine a suitable inflation level of said bladder by monitoring a rate of change of the depth signal with respect to the air pressure signal as the air pressure inside the bladder is changed.

2. The support of claim 1 wherein said controller determines the suitable inflation level after detecting an inflection point in a plot of the depth signal versus the air pressure signal.

3. The support of claim 1 wherein the controller monitors the rate of change of the depth signal with respect to the air pressure signal as the air pressure is lowered inside the bladder.

4. The support of claim 1 wherein the controller monitors the rate of change of the depth signal with respect to the air pressure signal as the air pressure is raised inside the bladder.

5. The support of claim 1 wherein said controller sets the suitable inflation level equal to an air pressure at which a derivative of the depth signal with respect to the air pressure signal is substantially equal to a local minimum.

6. The support of claim 1 wherein said inflatable bladder is incorporated into a mattress and positioned at a location adapted to support a patient'"'"'s sacral area.

7. The support of claim 1 wherein said patient support includes:

a plurality of inflatable bladders;

a plurality of depth sensors, each depth sensor positioned inside a corresponding one of said plurality of inflatable bladders, and each depth sensor adapted to generate a depth signal indicative of how deeply a patient positioned on the patient support sinks into the corresponding inflatable bladder;

a plurality of air pressure sensors, each air pressure sensor adapted to generate an air pressure signal indicative of a level of air pressure inside of a corresponding one of said inflatable bladders; and

wherein said controller is adapted to determine the suitable inflation level based on all of the depth signals and all of the air pressure signals.

8. The support of claim 1 wherein said patient support further includes a bed frame having a support surface on which said bladder may be supported, said bed frame including a control panel adapted to control inflation of said bladder, said control panel including a control for causing said controller to re-determine said suitable inflation level.

9. The support of claim 1 wherein said bladder is incorporated into a mattress positionable on a bed frame, and said controller automatically re-determines the suitable inflation level if more than a threshold amount of patient movement is detected, or if an angular orientation of a portion of the bed frame changes by more than a threshold angular amount.

10. The support of claim 1 wherein said depth sensor includes a capacitive plate positioned generally horizontally underneath said bladder, and a flexible, electrically conductive sheet positioned above said bladder.

11. A patient support comprising:

a first inflatable bladder;

a second inflatable bladder;

a depth sensor adapted to generate a depth signal indicative of how deeply a patient positioned on said patient support sinks into said first inflatable bladder;

an air pressure sensor adapted to generate an air pressure signal indicative of a level of air pressure inside of said first inflatable bladder; and

a controller adapted to determine a suitable inflation level of said first inflatable bladder based upon readings from said depth sensor, said controller further adapted to control an air pressure inside of said second bladder so as to be equal to a fixed ratio with respect to, or to have a non-zero fixed offset from, the air pressure inside of said first inflatable bladder, said fixed ratio having a value other than one.

12. A patient support comprising:

an inflatable bladder;

a first depth sensor adapted to generate a first depth signal indicative of how deeply a patient positioned on said patient support sinks into a first portion of said inflatable bladder;

a second depth sensor adapted to generate a second depth signal indicative of how deeply a patient positioned on said patient support sinks into a second portion of said inflatable bladder;

an air pressure sensor adapted to generate an air pressure signal indicative of a level of air pressure inside of said inflatable bladder; and

a controller adapted to determine a suitable inflation level of said bladder by monitoring a rate of change of the first depth signal with respect to the air pressure signal and by monitoring a rate of change of the second depth signal with respect to the air pressure signal.

13. The support of claim 12 wherein said controller sets the suitable inflation level equal to an air pressure at which a derivative of either the first depth signal with respect to the air pressure signal or the second depth signal with respect to the air pressure signal is substantially equal to a local minimum.

14. The support of claim 12 wherein said inflatable bladder is incorporated into a mattress and positioned at a location adapted to support a patient'"'"'s sacral area, and said inflatable bladder includes a plurality of pods.

15. The support of claim 12 wherein said first depth sensor includes:

(1) a first capacitive plate positioned generally horizontally underneath said first portion of said bladder, and (2) a flexible, electrically conductive sheet positioned above said bladder; and

said second depth sensor includes;

(1) a second capacitive plate positioned generally horizontally underneath said second portion of said bladder, and (2) said flexible, electrically conductive sheet.

16. The support of claim 12 wherein said controller re-determines the suitable inflation level by inflating the bladder to a desired pressure, allowing air to escape from said bladder, and monitoring the rate of change of the first and second depth signals with respect to the air pressure signal as the air pressure inside the bladder is decreased.

17. A patient support comprising:

a first section having a first inflatable bladder,

a second section having a second inflatable bladder, said second section being positioned in an area adapted to support a sacral region of a patient when the patient lies on the patient support;

a depth sensor adapted to generate depth signals indicative of how deeply a patient positioned on said patient support sinks into said second inflatable bladder;

an air pressure sensor adapted to generate air pressure signals indicative of a level of air pressure inside of said second inflatable bladder; and

a controller adapted to determine a suitable inflation level of said second bladder based upon said depth signals and said air pressure signals, and to determine a suitable inflation level of said first bladder based upon the suitable inflation level of said second bladder.

18. The support of claim 17 wherein said suitable inflation level of said first bladder is a fixed ratio, or has a fixed offset, with respect to the suitable inflation level of said second bladder.

19. The support of claim 17 wherein said controller determines the suitable inflation level of said second bladder by monitoring a rate of change of the depth signals with respect to the air pressure signals as the air pressure inside the bladder is changed.

20. The support of claim 17 wherein said first and second bladders both include a plurality of pods.

21. The support of claim 17 further including a third section having a third inflatable bladder, said third section being positioned on a side of said second section opposite said first section;

and

wherein said controller is adapted to determine a suitable inflation level of said third bladder based upon the suitable inflation level of said second bladder.

22. The support of claim 21 wherein said suitable inflation level of said third bladder has another fixed ratio, or fixed offset, with respect to the suitable inflation level of said second bladder.

23. The support of claim 21 further including a plurality of depth sensors for generating a plurality of depth signals indicative of how deeply a patient positioned on said patient support sinks into a plurality of different portions of said second inflatable bladder, wherein said controller determines the suitable inflation level of said second bladder by monitoring all of said plurality of depth signals.

24. The support of claim 23 wherein said controller determines the suitable inflation level of said second bladder by monitoring the rate of change of the depth signals with respect to the air pressure signals for each of the plurality of depth sensors.

25. The support of claim 24 wherein said controller determines the suitable inflation level of said second bladder by determining which of said plurality of depth sensors has the highest rate of change of its depth signal with respect to the air pressure signal.