Canister status determination

1. A method of operating a topical negative pressure (TNP) system comprising a negative pressure source, a pressure sensor, a canister, and a controller, the method comprising:

aspirating, by the negative pressure source, fluid from a wound;

collecting, by the canister, at least some fluid removed from the wound;

monitoring, by the pressure sensor, pressure pulses generated by the negative pressure source;

comparing, by the controller, a magnitude of the pressure pulses to a magnitude threshold, wherein the magnitude of the pressure pulses increases as a level of fluid in the canister increases;

by the controller, determining, before a canister filter associated with the canister becomes blocked, that the level of fluid in the canister is above a canister empty level and below a canister full level based on the comparison of the magnitude of the pressure pulses to the magnitude threshold; and

outputting, by the controller, to a user interface an indication for presentation to a user, the indication denoting that the level of fluid in the canister is above the canister empty level and below the canister full level.

2. The method of claim 1 , further comprising:

comparing a frequency of the pressure pulses to a frequency threshold; and

determining the level of fluid in the canister based on the comparison of the frequency of the pressure pulses to the frequency threshold.

3. The method of claim 2 , wherein said comparing the frequency of the pressure pulses comprises comparing the frequency of the pressure pulses to the frequency threshold over a period of time.

4. The method of claim 1 , wherein said comparing comprises comparing the magnitude of the pressure pulses to the magnitude threshold over a period of time.

5. The method of claim 1 , wherein said monitoring comprises monitoring the pressure pulses at an inlet of the negative pressure source.

6. The method of claim 1 , further comprising:

comparing, by the controller, the magnitude of the pressure pulses to another magnitude threshold;

by the controller, determining that the level of fluid in the canister is at the canister full level based on the comparison of the magnitude of the pressure pulses to the another magnitude threshold; and

outputting, by the controller, to the user interface another indication for presentation to the user, the another indication denoting that the level of fluid in the canister is at the canister full level.

7. The method of claim 1 , wherein that the level of fluid in the canister is above the canister empty level and below the canister full level is determined using pressure data from no pressure sensor other than the pressure sensor.

8. The method of claim 1 , further comprising audibly presenting the indication with the user interface to the user.

9. The method of claim 1 , further comprising visually presenting the indication with the user interface to the user.

10. A topical negative pressure (TNP) apparatus comprising:

a negative pressure source configured to aspirate fluid from a wound;

a canister configured to collect at least some fluid removed from the wound;

a canister filter associated with the canister;

a pressure sensor configured to monitor pressure pulses generated by the negative pressure source; and

a controller configured to:

compare a magnitude of the pressure pulses to a magnitude threshold, wherein the magnitude of the pressure pulses increases as a level of fluid in the canister increases; and

determine, before the canister filter becomes blocked, whether the level of fluid in the canister is above a canister empty level and below a canister full level based on the comparison of the magnitude of the pressure pulses to the magnitude threshold.

11. The TNP apparatus of claim 10 , wherein the controller is further configured to:

compare a frequency of the pressure pulses to a frequency threshold; and

determine the level of fluid in the canister based on the comparison of the frequency of the pressure pulses to the frequency threshold.

12. The TNP apparatus of claim 11 , wherein the controller is configured to compare the frequency of the pressure pulses to the frequency threshold over a period of time.

13. The TNP apparatus of claim 10 , wherein the controller is configured to compare the magnitude of the pressure pulses to the magnitude threshold over a period of time.

14. The TNP apparatus of claim 10 , wherein the pressure sensor is configured to monitor the pressure pulses at an inlet of the negative pressure source.

15. The TNP apparatus of claim 10 , further comprising a user interface configured to indicate that the level of fluid in the canister is above the canister empty level and below the canister full level.

16. The TNP apparatus of claim 15 , wherein the user interface is configured to audibly indicate that the level of fluid in the canister is above the canister empty level and below the canister full level.

17. The TNP apparatus of claim 15 , wherein the user interface is configured to visually indicate that the level of fluid in the canister is above the canister empty level and below the canister full level.

18. The TNP apparatus of claim 15 , wherein the user interface is configured to indicate with a percentage fullness indicator that the level of fluid in the canister is above the canister empty level and below the canister full level.

19. The TNP apparatus of claim 10 , wherein the controller is further configured to:

compare the magnitude of the pressure pulses to another magnitude threshold; and

determine whether the level of fluid in the canister is at the canister full level based on the comparison of the magnitude of the pressure pulses to the another magnitude threshold.

20. The TNP apparatus of claim 10 , wherein the controller is configured to determine, before the canister filter becomes blocked, whether the level of fluid in the canister is above the canister empty level and below the canister full level with pressure data from no pressure sensor other than the pressure sensor.