Exit alarm for a hospital bed triggered by individual load cell weight readings exceeding a predetermined threshold

A system for monitoring a patient, comprising:

• a patient support surface configured to support the patient,
• at least three load cells each configured to produce a signal indicative of weight bearing on that load cell via the patient support surface, and
• a controller responsive to the signals produced by each of the at least three load cells to determine a current distribution of patient weight on each of the load cells, the controller determining, without calculating a location of a center of gravity of the patient, that the patient is about to exit the bed if the current distribution of weight on at least some of the at least three load cells exceeds corresponding threshold values comprising one of a plurality of sets of exit conditions.

A system for monitoring a patient, comprising:

• a patient support surface configured to support the patient,
• at least three load cells each configured to produce a signal indicative of weight impressed on that load cell via the patient support surface, and
• a controller responsive to the signals produced by each of the at least three load cells to determine a total patient weight on the patient support surface, the controller computing weight change values for each of the at least three load cells according to a patient movement model as a function of the total patient weight on the bed for each of a plurality of sets of excessive patient movement conditions, the controller determining, without calculating a location of a center of gravity of the patient, that patient movement is excessive if at least some of the weight change values exceed corresponding ones of the first threshold values for at least one of the plurality of sets of excessive patient movement conditions.

A method of monitoring a patient in a hospital bed, the method comprising:

• determining whether the patient is within a safe arming zone of the hospital bed without calculating a location of a center of gravity of the patient, and
• enabling a patient monitoring system of the hospital bed to be armed only if the patient is within the safe arming zone.

A method of monitoring a patient in a hospital bed having a head section that may be controllably elevated, the method comprising:

• determining a total patient weight on the bed,
• enabling a monitoring system of the hospital bed to be armed if the total patient weight is greater than about 50 pounds and regardless of whether the head section of the bed is elevated in excess of 45 degrees relative to bed flat, and
• determining, without calculating a location of a center of gravity of the patient, whether at least one threshold condition is violated when the monitoring system is armed, the threshold condition being a first condition when the head section is at a first elevation and the threshold condition being a second condition when the head section is at a second elevation.

A method of monitoring a patient in a hospital bed according to a patient movement mode configured to determine whether patient movement relative to a reference distribution of weight on the bed is excessive, the bed having a head section that may be controllably elevated to a maximum head angle of at least about 65 degrees relative to bed flat, the method comprising:

• enabling a monitoring system of the hospital bed to be armed according to the patient movement mode regardless of elevation of the head section of the bed relative to bed flat,
• determining, without calculating a location of a center of gravity of the patient, whether at least one threshold condition is violated when the monitoring system is armed, the threshold condition changing in response to a articulation of the head section from a first position to a second position, and
• continuing to monitor patient movement according to the patient movement mode without activating an alarm if the head section is articulated to an elevation, between the maximum head angle and bed flat, that is different than the elevation of the head section when the patient movement mode was enabled.

A method of monitoring a patient in a hospital bed according to a patient movement mode configured to determine whether patient movement relative to a reference distribution of weight on the bed is excessive, the method comprising:

• enabling a monitoring system of the hospital bed to be armed according to the patient movement mode,
• determining, without calculating a location of a center of gravity of the patient, whether at least one threshold condition is violated when the monitoring system is armed, and
• continuing to monitor patient movement according to the patient movement mode without activating an alarm after further weight, less than a maximum further weight, is added to the bed regardless of total patient weight on the bed prior to adding the further weight.