Abstract:
A digitally controlled aspirator is provided with a processor that allows the user to select operating conditions including one or more default settings. The processor further includes sensors for sensing operational and environmental conditions and adjusts the operation of the aspirator to reflect the sensed conditions.

Description:
[0001]     This application claims priority on U.S. Provisional Patent Appl. No. 60/611,722, filed Sep. 21, 2004. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention relates to a medical aspirator and, more particularly, to a system that is microprocessor-controlled and methods of control and operation therefor.  
         [0004]     2. Description of the Related Art  
         [0005]     Suction, or the application of a vacuum to a patient, has many uses within medicine. It is used within the pre-hospital care, home care and hospital environments to help clear a patient&#39;s airway, to remove debris from a surgical site, to provide gastrointestinal and wound drainage, and in some cases to help inflate a collapsed lung by providing mild negative pressure in the pleural cavity. Because of diversity within the patient population range (infant through adult) and the variety of procedures that are possible, each procedure has its own permissible vacuum and airflow ranges, and as a result, almost all suction devices are designed for a specific procedural use.  
         [0006]     The usage environment has always dictated the types of suction apparatus that are commonly used.  
         [0007]     In the pre-hospital care environments the primary use of portable devices is to provide relatively high vacuum and high airflow to the unprotected upper airway and to provide low vacuum and high airflow to the protected airway. The home care environment requires electrically powered devices that have adjustable vacuum (low to high) and high airflow for the removal of airway secretions as part of a patient&#39;s pulmonary toilet.  
         [0008]     In the hospital environment a wide range of electrically powered suction devices is found. There are units whose performance is designed to provide suction and flow to the upper airway as described above; units that can provide high vacuum and high airflow to remove blood, bone and tissue debris from surgical sites; units that provide a mild vacuum and flow for drainage around wound sites; units that intermittently provide mild vacuum and flow for drainage of the gastrointestinal tract; units for draining the digestive tract; and units that provide low vacuum and high flow levels for pleural cavity evacuation. The required number of each type of suction apparatus is affected by seasonal patient population changes and the patient composition existing within these populations. This seasonal variability is quite common and results in many hospitals having to rent additional devices to augment their inventory.  
         [0009]     Previous devices were limited in their ability to perform in more than two of the modes described above because their simple pneumatic controls lacked the ability to meet the flow, pressure and timing requirements inherent in the various operating modes. If an economically viable aspirator were available that met the gamut of clinical requirements, then civilians and military providers would have a single unit that meets their clinical and mission needs. In addition, a need has always existed for a multi-function suction apparatus for military or other remote pre-hospital or hospital applications.  
         [0010]     Suction may be generated by pneumatic, manual power or electrical power.  
         [0011]     Suction derived from manual power is generated when an operator physically causes a mechanical pump mechanism to be cycled back and forth. Manually powered suction devices produce irregular and difficult to control suction and are used almost exclusively in the emergency environment. Not surprisingly, their use is restricted to emergency suctioning of a patient&#39;s upper airway.  
         [0012]     Suction derived from pneumatic power is generated when gas, flowing at high velocity past an orifice (venturi), produces a vacuum at the orifice. This occurrence is commonly referred to as the Bernoulli Effect. The amount of vacuum is controlled by increasing or decreasing the flow of gas past this orifice which may negatively impact the desired suction applied to the patient. This method typically uses oxygen as its source of gas power and is rarely used in the emergency and hospital environments anymore due to the large amounts of oxygen they consume. Pneumatically powered suction, when used, is limited mostly to emergency suctioning of a patients upper airway.  
         [0013]     Suction derived from electrically powered sources may obtain its operating power from alternating current (AC), or direct current (DC), or from a battery pack or fuel cell. Electrically powered suction devices use a motor driven vacuum pump or thermally-cycled mechanisms to create suction. The characteristics of the pumps will ultimately determine the medical application to which they are applied. Electrically powered suction devices are the most common and are in widespread use throughout the pre-hospital, home care and hospital environments.  
         [0014]     Designers have improved medical suction systems by incorporating smaller and/or more powerful pumps, state-of-the-art battery technology for portable variants and battery recharging technology related thereto, and via the use of more sophisticated collection reservoirs (both disposable and reusable) that incorporate mechanical shut-off valves and filters (both bacteriostatic and/or hydrophobic). Control of suction devices has been relegated to simple on/off switches and circuits, and vacuum limiting mechanisms that consist of bleed-type valves that entrain ambient air as a means by which to limit the vacuum applied to the patient. The interface to these devices consists of simple indicators such as illuminating lamps and/or mechanical vacuum gauges—typically of the bourdon-tube type.  
         [0015]     In a few instances, designers have produced devices, capable of providing more than one mode of operation. The resultant devices are invariably bigger, heavier, more complex, more prone to malfunction and predicatively more expensive.  
         [0016]     A very effective aspirator intended for use in ambulances is shown in U.S. Pat. No. 5,954,704. U.S. Pat. No. 5,954,704 is assigned to the assignee of the subject invention and the disclosure is incorporated herein by reference.  
       SUMMARY OF THE INVENTION  
       [0017]     The invention relates to an aspirator with a vacuum pump/motor assembly that has a performance range sufficient to encompass the complete vacuum and airflow spectrum for all anticipated clinical uses, including those described above. Thus, the vacuum pump/motor assembly can be used to provide suction and flow to help clear a patient&#39;s airway, to remove debris from a surgical site, to provide gastrointestinal and wound drainage and to help inflate a collapsed lung by providing mild negative pressure in the pleural cavity.  
         [0018]     The aspirator also may include a variable orifice valve that the processor uses to communicate with the vacuum pump for controlling vacuum levels. The processor preferably includes or communicates with one or more sensors for sensing vacuum pressure levels near the valve.  
         [0019]     The aspirator also may include a motor speed control component and a tachometer that the processor uses for controlling airflow. The processor that instructs the motor speed control component to operate at a speed to generate an airflow based on an existing control setting for the set operating mode. The tachometer component communicates measured motor speed information back to the processor. Motor speed determines airflow rate. The processor then compares the information to determine whether the set flow rate equals the measured flow rate. If the flow set does not equal the flow measured, the processor will adjust the signal to the motor speed control component for causing the motor to speed up or slow down accordingly.  
         [0020]     The aspirator further includes controls that enable an operator to vary the performance of the aspirator in accordance with a particular medical use. The controls enable the operator to set the duration of the vacuum from a continuous vacuum to an intermittent schedule in accordance with the needs of the particular medical procedure. The controls also enable the operator to select vacuum pressure levels and flow rates.  
         [0021]     The actual vacuum pressure level at the site of aspiration is dependent on factors other than the particular operational rate of the vacuum pump. For example, the load at the site of aspiration can vary in accordance with conditions of a patient at any point in time. Power levels applied to the vacuum pump may be affected by local conditions, particularly when the aspirator is used at an emergency or non-hospital setting and when using a diminishing power source, such as a battery. The vacuum level also is dependent upon the altitude at which the aspiration is being carried out. In this regard, an aspirator often is used in a medical evacuation helicopter or in geographical locations substantially higher than sea level. Accordingly, the aspirator apparatus of the subject preferably includes a closed loop feedback control. Thus, the operator may employ the control of the microprocessor to set a desired vacuum pressure level and airflow rate. The operator then may command the device to maintain this level and rate under various conditions. In a preferred embodiment, the apparatus automatically compensates for altitude variations by adjusting the operation of the vacuum pump in accordance with sensed changes in barometric pressure so that a preset vacuum pressure level can be maintained automatically.  
         [0022]     The control of the aspirator preferably is achieved by a microprocessor that communicates with the vacuum pump, the sensors and the controls. The microprocessor is operative to respond to signals from the controls and the sensors and to modify the vacuum output of the vacuum pump to meet a particular medical use.  
         [0023]     The aspirator of the subject invention further includes output means for outputting relevant information to the operator. The output means provides the operator with required operating information and may generate alarm signals under certain operating conditions. The output display preferably is operative to compensate for real time changes in ambient atmospheric conditions, such as those changes that are attributable to altitude changes in a non-pressurized or partly pressurized environment.  
         [0024]     The microprocessor of the aspirator preferably is preprogrammed with default settings for vacuum and airflow set points. The default settings preferably conform to current clinical standards. Thus, the aspirator can be used immediately upon receipt by the operator without prior calibration. However, the controls of the aspirator preferably enable the operator to reconfigure a default setting based on the preference of the operator or based on local operating conditions.  
         [0025]     The microprocessor may include an applications programming interface so that the operator may configure the microprocessor. Additionally, the applications programming interface enables the operator to request certain operational data and receive current status information based on the requests. The interface may further be configured to permit remote operation and control. Additionally, the interface may permit a plurality of aspirators to be controlled by a single controller. As a result, a single controller can provide input to several aspirators and can receive current status information from a plurality of aspirators.  
         [0026]     The operator controls preferably are simplified for ease of operation. In this regard, the controls may comprise a power switch. A rotary encoder may be provided as part of or separate from the power switch. The rotary encoder enables an operator to select an operational mode or operational settings from several optional parameters permitted by the logic of the processor.  
         [0027]     The controller may be operative to provide menu driven operating protocols. Thus, the user may select the appropriate mode of operation through a plurality of sequential command options. One selection of a mode of operation may be followed by prompts that guide the user to select safety defaults for protecting a patient from exposure to an inappropriate level of vacuum pressure or airflow.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]      FIG. 1  is a schematic view of an aspirator in accordance with one preferred embodiment of the subject invention.  
         [0029]      FIG. 2  is a flow chart illustrating one preferred operational method of the subject invention.  
         [0030]      FIG. 3  is a schematic illustration of a first preferred display provided by the LCD display of the apparatus.  
         [0031]      FIG. 4  is a schematic illustration of a second preferred display provided by the LCD display of the apparatus.  
         [0032]      FIG. 5  is a schematic illustration of a third preferred display provided by the LCD display of the apparatus.  
         [0033]      FIG. 6  is a flow chart illustrating a preferred procedure for changing operational modes, settings and defaults.  
         [0034]      FIG. 7  is a schematic illustration of a fourth preferred display provided by the LCD display of the apparatus.  
         [0035]      FIG. 8  is a schematic illustration of a fifth preferred display provided by the LCD display of the apparatus.  
         [0036]      FIG. 9  is a schematic illustration of a sixth preferred display provided by the LCD display of the apparatus.  
         [0037]      FIG. 10  is a schematic illustration of a seventh preferred display provided by the LCD display of the apparatus.  
         [0038]      FIG. 11  is a schematic illustration of a eighth preferred display provided by the LCD display of the apparatus.  
         [0039]      FIG. 12  is a schematic illustration of a ninth preferred display provided by the LCD display of the apparatus.  
         [0040]      FIG. 13  is a schematic illustration of a tenth preferred display provided by the LCD display of the apparatus.  
         [0041]      FIG. 14  is a schematic illustration of a eleventh preferred display provided by the LCD display of the apparatus.  
         [0042]      FIG. 15  is a schematic illustration of a twelfth preferred display provided by the LCD display of the apparatus.  
         [0043]      FIGS. 16A and 16B  are schematic illustrations of a thirteenth preferred display provided by the LCD display of the apparatus.  
         [0044]      FIG. 17  is a flow chart illustrating preferred operations pertaining to the triggering of the alarm. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0045]     An aspirator in accordance with a preferred embodiment of the subject invention is identified generally by the numeral  10  in  FIG. 1 . The aspirator  10  includes a suction apparatus  12 , a processor  14 , a power supply  16  and a display  18 . The apparatus  10  further include additional inputs and outputs as explained further below.  
         [0046]     The suction apparatus  12  includes a manifold  20  with a fluid inlet  22  and a fluid outlet  24 . A tube  26  is mounted to the fluid inlet  22  of the manifold  20  and communicates with a collection canister  27  disposed externally on the aspirator  10  and connected to the suction apparatus  12 . The collection canister  27  in turn communicates with a hose and an appropriate suction catheter (not shown) that can be placed in communication with the patient. The exact configuration of the collection canister  27  and the suction catheter will vary in accordance with the specific medical use for the apparatus  10  and may be of prior art design. In this regard, a known collection canister is shown in the above-referenced U.S. Pat. No. 5,954,704.  
         [0047]     The manifold  20  further includes a variable orifice electronic valve  30 , such as a solenoid valve, that controls an air bleed between the fluid inlet  22  and the fluid outlet  24 . The electronic valve  30  can adjust the amount of the air bleed over the range between a fully opened condition and a fully closed condition. Additionally, the variable orifice electronic valve  30  can be operative to open and close at a selected frequency or duty rate. Operation of the electronic valve  30  is controlled by the processor  14  as explained further herein. The manifold  20  further includes a transducer  31  for sensing the negative pressure level at the manifold  20  and for generating a signal indicative of the value of the sensed negative pressure. The transducer  31  communicates with the processor  14  as explained herein.  
         [0048]     The suction apparatus  12  further includes a vacuum pump motor  32  that communicates with a pump head  34 . The pump head  34  in turn communicates with the fluid outlet  24  of the manifold  20 . The vacuum pump motor  32  and the pump head  34  cooperate to generate a negative pressure when the suction catheter becomes fully or partially occluded. The suction apparatus  12  further includes a motor speed control and tachometer  36  for controlling the operating speed of the vacuum pump motor  32  and for producing an output signal to indicate the actual speed of the vacuum pump motor  32 . The motor speed control and tachometer  36  communicates with the processor  14 . The motor speed control component receives information from the processor  14  that tells it to generate an airflow based on the current control setting for the set operating mode. The tachometer component communicated information back to the processor  14  and compares the information to see whether the flow set equals the flow measured. If the flow set does not equal the flow measured, the processor will adjust the signal to the motor speed control component causing the motor to speed up or slow down accordingly.  
         [0049]     As illustrated herein, the vacuum pump motor  32 , the pump head  34  and the motor speed control and tachometer  36  are included in the housing  19  of the suction apparatus  12 . However, one or all of these components can be disposed externally of the housing  19 . For example, the vacuum pump motor  32  and the pump head  34  can be in the housing  19 , while the motor speed control and tachometer  36  can be in a separate external module that may include the processor  14 . Alternatively, the vacuum pump motor  32  and pump head  34  can be disposed externally of the housing  19  in a separate motor housing. The motor speed control and tachometer  36  can be in the same motor housing, in the suction apparatus  12  or in the processor  14 .  
         [0050]     The processor (CPU)  14  of the aspirator  10  is in two-way communication with the suction apparatus  12  to provide a closed-loop feedback between the suction apparatus  12  and the processor  14 . In particular, processor  14  has connections  38  to and from the variable orifice valve  30  and connections  40  to and from the negative pressure transducer  28  in the manifold  20 . The functional implications of the connections  38  and  40  as part of the closed-loop control feedback is described further below.  
         [0051]     The power supply  16  includes a connection  42  to a power input port  44  of the processor  14  so that the power supply  16  provides sufficient power for operating the suction apparatus  12 , the processor  14 , the display  18 , the motor speed control and tachometer  36 , the vacuum pump motor  32  and the variable orifice electronic valve  30 . The power supply  16  includes an internal power supply and power conditioning circuit  46  connected to the power input port  44  via the connection  42 . The power supply  16  further includes a battery pack  48  connected to the internal power supply and power conditioning circuit  46  for providing one optional power source. The power supply further includes an AC power supply and battery charger unit  50  connected to an external power supply and further connected to both the internal power supply and power conditioning circuit  46  and the battery pack  48 . A switch  52  is mounted to the power supply  16  and is operative for selectively switching between an off mode, a battery power mode and an AC power mode. When the switch is turned to the AC power mode, the AC power supply and battery charger  50  supplies power to the battery pack  48  for recharging the battery pack and further supplies power to the internal power supply and power conditioning circuit  46  for powering the aspirator  10 .  
         [0052]     The display  18  preferably is an LCD display that is connected directly to the processor  14 . The display  18  is operative for displaying a broad range of operating conditions as shown in  FIG. 1  and as described further herein. Additionally, the LCD display may be a touch sensitive display that permits the operator to select sequential arrays of menu options as described below.  
         [0053]     The processor  14  includes other inputs and outputs independent of the suction apparatus  12 , the power supply  16  and the display  18 . Significantly, the processor  14  is connected to a barometric sensor  54  that senses ambient barometric pressure conditions and provides barometric pressure data to the processor  14  on a real time basis. The processor  14  uses data from the barometric sensor  54  with data sensed by the pressure transducer  31  to vary the operation of the variable orifice valve  30  and the motor speed controller  36 .  
         [0054]     The aspirator  10  further includes an alarm  56  connected to the processor  14  and operative to produce an audible and/or visible alarm in response to certain conditions input to the processor  14 . For example, the processor  14  will trigger the alarm  56  in response to extreme ranges of vacuum, a pump failure, a power failure or the like as illustrated in  FIG. 1 .  
         [0055]     The processor  14  further includes a communication port  58 , such as a USB or RS-232. The communication port  58  enables connection to a remote controller which can monitor and control the aspirator  10  from a remote location. Hence, a plurality of aspirators  10  can be controlled from a single remote location, while each aspirator  10  provides real time data at the communication port  58 .  
         [0056]      FIGS. 2-11  show one optional operating procedure for the aspirator  10 . With reference to  FIG. 2 , a first step S 1  of the procedure requires the operator to actuate the switch  52  of the power supply  16  in  FIG. 1  for supplying power either from the battery pack  48  or the AC power supply  50 . The processor  14  then will perform a self check for the various components of the aspirator  10  as indicated schematically by step S 2  in  FIG. 2 . As part of this step, the processor  14  will cause the display  18  to display a screen image, such as the preferred image shown in  FIG. 3 .  
         [0057]     Upon completion of the self check in step S 2 , the processor  14  will allow the operator to choose between operations with the previous settings or with new settings as indicated at step S 3 . As part of this step, the processor  14  will cause the display  18  to display a screen image, such as the preferred image illustrated schematically in  FIG. 4 . More particularly, the screen image will display the previous operational mode (e.g., pharyngeal) and operational limits (e.g., pressure level in mm of mercury and flow rate in liters per minute LPM). In many instances, the operator will choose to begin operations with the previous setting, and the screen of  FIG. 4  will be programmed to indicate acceptance of the previous settings. As a result, the user need merely press the rotary encoder push button switch  60  shown in  FIG. 1  to enter the “YES” selection. The process then will proceed to step S 4  and to the operational start phase at input location J shown in  FIG. 2 . In other instances, the operator will want to select a new operating mode or program. As noted above, the processor  14  initially will cause the display  18  to display the acceptance of the previous settings. Thus, to change the setting, the operator will turn the rotary encoder push button switch  60  of  FIG. 1 . This will cause the “NO” image on the preferred display of  FIG. 4  to be illuminated. The operator then will press the rotary encoder push button switch  60  so that the processor  14  will direct the operator through the steps of selecting a new mode and/or program.  
         [0058]     The processor  14  will lead the operator through a series of menu options for selecting the appropriate mode and/or user program as indicated at step S 4 . At this step, the processor  14  will cause the display  18  to display an image, such as the preferred image shown in  FIG. 5 . The operator then will turn the rotary encoder push button switch  60  until the appropriate operational mode is illuminated. The operator then will push to rotary encoder push button switch  60  when the preferred operational mode has been illuminated. One option provided by the screen of  FIG. 5  is to select user programs distinct from the five optional operating modes of  FIG. 5 . Step S 5  indicates the process step where the processor  14  determines whether the user programs option has been selected. In those instances where the user programs are selected, the processor will proceed to step S 6  as illustrated in  FIG. 6 . In this step, the processor  14  will cause the display  18  to identify the optional user programs that can be changed or restored. A typical screen image is illustrated in  FIG. 7  and displays to the user the option of changing default mode, changing default settings, restoring factory settings or exiting from the user programs option. The user will employ the rotary encoder switch  60  until the processor  14  causes the display  18  to illuminate the selected program option.  
         [0059]     Step S 7  identifies a step where the processor  14  determines whether the operator has selected a change in the default mode. If this change has been selected, the processor  14  will proceed to step S 8  to permit the operator to select the new default mode or to “exit” if the operator determines that the existing default mode is acceptable.  FIG. 8  shows an optional preferred screen display that will permit the operator to select a new default mode or to exit from this user program option. Once again, the operator will use the rotary encoder push button switch  60  to choose the appropriate option in  FIG. 8  and then to confirm that selection.  
         [0060]     The processor  14  will require the operator to confirm the selection made in step S 8 . This confirmation step is a fail safe procedure and is illustrated by step S 9  in  FIG. 6 . If the user chooses in step S 9  not to accept the new default mode, the processor  14  will return the operator to step S 8  for selecting a new default mode or for exiting from this option. If the user chooses in step S 9  to exit from this changing default mode option, the processor  14  will return the operator to step S 6 . If the user chooses in step S 9  to accept the new default mode then the processor  14  will direct the user to steps for selecting default settings for the selected default mode as explained below.  
         [0061]     The operator, in step S 7 , may choose not to change the default mode. Under these conditions, the processor will determine in step S 10  whether the operator wants to change the default settings. The operator will indicate a desire to change the default setting by rotating the rotary encoder push button switch  60  until the change default setting has been identified, such as in the preferred screen image shown in  FIG. 7 . The operator then will press the rotary encoder push button switch  60 . Under these conditions, the processor will proceed to step S 11 .  FIG. 6  also shows that step S 11  will be reached under those conditions where the operator has chosen to accept the new default mode in step S 9 . The processor  14  will cause the display  18  to display the optional default settings as illustrated in the preferred screen image of  FIG. 9 . The operator then will use the rotary encoder push button switch  60  for choosing each of the optional settings. One of the optional settings shown in  FIG. 9  is “Exit” which will be selected if the operator has determined that a different user program option should have been selected. After making the selections offered by  FIG. 9  and as part of step S 11 , the processor will require the operator to confirm the new default settings, as illustrated in step S 12 . One option is for the operator to exit this decision making step. In response to a selection of the exit option, the processor  14  will direct the user back to step S 6  for selecting one of the optional programs. Alternatively, the operator could choose not to accept the default settings in step S 12 . Under this selection, the processor  14  will return the operator to step S 11  and  FIG. 9  so that the operator can choose new default settings or exits from this decision process. Of course, step S 12  permits the operator to accept the new default settings. Under these circumstances, the processor  14  will proceed to a step for restoring factory defaults. The processor  14  will proceed to determine whether the operator has chosen to restore the factory defaults.  
         [0062]     The operator may choose in step S 10  not to change the default settings. As a result, the processor then will determine in step S 13  whether the operator chooses to restore the factory default settings. This preferred decision making screen is illustrated in  FIG. 10 , and the operator is given the option of either exiting or restoring the factory default settings. An operator who chooses to restore factory defaults will be directed by the processor to step S 14  and to the preferred screen image shown in  FIG. 11 . The processor then will direct the operator in step S 15  to either accept the factory default setting or to exit from this decision making process. An operator who chooses to exit from step S 15  will be directed back to step S 6  and to the preferred screen of  FIG. 7 . A user who chooses to accept the factory default settings in step S 15  will be given an option in step S 16  to either exit from this decision making process or to return to the selection of user programs described above with respect to step S 6 -S 15 . A user who chooses not to exit this decision making process will be returned to step S 6 . An operator who chooses to exit will be returned to the primary process of  FIG. 2  at input location H.  
         [0063]     An operator who has chosen not to select user programs or who has completed the selection of user programs, as outlined above and shown in the preferred screen images of  FIGS. 6-11 , will be directed by the processor  14  to step S 17  in  FIG. 2 . In step S 17 , the processor  14  will display the current setting with a screen display similar to the preferred screen display of  FIG. 12 . The processor  14  then will give the operator the option in step S 18  of choosing whether to accept the current settings. An operator who chooses to accept the current settings (step S 19 ) will be directed to input J for commencing the operation of the aspirator  10 . An operator who chooses in step S 18  and in  FIG. 12  not to accept the current settings will be directed to step S 20  by the processor  14 . The processor  14  also will cause the display  18  to display an image such as the preferred image of  FIG. 13  as part of step S 20 . The operator then will use the rotary encoder push button switch  60  with the  FIG. 13  display to make changes to the current settings. The processor  14  then will require the operator in step S 21  to affirm the acceptance of the changed current settings. An operator could choose to exit ( FIG. 14 ) this part of the decision making and will be returned to step S 19  and then to input location J for starting the operation of the aspirator  10 . An operator could choose in step S 19  not to accept the changes ( FIG. 14 ). Under these conditions, the processor  14  will direct the operator back to step S 20  for further changing the current settings. However, the processor  14  further will give the operator the option in step S 21  and  FIG. 14  to accept the changes. The processor  14  then will direct the operator to step S 22  and onto the start of operations as indicated at step S 23 . The operator also will be directed to step S 23  (via input J) if the operator had chosen in step S 4  to begin operations with the previous setting or if the operator had chosen in step S 19  to begin or continue operations with the current settings.  
         [0064]     The processor  14  will cause the display  18  to display operating screens as shown, for example, in  FIGS. 16A and 16B . The version of the operating screens shown in  FIGS. 16A and 16B  will be displayed and will vary in accordance with sensed operating conditions throughout the entire operation of the aspirator  10 .  
         [0065]     The operation indicated generally by step S 23  normally will continue for a considerable time and can be monitored on the display, as shown in  FIGS. 16A and 16B . However, the operation may be interrupted intentionally by the operator or due to unintended operating conditions. This interruption of the operation at step S 23  is assessed by the processor  14  at step S 24 . More particularly, an operator may determine that operational settings need to be changed. Under these conditions, the operator will press the rotary encoder push button switch  60  twice in succession. This double pressing of the switch  60  identified in step S 24  will cause the processor to proceed to step S 25  and to the preferred screen image shown in  FIG. 15 . The operator then uses the rotary encoder push button switch  60  of  FIG. 1B  to choose a new mode (step S 26 ) vacuum, airflow, on/off time parameter (step S 27 ) or exit (step S 28 ). An operator who chooses in step S 26  to select a new mode will be directed by the processor  14  to input location B and step S 4 . An operator who chooses to select a new setting of vacuum, airflow, on/off time in step S 27  will be directed by the processor  14  to input location C and step S 20  as described above. An operator who chooses in step S 28  to exit will be directed by the processor to input location D and step S 19  and further to input location J as described above for beginning the operation.  
         [0066]     If the operation of step S 23  is interrupted and if step S 24  determines that the encoder  60  was not pressed twice, the processor  14  will determine whether the alarm  56  has been actuated. If the alarm  56  has not been actuated, the processor will return to step S 23  to continue operation. If the processor  14  determines in step S 29  that the alarm has been actuated, the processor  14  will proceed to input location K shown in  FIG. 17 .  FIG. 17  shows the preferred logic employed by the processor  14  to determine the reason for the alarm. In step S 30 , the processor  14  will determine whether the battery is low or has failed. If the battery is low, the processor in step S 31  will cause the display  18  to advise the operator that the alarm can be muted and to advise the operator as to conditions that should be undertaken to address the low battery condition. The processor  14  determines in step S 32  whether the alarm  56  has been muted. If the alarm  56  has not been muted, the audible and visual alarm signals will remain active as indicated by step S 33 . If the alarm  56  has been muted as determined in step S 32 , then the display will include an icon in step S 34  confirming that the alarm has been muted. A predetermined mute period is programmed in the processor  14 . In step S 35 , the processor  14  will determine whether the mute period has ended. If the mute period is continuing, as determined in step S 35 , the processor  14  will ensure that the message of step S 34  continues to be displayed. If the mute interval has elapsed, as determined in step S 35 , the processor  14  will return to step S 30 .  
         [0067]     The processor  14  may determine in step S 30  that the battery is not low. Under this condition, the processor will continue to step S 36  for determining whether external power is low. If the processor  14  determines in step S 36  that the external power is low, then the processor will proceed to steps S 37 -S 41  which substantially parallel the steps S 31 -S 35  as described above. If the processor  14  determines in step S 36  that the external power is not low, then the processor will proceed to step S 42  for determining whether the external power has failed or become disconnected. The processor  14  will proceed to step S 43  if a determination has been made that the external power has failed or has become disconnected. More particularly, step S 43  will give the operator the option of canceling the alarm message. The status of the alarm  56  is assessed in step S 44 . Here the processor will return to step D of  FIG. 2  if the alarm has been canceled. Thus, the processor  14  will continue through the operation, as indicated at input location J and step S 23 . On the other hand, the external power fail/disconnect alarm message will continue at step S 45  if the operator has not canceled the alarm  56  in step S 44 .  
         [0068]     The portion of  FIG. 17  from steps S 30  through steps S 45  assume that external power can be supplied or restored or a new battery can be activated so that the operation of step S 23  can proceed. However, the alarm sensed in step S 29  may be attributable to other causes. Hence, if the alarm  56  is sensed in step S 29  and is not attributable to power related issues of steps S 30 , S 36  and S 42 , the processor  14  will proceed to steps S 46 -S 49  sequentially. In particular, step S 46  determines whether a high vacuum condition exists. This may be determined by input received by the processor  14  from the closed loop control feedback signal and control lines  38  and  40  that connect the processor  14  to the valve  30  and the transducer  31 . The determination in step S 46  that a high vacuum exists will cause the processor  14  to transmit a signal to display  18  for displaying a high vacuum message. Additionally, audible and visual alarm signals remain active and cannot be muted. Furthermore, the processor  14  will cease operation of the aspirator  10 . This problem can be cleared by recycling the on/off switch  52 . However, further service may be required if the condition persists.  
         [0069]     Step S 47  determines whether the pump motor  32  has failed. This determination may be made by the connection  37  of the closed loop control signals in the control lines to and from the processor  14  and the motor speed control and tachometer  36 . Once again, a sensed pump failure in step S 47  will cause the operation to cease. Power can be recycled by operating the switch  52 . However, service may be required if the pump failure persists, and in this circumstance, the display  18  will indicate the need for such service. As with the high vacuum condition sensed in step S 46 , the pump failure sensed by step S 47  does not permit a muting of the alarm.  
         [0070]     Step S 48  determines whether the self check of step S 2  in  FIG. 2  has occurred. The determination in step S 48  that the start-up self check has failed will cause operation to cease. The alarm  56  cannot be muted and the operation is not allowed. Display  18  will display an appropriate service message.  
         [0071]     Step S 49  determines whether there is a system failure that is not addressed by any of steps S 30 , S 36 , S 42 , S 46 , S 47  or S 48 . Operation will cease if a system failure is sensed. However, a determination in step S 49  that there is no system failure will cause the processor to commence operation again at input location J and step S 23 .  
         [0072]     The preceding paragraphs describe optional ways for changing settings using the processor  14 . It should be understood, however, that the aspirator  10  continues to operate at its current setting until a change has been accepted. Furthermore, a change in a setting may be initiated but not completed for any number of reasons. Accordingly, the processor is programmed to return the screen to its previous setting image (e.g.,  FIGS. 16A, 16B ) if there is a pause in the setting change greater than the pre-programmed amount of time.  
         [0073]     While the invention has been described with respect to a preferred embodiment, it is apparent that various changes can be made without departing from the scope of the invention as defined by the appended claims. For example, the apparatus and process has been described with respect to user input from a rotary encoder push button switch  60 . However, a touch screen input can be provided as well. Of course, the screen images illustrated herein are only preferred examples, and many other screen images can be developed to convey similar information and to trigger similar decision making processes. Additionally, the user input can be provided from a remote location and may include input provided from the keyboard of a computing device.