Abstract:
An improved method of producing high frequency chest wall oscillations (HFCWO) includes generating oscillating pneumatic pressure and applying an oscillating force to a patient&#39;s chest that corresponds to the oscillating pneumatic pressure. The frequency of oscillations changes according to a prescribed treatment regimen.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to chest compression devices and in particular to a high frequency chest wall oscillator device.  
           [0002]    Manual percussion techniques of chest physiotherapy have been used for a variety of diseases, such as cystic fibrosis, emphysema, asthma and chronic bronchitis, to remove excess mucus that collects in the lungs. To bypass dependency on a caregiver to provide this therapy, chest compression devices have been developed to produce High Frequency Chest Wall Oscillation (HFCWO), a very successful method of airway clearance.  
           [0003]    The device most widely used to produce HFCWO is THE VEST™ airway clearance system by Advanced Respiratory, Inc. (f/k/a American Biosystems, Inc.), the assignee of the present application. A description of the pneumatically driven system is found in the Van Brunt et al. Patent, U.S. Pat. No. 6,036,662, which is assigned to Advanced Respiratory, Inc. Additional information regarding HFCWO and THE VEST™ system is found on the Internet at www.thevest.com. Other pneumatic chest compression devices have been described by Warwick in U.S. Pat. No. 4,838,263 and by Hansen in U.S. Pat. Nos. 5,543,081 and 6,254,556 and Int. Pub. No. WO 02/06673.  
           [0004]    These HFCWO systems may be used in the home, however, successful use in the home is dependent on regular use of the device by the patient. Patient compliance is also important to obtain insurance reimbursement. Ease of use is an important factor in gaining acceptable patient compliance.  
         BRIEF SUMMARY OF THE INVENTION  
         [0005]    The present invention is an improved method of providing high frequency chest wall oscillations to a patient. The method includes generating oscillating pneumatic pressure having a steady state pressure component and an oscillating pressure component and applying an oscillating compressive force to the patient&#39;s chest that includes a steady state force component corresponding to the steady state pressure component and an oscillating force component corresponding to the oscillating pressure component. The frequency of the oscillations change according to a predetermined pattern while maintaining the steady state pressure and force components. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    [0006]FIG. 1 is a perspective of the HFCWO system of the present invention.  
         [0007]    [0007]FIG. 2 is a perspective view of the air pulse generator of the present invention.  
         [0008]    [0008]FIG. 3 is a front view of the user interface.  
         [0009]    [0009]FIG. 4 is a table summarizing STEP and SWEEP modes.  
         [0010]    [0010]FIG. 5 is a table summarizing modes of the air pulse generator.  
         [0011]    [0011]FIG. 6 is a perspective view of one embodiment of the control switch.  
         [0012]    [0012]FIG. 7 is a perspective view of a second embodiment of the control switch.  
         [0013]    [0013]FIG. 8 is a perspective view of the inside of the air pulse generator with a front portion of the shell removed.  
         [0014]    [0014]FIG. 9 is an exploded view of the inside of the front portion of the shell.  
         [0015]    [0015]FIG. 10 is a perspective view of the inside of the back portion of the shell.  
         [0016]    [0016]FIG. 11 is a perspective view of the air pulse module.  
         [0017]    [0017]FIG. 12 is a perspective view of the back side of the air pulse module.  
         [0018]    [0018]FIG. 13 is a perspective view of the air chamber shell.  
         [0019]    [0019]FIG. 14 is a perspective view of the crankshaft assembly within the air pulse module.  
         [0020]    [0020]FIG. 15 is an exploded view of the crankshaft assembly.  
         [0021]    [0021]FIG. 16 is a perspective view of the heatsink on the control board.  
         [0022]    [0022]FIG. 17 is a perspective view of the electronic circuitry on the control board.  
         [0023]    [0023]FIG. 18 is a block diagram of a control system of the present invention.  
         [0024]    [0024]FIG. 19 is an electrical schematic diagram of the AC Mains circuit.  
         [0025]    [0025]FIG. 20 is an electrical schematic diagram of the Switching Power Supply circuitry.  
         [0026]    [0026]FIG. 21 is an electrical schematic diagram of the Power Up Clear &amp; Fault Reset circuitry.  
         [0027]    [0027]FIG. 22 is an electrical schematic diagram of the Diaphragm Motor controller.  
         [0028]    [0028]FIG. 23 is an electrical schematic diagram of the Blower Motor controller.  
         [0029]    [0029]FIG. 24 is a graph illustrating the performance of the present invention using an adult large vest for HFCWO.  
         [0030]    [0030]FIG. 25 is a graph illustrating the performance of the present invention using an adult medium vest for HFCWO.  
         [0031]    [0031]FIG. 26 is a graph illustrating the performance of the present invention using an adult small vest for HFCWO.  
         [0032]    [0032]FIG. 27 is a graph illustrating the performance of the present invention using a child large vest for HFCWO.  
         [0033]    [0033]FIG. 28 is a graph illustrating the performance of the present invention using a child medium vest for HFCWO. 
     
    
     DETAILED DESCRIPTION  
       [0034]    [0034]FIG. 1 shows a pneumatic HFCWO system of the present invention. FIG. 1 shows patient P having chest C and system  10  which includes inflatable vest  12 , hoses  14 , and air pulse generator  16 . Vest  12  is positioned on chest C of patient P. Hoses  14  are fluidly connected to vest  12  and air pulse generator  16 .  
         [0035]    In operation, air pulse generator  16  provides air pulses and a bias pressure to vest  12 . The air pulses oscillate vest  12 , while the bias pressure keeps vest  12  inflated. Vest  12  applies an oscillating compressive force to chest C of patient P. Thus, system  10  produces HFCWO to clear mucous or induce deep sputum from the lungs of patient P.  
         [0036]    Air pulse generator  16  produces a pressure having a steady state air pressure component (or “bias line pressure”) and an oscillating air pressure component. The pressure is a resulting composite waveform of the oscillating air pressure component and the steady state air pressure component. The oscillating air pressure component is substantially comprised of air pulses, while the steady state air pressure component is substantially comprised of bias line pressure.  
         [0037]    The force generated on the chest C by vest  12  has an oscillatory force component and a steady state force component. The steady state force component corresponds to the steady state air pressure component, and the oscillating force component corresponds to the oscillating air pressure component. In a preferred embodiment, the steady state air pressure is greater than atmospheric pressure with the oscillatory air pressure riding on the steady state air pressure. With this embodiment, the resulting composite waveform provides an entire oscillation cycle of vest  12  that is effective at moving chest C of patient P, because there is no point at which pressure applied to chest C by vest  12  is below atmospheric pressure. Chest movement can only be induced while vest  12  has an effective pressure (i.e. greater than atmospheric pressure) on chest C.  
         [0038]    [0038]FIG. 2 shows the preferred embodiment of air pulse generator  16 . Air pulse generator  16  includes shell or housing  18  having back portion  20  with handle  22 , front portion  24  and seam  26 . Front portion  24  further includes user interface  28 , air openings  30 , switch port  32  and control switch  34  having connection plug  36 , tube  38  and control bulb  40 . Handle  22  is connected on back portion  20  of shell  18 . Front portion  24  is removably connected to back portion  20  along seam  26 . Connection plug  36  connects to front portion  24  via switch port  32 , and connection plug  36  fluidly connects to control bulb  40  via tube  38 .  
         [0039]    Enclosure or shell  18  is composed of molded plastic such as polyvinyl chloride (PVC). Shell  18  is preferably about 13.5 in. wide, about 9.2 in. high and about 9.2 in. deep and provides the outer covering for air pulse generator  16 . Air pulse generator  16  preferably has a volume of about 1,200 in. 3 , a foot print of about 125 in. 2  and weighs about 17 lbs., which is significantly smaller and lighter than prior art HFCWO air pulse generators. These dimensions easily meet airline carry-on restrictions. Most airlines require that a carry-on weigh less than 40 lbs. and have a total length, width and height of less than 45 in., but restrictions vary from airline to airline. Typically, airlines also require that a carry-on have dimensions less than 9 in.×14 in.×22 in.  
         [0040]    In comparison, THE VEST™ system, as previously described, is about 22 in. high, 14.5 in. wide and 10.2 in. deep. THE VEST™ system, has a volume of about 3,300 in. 3 , a footprint of about 150 in. 2  and weighs about 34 lbs.  
         [0041]    Another HFCWO device, the Medpulse  2000 ™, from Electromed of New Prague, Minn. (various versions of which are depicted in U.S. Pat. No. 6,254,556 and Int. Pub. No. WO 02/06673) is about 20.5 in. wide, 16.75 in. deep and 9 in. high. The Medpulse  2000 ™ has a volume of about 3,100 in. 3 , a footprint of about 345 in. 2  and also weighs about 34 lbs.  
         [0042]    In operation, user interface  28  allows patient P to control air pulse generator  16 . Air openings  30  connect hoses  14  to generator  16 . Switch port  32  allows connection plug  36  to connect to air pulse generator  16 . Patient P controls activation/deactivation of air pulse generator  16  through control switch  34 .  
         [0043]    User interface  28  is shown in more detail in FIG. 3. User interface  28  includes display panel  110  and keypad  112  having the following buttons: ON button  114 , OFF button  116 , UL (Upper Left)  118 , LL (Lower Left)  120 , UM (Upper Middle)  122 , LM (Lower Middle)  124 , UR (Upper Right)  126  and LR (Lower Right)  128 .  
         [0044]    Display panel  110  is preferably an LCD panel display, although other displays, such as LED, could also be used. Display panel  110  shows the status of air pulse generator  16  and options available for usage. A single line of up to 24 characters is displayed. The characters are in a 5×8 pixel arrangement with each character measuring about 6 mm (0.24 in.)×14.54 mm (0.57 in.). A standard set of alphanumeric characters plus special symbols are used, and special characters that use any of the 40 (5×8) pixels are programmable. Display panel  110  is backlit for better character definition for all or some modes.  
         [0045]    Keypad  112  is preferably an elastomeric or rubber eight button keypad that surrounds display panel  110 . ON button  114  is located on the left side of display panel  110 , and OFF button  116  is located on the right side of display panel  110 . UL  118 , UM  122  and UR  126  are located along the top of display panel  110 , and LL  120 , LM  124  and LR  128  are located along the bottom of display panel  110 .  
         [0046]    Patient P may modify operation of air pulse generator  16 . Air pulse generator  16  also provides feed back to patient P as to its status. The messages are displayed as text on display panel  110 .  
         [0047]    Buttons  114 - 128  on user interface  28  are programmed based on the particular operating mode that is presently active. In particular, in showing operating mode choices, the arrow buttons are programed to wrap around. When showing time selection, frequency selection and pressure selection, the arrow buttons are programed to not wrap around.  
         [0048]    The function of UL  118 , LL  120 , UM  122 , LM  124 , UR  126  and LR  128  varies depending on the current mode of air pulse generator  16 . Each button is programmed to control various functions including the frequency of the oscillating air pressure component, or air pulses, the steady state air pressure component, or bias line pressure, and a timer, which deactivates air pulse generator  16  and will be more fully described below.  
         [0049]    User interface  28  also allows operation of air pulse generator  16  in several different modes, such as MANUAL, SWEEP or STEP. Any one of which is programmable as a default mode that automatically operates when ON button  114  is activated.  
         [0050]    MANUAL mode allows air pulse generator  16  to be manually programmed to set the oscillation frequency, bias line pressure and treatment time. MANUAL mode is similar to operation of the control knobs on THE VEST™ system. The oscillation frequency is set to a value ranging from 5 Hz to 20 Hz with a default frequency of 12 Hz. Likewise, the pressure control is set to a value ranging from 0 to 10 with a default pressure of 3. Treatment time is also set to a value ranging from 0 to 99 min with a default time of 10 min. Typically, treatment times are no more than 30 min.  
         [0051]    SWEEP mode presets air pulse generator  16  to sweep over a range of oscillation frequencies while maintaining the same bias or steady state air pressure component. SWEEP mode provides three different sweep ranges, although any number or range of frequencies are programmable through user interface  28 . The table shown in FIG. 4 summarizes and illustrates the three different sweep ranges, which are: HIGH, which sweeps the oscillation frequency between 10 to 20 Hz; NORMAL, which sweeps the oscillation frequency between 7 and 17 Hz and LOW, which sweeps the oscillation frequency between 5 and 15 Hz. In each of these modes, the oscillation frequency sweeps between the two end points incrementally changing the oscillation frequency. The oscillation frequency incrementally increases until it reaches the high frequency, then incrementally decreases the oscillation frequency to the low frequency, then the oscillation frequency incrementally increases again (FIG. 4). Alternatively, the oscillation frequency incrementally increases to the high frequency then returns to the low frequency and incrementally increases to the high frequency. The incremental increasing and decreasing continues throughout the treatment, or until the settings are reset. It is believed that the low frequencies are more effective at clearing small airways, and high frequencies more effective at clearing larger airways. The speed of the sweep is programmable through user interface  28  or preset. Preferably, the sweep speed is 1 cycle per 5 minutes. The default pressure setting in SWEEP mode is 3 with patient P able to modify the setting from 1 to 4 for comfort.  
         [0052]    STEP mode presets air pulse generator  16  to step over a range of oscillation frequencies while maintaining the same bias or steady state air pressure component. STEP mode provides three different step ranges, although any number or range of frequencies is programmable through user interface  28 . Again, the table shown in FIG. 4 summarizes and illustrates the different ranges of STEP mode, which are: HIGH, which steps through the oscillation frequencies 10 Hz, 13 Hz, 16 Hz and 19 Hz; NORMAL, which steps through the oscillation frequencies 8 Hz, 11 Hz, 14 Hz and 17 Hz and LOW, which steps through the oscillation frequencies 5 Hz, 8 Hz, 11 Hz and 14 Hz. In each of these modes the oscillation frequencies step from the low frequency to the high frequency, changing the oscillation frequency a fixed amount after a fixed period of time. The oscillation frequency increases by steps until it reaches the high frequency, then decreases the oscillation frequency until the low frequency is reached. If desired, the oscillation frequency increases by steps again. The pattern of increasing and decreasing continues throughout the treatment or until the settings are reset. The fixed step amount of oscillation frequency change and the fixed period between oscillation frequency changes is programmable through user interface  28 , or the fixed step amount and the fixed period are preset. Preferably, the fixed step amount is 3 Hz, and the fixed step time period is 5 minutes. The default mode for STEP and SWEEP modes is NORMAL, and the default pressure is 3 with patient P able to modify the pressure from 1 to 4.  
         [0053]    The table in FIG. 5 summarizes default mode settings and buttons  118 - 128  functionality in specific modes. The first column lists each mode. Columns  2 - 6  list the default settings for different parameters of HFCWO while in the various modes. Columns  7 - 9  list the function of buttons  118 - 128  while in the various modes.  
         [0054]    The following operating modes are software supported by air pulse generator  16 : A) UNPLUGGED, B) IDLE, C) AUTO READY, D) AUTO RUN, E) AUTO PAUSED, F) PROGRAM ADJUST, G) PROGRAM RUN, H) MANUAL ADJUST, I) ERROR, J) Pulsing therapy modes including SWEEP, STEP and MANUAL and K) status and user messages including pressure adjust and frequency adjust, session run time (including pulsing and pause time) and accumulated run time (updated in memory every one minute).  
         [0055]    In UNPLUGGED mode, display panel  110  is blank and air pulse generator  16  is disconnected from the supply mains.  
         [0056]    In IDLE mode, air pulse generator  16  is plugged in and both blower motor  50  and diaphragm motor  64  are non-operational. Display panel  110  is not back lit, but the displayed message can be read and indicates accumulated run time (either both pulsing or pause time or only pulsing time).  
         [0057]    The operation of control switch  34  is also programmed through user interface  28 . Control switch  34  is used in either an ON/OFF mode or a CONSTANTLY ON mode. The CONSTANTLY ON mode requires that control switch  34  be constantly depressed in order to activate air pulse generator  16 . The ON/OFF mode activates or deactivates air pulse generator  16  each time control switch  34  is pressed. The ON button  114  can also be used alternatively or to duplicate the functions of control switch  34 .  
         [0058]    Buttons  114 - 128  and control switch  34  have the following functionality in IDLE mode: A) control switch  34  causes air pulse generator  16  to enter AUTO RUN mode using the default settings, B) ON button  114  causes air pulse generator  16  to enter AUTO READY mode, C) OFF button  116  has no effect and air pulse generator  16  remains in IDLE mode and D) buttons  118 - 128  are nonfunctional.  
         [0059]    In AUTO READY mode, air pulse generator  16  pressurizes vest  12  for four seconds to the standby pressure level of 0.1 psi+0.05/−0.0.03 psi, and the backlit display panel  110  toggles between the default-remaining session time (e.g. “SWEEP NORMAL 20 MIN”) and status (e.g. “READY-PRESS AIR SWITCH”) messages every two seconds. Air pulse generator  16  continues alternating messages in AUTO READY mode for two minutes unless operator action occurs. After two minutes, air pulse generator  16  enters IDLE mode where vest  12  deflates, and a message displaying “INCOMPLETE XX MIN REMAIN” is displayed for five seconds.  
         [0060]    Buttons  114 - 128  and control switch  34  have the following functionality in AUTO READY mode: A) control switch  34  causes air pulse generator  16  to enter AUTO RUN mode, B) ON button  114  causes air pulse generator  16  to enter PROGRAM ADJUST mode, C) OFF button  116  causes air pulse generator  16  to enter IDLE mode and D) buttons  118 - 128  are nonfunctional. Air pulse generator  16  returns to IDLE mode after two minutes of inactivity and displays “INCOMPLETE XX MIN REMAIN.” 
         [0061]    In AUTO RUN mode, air pulse generator  16  inflates vest  12  for four seconds and then begins oscillation by initially performing a pressure characterization. During pressure characterization, sinusoidal pressure pulses are supplied over an average static pressure. During the initial few slow oscillation pulses of air pulse generator  16  during RUN mode, air pulse generator  16  monitors the system pressure and makes an adjustment to the average static pressure to compensate for different vest sizes and varying vest tightness. Patient P may be allowed to modify this average static pressure.  
         [0062]    The pressure in vest  12  is comparable to the pressure in the air chamber of air pulse generator  16  at low frequencies such as 5 Hz. The correlation between the pressure in the air chamber and the pressure in vest  12  is not as comparable at high frequencies such as 15 or 20 Hz. This method allows the pressure in vest  12  to be accurately measured and maintained by taking measurements in the air chamber instead of taking measurements in vest  12 . Eliminating electronics in the vest portion increases safety. Once the average static pressure is determined, the pressure is maintained by maintaining the speed of the blower providing the bias line pressure with the tip speed of the blower fan. By using a blower with a flat pressure curve over the range of air flow, the average static pressure is maintained by simply maintaining the speed of the blower.  
         [0063]    Oscillation proceeds using the default settings of SWEEP NORMAL for a duration of 20 minutes, while the backlit display panel  110  shows relative pressure (using vertical bars) and remaining session time. The message is displayed while air pulse generator  16  is delivering pulsed air pressure to vest  12 . The time counts down to zero in whole minute increments. When the session is complete, air pulse generator  16  reverts to IDLE mode and displays the message “SESSION COMPLETE” for five seconds.  
         [0064]    Buttons  114 - 128  and control switch  34  have the following functionality in AUTO RUN mode: A) control switch  34  causes air pulse generator  16  to enter AUTO PAUSE mode, B) ON button  114  has no effect, C) OFF button  116  causes air pulse generator  16  to enter IDLE mode, D) UL  118  and LL  120  adjust vest pressure and E) buttons  122 - 128  are nonfunctional.  
         [0065]    In AUTO PAUSED mode, air pulse generator  16  lowers vest pressure to the standby pressure level. Display panel  110  toggles between the default mode-remaining session time (e.g. “SWEEP NORMAL XX MIN”) and air pulse generator  16  status (e.g. “PAUSED PRESSED AIR SWITCH”) messages every two seconds. Air pulse generator  16  continues alternating messages in AUTO PAUSED mode for two minutes unless operator action occurs. After two minutes of inactivity, air pulse generator  16  enters IDLE mode causing vest  12  to deflate, and the message “INCOMPLETE XX MIN REMAIN” is displayed for five seconds.  
         [0066]    Buttons  114 - 128  and control switch  34  have the following functionality in AUTO PAUSED mode: A) control switch  34  causes air pulse generator  16  to enter AUTO RUN mode, continuing the paused therapy session, B) ON button  114  has no effect, C) OFF button  116  causes air pulse generator  16  to enter IDLE mode and D) buttons  118 - 128  are nonfunctional.  
         [0067]    PROGRAM ADJUST mode maintains the vest pressure established in AUTO READY mode, or lowers the vest pressure to the standby pressure level if pausing from RUN mode. If proceeding from AUTO READY mode, display panel  110  will toggle between “SWEEP NORMAL  20  MIN” and “READY-PRESS AIR SWITCH” messages every two seconds. If paused from PROGRAM RUN mode, display panel  110  toggles between the current settings of “MODE-FREQ MODIFIER-REMAINING SESSION TIME” (e.g. “SWEEP NORMAL  5  MIN”, “STEP HI  17  MIN”, OR “MANUAL ADJUST ?”) and “PAUSED-PRESS AIR SWITCH” messages every two seconds.  
         [0068]    The different modes (SWEEP, STEP and MANUAL) are accessed using UL  118  and LL  120 . When SWEEP and STEP modes are displayed, the frequency modifiers (HIGH, LOW and NORMAL) are adjusted using UM  122  and LM  124 , and the session time (in minutes) is set using UR  126  and LR  128 . As the modes and modifiers are changed, they replace the “SWEEP NORMAL TIME” message. The mode message continues to alternate with the “READY-PRESS AIR SWITCH” or “PAUSED-PRESS AIR SWITCH” messages every two seconds. (Note: “READY” is used when PROGRAM ADJUST mode is reached from AUTO READY mode, and “PAUSED” is used when reached from RUN mode.) Pressing control switch  34  at any time causes air pulse generator  16  to proceed to PROGRAM RUN mode using the displayed settings. If time is zero when control switch  34  is pressed, air pulse generator  16  reverts to IDLE mode. Pressing UL  118 , UM  122 , LL  120  or LM  124  while in “MANUAL ADJUST?” transfers air pulse generator  16  to MANUAL ADJUST mode where frequency, pressure and session time can be adjusted. Messages continue alternating in PROGRAM ADJUST mode for two minutes unless operator action occurs. After two minutes, air pulse generator  16  reverts to IDLE mode where vest  12  deflates, and a message “INCOMPLETE XX MIN REMAIN” is displayed for five seconds.  
         [0069]    Buttons  114 - 128  and control switch  34  have the following functionality in PROGRAM ADJUST mode: A) control switch  34  causes air pulse generator  16  to enter RUN mode (Actual RUN mode depends on setting at time of control switch  34  actuation. If control switch  34  is actuated with the session time at zero, air pulse generator  16  will reset to the IDLE mode.), B) ON button  114  has no effect, C) OFF button  116  causes air pulse generator  16  to enter IDLE mode, D) UL  118  and LL  120  toggle SWEEP, STEP and MANUAL modes, E) UM  122  and LM  124  adjust the frequency in SWEEP and STEP modes and cause transfer to MANUAL ADJUST in MANUAL mode and F) UR  126  and LR  128  adjust the time in SWEEP and STEP modes and cause transfer to MANUAL ADJUST in MANUAL mode. Air pulse generator  16  returns to IDLE mode after two minutes of inactivity displaying “INCOMPLETE XX MIN REMAIN.” 
         [0070]    MANUAL ADJUST mode maintains vest  12  inflation at standby pressure and pulsing action remains stopped. The backlit display panel  110  shows the default or previously paused session information of frequency setting in Hertz, relative pressure and remaining session time in minutes. Adjustments to each of the parameters (frequency, pressure or time) are made by pressing the respective up or down arrow buttons.  
         [0071]    Buttons  114 - 128  and control switch  34  have the following functionality in MANUAL ADJUST mode: A) control switch  34  causes air pulse generator  16  to enter MANUAL RUN mode (if control switch  34  is activated with the session time at zero, air pulse generator  16  will revert to IDLE mode), B) ON button  114  has no effect, C) OFF button  116  causes air pulse generator  16  to enter IDLE mode, D) UL  118  and LL  120  adjust frequency in Hertz, E) UM  122  and LM  124  adjust relative pressure and F) UR  126  and LR  128  adjust session time in minutes.  
         [0072]    Air pulse generator  16  returns to IDLE mode after two minutes. If the session time has elapsed, air pulse generator  16  returns to PROGRAM ADJUST mode displaying “SESSION COMPLETE” for five seconds and then displaying “MANUAL ADJUST?” 
         [0073]    In PROGRAM RUN mode, vest  12  inflates for four seconds and air pulse generator  16  begins pulsing in the selected mode: SWEEP, STEP or MANUAL. Each mode is described below in further detail.  
         [0074]    In MANUAL RUN mode, vest  12  inflates for four seconds and air pulse generator  16  begins pulsing the selected or default parameters. No pressure characterization is required in MANUAL RUN mode. Display panel  110  is backlit and shows frequency settings in Hertz, relative pressure setting and remaining session time in minutes. The message is displayed while air pulse generator  16  is delivering pulsed air pressure to vest  12 . The time counts down to zero as whole minute increments. Adjustments to each of the parameters can be made by pressing the adjacent up or down arrow buttons.  
         [0075]    Buttons  114 - 128  and control switch  34  have the following functionality in MANUAL RUN mode: A) control switch  34  causes air pulse generator  16  to enter PROGRAM ADJUST mode and the settings are remembered, B) ON button  114  has no effect, C) OFF button  116  causes air pulse generator  16  to enter IDLE mode, D) UL  118  and LL  120  adjust frequency in Hertz, E) UM  122  and LM  124  adjust relative vest pressure and F) UR  126  and LR  128  adjust time in minutes.  
         [0076]    Once the session time is completed, air pulse generator  16  returns to PROGRAM ADJUST mode with initial session settings. When the session timer counts to zero, the pulsing stops, vest pressure drops to standby, and air pulse generator  16  resets to the session values previously entered. If air pulse generator  16  is further reset to IDLE mode, the session values of frequency, pressure and time are lost, and the default values are loaded.  
         [0077]    In SWEEP RUN and STEP RUN modes, air pulse generator  16  inflates vest  12  for four seconds and then begins oscillation by initially performing the pressure characterization described above. Oscillation proceeds through the pre-selected or default sweep settings while the backlit display panel  110  shows relative pressure (using vertical bars) and remaining session time. The message on display panel  110  is displayed while air pulse generator  16  is delivering pulsed air pressure to vest  12 . The time counts down to zero in whole minute increments.  
         [0078]    Buttons  114 - 128  and control switch  34  have the following functionality in SWEEP RUN and STEP RUN modes: A) control switch  34  causes air pulse generator  16  to enter PROGRAM ADJUST mode, B) ON button  114  has no effect, C) OFF button  116  causes air pulse generator  16  to enter IDLE mode, D) UL  118  and LL  120  adjust vest pressure and E) buttons  122 - 128  are nonfunctional.  
         [0079]    Once time is completed, air pulse generator  16  returns to IDLE mode and displays “SESSION COMPLETE” for five seconds. Pulsing stops, vest  12  deflates, session settings are lost, and the default values are loaded if SWEEP RUN or STEP RUN mode is re-entered.  
         [0080]    When an error is detected, air pulse generator  16  reverts to IDLE mode and displays the non-backlit error message “See Manual.” Only UNPLUGGED mode is allowed. If air pulse generator  16  is unplugged and replugged, the message clears, and air pulse generator  16  attempts to run again. Buttons  114 - 128  and control switch  34  have no effect. Air pulse generator  16  continues to alternate Error and Call messages.  
         [0081]    Air pulse generator  16  provides a static pressure produced by a centrifugal blower with an electric feedback speed control loop for controlling the pressure. A pressure offset is generated during the startup period, which compensates for the different bladder sizes available in the assorted vest options. Average minimum output pressure is 0.28 psi minium, the average maximum output pressure is 0.70 psi minimum, and the average IDLE output pressure is 0.1 psi nominal and the maximum pressure is 1.2 psi. The pressure setting and the actual operating average pressure tolerance is 0.2 psi.  
         [0082]    The air pulse frequency is generated by a DC brushless motor driving a double linkage connected to two natural rubber diagrams, which is described in more detail below. The minimum air pulse frequency is 5 Hz, and the maximum air pulse frequency is 20 Hz. The pulse frequency delivered by air pulse generator  16  is 20% of the selected parameter. The maximum peak pressure, measured at the input port of vest  12 , does not exceed 1.2 psi at any pulse frequency (5-20 Hz), using any vest size and any pressure setting.  
         [0083]    The pressure oscillates causing pressure fluctuations that are the result of dual diaphragm oscillations of a fixed volume displacement of 29.2 in. 3  per cycle. The pressure fluctuations at vest  12  are: A) a minimum level of 0 psi, B) a maximum level of 1.2 psi maximum, C) a maximum of 0.45 psi minimum and D) a minimum pressure delta of 0.15 psi.  
         [0084]    [0084]FIG. 6 shows one embodiment of control switch  34  in more detail. FIG. 6 includes shell  18  with switch port  32  and control switch  34  having connection plug  36 , tube  38  and control bulb  40 . Connection plug  36  connects control switch  34  to air pulse generator  16 .  
         [0085]    Control switch  34  is similar to control switches used on prior art devices, such as the pneumatic control switch used with THE VEST™ airway clearance system from Advance Respiratory, Inc., St. Paul, Minn. Control switch  34  is activated by compressing control bulb  40 , such as with a hand or a foot of patient P. Upon compression, control bulb  40  sends an air pulse through tube  38  to a pneumatic switch, which activates/deactivates air pulse generator  16 . Control switch  34  operates as a toggle switch when depressed and released.  
         [0086]    [0086]FIG. 7 shows a second embodiment of control switch  34 . Here, control switch  34  includes connection plug  36  and button bulb  42 . Button bulb  42  is a small pneumatic bulb comprised of plastic, such as 60 durometer PVC, directly connected to connection plug  36 . Button bulb  42  may have a bleed hole to relieve pressure. Control switch  34  is inserted in switch port  32  of shell  18 . Button bulb  42  eliminates the need for tube  38  and provides an on/off/pause control next to user interface  28  for convenience and ease of use. Similar to the first embodiment described in FIG. 6, control switch  34  shown in FIG. 7 sends an air pulse to a pneumatic switch, which activates/deactivates air pulse generator  16 . Again, control switch  34  operates as a toggle switch when depressed and released.  
         [0087]    [0087]FIG. 8 shows air pulse generator  16  with front portion  24  removed. Air pulse generator  16  includes back portion  20  with handle  22 , air pulse module  44 , mounting plate  46  and main control board  60 . Air pulse module  44  further includes blower motor  50 , blower  52 , tube  54  and air chamber assembly  56  with air ports  58 , first diaphragm assembly  68  and second diaphragm assembly  70 . In the one embodiment, mounting plate  46  secures air pulse module  44  to shell  18 . Blower motor  50  is connected to blower  52 . Tube  54  fluidly connects blower  52  to air chamber assembly  56 , and first and second diaphragm assemblies  68  and  70  are positioned on opposite sides of air chamber assembly  56 . Main control board  60  is preferably secured within shell  18  opposite mounting plate  46 .  
         [0088]    The oscillatory air pressure component is created by the pulsing action of first and second diaphragm assemblies  68  and  70 , which oscillates the air within air chamber assembly  56  at a selected frequency. The oscillatory pressure created by first and second diaphragm  68  and  70  follows a sinusoidal waveform pattern.  
         [0089]    To create the steady state air pressure, blower motor  50  powers blower  52  to provide a bias line pressure to air chamber assembly  56  through tube  54 . Air within air chamber assembly  56  oscillates to provide the air pulses to vest  12 . Blower motor  50  and blower  52  may be, for example, an Ametek model 119319 or Torrington 1970-95-0168. Preferably, the steady state air pressure created by blower  52  is greater than atmospheric pressure, so that a whole oscillatory cycle is effective at moving chest C of patient P.  
         [0090]    [0090]FIG. 9 shows an exploded view of front portion  24  of shell  18 . Front portion  24  includes keypad  112 , surround  113 , anchors  111 , display panel  110 , secondary control board  29 , fasteners  109 , air openings  30  and seal  62 . Keypad  112  fits into surround  113 , which fits onto the outside of front portion  24 . Anchors  111  are on the inside of front portion  24  such that display panel  110  fits between anchors  111  to secure display panel  110  in place. Secondary control board  29  is attached on the back side of display panel  110  and contains electronic circuitry for user interface  28 , which is detailed below. Fasteners  109  secure keypad  112 , surround  113 , anchors  111  and display panel  10  with secondary control board  29  together to form user interface  28 . Fasteners  109  further secure user interface  28  to front portion  24 .  
         [0091]    Seal  62  is positioned between the front of air pulse module  44  and front portion  24 . Seal  62  is fitted around air openings  30  and air ports  58  to form an air tight connection between hoses  14  and air pulse module  44 .  
         [0092]    When air pulse generator  16  is operating, essentially all of the pulsed air is transferred from air pulse module  44  to hoses  14 . Seal  62  is preferably comprised of an elastomer such as black nitrile having a durometer of 80+/− 5 . However, seal  62  may also be comprised of closed cell foam tape, or black vinyl type foam.  
         [0093]    [0093]FIG. 10 is an inside view of back portion  20  of shell  18 . Back portion  20  includes vent  71  and support  72 . Support  72  is positioned between the back of air pulse module  44  and back portion  20  to secure air pulse module  44  within shell  18  and reduce noise and vibration produced by air pulse generator  16 . Support  72  is also designed such that air circulates around diaphragm motor  64  (FIG. 12) to dissipate heat, thus preventing diaphragm motor  64  from overheating. Support  72  is preferably one piece but may be comprised of two or more individual supports. Support  72  is comprised of an elastomer such as black nitrile having a durometer of 60+/− 5  shaped to conform to the surrounding parts but may alternatively be comprised of closed cell foam tape or black vinyl type foam.  
         [0094]    Vent  71  is a region of back portion  20  having openings through shell  18 . Vent  71  is positioned such that heat from diaphragm motor  64 , secondary control board  29  and/or main control board  60  is released through vent  71  to prevent overheating.  
         [0095]    [0095]FIG. 11 shows the front of air pulse module  44  with more clarity. Air pulse module  44  includes blower motor  50 , blower  52 , tube  54  and air chamber assembly  56  with air ports  58 , first diaphragm assembly  68  and second diaphragm assembly  70 . Refer to FIG. 8 for a description of the general function of air pulse module  44 .  
         [0096]    [0096]FIG. 12 shows the back of air pulse module  44 . Air pulse module  44  includes blower motor  50 , blower  52 , tube  54  and air chamber assembly  56  having diaphragm motor  64 , air chamber shell  66 , first diaphragm assembly  68  and second diaphragm assembly  70 . First diaphragm assembly  68  further includes plate  68   a  and diaphragm seal  68   b . Second diaphragm assembly  70  further includes plate  70   a  (not shown) and diaphragm seal  70   b.    
         [0097]    Diaphragm motor  64  is directly mounted on air chamber shell  66  at the back of air pulse module  44 . Diaphragm motor  64  may be an Aspen Motion Research Part No. 11702 or an equivalent motor. First diaphragm assembly  68  and second diaphragm assembly  70  are movably attached on opposite sides of air chamber shell  66 .  
         [0098]    Diaphragm seals  68   b  and  70   b  have an annular U shape and are comprised of a flexible material such as natural rubber, silicon rubber, or nitrite rubber. Plates  68   a  and  70   a  are comprised of metal, such as aluminum, and are substantially flat. Diaphragm seals  68   b  and  70   b  provide a fluid type seal between plates  68   a  and  70   a , respectively, and air chamber shell  66 . Air chamber shell  66 , first diaphragm assembly  68 , second diaphragm assembly  70  and diaphragm motor  64  substantially define an air chamber. In operation, diaphragm motor  64  powers movement of first diaphragm assembly  68  and second diaphragm assembly  70  to oscillate air within the air chamber, which is detailed below.  
         [0099]    [0099]FIG. 13 is a front view of air chamber shell  66 . Air chamber shell  66 , with curvilinear walls  66   a  and  66   b , is comprised of first portion  74 , second portion  76 , top joint  78 , bottom joint  80 , first diaphragm opening  82  (not shown) and second diaphragm opening  84 . First portion  74  further includes air ports  58  and blower inlet  86 . Second portion  76  further includes motor mount  90  and motor opening  92 .  
         [0100]    First portion  74  and second portion  76  are secured together along top joint  78  and bottom joint  80  to form air chamber shell  66 . Formation of air chamber shell  66  also defines first diaphragm opening  82  and second diaphragm opening  84  on either side of air chamber shell  66 . First diaphragm assembly  68  and second diaphragm assembly  70  (FIG. 11) are positioned over first diaphragm opening  82  and second diaphragm opening  84 , respectively, and are substantially parallel to each other.  
         [0101]    Preferably, first portion  74  is comprised of plastic and second portion  76  is comprised of metal. The plastic reduces the weight of air pulse generator  16 , while the metal dissipates heat from diaphragm motor  64  to prevent overheating.  
         [0102]    Air ports  58  discharge air from the air chamber of air chamber assembly  56  and fluidly connect with air openings  30  of shell  18 , such as by physically aligning with air openings  30  via seal  62 . Blower inlet  86  fluidly connects with the discharge of blower  52 , such as with a pipe or tube  54  (FIG. 11) to transfer air pressure to the air chamber.  
         [0103]    Air chamber shell  66  has at least one of curvilinear walls  66   a  and  66   b . Curvilinear walls  66   a  and  66   b  smooth the air flow movement between diaphragm openings  82  and  84 . Curvilinear walls  66   a  and  66   b  have a substantially parabolic shape, but other curvilinear shapes, such as more circular curvilinear shapes, also smooth the air flow movement. The smoothed air flow movement reduces noise and vibration over prior art air pulse generators.  
         [0104]    Within second portion  76 , diaphragm motor  64  is mounted to motor mount  88 . Diaphragm motor  64  fluidly seals motor opening  90  to further define the air chamber within air chamber assembly  56 .  
         [0105]    [0105]FIG. 14 shows the crankshaft assembly within air pulse module  44 . Air pulse module  44  includes crankshaft assembly  92 , first diaphragm assembly  68  and second diaphragm assembly  70 . When in use, crankshaft assembly  92  operates, as described below in reference to FIG. 15, to move first diaphragm assembly  68  and second diaphragm assembly  70  in a manner that oscillates air within the air chamber.  
         [0106]    [0106]FIG. 15 is an exploded view of crankshaft assembly  92 . FIG. 15 shows crankshaft assembly  92 , diaphragm motor  64  with drive shaft  96 , air chamber shell  66 , plates  68   a  and  70   a  and line of motion  108 . Crankshaft assembly  92  further includes flywheel  94  having opening  94   a  centered on one face and opening  94   b  off-set on the opposite face, c-ring  97 , stub shaft  98 , member  100  having bearing  100   a  and opening  100   b, c -ring  101 , cam  102  having openings  102   a  and  102   b, c -ring  103 , member  106  having bearing  106   a  and opening  106   b , stub shaft  104  and c-ring  105 .  
         [0107]    Drive shaft  96  is attached to diaphragm motor  64  at one end and attached at the other end to opening  94   a  of flywheel  94 . Stub shaft  98  is attached to flywheel  94  at opening  94   b . C-ring  97  secures stub shaft  98  within opening  94   b . Bearing  100   a  is set within one end of member  100  allowing stub shaft  98  to pass through opening  100   b . Bearing  100   a  allows stub shaft  98  to rotate within member  100 . C-ring  101  secures stub shaft  98  within opening  10   b . Stub shaft  98  is secured off-center through opening  102   a  of cam  102  by c-ring  101 . Stub shaft  104  is secured off-center through opening  102   b  to the opposite face of cam  102  by c-ring  103  such that stub shafts  98  and  104  are positioned equally but oppositely spaced from the center of cam  102 . Bearing  106   b  is set within one end of member  106  allowing stub shaft  104  to pass through opening  106   a . Stub shaft  104  is secured to member  106  by c-ring  105  but is able to rotate within member  106 . Member  100  is rigidly or integrally attached to plate  70   a  at an end opposite of bearing  100   a , and member  106  is similarly rigidly or integrally attached to plate  68   a  at an end opposite of bearing  106   b.    
         [0108]    In operation, diaphragm motor  64  turns drive shaft  96  which, in turn, rotates flywheel  94  causing stub shaft  98  to rotate in a circular fashion. The rotary motion generated by stub shaft  98  is converted to a generally reciprocating motion, shown by line of motion  108 , via member  100 . The reciprocating motion of member  100  in turn reciprocates plate  70   a  generally along line of motion  108 .  
         [0109]    The rotary motion of stub shaft  98  is transferred to cam  102  causing cam  102  to rotate, and, in turn, stub shaft  104  rotates in an identical circular fashion. The rotary motion generated by stub shaft  104  is converted to a generally reciprocating motion, shown by line of motion  108 , via member  106 . The reciprocating motion of member  106  in turn reciprocates plate  68   a  generally along line of motion  108 .  
         [0110]    The generally reciprocating motion exhibited by members  100  and  106  is more precisely defined as elliptical motion. The elliptical motion is transferred to plates  68   a  and  70   a  such that plates  68   a  and  70   a  “wobble” relative to line of motion  108 . When first diaphragm assembly  68  and second diaphragm assembly  70  are fully assembled, such as shown in FIG. 14, the flexible nature of diaphragm seals  68   b  and  70   b  allow plates  68   a  and  70   a  to tip inwardly and outwardly as they reciprocate in and out of diaphragm openings  82  and  84 , respectively, relative to air chamber shell  66 . In addition, crankshaft assembly  92  operates such that plates  68   a  and  70   a  reciprocate in opposite directions relative to each other. The reciprocating motion of plates  68   a  and  70   a  create the oscillatory air pressure component for delivering HFCWO to patient P.  
         [0111]    Using a pair of reciprocating diaphragms or plates  68   a  and  70   a  helps to balance the vibration forces that are created by air pulse generator  16 . The use of more than one diaphragm assembly would appear to add size and weight. However, adding a second diaphragm assembly in combination with improved motor control, as discussed above, results in a net weight savings. The reduction in vibration forces due to the balancing nature of opposed reciprocating diaphragm assemblies  68  and  70  allows for a reduced flywheel resulting in significant weight savings. Balanced motions allow for reduced peaks and variations in force which produce less noise and vibration and allow lighter and smaller mechanical components.  
         [0112]    The air chamber defined by air chamber shell  66 , first diaphragm assembly  68 , second diaphragm assembly  70  and diaphragm motor  64  has a volume of about 130 in. 3  and an effective diaphragm area of about 56 in. 2 . The effective diaphragm area is defined as the sum of the area of diaphragm openings  82  and  84 . In comparison, THE VEST™ system has an effective diaphragm area of about 78 in. 2  and an air chamber volume of about 39 in. 3 , and the Medpulse 2000™ system has an effective diaphragm area of about 144 in. 2  and an air chamber volume of about 182 in. 3 .  
         [0113]    The air chamber of air pulse generator  16  has a VA ratio of about 2.32. The VA ratio is defined as the air chamber volume divided by the effective diaphragm area. In comparison, THE VEST™ system has a VA ratio of about 0.5, and the Medpulse 2000™ system has a VA ratio of about 1.26.  
         [0114]    Plates  68   a  and  70   a  reciprocate with a stroke length of about 0.5 in. In comparison, THE VEST™ system has a stroke length of about 0.375 in., and the Medpulse 2000™ system has a stroke length of about 0.312 in.  
         [0115]    [0115]FIG. 16 shows main control board  60  having heatsink  129 . In the one embodiment, air pulse generator  16  includes heatsink  129  for dissipating internal heat from main control board  60 . Heatsink  129  is made of metal and absorbs and dissipates heat from circuitry (FIG. 17) on the opposite side of main control board  60 .  
         [0116]    Alternatively, air from blower  52  may be diverted to cool main control board  60 . However, the efficiency of blower  52  is compromised with this embodiment.  
         [0117]    [0117]FIG. 17 shows the electronic circuitry of main control board  60  in more detail. Main control board  60  includes AC/DC Power module M 1 , Switching Power Supply inductor L 1 , Switching Power Supply capacitors C 3  and C 4 , Diaphragm Output Voltage capacitor C  13 , Blower Output Voltage capacitor C  14 , AC Power input J  1 , Diaphragm Motor connector J 3 , Blower Motor connector J 2  and User Interface connector J 4 .  
         [0118]    The input power electrical system allows air pulse generator  16  to operate within specifications when the mains voltage is about 100-265 VAC, and the mains frequency is about 50 or 60 Hz+/−1 Hz. Air pulse generator  16  requires 3 Amps maximum. The rated running current is 2.5 Amps at 120 VAC or 0.25 Amps at 240 VAC. Typical idle current (plugged in but not running) is 30 mAmps at 120 VAC or 15 mAmps at 240 VAC. Ground Leakage current does not exceed 300 μAmps. The rated operating power is 300 watts, and the idle power is less than 4 watts.  
         [0119]    The input power electrical system is designed to accommodate power irregularities as listed by UL 2601/EN 60601. In addition, it provides the required filtering for air pulse generator  16  to meet the requirements of EN 55011 (CISPR  11 ) Class B. The power inlet module provides filtering and fuse protection of both line and neutral, meeting the requirements of UL 2601/EN 60601.  
         [0120]    Connection to AC mains is supplied by a 6 ft. long minimum detachable power cord meeting the appropriate agency approvals including UL 2601/EN 60601. Power cords in the United States are “Hospital Grade” power cords.  
         [0121]    The internal circuitry, described in more detail below, utilizes the mains AC input voltage and converts it to DC power for use by the various components. The internal power supply circuitry produces 5 VDC+/−3%,  12  VDC+/−3%,  18  VDC and  80  VDC. The 18 and 80 volt supplies are variable voltages (and, therefore, have no tolerance rating) that are microprocessor controlled to provide the correct blower and diaphragm motor speeds. The low voltage 5 and 12 volt supplies are for the display and control logic, microprocessor and related circuitry. The 5 and 12 volt supplies have a relatively small current requirement and are designed to be on when air pulse generator  16  is plugged in.  
         [0122]    Switching Power Supply inductor L 1  generates the required current to produce a of 6 VDC to  18  VDC for brushless blower motor  50 . The maximum current draw is 4 Amps. This variable voltage is controlled by a feedback loop comprised of microprocessor based Switching Power Supply, motor voltage comparater, motor controller and Hall Effect motor sensor speed.  
         [0123]    Switching Power Supply inductor L 1  generates the required current to produce a voltage of 15 VDC to  80  VDC for diaphragm motor  64 . The maximum current draw is 2 amps. This variable voltage is controlled by a feedback loop comprised of microprocessor based Switching Power Supply, motor voltage comparater, motor controller and Hall Effect motor sensor speed.  
         [0124]    The backlight of display panel  110  requires  5  VDC at 500 mAmps. This circuitry is on only when air pulse generator  16  is plugged in and not in IDLE mode.  
         [0125]    Air pulse generator  16  is controlled through user interface  28  using a combination of software and hardware. Patient P controls air pulse generator  16  via buttons  114 - 128  as described above. The status, settings and user messages are displayed on display panel  110 .  
         [0126]    [0126]FIG. 18 is a block diagram showing a control system of air pulse generator  16 . The control system includes User Interface control  200 , Power Supply control  202 , Diagram Motor control  204 , Blower Motor control  206 , Real Time clock  208 , FLASH memory  210 , and external port  212 . User Interface control  200  monitors inputs from buttons  114 - 128  and from control switch  34  and provides outputs to control the operation of display panel  110  of user interface  28 . In addition, User Interface control  200  coordinates the operation of Power Supply control  202 , Diaphragm Motor control  204 , and Blower Motor control  206 .  
         [0127]    User Interface control  200  provides a diaphragm power request signal and a blower power request signal to Power Supply control  202 . The power request signals are analog signals which represent a desired motor drive voltage to be supplied to diaphragm motor  64  and blower motor  50 , respectively.  
         [0128]    User Interface control  200  receives a Hall-A signal from one Hall sensor of blower motor  50  and a composite Hall pulse train from Diaphragm Motor control  204 . The Hall-A signal is used by User Interface control  200  to monitor the speed of blower motor  50 . The composite Hall pulse train, which provides pulses for each signal transition of each of three Hall sensors of diaphragm motor  64  allows User Interface control  200  to monitor instantaneous speed of diaphragm motor  64 . The composite Hall pulse train allows User Interface control  200  to monitor diaphragm instantaneous speed for every 12 degrees of rotation of diaphragm motor  64 . Since diaphragm motor  64  is rotating at a relatively low speed (up to about 20 cycles per second maximum) and is subjected to uneven loads during each cycle, there is a need for monitoring instantaneous speed of diaphragm motor  64  closely in order to insure stable operation.  
         [0129]    Based upon the desired operating parameters which have been set by patient P through buttons  114 - 128  and the sensed motor speeds provided by the composite Hall pulse train from Diaphragm Motor control  204  and the Hall-A sensor signal from blower motor  64 , User Interface control  200  controls the rate of diaphragm power requests and the blower power requests supplied to Power Supply control  202 . This can be accomplished by direct UIC  200  control or by the UIC  200  producing a refernce voltage to the motor voltage comparater.  
         [0130]    User Interface control  200  also receives a diaphragm pressure signal from a pressure sensor connected to the air chamber. The pressure signal is used as described above to derive a relationship between air chamber and vest pressure.  
         [0131]    Power Supply control  202 , Diaphragm Motor control  204 , and Blower Motor control  206  are located on main control board  60  shown in FIG. 17. User Interface control  200 , Real Time clock  208  and FLASH memory  210  are located on secondary control board  29  shown in FIG. 9.  
         [0132]    Under normal operation, the software monitors requests from user interface  28  and control switch  34  and generates the appropriate electrical signals that operate air pulse generator  16  at the user specified parameters. In addition, the software maintains a timer to allow reporting of therapy session time and total usage time.  
         [0133]    Control switch  34  is an input method to activate pulsing of air, alternatively ON switch  114  may be used to activate pulsing of air. The software provides user control to operate air pulse generator  16  in the various modes described above. Pausing during a therapy session to cough, remove mucus or take medication is controlled by the software via control switch  34 . Lack of input by patient P while air pulse generator  16  is paused causes the software to begin IDLE mode.  
         [0134]    The software also operates a timer that provides the user information about the current therapy session. The remaining session time is displayed on display panel  110 . Session time consists of either both pulsing and paused time or just pause time, and the time is displayed in minutes (e.g. 17 Minutes To Go).  
         [0135]    The software additionally operates another timer that provides cumulative operating hours. Compliance information is displayed on display panel  110  each time air pulse generator  16  is plugged in and in IDLE mode. Cumulative operating time includes both pulsing and paused time, and the time is displayed in hours and tenths of hours (e.g. Total Use 635.6 Hours).  
         [0136]    An I/O data port is available for interfacing to air pulse generator  16  through user interface  28 . The interface is an I/O data port serial protocol accessible via a special adapter designed to connect to the main board via a stereo jack style plug. All microprocessors are selected such that they have the  110  data port bus inherent in their design. The I/O data port bus master is the User Interface control (UIC)  200  and the slaves are the Power Supply control (PSC)  202 , the Blower Motor control (BMC)  206  and the Diaphragm Motor control (DMC)  204 . See FIG. 18.  
         [0137]    The I/O data port allows the following functionality: A) user compliance information, specifically, a time and date stamp (cumulative operating time), is stored in memory for reading via user interface  28  or the I/O data port. Air pulse generator  16  contains memory capable of storing six months of cumulative operating time. Once the memory is full, storage of new information will overwrite the oldest data and maintain the most recent information.  
         [0138]    B) Operating parameters are loaded in the microcontroller memory. Downloading the functional parameters (frequency, pressure and time) via this port is available to automate manufacturing final test and checkout.  
         [0139]    C) Operational states and failures of air pulse generator  16  are transferred to user interface  28  or to the I/O data port for troubleshooting or customer feedback.  
         [0140]    D) Software upgrades may be transferred to the microcontroller via the I/O data port.  
         [0141]    The software is written in a Microchip PIC compatible version of the C programming language and may contain some assembly language. Executable code is generated by the HI-TECH C compiler specifically designed for the Microchip PIC controller family. The code is tested utilizing the MPLAB simulator from Micrchip, a proto-type version of hardware, and a PIC-ICE (in-circuit emulator) from Phyton.  
         [0142]    Air pulse generator  16  uses Microchip microcontrollers (or microprocessors) running with an oscillator speed of 8 MHz minimum to host the required software. These microcontrollers are selected based on the required functionality while allowing for future development. PSC  202 , BMC  206 , DMC  204  and UIC  200  are four microprocessor controllers used.  
         [0143]    PSC  202  software delays startup for ⅓ second to allow charging of capacitors, receives requests from the DMC  204  and the BMC  206 , controls the switching of the power supply capacitors and selects the appropriate switch for the output.  
         [0144]    BMC  206  software controls commutation for blower motor  50 , receives blower motor  50 .  
         [0145]    DMC  204  software controls commutation for diaphragm motor  64 , and sense motor speed information such as the composite Hall pulse train to the UIC  200 .  
         [0146]    UIC  200  software manages display panel  110 , reads button presses, times the session and stops air pulse generator  16  when finished, maintains cumulative operating time, sends pressure and frequency requests to the DMC  204  and BMC  206 , writes parameters to FLASH memory  210  (using I/O data port), reads default parameter/messages from on board memory on the UIC  200  or from FLASH memory  210  (using I/O data port), reads messages/commands from an external port (using I/O data port), reads/writes Real Time Clock  208  (using I/O data port) and analyzes diaphragm pressure measurement.  
         [0147]    External memory, such as FLASH memory  210  or on chip memory such as on UIC  200  stores patient use information, default parameter limits and display messages. All program instructions and variables are contained in the microcontroller on chip memory.  
         [0148]    [0148]FIG. 19 is an electrical schematic diagram of AC Mains circuit  220 , which is a portion of power supply control  202 . AC Mains circuit includes AC Power Input connector J 1  with terminals J 1 - 1 , J 1 - 2  and J 1 - 3 , Positive Phase Power circuit  222 , Negative Phase Power circuit  224 , AC/DC Converter circuit  226  and Power On circuit  228 .  
         [0149]    AC Mains circuit  220  receives AC line power at connector J 1  and supplies power to drive diaphragm motor  64  and blower motor  50  (+PHASE PWR and −PHASE PWR). In addition, AC Mains circuit  220  produces +5 V and +12 V signals which are used by the circuitry of the control system shown in FIG. 18.  
         [0150]    Positive Phase Power circuit  222  includes resistor R 1 , diodes D 1  and D 2 , capacitors C 1  and C 3 , and fuse F 1 . Circuit  222  stores electrical power from the AC mains line power on capacitor C 1 . Approximately a 170 volt DC voltage is established at the +PHASE power output of circuit  222 .  
         [0151]    Similarly, circuit  224  produces the −PHASE power value based upon the other half cycle of AC power. Circuit  224  includes resistor R 2 , diodes D 3  and D 4 , capacitors C 2  and C 4 , and fuse F 2 . Circuit  224  stores electrical power from the AC mains line power on capacitor C 2 . A voltage of approximately 170 volts DC is established as the −PHASE power signal.  
         [0152]    The +PHASE power and −PHASE power are supplied alternatively based upon the +PHASE signal which is derived from terminal J 1 - 1  of connector J 1 . The +PHASE signal allows switching circuitry of Power Supply control  202  to alternately draw power from the +PHASE power and the −PHASE power in such a way that power is drawn from whichever capacitor is currently not being charged. This provides isolation between the AC line and the remaining circuitry of the control system, without the need for expensive and heavy line noise reduction circuitry.  
         [0153]    The DC voltage levels used by the circuitry of the control system are produced by AC/DC circuit  226 , which includes AC/DC module M 1  and capacitors C 5  and C 6 . Module M 1  is a conventional AC to DC converter.  
         [0154]    Also shown in FIG. 19 is Line Surge protector Z 1 . It is connected between terminals J 1 - 1  and J 1 - 3  of connector J 1 .  
         [0155]    AC Mains circuit  220  also includes Power On circuit  228  which includes resistors R 3  and R 4 , relay K 1 , transistor Q 1 , and diode D 5 .  
         [0156]    Power On circuit  228  utilizes relay K 1  in combination resistor R 3  to provide a ⅓ second delay in startup. This allows capacitors C 1  and C 2  to precharge. Allowing ⅓ second for startup delay and 5 RC time constants for capacitors to fully charge, the resistance of resistor R 3  is calculated as follows:  
           R =(0.33)/(5×560  μF)    
           R= 118 Ohms(use 100 Ohms)  
         [0157]    Choosing 100 Ohms limits I rms  to 2.65 A (at V rms =265 volts). 560μF capacitors were sized for +/−PHASE power to stay above 100V with ripple at I max  (which occurs at V min ). At 100 VAC in , VDC max =140volts. If VDC min 100 VDC, then VDC avg =120 VDC. With 300 watts max power, I c3/c4 =300 watts/120 volts=2.5 amps. Each capacitor will be discharging for ½ an AC cycle (60 Hz) or 8.3 msec. The size of the capacitor required is calculated as follows: C=i(t)/V=(2.5)(0.0083)/40=519μF (V=Vmax−Vmin=140−100=40). Diode D 5  protects transistor Q 1  from flyback current induced from relay K 1 .  
         [0158]    [0158]FIG. 20 shows Switching Power Supply circuitry  230 , which uses the +PHASE power and −PHASE power received from AC Mains circuit  220  to produce variable voltages used to control the speed of diaphragm motor  64  and blower motor  50 . Switching Power Supply circuitry  230  reduces electrical noise and allows several dynamically variable voltages to be produced by a single switching structure. The variable voltage used to control diaphragm motor  64  is labeled DIAPH_PWR, and the variable voltage used to control blower motor  50  is labeled BLOWER_PWR.  
         [0159]    Switching Power Supply circuit  230  includes +PHASE Switching circuit  232 , −PHASE Switching circuit  234 , Switching Power Supply inductor L 1 , Phase Detection Input circuit  236 , microprocessor IC 8 , Diaphragm Power Storage capacitor C 13 , Blower Power Storage capacitor C  14 , Diaphragm Power Charging circuit  238 , Blower Power Charging circuit  240 , Voltage Fault Sensing circuit  242 , 5V/12V convertors M 2 , M 3 , and M 4 , and crystal oscillator X 1 .  
         [0160]    Switching circuits  232  and  234  produce 10 Amp pulses which are supplied through inductor L 1 . When the +PHASE signal received by Phase Detection Input circuit  236  indicates that the −PHASE capacitors are being charged, circuit  232  supplies the to amp pulses. Conversely, when the +PHASE signal supplied from circuit  236  to the RAO input of microprocessor ICS indicates that the +PHASE power storage capacitors are being charged, microprocessor IC 8  activates circuit  234  to supply the current pulses using the −PHASE power. In this way, current is drawn from the +PHASE and −PHASE storage capacitors only during the times when they are not being charged. +Phase Switching circuit  232  includes diode D 6 , transistor Q 2 , Current Sensing driver IC 3 , resistors R 5  and R 111 , capacitors C 40  and C 8  and Current Sensing resistor R 7 .  
         [0161]    The +PHASE power is supplied through diode D 6  to transistor Q 2 . IC 3  is a high voltage, high speed power driver which supplies a control plus to a gate of Q 2  to allow current from +PHASE power to flow through diode D 6 , transistor Q 2  and Sensing resistor R 7  to inductor L 1 . Microprocessor IC 8  activates IC 3  based upon the +PHASE sense signal by supplying an input signal to the input terminal IN of IC 3 . Q 2  is turned on by IC 3  for a time duration to produce a 10 amp pulse. IC 3  senses the current through Sensing resistor R 7  to control the current pulses.  
         [0162]    −Phase Switching circuit  234  is similar to +Phase Switching circuit  232 . It includes diode D 7 , transistor Q 3 , Current Sensing driver IC 4 , resistors R 6  and R 112 , capacitor C 41 , and Current Sensing resistor R 8 .  
         [0163]    When IC 4  is turned on by microprocessor IC 8 , it switches transistor Q 3  on and off to produce  10  amp pulses, which are sensed by IC 4  using Sensing resistor R 8 . The 10 amp pulses are supplied through R 8  to inductor L 1 .  
         [0164]    Phase Detection Input circuit  236  includes resistors R 9  and R 10 , capacitor C 100  and diodes D 101  and D 102 . The +PHASE signal is received from AC Mains circuit  220  and is supplied to the RAO input of microprocessor ICS.  
         [0165]    Microprocessor IC 8  controls the charging of capacitor C  13  by Charging circuit  238  depending upon whether the diaphragm power request, DIAPH_PWR_REQ, signal at input RB 4  is high or low. If the signal is high, circuit  238  is activated so that current pulses supplied through inductor L 1  are used to charge capacitor C 13 .  
         [0166]    Similarly, charging of capacitor C 14  is controlled by microcontroller IC 8  through Charging circuit  238  as a function of the BLOWER_PWR_REQ signal input at RB 5 . When circuit  240  is activated, current from inductor L 1  is supplied to capacitor C 14  to increase the BLOWER_PWR voltage.  
         [0167]    Diaphragm Power Charging circuit  238  includes resistor R  1 , Optoisolator driver IC 6 , diode D 8 , resistors R 13  and R 14 , and transistor Q 4 . When the output of IC 8  at RBO goes high, IC 6  is activated to turn on transistor Q 4 . That allows current pulses from L 1  to pass through Q 4  and charge Diaphragm Power Storage capacitor C 13 . As the pulses are received, the voltage on capacitor C 13  will tend to increase. When the diaphragm power request signal supplied to IC 8  goes low, circuit  238  turns off and charging of capacitor C 13  ceases.  
         [0168]    Blower Power Charging circuit  240  is similar to Diaphragm Power Charging circuit  238 . It includes resistor R 12 , optoisolator driver IC 7 , diode D 9 , resistors R 15  and R 16 , and transistor Q 5 . Microprocessor IC 8  turns on IC 7  and Q 5  in response to the BLOWER_PWR_REQ signal being high. As long as that signal stays high, transistor Q 5  is turned on and current pulses from L 1  are used to charge capacitor C 14 .  
         [0169]    Voltage Fault Sensing circuit  242  senses over voltage conditions on either capacitor C 13  or C 14 . Voltage Fault Sensing circuit  242  includes zener diodes D 13  and Dl 4 , resistors R 17 , R 18 , and R 19 , capacitor C  15 , and transistor Q 29 . The output of circuit  242  is a /V fault signal which is high as long as the voltage on C  13  does not exceed the break down voltage of zener diode D 13 , or the lower power voltage on capacitor C 14  does not exceed the break down voltage of zener diode D 14 .  
         [0170]    [0170]FIG. 21 shows additional components of the Power Supply control  202 .  
         [0171]    Power Up Clear &amp; Fault Reset circuit  250  provides a fault reset signal to microprocessor IC 8  during power up conditions and in the event of a fault. Circuit  250  includes diode D 28 , resistors R 53 , R 54 , R 55 , and R 56 , capacitor C 22 , transistor Q 30 , and gates U 15 -Ul 8  and power on Reset Pulse generator U  19 . The two fault conditions sensed by circuit  250  based upon the L 1 _LOW_SIDE signal drive from the low voltage side of inductor L 1  (see FIG. 20) and the /V FAULT signal produced by circuit  242  of FIG. 20.  
         [0172]    Also shown in FIG. 21 is connector J 4 , which provides electrical connections between User Interface control  200  and Power Supply control  202 , Diaphragm Motor control  204  and Blower Motor control  206 . User Interface control  200  is on a separate circuit board, such as secondary control board  29 , from controls  202 ,  204 , and  206 , which may be located on main control board  60 . FIG. 21 also shows Diaphragm Power Comparater circuit  252  and Blower Power Comparater circuit  254 .  
         [0173]    As shown in FIG. 21, circuit  252  includes resistors R 61 -R 64 , R 67 , and R 68  and comparator U 21 . Diaphragm Power Comparator circuit  252  produces the DIAPH_PWR_REQ input to microprocessor IC 8  as a function of a DIAPHRAGM_PWR_REQ voltage supplied by User Interface control  200  through connector J 4 , and the DIAPH_PWR voltage stored on capacitor C  13 .  
         [0174]    User Interface control  200  generates the DIAPHRAGM_PWR_REQ signal as a function of the desired oscillation frequency set by patient P (or automatically determined) and the sensed diaphragm motor speed based upon the composite Hall pulse train. The DIAPHRAGM_PWR_REQ signal is a speed command voltage which is compared to the stored voltage DIAP_PWR on capacitor C 13 . As long as DIAPH_PWR is less then the DIAPHRAGM_PWR_REQ level, the output DIAPH_PWR_REQ is high. As long as that signal is high, microprocessor IC 8  turns Charging circuit  238  on to allow current pulses to be supplied to capacitor C 13 . When DIAPH_PWR exceeds the speed command signal DIAPHRAGM_PWR_REQ, the output of circuit  252  goes low, which causes microprocessor ICS to turn off Charging circuit  238 .  
         [0175]    Blower Power Comparator circuit  254  is generally similar to Diaphragm Power comparator  252 . It includes resistors R 57 -R 60 , R 65 , and R 66  and comparator U 20 .  
         [0176]    The speed command signal for blower motor  50  is BLOWER_REQ which is produced by User Interface control  200  as a function of the bias line pressure setting selected by patient P and the blower speeds as indicated by the Hall-A feed back signal from blower motor  50 . That speed command signal is compared to the voltage on capacitor C 14 , BLOWER_PWR. As long as BLOWER_PWR is less than the BLOWER_REQ command, the output of circuit  242 , BLOWER_PWR_REQ is high. That causes microprocessor IC 8  to turn on Charging circuit  240  to charge capacitor C 14 . When the command voltage BLOWER_REQ is reached or exceeded by BLOWER_PWR, the output of Comparator circuit  254  goes low, which causes microprocessor ICS to turn off Charging circuit  240 .  
         [0177]    [0177]FIG. 22 shows Diaphragm Motor control  204 , which includes microprocessor IC 10 , crystal oscillator X 3 , connector J 3  (which includes terminals J 3 - 1  through J 3 - 8 ), Phase A Drive circuit  250 A, Phase B Drive circuit  250 B, and Phase C Drive circuit  250 C, and Hall Effect Sensor Interface circuit  260 .  
         [0178]    Diaphragm Motor control  204  receives the variable voltage DIAPH_PWR from Power Supply control  202 . That variable voltage has supplied each of the three Phase Drive circuits  250 A,  250 B,  250 C. Microprocessor IC 10  acts as a sequencer or commutator to selectively turn on and off transistors of Drive circuits  250 A,  250 B, and  250 C to cause rotation of diaphragm motor  64 . The commutation is based upon on the Hall Effect sensor signals S A , S B  and S C  which are received from the three Hall Effect sensors of the BC diaphragm motor. The Hall Effect sensor signals are supplied through terminals J 3 - 6  through J 3 - 8  to inputs of microprocessor IC 10   
         [0179]    In addition, microprocessor IC 10  supplies the HALL_TRANSITION signal which is the composite Hall pulse train supplied to User Interface control  200 , so that User Interface control  200  can determine the speed of diaphragm motor  64 .  
         [0180]    Drive circuit  250 A is controlled by RB 1  and RB 2  outputs of microprocessor IC 10 . It includes resistors R 39 , R 42 , R 45  and R 48 , diodes D 22  and D 25 , capacitor C 19 , ferrite chip L 10 , transistor Q 22 , and Power Switching transistors Q 16  and Q 17 .  
         [0181]    Phase B Drive circuit  250 B is controlled by RB 4  and RB 5  outputs of microprocessor IC 10 . It includes resistors R 40 , R 43 , R 46 , and R 49 , diodes D 23  and D 26 , capacitor C 20 , ferrite chip L 11 , transistor Q 23  and Power Switching transistors Q 18  and Q 19 .  
         [0182]    Similarly, Phase C Drive circuit  250 C is controlled by RB 6  and RB 7  outputs of microprocessor IC 10 . It includes resistors R 41 , R 44 , R 47 , and R 50 , diodes D 24  and D 27 , capacitor C 21 , ferrite chip L 12 , transistor Q 24 , and Power Switching transistors Q 20  and Q 21 .  
         [0183]    Hall Effect Sensor Interface circuit  260  includes ferrite chips L 13 -L 17  and Pull Up resistors R 106 -R 108 .  
         [0184]    [0184]FIG. 23 is a schematic diagram of Blower Motor control  206 . It includes microprocessor IC 9 , Phase A Drive circuit  270 A, Phase B Drive circuit  270 B, and Phase C Drive circuit  270 C, and Hall Effect Sensor Interface circuit  280  and crystal oscillator X 2 .  
         [0185]    Microprocessor IC 9  controls Phase A, B, and C Drive circuits  270 A- 270 C as a sequencer or commutator based upon the Hall Effect sensor signals SA, SB and S C . Drive circuits  270 A- 270 C selectively supply the variable voltage BLOWER-PWR through the phase A, phase B, and phase C windings of blower motor  50 . The operation of Blower Motor control  206  is similar to that of Diaphragm Motor control  204  with one exception. Because blower motor  50  runs at a much higher speed than diaphragm motor  64 , a single Hall Effect sensor signal Blower_Hall_A can be supplied to User Interface control  202  as the speed feedback signal.  
         [0186]    Drive circuit  270 A is controlled by RB 1  and RB 2  outputs of microprocessor IC 9 . Drive circuit  270 A includes resistors R 27 , R 30 , R 33  and RR 36 , diodes D 16  and D 19 , capacitor C 16 , ferrite chip L 2 , transistor Q 13  and Power Switching resistors Q 7 A and Q 7 B.  
         [0187]    Drive circuit  270 B is controlled by RB 4  and RB 5  outputs of microprocessor IC 9 . Drive circuit  270 B includes resistors R 28 , R 31 , R 34  and R 37 , diodes D 17  and D 20 , capacitor C 17 , ferrite chip L 3 , transistor Q 14  and Power Switching transistors Q 9 A and Q 9 B.  
         [0188]    Similarly, Phase C Drive circuit  270 C is controlled by RB 6  and RB 7  outputs of microprocessor IC 9 . It includes resistors R 29 , R 32 , R 35 , and R 38 , diodes D 18  and D 21 , capacitor C 18 , ferrite chip L 4 , transistor Q 15 , and Power Switching transistors Q 11 A and Q 11 B.  
         [0189]    FIGS.  24 - 28  are graphs illustrating the performance of air pulse generator  16  with and without internal heat dissipation compared to prior art air pulse generators. A prior art air pulse generator,  103 ; air pulse generator  16  with air from blower  52  diverted to cool main control board  60 ,  104  cool; and air pulse generator  16  without diversion of air from blower  52 ,  104  were performance tested at 5 Hz, 10 Hz, 15 Hz and 20 Hz. The testing consists of measuring pressure inside a vest&#39;s air reserve (bladder) with a Viatron pressure transducer attached to the vest&#39;s connector port, and the output of the transducer is connected to an oscilloscope. A vest is connected to each of the air pulse generators and the observed pulse maximum (PMAX) and pulse minimum (PMIN) are recorded at each frequency, with the exception that  104  cool was not tested at 5 Hz. The delta, or pressure stroke, is calculated by subtracting the PMIN from PMAX.  
         [0190]    [0190]FIG. 24 shows the results using an adult large vest, FIG. 25 is the results using an adult medium vest, FIG. 26 is the results using an adult small vest, FIG. 27 is the results using a child large vest and FIG. 28 is the results using a child medium vest. As depicted in each of the graphs,  104  and  104  cool exhibit pressure consistent with the prior art air pulse generator.  
         [0191]    Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.